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He S, Du J, Wang Y, Cui L, Liu W, Xiao Y, Ran Q, Li L, Zhang Z, Tang L, Hu R, Hao Y, Cui X, Xue K. Differences in background environment and fertilization method mediate plant response to nitrogen fertilization in alpine grasslands on the Qinghai-Tibetan Plateau. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 906:167272. [PMID: 37774870 DOI: 10.1016/j.scitotenv.2023.167272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 07/20/2023] [Accepted: 09/20/2023] [Indexed: 10/01/2023]
Abstract
Grassland degradation threatens ecosystem function and livestock production, partly induced by soil nutrient deficiency due to the lack of nutrient return to soils, which is largely ascribed to the intense grazing activities. Therefore, nitrogen (N) fertilization has been widely adopted to restore degraded Qinghai-Tibetan Plateau (QTP) grasslands. Despite numerous field manipulation studies investigating its effects on alpine grasslands, the patterns and thresholds of plant response to N fertilization remain unclear, thus hindering the prediction of its influences on the regional scale. Here, we established a random forest model to predict N fertilization effects on plant productivity based on a meta-analysis synthesizing 88 publications in QTP grasslands. Our results showed that N fertilization increased the aboveground biomass (AGB) by 46.51 %, varying wildly among plant functional groups. The positive fertilization effects intensified when the N fertilization rate increased to 272 kg ha-1 yr-1, and decreased after three years of continuous fertilization. These effects were more substantial when applying ammonium nitrate compared to urea. Further, a machine learning model was used to predict plant productivity response to N fertilization. The total explained variance and mean squared residuals ranged from 49.41 to 75.13 % and 0.011-0.058, respectively, both being the highest for grasses. The crucial predictors were identified as climatic and geographic factors, background AGB without N fertilization, and fertilization methods (i.e., rate, form, and duration). These predictors with easy access contributed 62.47 % of the prediction power of grasses' response, thus enhancing the generalizability and replicability of our model. Notably, if 30 % of yak dung is returned to soils on the QTP, the grassland productivity and plant carbon pool are predicted to increase by 5.90-6.51 % and 9.35-10.31 g C m-2 yr -1, respectively. Overall, the predictions of this study based on literature synthesis enhance our understanding of plant responses to N fertilization in QTP grasslands, thereby providing helpful information for grassland management policies. Conflict of interest: The authors declare no conflict of interest.
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Affiliation(s)
- Shun He
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jianqing Du
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China; Beijing Yanshan Earth Critical Zone National Research Station, University of Chinese Academy of Sciences, Beijing 101408, China
| | - Yanfen Wang
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China; Beijing Yanshan Earth Critical Zone National Research Station, University of Chinese Academy of Sciences, Beijing 101408, China; State Key Laboratory of Tibetan Plateau Earth System, Environment and Resources (TPESER), Chinese Academy of Sciences, Beijing 100101, China.
| | - Lizhen Cui
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Wenjing Liu
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yifan Xiao
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Qinwei Ran
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Linfeng Li
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zuopei Zhang
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Li Tang
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ronghai Hu
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China; Beijing Yanshan Earth Critical Zone National Research Station, University of Chinese Academy of Sciences, Beijing 101408, China
| | - Yanbin Hao
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China; Beijing Yanshan Earth Critical Zone National Research Station, University of Chinese Academy of Sciences, Beijing 101408, China
| | - Xiaoyong Cui
- College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China; Beijing Yanshan Earth Critical Zone National Research Station, University of Chinese Academy of Sciences, Beijing 101408, China
| | - Kai Xue
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China; Beijing Yanshan Earth Critical Zone National Research Station, University of Chinese Academy of Sciences, Beijing 101408, China; Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining 810001, China; Binzhou Institute of Technology, Weiqiao-UCAS Science and Technology Park, Binzhou 256606, China
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McDonnell TC, Phelan J, Talhelm AF, Cosby BJ, Driscoll CT, Sullivan TJ, Greaver T. Protection of forest ecosystems in the eastern United States from elevated atmospheric deposition of sulfur and nitrogen: A comparison of steady-state and dynamic model results. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2023; 318:120887. [PMID: 36535424 PMCID: PMC10348011 DOI: 10.1016/j.envpol.2022.120887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 12/13/2022] [Accepted: 12/14/2022] [Indexed: 06/17/2023]
Abstract
Critical loads (CLs) and target loads (TLs) of atmospheric deposition of sulfur (S) and nitrogen (N) specify the thresholds of air pollution above which damage to ecosystems is expected to occur and are used to inform environmental regulation and natural resource management. Model estimates of CL and TL can vary for a given location, and these differences can be important for characterization of ecosystem effects from elevated S and N deposition. Moreover, TLs are used to evaluate associated timeframes of ecosystem recovery. We compared published CLs and TLs based on soil acidity criteria derived from steady-state versus dynamic models for terrestrial ecosystems. We examined the magnitude of differences in the CL/TL results from the two types of models for the same regions in the Eastern U.S. Results showed that CLs/TLs from dynamic models (or from steady state modeling using soil base cation weathering estimates from dynamic models) generally produce a broader range of values of acid-sensitivity, including lower CLs/TLs, as compared with a steady-state approach. Applications of dynamic biogeochemical models capable of developing CLs/TLs are relatively data intensive and typically limited to locations where measured soil and soil solution (or nearby stream water) chemistry are available for model parameterization, calibration, and testing. We recommend that CLs/TLs derived from dynamic models be used, where data permit, as they are likely more accurate and allow for evaluation of time-dependent phenomena and period needed for recovery. However, CLs derived from steady-state models remain a useful tool for understanding broad spatial patterns in soil acid-sensitivity throughout the U.S. Future work should focus on the development of more reliable model input parameters, particularly soil base cation weathering, and the extent to which CLs and TLs at a given location may vary and be altered with anticipated future climate change. In addition, dynamic models could be further developed to estimate CLs/TLs for nutrient N.
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Affiliation(s)
| | | | - Alan F Talhelm
- College of Natural Resources, University of Idaho, Moscow, ID, USA
| | - Bernard J Cosby
- UK Centre for Ecology and Hydrology Environment Centre Wales, Bangor, Gwynedd, UK
| | - Charles T Driscoll
- Department of Civil and Environmental Engineering, Syracuse University, Syracuse, NY, 13244, USA
| | | | - Tara Greaver
- Center for Public Health and Environmental Assessment, Office of Research and Development, U.S. Environmental Protection Agency, RTP, NC 27711, USA
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LeDuc SD, Clark CM, Phelan J, Belyazid S, Bennett M, Boaggio K, Buckley J, Cajka J, Jones P. Nitrogen and sulfur deposition reductions projected to partially restore forest soil conditions in the US Northeast, while understory composition continues to shift with future climate change. WATER, AIR, AND SOIL POLLUTION 2022; 233:1-26. [PMID: 36312741 PMCID: PMC9610802 DOI: 10.1007/s11270-022-05793-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Accepted: 07/13/2022] [Indexed: 06/16/2023]
Abstract
Human activities have dramatically increased nitrogen (N) and sulfur (S) deposition, altering forest ecosystem function and structure. Anticipating how changes in deposition and climate impact forests can inform decisions regarding these environmental stressors. Here, we used a dynamic soil-vegetation model (ForSAFE-Veg) to simulate responses to future scenarios of atmospheric deposition and climate change across 23 Northeastern hardwood stands. Specifically, we simulated soil percent base saturation, acid neutralizing capacity (ANC), nitrate (NO3 -) leaching, and understory composition under 13 interacting deposition and climate change scenarios to the year 2100, including anticipated deposition reductions under the Clean Air Act (CAA) and Intergovernmental Panel on Climate Change-projected climate futures. Overall, deposition affected soil responses more than climate did. Soils recovered to historic conditions only when future deposition returned to pre-industrial levels, although anticipated CAA deposition reductions led to a partial recovery of percent base saturation (60 to 72%) and ANC (65 to 71%) compared to historic values. CAA reductions also limited NO3 - leaching to 30 to 66% above historic levels, while current levels of deposition resulted in NO3 - leaching 150 to 207% above historic values. In contrast to soils, understory vegetation was affected strongly by both deposition and climate. Vegetation shifted away from historic and current assemblages with increasing deposition and climate change. Anticipated CAA reductions could maintain current assemblages under current climate conditions or slow community shifts under increased future changes in temperature and precipitation. Overall, our results can inform decision makers on how these dual stressors interact to affect forest health, and the efficacy of deposition reductions under a changing climate.
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Affiliation(s)
- Stephen D. LeDuc
- US Environmental Protection Agency, Office of Research and Development, Center for Public Health and Environmental Assessment, Research Triangle Park, NC, USA
| | - Christopher M. Clark
- US Environmental Protection Agency, Office of Research and Development, Center for Public Health and Environmental Assessment, Washington, DC, USA
| | | | | | - Micah Bennett
- US Environmental Protection Agency, Region 5 Headquarters, Chicago, IL, USA
| | - Katie Boaggio
- US Environmental Protection Agency, Office of Research and Development, Center for Public Health and Environmental Assessment, Research Triangle Park, NC, USA
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Díaz-Álvarez EA, de la Barrera E. Influence of Land Use on the C and N Status of a C 4 Invasive Grass in a Semi-Arid Region: Implications for Biomonitoring. PLANTS (BASEL, SWITZERLAND) 2021; 10:plants10050942. [PMID: 34065049 PMCID: PMC8151467 DOI: 10.3390/plants10050942] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Revised: 05/03/2021] [Accepted: 05/04/2021] [Indexed: 06/12/2023]
Abstract
Biomonitoring of atmospheric pollution is an increasingly accepted practice. However, most existing biomonitors are usually epiphytic species from mesic environments. This work assessed the suitability of buffelgrass (Cenchrus ciliaris), an invasive C4 grass in northwestern Mexico, as a biomonitor, by means of the spatial distribution of the carbon and nitrogen content and isotopic signatures for grass samples collected from urban, agricultural, and natural areas throughout the state of Sonora. We found the highest tissue carbon content of 45.6% (on a dry weight basis) and highest nitrogen content of 3.31% for buffelgrass from the Yaqui Valley. We also found the lowest δ13C of -15.9‰, and the highest δ15N of 16.7‰ in the same region. In contrast, the lowest carbon and nitrogen content of 39.4 and 1.49% were found for Bahía de Kino and Río Sonora mountains, respectively. The lowest δ15N of 2.18‰ and the highest δ13C of -13.7‰ were measured for two remote locations. These results show the influence that pollutant emissions, including agriculture and transportation, have on elemental and isotopic composition of vegetation. Buffelgrass is most adequate for tracking carbon and nitrogen emissions in arid environments and for determining alterations on nitrogen soil reactions, as a first approximation for saturation.
