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Mathias JM, Smith KR, Lantz KE, Allen KT, Wright MJ, Sabet A, Anderson-Teixeira KJ, Thomas RB. Differences in leaf gas exchange strategies explain Quercus rubra and Liriodendron tulipifera intrinsic water use efficiency responses to air pollution and climate change. GLOBAL CHANGE BIOLOGY 2023; 29:3449-3462. [PMID: 36897273 DOI: 10.1111/gcb.16673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Accepted: 03/01/2023] [Indexed: 05/16/2023]
Abstract
Trees continuously regulate leaf physiology to acquire CO2 while simultaneously avoiding excessive water loss. The balance between these two processes, or water use efficiency (WUE), is fundamentally important to understanding changes in carbon uptake and transpiration from the leaf to the globe under environmental change. While increasing atmospheric CO2 (iCO2 ) is known to increase tree intrinsic water use efficiency (iWUE), less clear are the additional impacts of climate and acidic air pollution and how they vary by tree species. Here, we couple annually resolved long-term records of tree-ring carbon isotope signatures with leaf physiological measurements of Quercus rubra (Quru) and Liriodendron tulipifera (Litu) at four study locations spanning nearly 100 km in the eastern United States to reconstruct historical iWUE, net photosynthesis (Anet ), and stomatal conductance to water (gs ) since 1940. We first show 16%-25% increases in tree iWUE since the mid-20th century, primarily driven by iCO2 , but also document the individual and interactive effects of nitrogen (NOx ) and sulfur (SO2 ) air pollution overwhelming climate. We find evidence for Quru leaf gas exchange being less tightly regulated than Litu through an analysis of isotope-derived leaf internal CO2 (Ci ), particularly in wetter, recent years. Modeled estimates of seasonally integrated Anet and gs revealed a 43%-50% stimulation of Anet was responsible for increasing iWUE in both tree species throughout 79%-86% of the chronologies with reductions in gs attributable to the remaining 14%-21%, building upon a growing body of literature documenting stimulated Anet overwhelming reductions in gs as a primary mechanism of increasing iWUE of trees. Finally, our results underscore the importance of considering air pollution, which remains a major environmental issue in many areas of the world, alongside climate in the interpretation of leaf physiology derived from tree rings.
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Affiliation(s)
- Justin M Mathias
- Department of Biology, West Virginia University, Morgantown, West Virginia, USA
| | - Kenneth R Smith
- Department of Biology, West Virginia University, Morgantown, West Virginia, USA
| | - Kristin E Lantz
- Department of Biology, West Virginia University, Morgantown, West Virginia, USA
| | - Keanan T Allen
- Department of Biology, West Virginia University, Morgantown, West Virginia, USA
| | - Marvin J Wright
- Department of Biology, West Virginia University, Morgantown, West Virginia, USA
| | - Afsoon Sabet
- Department of Biology, West Virginia University, Morgantown, West Virginia, USA
| | - Kristina J Anderson-Teixeira
- Conservation Ecology Center, Smithsonian's National Zoo & Conservation Biology Institute, Front Royal, Virginia, USA
- Forest Global Earth Observatory, Smithsonian Tropical Research Institute, Panama City, Republic of Panama
| | - Richard B Thomas
- Department of Biology, West Virginia University, Morgantown, West Virginia, USA
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Savard MM, Marion J, Bégin C, Laganière J. On the significance of long-term trends in tree-ring N isotopes - The interplay of soil conditions and regional NOx emissions. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 857:159580. [PMID: 36280071 DOI: 10.1016/j.scitotenv.2022.159580] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 10/14/2022] [Accepted: 10/16/2022] [Indexed: 06/16/2023]
Abstract
As anthropogenic nitrogen (N) emissions have been rising for decades, it is critical to develop natural archives that help understand how natural processes were modified in the past. Tree-ring δ15N values may represent such an indicator but its validity as faithful record of N cycling changes is still debated. Here we produce long-tree-ring δ15N series for five white spruce stands from two boreal regions submitted to moderate industrial N inputs. The obtained δ15N series show sharp differences among stands, even from the same region, despite the fact that they show similar increases in intrinsic water use efficiency (iWUE), a proxy for foliar strategies derived from δ13C values. The statistical modeling of these series and the basal area increment (BAI) of the trees allow to suggest that the mechanisms controlling the isotopic fractionation of N assimilated by tree rings are decoupled from the foliar strategies under the anthropogenic N emissions. The iWUE trends mainly reflect rise of pCO2 and changes in air quality. The long-term δ15N trends echo different biogeochemical processes responding to N deposition due to distinct original soil pH at the various sites. We contend that tree-ring δ15N series can record changes in the forest N cycle, but their rigorous interpretation requires laborious work, particularly an understanding of the biogeochemistry in the soil immediately around the investigated trees. "Seek simplicity and distrust it", Alfred North Whitehead.