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Affiliation(s)
- Edison A. Díaz-Álvarez
- Instituto de Investigaciones Forestales, Universidad Veracruzana, Parque Ecológico “El Haya”, Carretera Antigua a Coatepec-Coapexpan, Xalapa, Veracruz 91070, Mexico;
| | - Erick de la Barrera
- Instituto de Investigaciones en Ecosistemas y Sustentabilidad, Universidad Nacional Autónoma de México, Antigua Carretera a Pátzcuaro 8701, Col. Ex-Hacienda de San José del Cerrito, Morelia Michoacán 58190, Mexico
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5
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The Effect of Nitrogen Fertilization on Tree Growth, Soil Organic Carbon and Nitrogen Leaching—A Modeling Study in a Steep Nitrogen Deposition Gradient in Sweden. FORESTS 2021. [DOI: 10.3390/f12030298] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Nitrogen (N) fertilization in forests has the potential to increase tree growth and carbon (C) sequestration, but it also means a risk of N leaching. Dynamic models can, if the important processes are well described, play an important role in assessing benefits and risks of nitrogen fertilization. The aim of this study was to test if the ForSAFE model is able to simulate correctly the effects of N fertilization when considering different levels of N availability in the forest. The model was applied for three sites in Sweden, representing low, medium and high nitrogen deposition. Simulations were performed for scenarios with and without fertilization. The effect of N fertilization on tree growth was largest at the low deposition site, whereas the effect on N leaching was more pronounced at the high deposition site. For soil organic carbon (SOC) the effects were generally small, but in the second forest rotation SOC was slightly higher after fertilization, especially at the low deposition site. The ForSAFE simulations largely confirm the N saturation theory which state that N will not be retained in the forest when the ecosystem is N saturated, and we conclude that the model can be a useful tool in assessing effects of N fertilization.
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6
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Long- and Short-Term Inorganic Nitrogen Runoff from a Karst Catchment in Austria. FORESTS 2020. [DOI: 10.3390/f11101112] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Excess nitrogen (N) deposition and gaseous N emissions from industrial, domestic, and agricultural sources have led to increased nitrate leaching, the loss of biological diversity, and has affected carbon (C) sequestration in forest ecosystems. Nitrate leaching affects the purity of karst water resources, which contribute around 50% to Austria’s drinking water supply. Here we present an evaluation of the drivers of dissolved inorganic N (DIN) concentrations and fluxes from a karst catchment in the Austrian Alps (LTER Zöbelboden) from 27 years of records. In addition, a hydrological model was used together with climatic scenario data to predict expected future runoff dynamics. The study area was exposed to increasing N deposition during the 20th century (up to 30 to 35 kg N ha−1 y−1), which are still at levels of 25.5 ± 3.6 and 19.9 ± 4.2 kg N ha−1 y−1 in the spruce and the mixed deciduous forests, respectively. Albeit N deposition was close to or exceeded critical loads for several decades, 70–83% of the inorganic N retained in the catchment from 2000 to 2018, and NO3- concentrations in the runoff stayed <10 mg L−1 unless high-flow events occurred or forest stand-replacing disturbances. We identified tree growth as the main sink for inorganic N, which might together with lower runoff, increase retention of only weakly decreasing N deposition in the future. However, since recurring forest stand-replacement is predicted in the future as a result of a combination of climatically driven disturbance agents, pulses of elevated nitrate concentrations in the catchment runoff will likely add to groundwater pollution.
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7
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Braun S, Tresch S, Augustin S. Soil solution in Swiss forest stands: A 20 year's time series. PLoS One 2020; 15:e0227530. [PMID: 32663212 PMCID: PMC7360040 DOI: 10.1371/journal.pone.0227530] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 06/22/2020] [Indexed: 11/19/2022] Open
Abstract
Soil solution chemistry is influenced by atmospheric deposition of air pollutants, exchange processes with the soil matrix and soil-rhizosphere-plant interactions. In this study we present the results of the long-term Intercantonal Forest Observation Program in Switzerland with soil solution measurements since 1998 on a current total of 47 plots. The forest sites comprise two major forest types of Switzerland including a wide range of ecological gradients such as different nitrogen (N) deposition and soil conditions. The long-term data set of 20 years of soil solution measurements revealed an ongoing, but site-specific soil acidification. In strongly acidified soils (soil pH below 4.2), acidification indicators changed only slowly over the measured period, possibly due to high buffering capacity of the aluminum buffer (pH 4.2-3.8). In contrast, in less acidified sites we observed an increasing acidification rate over time, reflected, for example, by the continuous decrease in the ratio of base cations to aluminum (BC/Al ratio). Nowadays, the main driver of soil acidification is the high rate of N deposition, causing cation losses and hampering sustainable nutrient balances for tree nutrition. Mean nitrate leaching rates for the years 2005-2017 were 9.4 kg N ha-1 yr-1, ranging from 0.04 to 53 kg N ha-1 yr-1. Three plots with high N input had a remarkable low nitrate leaching. Both N deposition and nitrate leaching have decreased since 2000. However, the latter trend may be partly explained due to increased drought in recent years. Nonetheless, those high N depositions are still affecting the majority of the forest sites. Taken together, this study gives evidence of anthropogenic soil acidification in Swiss forest stands. The underlying long-term measurements of soil solution provides important information on nutrient leaching losses and the impact climate change effects such as droughts. Furthermore, this study improves the understanding of forest management and tree mortality regarding varying nitrate leaching rates.
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Affiliation(s)
- Sabine Braun
- Institute for Applied Plant Biology, Witterswil, Switzerland
| | - Simon Tresch
- Institute for Applied Plant Biology, Witterswil, Switzerland
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8
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Sebestyen SD, Ross DS, Shanley JB, Elliott EM, Kendall C, Campbell JL, Dail DB, Fernandez IJ, Goodale CL, Lawrence GB, Lovett GM, McHale PJ, Mitchell MJ, Nelson SJ, Shattuck MD, Wickman TR, Barnes RT, Bostic JT, Buda AR, Burns DA, Eshleman KN, Finlay JC, Nelson DM, Ohte N, Pardo LH, Rose LA, Sabo RD, Schiff SL, Spoelstra J, Williard KWJ. Unprocessed Atmospheric Nitrate in Waters of the Northern Forest Region in the U.S. and Canada. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:3620-3633. [PMID: 30830765 DOI: 10.1021/acs.est.9b01276] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Little is known about the regional extent and variability of nitrate from atmospheric deposition that is transported to streams without biological processing in forests. We measured water chemistry and isotopic tracers (δ18O and δ15N) of nitrate sources across the Northern Forest Region of the U.S. and Canada and reanalyzed data from other studies to determine when, where, and how unprocessed atmospheric nitrate was transported in catchments. These inputs were more widespread and numerous than commonly recognized, but with high spatial and temporal variability. Only 6 of 32 streams had high fractions (>20%) of unprocessed atmospheric nitrate during baseflow. Seventeen had high fractions during stormflow or snowmelt, which corresponded to large fractions in near-surface soil waters or groundwaters, but not deep groundwater. The remaining 10 streams occasionally had some (<20%) unprocessed atmospheric nitrate during stormflow or baseflow. Large, sporadic events may continue to be cryptic due to atmospheric deposition variation among storms and a near complete lack of monitoring for these events. A general lack of observance may bias perceptions of occurrence; sustained monitoring of chronic nitrogen pollution effects on forests with nitrate source apportionments may offer insights needed to advance the science as well as assess regulatory and management schemes.
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Affiliation(s)
- Stephen D Sebestyen
- USDA Forest Service , Northern Research Station , 1831 Highway 169 E , Grand Rapids , Minnesota 55744-3399 , United States
| | - Donald S Ross
- University of Vermont , Dept. of Plant and Soil Science , Burlington , Vermont 05405-1737 , United States
| | - James B Shanley
- U.S. Geological Survey (USGS) , New England Water Science Center , Montpelier , Vermont 05602 , United States
| | - Emily M Elliott
- University of Pittsburgh , Dept. of Geology and Environmental Science , Pittsburgh , Pennsylvania 15260-3332 , United States
| | - Carol Kendall
- USGS , Menlo Park , California 94025 , United States
| | - John L Campbell
- USDA Forest Service , Northern Research Station , Durham , New Hampshire 03824 , United States
| | - D Bryan Dail
- University of Maine , Department of Plant, Soil, and Environmental Science , Orono , Maine 04469 , United States
| | - Ivan J Fernandez
- University of Maine , School of Forest Resources , Orono , Maine 04469 , United States
| | - Christine L Goodale
- Cornell University , Ecology and Evolutionary Biology , Ithaca , New York 14850 , United States
| | | | - Gary M Lovett
- Cary Institute of Ecosystem Studies , Millbrook , New York 12545 , United States
| | - Patrick J McHale
- State University of New York College of Environmental Science and Forestry , Department of Environmental and Forest Biology , Syracuse , New York 13210 , United States
| | - Myron J Mitchell
- State University of New York College of Environmental Science and Forestry , Department of Environmental and Forest Biology , Syracuse , New York 13210 , United States
| | - Sarah J Nelson
- University of Maine , School of Forest Resources , Orono , Maine 04469 , United States
| | - Michelle D Shattuck
- University of New Hampshire , Dept. of Natural Resources and the Environment , Durham , New Hampshire 03824 , United States
| | - Trent R Wickman
- USDA Forest Service , National Forest System - Eastern Region , Duluth , Minnesota 55808 , United States
| | - Rebecca T Barnes
- Colorado College , Environmental Program , Colorado Springs , Colorado 80903 , United States
| | - Joel T Bostic
- University of Maryland Center for Environmental Science , Appalachian Laboratory , Frostburg , Maryland 21532 , United States
| | - Anthony R Buda
- USDA Agricultural Research Service , Pasture Systems and Watershed Management Research Unit , University Park , Pennsylvania 16802-3702 , United States
| | - Douglas A Burns
- USGS , NY Water Science Center , Troy , New York 12180 , United States
| | - Keith N Eshleman
- University of Maryland Center for Environmental Science , Appalachian Laboratory , Frostburg , Maryland 21532 , United States
| | - Jacques C Finlay
- University of Minnesota , Ecology, Evolution, and Behavior , St. Paul , Minnesota 55108 , United States
| | - David M Nelson
- University of Maryland Center for Environmental Science , Appalachian Laboratory , Frostburg , Maryland 21532 , United States
| | - Nobuhito Ohte
- Kyoto University , Department of Social Informatics , Kyoto , Kyoto Prefecture 6068501 , Japan
| | - Linda H Pardo
- USDA Forest Service , Northern Research Station , Burlington , Vermont 05405 , United States
| | - Lucy A Rose
- University of Minnesota , Department of Forest Resources , St. Paul , Minnesota 55108 , United States
| | - Robert D Sabo
- USDA Forest Service , Northern Research Station , Burlington , Vermont 05405 , United States
| | - Sherry L Schiff
- University of Waterloo , Department of Earth and Environmental Sciences , Waterloo , Ontario N2L 3G1 , Canada
| | - John Spoelstra
- Environment and Climate Change Canada , Canada Center for Inland Waters , Burlington , Ontario L7S 1A1 , Canada
| | - Karl W J Williard
- Southern Illinois University , Forestry Center for Ecology , Carbondale , Illinois 62901 , United States
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Bowman WD, Ayyad A, Bueno de Mesquita CP, Fierer N, Potter TS, Sternagel S. Limited ecosystem recovery from simulated chronic nitrogen deposition. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2018; 28:1762-1772. [PMID: 30179279 DOI: 10.1002/eap.1783] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 05/22/2018] [Accepted: 07/05/2018] [Indexed: 06/08/2023]
Abstract
The realization that anthropogenic nitrogen (N) deposition is causing significant environmental change in many ecosystems has led to lower emissions of reactive N and deposition rates in many regions. However, the impacts of N deposition on terrestrial ecosystems can be long lasting, with significant inertia in the return of the biota and biogeochemical processes to baseline levels. To better understand patterns of recovery and the factors that may contribute to slow or no responses following declines in N deposition, we followed plant species composition, microbial abundance, N cycling rates, soil pH, and pools of NO3- and extractable cations in an impacted alpine ecosystem following cessation of 12-yr experiment increasing N deposition rates by 0, 20, 40, and 60 kg N·ha-1 ·yr-1 . Simulated N deposition had resulted in a tripling in the cover of the nitrophilic species Carex rupestris, while the dominant sedge Kobresia myosuroides had decreased by more than half at the highest N input level. In addition, nitrification rates were elevated, soil extractable magnesium (Mg2+ ) and pH decreased, and aluminum (Al3+ ) and manganese (Mn2+ ) were elevated at the highest N treatment inputs. Over the nine years following cessation of N additions to the impacted plots, only the cover of the nitrophilic C. rupestris showed any recovery to prior levels. Abundances of both bacteria and fungi were lower with N addition in both treatment and recovery plots. Rates of nitrification and pools of NO3- remained elevated in the recovery plots, likely contributing to the lack of biotic response to the cessation of N inputs. In addition, nutrient base cations (Ca2+ and Mg2+ ) and soil pH remained depressed, and the toxic metal cations (Al3+ and Mn2+ ) remained elevated in recovery plots, also potentially influencing biotic recovery. These results emphasize the importance of considering long-term environmental impacts of N deposition associated with legacy effects, such as elevated N cycling and losses of base cations, in determining environmental standards such as the metrics used for critical loads.
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Affiliation(s)
- William D Bowman
- Department of Ecology and Evolutionary Biology and Institute of Arctic and Alpine Research, University of Colorado, Boulder, Colorado, 80309-0334, USA
| | - Asma Ayyad
- Department of Botany and Plant Sciences, University of California, Riverside, California, 92521, USA
| | - Clifton P Bueno de Mesquita
- Department of Ecology and Evolutionary Biology and Institute of Arctic and Alpine Research, University of Colorado, Boulder, Colorado, 80309-0334, USA
| | - Noah Fierer
- Department of Ecology and Evolutionary Biology and Institute of Arctic and Alpine Research, University of Colorado, Boulder, Colorado, 80309-0334, USA
- Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, 80309-0216, USA
| | - Teal S Potter
- Department of Ecology and Evolutionary Biology and Institute of Arctic and Alpine Research, University of Colorado, Boulder, Colorado, 80309-0334, USA
| | - Stefanie Sternagel
- Department of Ecology and Evolutionary Biology and Institute of Arctic and Alpine Research, University of Colorado, Boulder, Colorado, 80309-0334, USA
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10
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Taboada A, Calvo-Fernández J, Marcos E, Calvo L. Plant and vegetation functional responses to cumulative high nitrogen deposition in rear-edge heathlands. THE SCIENCE OF THE TOTAL ENVIRONMENT 2018; 637-638:980-990. [PMID: 29763879 DOI: 10.1016/j.scitotenv.2018.05.092] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 05/07/2018] [Accepted: 05/07/2018] [Indexed: 06/08/2023]
Abstract
Elevated atmospheric nitrogen (N) deposition is a major driver of change, altering the structure/functioning of nutrient-poor Calluna vulgaris-heathlands over Europe. These effects amply proven for north-western/central heathlands may, however, vary across the ecosystem's distribution, especially at the range limits, as heathlands are highly vulnerable to land-use changes combined with present climate change. This is an often overlooked and greatly understudied aspect of the ecology of heathlands facing global change. We investigated the effects of five N-fertilisation treatments simulating a range of N deposition rates (0, 10, 20, and 50 kg N ha-1 yr-1 for 1 year; and 56 kg N ha-1 yr-1 for 9 years) on the Calluna-plants, the plant functional groups, species composition and richness of two life-cycle stages (building/young- and mature-phase) of Calluna-heathlands at their rear-edge limit. Our findings revealed a dose-related response of the shoot length and number of flowers of young and mature Calluna-plants to the addition of N, adhering to the findings from other heathland locations. However, cumulative high-N loading reduced the annual growth and flowering of young plants, showing early signs of N saturation. The different plant functional groups showed contrasting responses to the cumulative addition of N: annual/perennial forbs and annual graminoids increased with quite low values; perennial graminoids were rather abundant in young heathlands but only slightly augmented in mature ones; while bryophytes and lichens strongly declined at the two heathland life-cycle stages. Meanwhile there were no significant N-driven changes in plant species composition and richness. Our results demonstrated that Calluna-heathlands at their low-latitude distribution limit are moderately resistant to cumulative high-N loading. As north-western/central European heathlands under high-N inputs broadly experienced the loss of plant diversity and pronounced changes in plant species dominance, rear-edge locations may be of critical importance to unravel the mechanisms of heathland resilience to future global change.
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Affiliation(s)
- Angela Taboada
- Area of Ecology, University of León, E-24071 León, Spain; Institute of Environmental Research (IMA), University of Léon, E-24071 León, Spain.
| | - Javier Calvo-Fernández
- Area of Ecology, University of León, E-24071 León, Spain; Institute of Environmental Research (IMA), University of Léon, E-24071 León, Spain
| | - Elena Marcos
- Area of Ecology, University of León, E-24071 León, Spain; Institute of Environmental Research (IMA), University of Léon, E-24071 León, Spain
| | - Leonor Calvo
- Area of Ecology, University of León, E-24071 León, Spain; Institute of Environmental Research (IMA), University of Léon, E-24071 León, Spain
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11
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Patel KF, Fernandez IJ. Nitrogen mineralization in O horizon soils during 27 years of nitrogen enrichment at the Bear Brook Watershed in Maine, USA. ENVIRONMENTAL MONITORING AND ASSESSMENT 2018; 190:563. [PMID: 30167903 DOI: 10.1007/s10661-018-6945-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 08/22/2018] [Indexed: 06/08/2023]
Abstract
Chronic elevated nitrogen (N) deposition has altered the N status of temperate forests, with significant implications for ecosystem function. The Bear Brook Watershed in Maine (BBWM) is a whole paired watershed manipulation experiment established to study the effects of N and sulfur (S) deposition on ecosystem function. N was added bimonthly as (NH4)2SO4 to one watershed from 1989 to 2016, and research at the site has studied the evolution of ecosystem response to the treatment through time. Here, we synthesize results from 27 years of research at the site and describe the temporal trend of N availability and N mineralization at BBWM in response to chronic N deposition. Our findings suggest that there was a delayed response in soil N dynamics, since labile soil N concentrations did not show increases in the treated watershed (West Bear, WB) compared to the reference watershed (East Bear, EB) until after the first 4 years of treatment. Labile N became increasingly available in WB through time, and after 25 years of manipulations, treated soils had 10× more extractable ammonium than EB soils. The WB soils had 200× more extractable nitrate than EB soils, driven by both, high nitrate concentrations in WB and low nitrate concentrations in EB. Nitrification rates increased in WB soils and accounted for ~ 50% of net N mineralization, compared to ~ 5% in EB soils. The study provides evidence of the decadal evolution in soil function at BBWM and illustrates the importance of long-term data to capture ecosystem response to chronic disturbance.
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Affiliation(s)
- Kaizad F Patel
- School of Forest Resources, University of Maine, 5755 Nutting Hall, Orono, ME, 04469, USA.
| | - Ivan J Fernandez
- School of Forest Resources, University of Maine, 5755 Nutting Hall, Orono, ME, 04469, USA
- Climate Change Institute, University of Maine, 5764 Sawyer Research Center, Orono, ME, 04469, USA
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12
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McDonnell TC, Belyazid S, Sullivan TJ, Bell M, Clark C, Blett T, Evans T, Cass W, Hyduke A, Sverdrup H. Vegetation dynamics associated with changes in atmospheric nitrogen deposition and climate in hardwood forests of Shenandoah and Great Smoky Mountains National Parks, USA. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2018; 237:662-674. [PMID: 29549857 DOI: 10.1016/j.envpol.2018.01.112] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 01/30/2018] [Accepted: 01/31/2018] [Indexed: 06/08/2023]
Abstract
Ecological effects of atmospheric nitrogen (N) and sulfur (S) deposition on two hardwood forest sites in the eastern United States were simulated in the context of a changing climate using the dynamic coupled biogeochemical/ecological model chain ForSAFE-Veg. The sites are a mixed oak forest in Shenandoah National Park, Virginia (Piney River) and a mixed oak-sugar maple forest in Great Smoky Mountains National Park, Tennessee (Cosby Creek). The sites have received relatively high levels of both S and N deposition and the climate has warmed over the past half century or longer. The model was used to evaluate the composition of the understory plant communities, the alignment between plant species niche preferences and ambient conditions, and estimate changes in relative species abundances as reflected by plant cover under various scenarios of future atmospheric N and S deposition and climate change. The main driver of ecological effects was soil solution N concentration. Results of this research suggested that future climate change might compromise the capacity for the forests to sustain habitat suitability. However, vegetation results should be considered preliminary until further model validation can be performed. With expected future climate change, preliminary estimates suggest that sustained future N deposition above 7.4 and 5.0 kg N/ha/yr is expected to decrease contemporary habitat suitability for indicator plant species located at Piney River and Cosby Creek, respectively.
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Affiliation(s)
- T C McDonnell
- E&S Environmental Chemistry, Inc., PO Box 609, Corvallis, OR 97339, United States.
| | - S Belyazid
- Belyazid Consulting & Communication AB, Hyby Kyrkoväg 170, SE-233 76 Klågerup, Sweden.
| | - T J Sullivan
- E&S Environmental Chemistry, Inc., PO Box 609, Corvallis, OR 97339, United States.
| | - M Bell
- National Park Service-Air Resources Division, PO Box 25287, Denver, CO 80225-0287, United States.
| | - C Clark
- US EPA, Office of Research and Development, National Center for Environmental Assessment, Washington, DC 20460, United States.
| | - T Blett
- National Park Service-Air Resources Division, PO Box 25287, Denver, CO 80225-0287, United States.
| | - T Evans
- National Park Service - Great Smoky Mountains National Park, 107 Park Headquarters Rd, Gatlinburg, TN 37738, United States.
| | - W Cass
- Shenandoah National Park, 3655 US Highway 211 E, Luray, VA 22835-4702, United States.
| | - A Hyduke
- Shenandoah National Park, 3655 US Highway 211 E, Luray, VA 22835-4702, United States.
| | - H Sverdrup
- School of Engineering and Natural Sciences, University of Iceland, Sæmundargötu 2, 101 Reykjavík, Iceland.
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13
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Díaz-Álvarez EA, Lindig-Cisneros R, de la Barrera E. Biomonitors of atmospheric nitrogen deposition: potential uses and limitations. CONSERVATION PHYSIOLOGY 2018; 6:coy011. [PMID: 29564134 PMCID: PMC5848806 DOI: 10.1093/conphys/coy011] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2017] [Revised: 02/13/2018] [Accepted: 02/20/2018] [Indexed: 05/30/2023]
Abstract
Atmospheric nitrogen deposition is the third largest cause of global biodiversity loss, with rates that have more than doubled over the past century. This is especially threatening for tropical regions where the deposition may soon exceed 25 kg of N ha-1 year-1, well above the threshold for physiological damage of 12-20 kg of N ha-1 year-1, depending on plant species and nitrogenous compound. It is thus urgent to monitor these regions where the most diverse biotas occur. However, most studies have been conducted in Europe, the USA and recently in China. This review presents the case for the potential use of biological organisms to monitor nitrogen deposition, with emphasis on tropical plants. We first present an overview of atmospheric chemistry and the nitrogen metabolism of potential biomonitors, followed by a framework for monitoring nitrogen deposition based on the simultaneous use of various functional groups. In particular, the tissue nitrogen content responds to the rate of deposition, especially for mosses, whose nitrogen content increases by 1‰ per kilogram of N ha-1 year-1. The isotopic signature, δ15N, is a useful indicator of the nitrogen source, as the slightly negative values (e.g. 5‰) of plants from natural environments can become very negative (-11.2‰) in sites with agricultural and husbandry activities, but very positive (13.3‰) in urban environments with high vehicular activity. Mosses are good biomonitors for wet deposition and atmospheric epiphytes for dry deposition. In turn, the nitrogen saturation of ecosystems can be monitored with trees whose isotopic values increase with saturation. Although given ecophysiological limitations of different organisms, particular studies should be conducted in each area of interest to determine the most suitable biomonitors. Overall, biomonitors can provide an integrative approach for characterizing nitrogen deposition in regions where the deployment of automated instruments or passive monitoring is not feasible or can be complementary.
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Affiliation(s)
- Edison A Díaz-Álvarez
- Posgrado en Ciencias Biológicas, Universidad Nacional Autónoma de México, Av. Universidad 3000, C.U., Mexico City 04510, Mexico
- Instituto de Investigaciones en Ecosistemas y Sustentabilidad, Universidad Nacional Autónoma de México, Ant. Ctra. a Pátzcuaro 8701, Morelia, Michoacán 58190, Mexico
| | - Roberto Lindig-Cisneros
- Instituto de Investigaciones en Ecosistemas y Sustentabilidad, Universidad Nacional Autónoma de México, Ant. Ctra. a Pátzcuaro 8701, Morelia, Michoacán 58190, Mexico
| | - Erick de la Barrera
- Instituto de Investigaciones en Ecosistemas y Sustentabilidad, Universidad Nacional Autónoma de México, Ant. Ctra. a Pátzcuaro 8701, Morelia, Michoacán 58190, Mexico
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14
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Braun S, Schindler C, Rihm B. Growth trends of beech and Norway spruce in Switzerland: The role of nitrogen deposition, ozone, mineral nutrition and climate. THE SCIENCE OF THE TOTAL ENVIRONMENT 2017; 599-600:637-646. [PMID: 28494288 DOI: 10.1016/j.scitotenv.2017.04.230] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 04/28/2017] [Accepted: 04/28/2017] [Indexed: 06/07/2023]
Abstract
Understanding the effects of nitrogen deposition, ozone and climate on tree growth is important for planning sustainable forest management also in the future. The complex interplay of all these factors cannot be covered by experiments. Here we use observational data of mature forests for studying associations of various biotic and abiotic factors with tree growth. A 30year time series on basal area increment of Fagus sylvatica L. and Picea abies Karst. in Switzerland was analyzed to evaluate the development in relation to a variety of predictors. Basal area increment of Fagus sylvatica has clearly decreased during the observation period. For Picea abies no trend was observed. N deposition of more than 26 (beech) or 20-22kgNha-1year-1 (Norway spruce) was negatively related with basal area increment, in beech stronger than in Norway spruce. High N deposition loads and low foliar K concentrations in Fagus were correlated with increased drought sensitivity. High air temperatures in winter were negatively related with basal area increment in Norway spruce in general and in beech at high N:Mg ratio or high N deposition while on an average the relation was positive in beech. Fructification in beech was negatively related to basal area increment. The increase of fructification observed during the last decades contributed thus to the growth decrease. Ozone flux was significantly and negatively correlated with basal area increment both in beech and Norway spruce. The results show clear non-linear effects of N deposition on stem increment of European beech and Norway spruce as well as strong interactions with climate which have contributed to the growth decrease in beech and may get more important in future. The results not only give suggestions for ecological processes but also show the potential of an integral evaluation of observational data.
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Affiliation(s)
- Sabine Braun
- Institute for Applied Plant Biology, Sandgrubenstrasse 25, 4124 Schönenbuch, Switzerland.
| | | | - Beat Rihm
- Meteotest, Fabrikstrasse 14, 3012 Berne, Switzerland.
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15
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Simulated effects of nitrogen saturation on the global carbon budget using the IBIS model. Sci Rep 2016; 6:39173. [PMID: 27966643 PMCID: PMC5155240 DOI: 10.1038/srep39173] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 11/18/2016] [Indexed: 11/08/2022] Open
Abstract
Over the past 100 years, human activity has greatly changed the rate of atmospheric N (nitrogen) deposition in terrestrial ecosystems, resulting in N saturation in some regions of the world. The contribution of N saturation to the global carbon budget remains uncertain due to the complicated nature of C-N (carbon-nitrogen) interactions and diverse geography. Although N deposition is included in most terrestrial ecosystem models, the effect of N saturation is frequently overlooked. In this study, the IBIS (Integrated BIosphere Simulator) was used to simulate the global-scale effects of N saturation during the period 1961-2009. The results of this model indicate that N saturation reduced global NPP (Net Primary Productivity) and NEP (Net Ecosystem Productivity) by 0.26 and 0.03 Pg C yr-1, respectively. The negative effects of N saturation on carbon sequestration occurred primarily in temperate forests and grasslands. In response to elevated CO2 levels, global N turnover slowed due to increased biomass growth, resulting in a decline in soil mineral N. These changes in N cycling reduced the impact of N saturation on the global carbon budget. However, elevated N deposition in certain regions may further alter N saturation and C-N coupling.
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16
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Response of aboveground biomass and diversity to nitrogen addition - a five-year experiment in semi-arid grassland of Inner Mongolia, China. Sci Rep 2016; 6:31919. [PMID: 27573360 PMCID: PMC5004133 DOI: 10.1038/srep31919] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 07/28/2016] [Indexed: 11/24/2022] Open
Abstract
Understanding the response of the plant community to increasing nitrogen (N) deposition is helpful for improving pasture management in semi-arid areas. We implemented a 5-year N addition experiment in a Stipa krylovii steppe of Inner Mongolia, northern China. The aboveground biomass (AGB) and species richness were measured annually. Along with the N addition levels, the species richness declined significantly, and the species composition changed noticeably. However, the total AGB did not exhibit a noticeable increase. We found that compensatory effects of the AGB occurred not only between the grasses and the forbs but also among Gramineae species. The plant responses to N addition, from the community to species level, lessened in dry years compared to wet or normal years. The N addition intensified the reduction of community productivity in dry years. Our study indicated that the compensatory effects of the AGB among the species sustained the stability of grassland productivity. However, biodiversity loss resulting from increasing N deposition might lead the semi-arid grassland ecosystem to be unsustainable, especially in dry years.
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17
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Gilliam FS, Welch NT, Phillips AH, Billmyer JH, Peterjohn WT, Fowler ZK, Walter CA, Burnham MB, May JD, Adams MB. Twenty‐five‐year response of the herbaceous layer of a temperate hardwood forest to elevated nitrogen deposition. Ecosphere 2016. [DOI: 10.1002/ecs2.1250] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- Frank S. Gilliam
- Department of Biological Sciences Marshall University Huntington West Virginia 25755‐2510 USA
| | - Nicole Turrill Welch
- Department of Sciences & Mathematics Mississippi University for Women Columbus Mississippi 39701 USA
| | | | - Jake H. Billmyer
- Department of Biological Sciences Marshall University Huntington West Virginia 25755‐2510 USA
| | - William T. Peterjohn
- Department of Biology West Virginia University Morgantown West Virginia 26506 USA
| | - Zachariah K. Fowler
- Department of Biology West Virginia University Morgantown West Virginia 26506 USA
| | | | - Mark B. Burnham
- Department of Biology West Virginia University Morgantown West Virginia 26506 USA
| | - Jeffrey D. May
- Department of Biological Sciences Marshall University Huntington West Virginia 25755‐2510 USA
| | - Mary Beth Adams
- Northern Research Station USDA Forest Service Morgantown West Virginia 26505 USA
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18
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The Importance of Ectomycorrhizal Networks for Nutrient Retention and Carbon Sequestration in Forest Ecosystems. ACTA ACUST UNITED AC 2015. [DOI: 10.1007/978-94-017-7395-9_3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/08/2023]
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19
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Response of aboveground biomass and diversity to nitrogen addition along a degradation gradient in the Inner Mongolian steppe, China. Sci Rep 2015; 5:10284. [PMID: 26194184 PMCID: PMC4508527 DOI: 10.1038/srep10284] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Accepted: 04/09/2015] [Indexed: 11/13/2022] Open
Abstract
Although nitrogen addition and recovery from degradation can both promote production of grassland biomass, these two factors have rarely been investigated in combination. In this study, we established a field experiment with six N-treatment (CK, 10, 20, 30, 40, 50 g N m−2 yr−1) on five fields with different degradation levels in the Inner Mongolian steppe of China from 2011–2013. Our observations showed that while the external nitrogen increased the aboveground biomass in all five grasslands, the magnitude of the effects differed with the severity of degradation. Fields with a higher level of degradation tended to have a higher saturation value (20 g N m−2 yr−1) than those with a lower degradation level ( < 10 g N m−2 yr−1). After three years of experimentation, species richness showed little change across degradation levels. Among the four functional groups of grasses, sedges, forbs and legumes, grasses shared the most similar response patterns with those of the whole community, demonstrating the predominant role that they play in the restoration of grassland under a stimulus of nitrogen addition.
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20
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McDonough AM, Watmough SA. Impacts of nitrogen deposition on herbaceous ground flora and epiphytic foliose lichen species in southern Ontario hardwood forests. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2015; 196:78-88. [PMID: 25305468 DOI: 10.1016/j.envpol.2014.09.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Revised: 09/04/2014] [Accepted: 09/06/2014] [Indexed: 06/04/2023]
Abstract
In this study 70 sugar maple (Acer saccharum Marsh.) dominated plots in Ontario, Canada were sampled in the spring of 2009 and 2010 and herbaceous plant and epiphytic foliose lichen species data were compared against modeled N and S deposition data, climate parameters and measured soil and plant/lichen S and N concentration. Herbaceous plant species richness was positively correlated with temperature and indices of diversity (Shannon Weiner and Simpson's Index) were positively correlated with soil pH but not N or S deposition or standardized foliar N scores. Herbaceous community composition was strongly controlled by traditional factors, but there was a small and significant influence of atmospheric S and N deposition. Epiphytic lichen species richness exhibited a strong negative relationship with standardized foliar N score and only one lichen species (Phaeophyscia rubropulchra) was observed at sites with a standardized foliar N score of 0.76.
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Affiliation(s)
- Andrew M McDonough
- Environmental and Life Science Program, Trent University, Peterborough, Ontario K9J 7B8, Canada.
| | - Shaun A Watmough
- Environmental Resource Studies Program, Trent University, Peterborough, Ontario K9J 7B8, Canada
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21
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Response of canopy nitrogen uptake to a rapid decrease in bulk nitrate deposition in two eastern Canadian boreal forests. Oecologia 2014; 177:29-37. [DOI: 10.1007/s00442-014-3118-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2014] [Accepted: 10/14/2014] [Indexed: 10/24/2022]
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22
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Helliwell RC, Wright RF, Jackson-Blake LA, Ferrier RC, Aherne J, Cosby BJ, Evans CD, Forsius M, Hruska J, Jenkins A, Kram P, Kopáček J, Majer V, Moldan F, Posch M, Potts JM, Rogora M, Schöpp W. Assessing recovery from acidification of European surface waters in the year 2010: evaluation of projections made with the MAGIC model in 1995. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:13280-13288. [PMID: 25325669 DOI: 10.1021/es502533c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In 1999 we used the MAGIC (Model of Acidification of Groundwater In Catchments) model to project acidification of acid-sensitive European surface waters in the year 2010, given implementation of the Gothenburg Protocol to the Convention on Long-Range Transboundary Air Pollution (LRTAP). A total of 202 sites in 10 regions in Europe were studied. These forecasts can now be compared with measurements for the year 2010, to give a "ground truth" evaluation of the model. The prerequisite for this test is that the actual sulfur and nitrogen deposition decreased from 1995 to 2010 by the same amount as that used to drive the model forecasts; this was largely the case for sulfur, but less so for nitrogen, and the simulated surface water [NO3(-)] reflected this difference. For most of the sites, predicted surface water recovery from acidification for the year 2010 is very close to the actual recovery observed from measured data, as recovery is predominantly driven by reductions in sulfur deposition. Overall these results show that MAGIC successfully predicts future water chemistry given known changes in acid deposition.
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23
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Priputina I, Zubkova E, Shanin V, Smirnov V, Komarov A. Evidence of plant biodiversity changes as a result of nitrogen deposition in permanent pine forest plots in central Russia. ECOSCIENCE 2014. [DOI: 10.2980/21-(3-4)-3681] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Irina Priputina
- Institute of Physicochemical and Biological Problems in Soil Science, in Soil Science of the Russian Academy of Sciences, Institutskaya str. 2, Puschino, Moscow region, Russia,
| | - Elena Zubkova
- Institute of Physicochemical and Biological Problems in Soil Science, in Soil Science of the Russian Academy of Sciences, Institutskaya str. 2, Puschino, Moscow region, Russia,
| | - Vladimir Shanin
- Institute of Physicochemical and Biological Problems in Soil Science, in Soil Science of the Russian Academy of Sciences, Institutskaya str. 2, Puschino, Moscow region, Russia,
| | - Vadim Smirnov
- Institute of Mathematical Problems in Biology, Russian Academy of Sciences Institutskaya str. 4, Puschino, Moscow region, Russia
| | - Alexander Komarov
- Institute of Physicochemical and Biological Problems in Soil Science, Russian Academy of Sciences Institutskaya str. 2, Puschino, Moscow region, Russia
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24
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García-Gómez H, Garrido JL, Vivanco MG, Lassaletta L, Rábago I, Àvila A, Tsyro S, Sánchez G, González Ortiz A, González-Fernández I, Alonso R. Nitrogen deposition in Spain: modeled patterns and threatened habitats within the Natura 2000 network. THE SCIENCE OF THE TOTAL ENVIRONMENT 2014; 485-486:450-460. [PMID: 24742555 DOI: 10.1016/j.scitotenv.2014.03.112] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 03/13/2014] [Accepted: 03/23/2014] [Indexed: 05/25/2023]
Abstract
The Mediterranean Basin presents an extraordinary biological richness but very little information is available on the threat that air pollution, and in particular reactive nitrogen (N), can pose to biodiversity and ecosystem functioning. This study represents the first approach to assess the risk of N enrichment effects on Spanish ecosystems. The suitability of EMEP and CHIMERE air quality model systems as tools to identify those areas where effects of atmospheric N deposition could be occurring was tested. For this analysis, wet deposition of NO3(-) and NH4(+) estimated with EMEP and CHIMERE model systems were compared with measured data for the period 2005-2008 obtained from different monitoring networks in Spain. Wet N deposition was acceptably predicted by both models, showing better results for oxidized than for reduced nitrogen, particularly when using CHIMERE. Both models estimated higher wet deposition values in northern and northeastern Spain, and decreasing along a NE-SW axis. Total (wet+dry) nitrogen deposition in 2008 reached maxima values of 19.4 and 23.0 kg N ha(-1) year(-1) using EMEP and CHIMERE models respectively. Total N deposition was used to estimate the exceedance of N empirical critical loads in the Natura 2000 network. Grassland habitats proved to be the most threatened group, particularly in the northern alpine area, pointing out that biodiversity conservation in these protected areas could be endangered by N deposition. Other valuable mountain ecosystems can be also threatened, indicating the need to extend atmospheric deposition monitoring networks to higher altitudes in Spain.
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Affiliation(s)
- H García-Gómez
- Atmospheric Pollution Division, CIEMAT, Av. Complutense 40, Madrid 28040, Spain.
| | - J L Garrido
- Atmospheric Pollution Division, CIEMAT, Av. Complutense 40, Madrid 28040, Spain.
| | - M G Vivanco
- Atmospheric Pollution Division, CIEMAT, Av. Complutense 40, Madrid 28040, Spain.
| | - L Lassaletta
- CNRS/Université Pierre et Marie Curie, UMR Sisyphe, 4 Place Jussieu, Paris 75005, France.
| | - I Rábago
- Atmospheric Pollution Division, CIEMAT, Av. Complutense 40, Madrid 28040, Spain.
| | - A Àvila
- CREAF (Center for Ecological Research and Forestry Applications), Universitat Autònoma de Barcelona, Bellaterra 08193, Spain.
| | - S Tsyro
- MSC-W of EMEP, Norwegian Meteorological Institute, Henrik Mohns plass 1, Oslo 0313, Norway.
| | - G Sánchez
- Spanish Ministry of Agriculture, Food and Environment (ICP Forests), c/Ríos Rosas 24-6°, Madrid 28003, Spain.
| | - A González Ortiz
- Spanish Ministry of Agriculture, Food and Environment (Air Quality and Industrial Environment), Pza. S. Juan de la Cruz, s/n, Madrid 28071, Spain.
| | - I González-Fernández
- Atmospheric Pollution Division, CIEMAT, Av. Complutense 40, Madrid 28040, Spain.
| | - R Alonso
- Atmospheric Pollution Division, CIEMAT, Av. Complutense 40, Madrid 28040, Spain.
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25
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Tipping E, Henrys PA, Maskell LC, Smart SM. Nitrogen deposition effects on plant species diversity; threshold loads from field data. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2013; 179:218-223. [PMID: 23688734 DOI: 10.1016/j.envpol.2013.04.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2013] [Revised: 04/03/2013] [Accepted: 04/06/2013] [Indexed: 06/02/2023]
Abstract
National-scale plant species richness data for Great Britain in 1998 were related to modelled contemporary N deposition (N(dep)) using a broken stick median regression, to estimate thresholds above which N(dep) definitely has had an effect. The thresholds (kg N ha⁻¹ a⁻¹) are 7.9 for acid grassland 14.9 for bogs, 23.6 for calcareous grassland, 7.8 for deciduous woodland and 8.8 for heath. The woodland and heath thresholds are not significantly greater than the lowest N(dep), which implies that species loss may occur over the whole range of contemporary N(dep). This also applies to acid grassland if it is assumed that N(dep) has substituted for previous N fixation. The thresholds for bog and calcareous grassland are both significantly above the lowest N(dep). The thresholds are lower than the mid-range empirical Critical Loads for acid grassland, deciduous woodland and heath, higher for bogs, and approximately equal for calcareous grassland.
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Affiliation(s)
- E Tipping
- Centre for Ecology and Hydrology, Lancaster Environment Centre, Library Avenue, Lancaster LA1 4AP, United Kingdom.
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26
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Burke IC, Bontti EE, Barrett JE, Lowe PN, Lauenroth WK, Riggle R. Impact of labile and recalcitrant carbon treatments on available nitrogen and plant communities in a semiarid ecosystem. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2013; 23:537-545. [PMID: 23734484 DOI: 10.1890/12-0015.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
In a 10-year study, we assessed the influence of five carbon (C) treatments on the labile C and nitrogen (N) pools of historically N-enriched plots on the Shortgrass Steppe Long Term Ecological Research site located in northeastern Colorado. For eight years, we applied sawdust, sugar, industrial lignin, sawdust + sugar, and lignin + sugar to plots that had received N and water additions in the early 1970s. Previous work showed that past water and N additions altered plant species composition and enhanced rates of nutrient cycling; these effects were still apparent 25 years later. We hypothesized that labile C amendments would stimulate microbial activity and suppress rates of N mineralization, whereas complex forms of carbon (sawdust and lignin) could enhance humification and lead to longer-term reductions in N availability. Results indicated that, of the five carbon treatments, sugar, sawdust, and sawdust + sugar suppressed N availability, with sawdust + sugar being the most effective treatment to reduce N availability. The year after treatments stopped, N availability remained less in the sawdust + sugar treatment plots than in the high-N control plots. Three years after treatments ended, reductions in N availability were smaller (40-60%). Our results suggest that highly labile forms of carbon generate strong short-term N sinks, but these effects dissipate within one year of application, and that more recalcitrant forms reduce N longer. Sawdust + sugar was the most effective treatment to decrease exotic species canopy cover and increase native species density over the long term. Labile carbon had neither short- nor long-term effects on exotic species. Even though the organic amendments did not contribute to recovery of the dominant native species Bouteloua gracilis, they were effective in increasing another native species, Carex eleocharis. These results indicate that organic amendments may be a useful tool for restoring some native species in the shortgrass steppe, though not all.
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Affiliation(s)
- I C Burke
- Haub School of Environment and Natural Resources, Department of Botany, University of Wyoming, Laramie, Wyoming 82072, USA.
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Does background nitrogen deposition affect the response of boreal vegetation to fertilization? Oecologia 2013; 173:615-24. [DOI: 10.1007/s00442-013-2638-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Accepted: 02/25/2013] [Indexed: 11/26/2022]
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Edmondson J, Terribile E, Carroll JA, Price EAC, Caporn SJM. The legacy of nitrogen pollution in heather moorlands: ecosystem response to simulated decline in nitrogen deposition over seven years. THE SCIENCE OF THE TOTAL ENVIRONMENT 2013; 444:138-144. [PMID: 23262328 DOI: 10.1016/j.scitotenv.2012.11.074] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Revised: 11/15/2012] [Accepted: 11/21/2012] [Indexed: 06/01/2023]
Abstract
Eutrophication and acidification of heather moorlands by chronic atmospheric nitrogen (N) pollution, is of major concern within these internationally important ecosystems. However, in the UK and Western Europe generally emissions of NO(y) and NH(x) peaked during the 20th century. Due to the history and scale of atmospheric N pollution, the legacy of these high levels of N deposition, through accumulation in soil, may hinder or prevent ecosystem recovery. Effects of N pollution on heather moorland were investigated throughout the ecosystem including; the dominant plant species, Calluna vulgaris, the bryophyte and lichen community and the soil system using a long-term experiment simulating wet N deposition. We observed an increase in C. vulgaris height, shoot extension and canopy density, litter mineral N, total N concentration, N:P and C:N ratios in response to N addition. Bryophyte species diversity, bryophyte and lichen frequency and the frequency of two individual bryophyte species (Lophozia ventricosa and Campylopus flexuosus) were significantly reduced by N addition. We developed an N recovery experiment, using a split-plot design, on the long-term N treatment plots to investigate ecosystem response to a simulated decline in N deposition. Two years after cessation of N treatment the only ecosystem component that responded to the recovery experiment was C. vulgaris shoot extension, however after seven years of recovery there were significant declines in litter total N concentration and mineral N and an increase in litter C:N ratio. Although bryophytes and lichens form a close relationship with atmospheric N deposition these organisms did not show a significant response to the N recovery experiment, two years after cessation of N treatment. These data indicate that low nutrient ecosystems, such as moorlands, have the capacity to respond to declines in N deposition however the accumulation of pollution may hinder recovery of sensitive organisms, such as bryophytes and lichens.
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Affiliation(s)
- J Edmondson
- School of Science and the Environment, Manchester Metropolitan University, Manchester, Oxford Road, M1 5GD, UK.
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Eugster W, Haeni M. Nutrients or Pollutants? Nitrogen Deposition to European Forests. DEVELOPMENTS IN ENVIRONMENTAL SCIENCE 2013. [DOI: 10.1016/b978-0-08-098349-3.00003-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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De Marco A, Screpanti A, Attorre F, Proietti C, Vitale M. Assessing ozone and nitrogen impact on net primary productivity with a Generalised non-Linear Model. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2013; 172:250-263. [PMID: 23078996 DOI: 10.1016/j.envpol.2012.08.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2012] [Revised: 08/17/2012] [Accepted: 08/28/2012] [Indexed: 06/01/2023]
Abstract
Some studies suggest that in Europe the majority of forest growth increment can be accounted for N deposition and very little by elevated CO(2). High ozone (O(3)) concentrations cause reductions in carbon fixation in native plants by offsetting the effects of elevated CO(2) or N deposition. The cause-effect relationships between primary productivity (NPP) of Quercus cerris, Q. ilex and Fagus sylvatica plant species and climate and pollutants (O(3) and N deposition) in Italy have been investigated by application of Generalised Linear/non-Linear regression model (GLZ model). The GLZ model highlighted: i) cumulative O(3) concentration-based indicator (AOT40F) did not significantly affect NPP; ii) a differential action of oxidised and reduced nitrogen depositions to NPP was linked to the geographical location; iii) the species-specific variation of NPP caused by combination of pollutants and climatic variables could be a potentially important drive-factor for the plant species' shift as response to the future climate change.
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Affiliation(s)
- Alessandra De Marco
- Italian National Agency for New Technologies, Energy and the Environment (ENEA), C.R. Casaccia, Via Anguillarese 301, 00123 S. Maria di Galeria, Rome, Italy.
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31
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Tipping E, Rowe E, Evans C, Mills R, Emmett B, Chaplow J, Hall J. N14C: A plant–soil nitrogen and carbon cycling model to simulate terrestrial ecosystem responses to atmospheric nitrogen deposition. Ecol Modell 2012. [DOI: 10.1016/j.ecolmodel.2012.08.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Song MH, Yu FH, Ouyang H, Cao GM, Xu XL, Cornelissen JHC. Different inter-annual responses to availability and form of nitrogen explain species coexistence in an alpine meadow community after release from grazing. GLOBAL CHANGE BIOLOGY 2012; 18:3100-3111. [PMID: 28741827 DOI: 10.1111/j.1365-2486.2012.02738.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Accepted: 04/26/2012] [Indexed: 05/18/2023]
Abstract
Plant species and functional groups in nitrogen (N) limited communities may coexist through strong eco-physiological niche differentiation, leading to idiosyncratic responses to multiple nutrition and disturbance regimes. Very little is known about how such responses depend on the availability of N in different chemical forms. Here we hypothesize that idiosyncratic year-to-year responses of plant functional groups to availability and form of nitrogen explain species coexistence in an alpine meadow community after release from grazing. We conducted a 6 year N addition experiment in an alpine meadow on the Tibetan Plateau released from grazing by livestock. The experimental design featured three N forms (ammonium, nitrate, and ammonium nitrate), crossed with three levels of N supply rates (0.375, 1.500 and 7.500 g N m-2 yr-1 ), with unfertilized treatments without and with light grazing as controls. All treatments showed increasing productivity and decreasing species richness after cessation of grazing and these responses were stronger at higher N rates. Although N forms did not affect aboveground biomass at community level, different functional groups did show different responses to N chemical form and supply rate and these responses varied from year to year. In support of our hypothesis, these idiosyncratic responses seemed to enable a substantial diversity and biomass of sedges, forbs, and legumes to still coexist with the increasingly productive grasses in the absence of grazing, at least at low and intermediate N availability regimes. This study provides direct field-based evidence in support of the hypothesis that idiosyncratic and annually varying responses to both N quantity and quality may be a key driver of community structure and species coexistence. This finding has important implications for the diversity and functioning of other ecosystems with spatial and temporal variation in available N quantity and quality as related to changing atmospheric N deposition, land-use, and climate-induced soil warming.
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Affiliation(s)
- Ming-Hua Song
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China
| | - Fei-Hai Yu
- College of Nature Conservation, Beijing Forestry University, Beijing, 100083, China
| | - Hua Ouyang
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China
| | - Guang-Min Cao
- Northwest Institute of Plateau Biology, Chinese Academy of Sciences, 59 Xiguan Dajie, Xining, 810008, China
| | - Xing-Liang Xu
- Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China
| | - Johannes H C Cornelissen
- Systems Ecology, Dept. of Ecological Science, Faculty of Earth and Life Sciences, VU University, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands
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Pihl Karlsson G, Akselsson C, Hellsten S, Karlsson PE. Reduced European emissions of S and N--effects on air concentrations, deposition and soil water chemistry in Swedish forests. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2011; 159:3571-82. [PMID: 21862190 DOI: 10.1016/j.envpol.2011.08.007] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Revised: 07/15/2011] [Accepted: 08/01/2011] [Indexed: 05/06/2023]
Abstract
Changes in sulphur and nitrogen pollution in Swedish forests have been assessed in relation to European emission reductions, based on measurements in the Swedish Throughfall Monitoring Network. Measurements were analysed over 20 years with a focus on the 12-year period 1996 to 2008. Air concentrations of SO(2) and NO(2), have decreased. The SO(4)-deposition has decreased in parallel with the European emission reductions. Soil water SO(4)-concentrations have decreased at most sites but the pH, ANC and inorganic Al-concentrations indicated acidification recovery only at some of the sites. No changes in the bulk deposition of inorganic nitrogen could be demonstrated. Elevated NO(3)-concentrations in the soil water occurred at irregular occasions at some southern sites. Despite considerable air pollution emission reductions in Europe, acidification recovery in Swedish forests soils is slow. Nitrogen deposition to Swedish forests continues at elevated levels that may lead to leaching of nitrate to surface waters.
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Affiliation(s)
- Gunilla Pihl Karlsson
- IVL Swedish Environmental Research Institute, Box 5302, SE-400 14 Gothenburg, Sweden.
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Harmens H, Norris DA, Cooper DM, Mills G, Steinnes E, Kubin E, Thöni L, Aboal JR, Alber R, Carballeira A, Coşkun M, De Temmerman L, Frolova M, González-Miqueo L, Jeran Z, Leblond S, Liiv S, Maňkovská B, Pesch R, Poikolainen J, Rühling A, Santamaria JM, Simonèiè P, Schröder W, Suchara I, Yurukova L, Zechmeister HG. Nitrogen concentrations in mosses indicate the spatial distribution of atmospheric nitrogen deposition in Europe. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2011; 159:2852-2860. [PMID: 21620544 DOI: 10.1016/j.envpol.2011.04.041] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Revised: 04/21/2011] [Accepted: 04/29/2011] [Indexed: 05/30/2023]
Abstract
In 2005/6, nearly 3000 moss samples from (semi-)natural location across 16 European countries were collected for nitrogen analysis. The lowest total nitrogen concentrations in mosses (<0.8%) were observed in northern Finland and northern UK. The highest concentrations (≥ 1.6%) were found in parts of Belgium, France, Germany, Slovakia, Slovenia and Bulgaria. The asymptotic relationship between the nitrogen concentrations in mosses and EMEP modelled nitrogen deposition (averaged per 50 km × 50 km grid) across Europe showed less scatter when there were at least five moss sampling sites per grid. Factors potentially contributing to the scatter are discussed. In Switzerland, a strong (r(2) = 0.91) linear relationship was found between the total nitrogen concentration in mosses and measured site-specific bulk nitrogen deposition rates. The total nitrogen concentrations in mosses complement deposition measurements, helping to identify areas in Europe at risk from high nitrogen deposition at a high spatial resolution.
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Affiliation(s)
- H Harmens
- Centre for Ecology and Hydrology, Environment Centre Wales, Deiniol Road, Bangor, Gwynedd LL57 2UW, UK.
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35
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Cornell SE. Atmospheric nitrogen deposition: revisiting the question of the importance of the organic component. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2011; 159:2214-22. [PMID: 21131113 DOI: 10.1016/j.envpol.2010.11.014] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Revised: 11/09/2010] [Accepted: 11/11/2010] [Indexed: 05/11/2023]
Abstract
The organic component of atmospheric reactive nitrogen plays a role in biogeochemical cycles, climate and ecosystems. Although its deposition has long been known to be quantitatively significant, it is not routinely assessed in deposition studies and monitoring programmes. Excluding this fraction, typically 25-35%, introduces significant uncertainty in the determination of nitrogen deposition, with implications for the critical loads approach. The last decade of rainwater studies substantially expands the worldwide dataset, giving enough global coverage for specific hypotheses to be considered about the distribution, composition, sources and effects of organic-nitrogen deposition. This data collation and meta-analysis highlights knowledge gaps, suggesting where data-gathering efforts and process studies should be focused. New analytical techniques allow long-standing conjectures about the nature and sources of organic N to be investigated, with tantalising indications of the interplay between natural and anthropogenic sources, and between the nitrogen and carbon cycles.
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Affiliation(s)
- Sarah E Cornell
- QUEST, Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK.
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36
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Ochoa-Hueso R, Allen EB, Branquinho C, Cruz C, Dias T, Fenn ME, Manrique E, Pérez-Corona ME, Sheppard LJ, Stock WD. Nitrogen deposition effects on Mediterranean-type ecosystems: an ecological assessment. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2011; 159:2265-79. [PMID: 21277663 DOI: 10.1016/j.envpol.2010.12.019] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Revised: 12/14/2010] [Accepted: 12/21/2010] [Indexed: 05/22/2023]
Abstract
We review the ecological consequences of N deposition on the five Mediterranean regions of the world. Seasonality of precipitation and fires regulate the N cycle in these water-limited ecosystems, where dry N deposition dominates. Nitrogen accumulation in soils and on plant surfaces results in peaks of availability with the first winter rains. Decoupling between N flushes and plant demand promotes losses via leaching and gas emissions. Differences in P availability may control the response to N inputs and susceptibility to exotic plant invasion. Invasive grasses accumulate as fuel during the dry season, altering fire regimes. California and the Mediterranean Basin are the most threatened by N deposition; however, there is limited evidence for N deposition impacts outside of California. Consequently, more research is needed to determine critical loads for each region and vegetation type based on the most sensitive elements, such as changes in lichen species composition and N cycling.
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Affiliation(s)
- Raúl Ochoa-Hueso
- Department of Plant Physiology and Ecology, Centro de Ciencias Medioambientales, Consejo Superior de Investigaciones Científicas, 28006 Madrid, Spain.
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37
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Curtis CJ, Evans CD, Goodale CL, Heaton TH. What Have Stable Isotope Studies Revealed About the Nature and Mechanisms of N Saturation and Nitrate Leaching from Semi-Natural Catchments? Ecosystems 2011. [DOI: 10.1007/s10021-011-9461-7] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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38
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Lovett GM, Goodale CL. A New Conceptual Model of Nitrogen Saturation Based on Experimental Nitrogen Addition to an Oak Forest. Ecosystems 2011. [DOI: 10.1007/s10021-011-9432-z] [Citation(s) in RCA: 186] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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39
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The Cycling of Pollutants in Nonurban Forested Environments. FOREST HYDROLOGY AND BIOGEOCHEMISTRY 2011. [DOI: 10.1007/978-94-007-1363-5_34] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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40
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Akselsson C, Belyazid S, Hellsten S, Klarqvist M, Pihl-Karlsson G, Karlsson PE, Lundin L. Assessing the risk of N leaching from forest soils across a steep N deposition gradient in Sweden. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2010; 158:3588-3595. [PMID: 20864233 DOI: 10.1016/j.envpol.2010.08.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2010] [Revised: 07/29/2010] [Accepted: 08/18/2010] [Indexed: 05/29/2023]
Abstract
Nitrogen leaching from boreal and temporal forests, where normally most of the nitrogen is retained, has the potential to increase acidification of soil and water and eutrophication of the Baltic Sea. In parts of Sweden, where the nitrogen deposition has been intermediate to high during recent decades, there are indications that the soils are close to nitrogen saturation. In this study, four different approaches were used to assess the risk of nitrogen leaching from forest soils in different parts of Sweden. Nitrate concentrations in soil water and C:N ratios in the humus layer where interpreted, together with model results from mass balance calculations and detailed dynamic modelling. All four approaches pointed at a risk of nitrogen leaching from forest soils in southern Sweden. However, there was a substantial variation on a local scale. Basing the assessment on four different approaches makes the assessment robust.
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Affiliation(s)
- Cecilia Akselsson
- Department of Earth and Ecosystem Sciences, Lund University, Sölvegatan 12, SE-223 62 Lund, Sweden.
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41
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Edmondson JL, Carroll JA, Price EAC, Caporn SJM. Bio-indicators of nitrogen pollution in heather moorland. THE SCIENCE OF THE TOTAL ENVIRONMENT 2010; 408:6202-6209. [PMID: 20888029 DOI: 10.1016/j.scitotenv.2010.08.060] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2010] [Revised: 08/26/2010] [Accepted: 08/30/2010] [Indexed: 05/29/2023]
Abstract
Heather moorlands are internationally important ecosystems that are highly sensitive to eutrophication and acidification by reactive atmospheric nitrogen (N) deposition. We used a long-term experiment simulating wet-deposition of N on heather moorland to identify potential bio-indicators of N deposition. These indicators were subsequently employed in a survey covering a N deposition gradient ranging from approximately 7 to 31kg N ha(-1) yr(-1), at selected sites throughout the UK. In this regional survey litter phenol oxidase activity and bryophyte species richness were negatively associated with N deposition. Calluna vulgaris N:P ratios and litter extractable N were positively correlated with N deposition. The use of the suite of four bio-indicators has the potential to provide rapid assessment of the extent of N saturation of heather moorland sites and moorland ecosystem functioning, and has significant advantages over reliance on single measures such as soil N status or an individual bio-indicator species.
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Affiliation(s)
- J L Edmondson
- Department of Environmental and Geographical Sciences, Manchester Metropolitan University, Chester Street, Manchester, M1 5GD, UK.
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42
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Nitrogen deposition, competition and the decline of a regionally threatened legume, Desmodium cuspidatum. Oecologia 2010; 165:261-9. [DOI: 10.1007/s00442-010-1818-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2009] [Accepted: 10/11/2010] [Indexed: 10/18/2022]
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Stevens CJ, Duprè C, Dorland E, Gaudnik C, Gowing DJG, Bleeker A, Diekmann M, Alard D, Bobbink R, Fowler D, Corcket E, Mountford JO, Vandvik V, Aarrestad PA, Muller S, Dise NB. Nitrogen deposition threatens species richness of grasslands across Europe. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2010; 158:2940-5. [PMID: 20598409 DOI: 10.1016/j.envpol.2010.06.006] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Revised: 06/01/2010] [Accepted: 06/04/2010] [Indexed: 05/22/2023]
Abstract
Evidence from an international survey in the Atlantic biogeographic region of Europe indicates that chronic nitrogen deposition is reducing plant species richness in acid grasslands. Across the deposition gradient in this region (2-44 kg N ha(-1) yr(-1)) species richness showed a curvilinear response, with greatest reductions in species richness when deposition increased from low levels. This has important implications for conservation policies, suggesting that to protect the most sensitive grasslands resources should be focussed where deposition is currently low. Soil pH is also an important driver of species richness indicating that the acidifying effect of nitrogen deposition may be contributing to species richness reductions. The results of this survey suggest that the impacts of nitrogen deposition can be observed over a large geographical range.
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Affiliation(s)
- Carly J Stevens
- Department of Life Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK.
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Watmough SA. An assessment of the relationship between potential chemical indices of nitrogen saturation and nitrogen deposition in hardwood forests in southern Ontario. ENVIRONMENTAL MONITORING AND ASSESSMENT 2010; 164:9-20. [PMID: 19353289 DOI: 10.1007/s10661-009-0870-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2008] [Accepted: 03/10/2009] [Indexed: 05/27/2023]
Abstract
Southern Ontario receives the highest levels of atmospheric nitrogen (N) deposition in Canada and there are concerns that forests in the region may be approaching a state of 'N saturation'. In order to evaluate whether potential chemical indices provide evidence of N saturation, 23 hardwood plots were sampled along a modeled N-deposition gradient ranging from 9.3 to 12.8 kg/ha/year. All plots were dominated by sugar maple (Acer saccharum Marsh.) and foliar N and foliar delta(15)N were positively correlated with modeled N deposition. However, forest floor N content and the C:N ratio were unrelated to N deposition, but were instead related to soil pH and annual temperature; lower C:N ratios and higher N content in the forest floor were found at the most acidic sites in the cooler, northern part of the study region despite lower N deposition. Likewise, delta(15)N values in surface mineral soil and the (15)N enrichment factor of foliage (delta(15)N foliage - delta(15)N soil) are correlated to soil pH and temperature and not N deposition. Further, potential N mineralization, ammonification, and nitrification in Ontario maple stands were highest in the northern part of the region with the lowest modeled N deposition. Nitrogen cycling in soil appears to be primarily influenced by the N status of the forest floor and other soil properties rather than N deposition, indicating that chemical indices in soil in these hardwood plots may not provide an early indicator of N saturation.
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Affiliation(s)
- Shaun A Watmough
- Environmental and Resource Studies, Trent University, 1600 West Bank Drive, Peterborough, ON, K9J 7B8, Canada.
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Vanguelova EI, Benham S, Pitman R, Moffat AJ, Broadmeadow M, Nisbet T, Durrant D, Barsoum N, Wilkinson M, Bochereau F, Hutchings T, Broadmeadow S, Crow P, Taylor P, Durrant Houston T. Chemical fluxes in time through forest ecosystems in the UK - soil response to pollution recovery. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2010; 158:1857-69. [PMID: 19962801 DOI: 10.1016/j.envpol.2009.10.044] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Revised: 10/13/2009] [Accepted: 10/27/2009] [Indexed: 05/22/2023]
Abstract
Long term trend analysis of bulk precipitation, throughfall and soil solution elemental fluxes from 12 years monitoring at 10 ICP Level II forest sites in the UK reveal coherent national chemical trends indicating recovery from sulphur deposition and acidification. Soil solution pH increased and sulphate and aluminium decreased at most sites. Trends in nitrogen were variable and dependant on its form. Dissolved organic nitrogen increased in bulk precipitation, throughfall and soil solution at most sites. Nitrate in soil solution declined at sites receiving high nitrogen deposition. Increase in soil dissolved organic carbon was detected - a response to pollution recovery, changes in soil temperature and/or increased microbial activity. An increase of sodium and chloride was evident - a possible result of more frequent storm events at exposed sites. The intensive and integrated nature of monitoring enables the relationships between climate/pollutant exposure and chemical/biological response in forestry to be explored.
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Affiliation(s)
- E I Vanguelova
- Centre of Forestry and Climate Change, Forest Research, Alice Holt Lodge, Farnham, Surrey GU10 4LH, UK.
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De Vries W, Wamelink GWW, Van Dobben H, Kros J, Reinds GJ, Mol-Dijkstra JP, Smart SM, Evans CD, Rowe EC, Belyazid S, Sverdrup HU, Van Hinsberg A, Posch M, Hettelingh JP, Spranger T, Bobbink R. Use of dynamic soil-vegetation models to assess impacts of nitrogen deposition on plant species composition: an overview. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2010; 20:60-79. [PMID: 20349830 DOI: 10.1890/08-1019.1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Field observations and experimental data of effects of nitrogen (N) deposition on plant species diversity have been used to derive empirical critical N loads for various ecosystems. The great advantage of such an approach is the inclusion of field evidence, but there are also restrictions, such as the absence of explicit criteria regarding significant effects on the vegetation, and the impossibility to predict future impacts when N deposition changes. Model approaches can account for this. In this paper, we review the possibilities of static and dynamic multispecies models in combination with dynamic soil-vegetation models to (1) predict plant species composition as a function of atmospheric N deposition and (2) calculate critical N loads in relation to a prescribed protection level of the species composition. The similarities between the models are presented, but also several important differences, including the use of different indicators for N and acidity and the prediction of individual plant species vs. plant communities. A summary of the strengths and weaknesses of the various models, including their validation status, is given. Furthermore, examples are given of critical load calculations with the model chains and their comparison with empirical critical N loads. We show that linked biogeochemistry-biodiversity models for N have potential for applications to support European policy to reduce N input, but the definition of damage thresholds for terrestrial biodiversity represents a major challenge. There is also a clear need for further testing and validation of the models against long-term monitoring or long-term experimental data sets and against large-scale survey data. This requires a focused data collection in Europe, combing vegetation descriptions with variables affecting the species diversity, such as soil acidity, nutrient status and water availability. Finally, there is a need for adaptation and upscaling of the models beyond the regions for which dose-response relationships have been parameterized, to make them generally applicable.
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Affiliation(s)
- W De Vries
- Alterra, Wageningen University and Research Centre, P.O. Box 47, 6700 AA Wageningen, The Netherlands.
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47
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Bobbink R, Hicks K, Galloway J, Spranger T, Alkemade R, Ashmore M, Bustamante M, Cinderby S, Davidson E, Dentener F, Emmett B, Erisman JW, Fenn M, Gilliam F, Nordin A, Pardo L, De Vries W. Global assessment of nitrogen deposition effects on terrestrial plant diversity: a synthesis. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2010; 20:30-59. [PMID: 20349829 DOI: 10.1890/08-1140.1] [Citation(s) in RCA: 911] [Impact Index Per Article: 65.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Atmospheric nitrogen (N) deposition is a recognized threat to plant diversity in temperate and northern parts of Europe and North America. This paper assesses evidence from field experiments for N deposition effects and thresholds for terrestrial plant diversity protection across a latitudinal range of main categories of ecosystems, from arctic and boreal systems to tropical forests. Current thinking on the mechanisms of N deposition effects on plant diversity, the global distribution of G200 ecoregions, and current and future (2030) estimates of atmospheric N-deposition rates are then used to identify the risks to plant diversity in all major ecosystem types now and in the future. This synthesis paper clearly shows that N accumulation is the main driver of changes to species composition across the whole range of different ecosystem types by driving the competitive interactions that lead to composition change and/or making conditions unfavorable for some species. Other effects such as direct toxicity of nitrogen gases and aerosols, long-term negative effects of increased ammonium and ammonia availability, soil-mediated effects of acidification, and secondary stress and disturbance are more ecosystem- and site-specific and often play a supporting role. N deposition effects in mediterranean ecosystems have now been identified, leading to a first estimate of an effect threshold. Importantly, ecosystems thought of as not N limited, such as tropical and subtropical systems, may be more vulnerable in the regeneration phase, in situations where heterogeneity in N availability is reduced by atmospheric N deposition, on sandy soils, or in montane areas. Critical loads are effect thresholds for N deposition, and the critical load concept has helped European governments make progress toward reducing N loads on sensitive ecosystems. More needs to be done in Europe and North America, especially for the more sensitive ecosystem types, including several ecosystems of high conservation importance. The results of this assessment show that the vulnerable regions outside Europe and North America which have not received enough attention are ecoregions in eastern and southern Asia (China, India), an important part of the mediterranean ecoregion (California, southern Europe), and in the coming decades several subtropical and tropical parts of Latin America and Africa. Reductions in plant diversity by increased atmospheric N deposition may be more widespread than first thought, and more targeted studies are required in low background areas, especially in the G200 ecoregions.
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Affiliation(s)
- R Bobbink
- B-WARE Research Centre, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands.
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48
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Sebestyen SD, Boyer EW, Shanley JB. Responses of stream nitrate and DOC loadings to hydrological forcing and climate change in an upland forest of the northeastern United States. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008jg000778] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Stephen D. Sebestyen
- Northern Research Station, Forest Service; U.S. Department of Agriculture; Grand Rapids Minnesota USA
| | - Elizabeth W. Boyer
- School of Forest Resources; Pennsylvania State University; University Park Pennsylvania USA
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Plassmann K, Edwards-Jones G, Jones MLM. The effects of low levels of nitrogen deposition and grazing on dune grassland. THE SCIENCE OF THE TOTAL ENVIRONMENT 2009; 407:1391-1404. [PMID: 19013634 DOI: 10.1016/j.scitotenv.2008.10.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Revised: 10/01/2008] [Accepted: 10/02/2008] [Indexed: 05/27/2023]
Abstract
Coastal sand dunes are considered to be threatened by the atmospheric deposition of nitrogen (N); however, experimental investigations of the effects of N deposition on dune vegetation and soil using realistic N loads and sites with low background deposition are scarce. This study reports the effects of low levels of fertilisation with N and phosphorus (P) on the vegetation, above-ground biomass, plant tissue chemistry and soil chemistry of fixed dune grasslands. In addition, the impacts of grazing management and its potential to mitigate adverse effects of N fertilisation were examined. Four N treatments (unwatered control, watered control, +7.5 kg ha(-1) year(-1), +15 kg ha(-1) year(-1)) were combined with three grazing treatments (ungrazed, rabbit grazed, rabbit and pony grazed). In a separate experiment, effects of fertilisation with both N (15 kg ha(-1) year(-1)) and P (20 kg ha(-1) year(-1)) were investigated. Vegetation composition was assessed using the point quadrat method. Above-ground biomass, sward heights, tissue N and P concentrations and soil chemical parameters were also measured. After two years, N addition resulted in greater amounts of total above-ground biomass, bryophyte biomass and changes in bryophyte tissue chemistry. No effects on vegetation composition, sward height or soil parameters occurred. Fertilisation with both nutrients had a greater impact on above-ground biomass, sward heights and sward structure than N addition alone. The grazing treatments differed in their species composition. The changes observed after only two years of fertilisation may lead to community changes over longer time scales. Effects were observed even under heavy grazing with phosphorus limitation. Therefore, the upper critical load for N for dune grasslands may be below the previously proposed 20 kg ha(-1) year(-1) and grazing may not mitigate all negative effects of N deposition.
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Affiliation(s)
- Katharina Plassmann
- School of the Environment and Natural Resources, Bangor University, Gwynedd LL57 2UW, United Kingdom.
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50
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Evans CD, Norris D, Ostle N, Grant H, Rowe EC, Curtis CJ, Reynolds B. Rapid immobilisation and leaching of wet-deposited nitrate in upland organic soils. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2008; 156:636-643. [PMID: 18653264 DOI: 10.1016/j.envpol.2008.06.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2008] [Revised: 06/06/2008] [Accepted: 06/11/2008] [Indexed: 05/26/2023]
Abstract
Nitrate (NO3-) is often observed in surface waters draining terrestrial ecosystems that remain strongly nitrogen (N) limited. It has been suggested that this occurs due to hydrological bypassing of soil or vegetation N retention, particularly during high flows. To test this hypothesis, artificial rain events were applied to 12 replicate soil blocks on a Welsh podzolic acid grassland hillslope, labelled with 15N-enriched NO3- and a conservative bromide (Br-) tracer. On average, 31% of tracer-labelled water was recovered within 4 h, mostly as mineral horizon lateral flow, indicating rapid vertical water transfer through the organic horizon via preferential flowpaths. However, on average only 6% of 15N-labelled NO3- was recovered. Around 80% of added NO3- was thus rapidly immobilised, probably by microbial communities present on the surfaces of preferential flowpaths. Transitory exceedance of microbial N-uptake capacity during periods of high water and N flux may therefore provide a mechanism for NO3- leaching.
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Affiliation(s)
- Chris D Evans
- Centre for Ecology and Hydrology, Environment Centre Wales, Deiniol Road, Bangor, Wales LL572UW, UK.
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