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Affiliation(s)
- Martine M Savard
- Commission géologique du Canada (Ressources naturelles Canada), 490 de la Couronne, Québec, QC G1K 9A9, Canada.
| | - Joëlle Marion
- Commission géologique du Canada (Ressources naturelles Canada), 490 de la Couronne, Québec, QC G1K 9A9, Canada
| | - Christian Bégin
- Commission géologique du Canada (Ressources naturelles Canada), 490 de la Couronne, Québec, QC G1K 9A9, Canada
| | - Jérôme Laganière
- Centre de Foresterie des Laurentides, Service canadien des Forêts (Ressources naturelles Canada), 1055 rue du P.E.P.S., Stn. Sainte-Foy, P.O. Box 10380, Québec, QC G1V 4C7, Canada
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Mathias JM, Hudiburg TW. isocalcR: An R package to streamline and standardize stable isotope calculations in ecological research. GLOBAL CHANGE BIOLOGY 2022; 28:7428-7436. [PMID: 36002391 DOI: 10.1111/gcb.16407] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Accepted: 08/19/2022] [Indexed: 06/15/2023]
Abstract
The use of stable isotopes to characterize ecosystem dynamics and infer leaf gas exchange processes has become increasingly prevalent over the last few decades within the ecological community. While advancements in theory and our understanding of the physiological processes controlling isotopic signatures in plants has been well-documented, no standardized tool currently exists to facilitate the computation of common isotope-derived plant physiological indices. Here, we present isocalcR, an R package intended to facilitate the use of stable isotope data from plant tissues by providing an integrated collection of functions and recommended reference data. The isocalcR R package contains a suite of functions that compute leaf carbon isotope discrimination (∆13 C), leaf intercellular [CO2 ], the ratio of leaf intercellular to atmospheric [CO2 ], the difference between atmospheric and leaf intercellular [CO2 ], and intrinsic water use efficiency from carbon isotope signatures in leaf or wood tissue with minimal inputs from the user. isocalcR also implements and provides recommended input atmospheric [CO2 ] (ppm) and atmospheric δ13 CO2 (‰) data for the period 0-2021 C.E. A major goal of isocalcR is to provide a standardized, open-source tool to streamline the calculation of reproducible physiological indices from stable isotope signatures in plant tissues, incorporating the most up-to-date theory, while simultaneously eliminating potential errors associated with complex calculations. isocalcR can be used for any location globally as long as the user provides information regarding temperature and elevation to the main workhorse functions.
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Affiliation(s)
- Justin M Mathias
- Department of Forest, Rangeland, and Fire Sciences, University of Idaho, Moscow, Idaho, USA
| | - Tara W Hudiburg
- Department of Forest, Rangeland, and Fire Sciences, University of Idaho, Moscow, Idaho, USA
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Treml V, Tumajer J, Jandová K, Oulehle F, Rydval M, Čada V, Treydte K, Mašek J, Vondrovicová L, Lhotáková Z, Svoboda M. Increasing water-use efficiency mediates effects of atmospheric carbon, sulfur, and nitrogen on growth variability of central European conifers. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 838:156483. [PMID: 35675888 DOI: 10.1016/j.scitotenv.2022.156483] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 05/31/2022] [Accepted: 05/31/2022] [Indexed: 06/15/2023]
Abstract
Climate controls forest biomass production through direct effects on cambial activity and indirectly through interactions with CO2, air pollution, and nutrient availability. The atmospheric concentration of CO2, sulfur and nitrogen deposition can also exert a significant indirect control on wood formation since these factors influence the stomatal regulation of transpiration and carbon uptake, that is, intrinsic water use efficiency (iWUE). Here we provide 120-year long tree-ring time series of iWUE, stem growth, climatic and combined sulfur and nitrogen (SN) deposition trends for two common tree species, Pinus sylvestris (PISY) and Picea abies (PCAB), at their lower and upper distribution margins in Central Europe. The main goals were to explain iWUE trends using theoretical scenarios including climatic and SN deposition data, and to assess the contribution of climate and iWUE to the observed growth trends. Our results showed that after a notable increase in iWUE between the 1950s and 1980s, this positive trend subsequently slowed down. The substantial rise of iWUE since the 1950s resulted from a combination of an accelerated increase in atmospheric CO2 concentrations (Ca) and a stable level of leaf intercellular CO2 (Ci). The offset of observed iWUE values above the trajectory of a constant Ci/Ca scenario was explained by trends in SN deposition (all sites) together with the variation of drought conditions (low-elevation sites only). Increasing iWUE over the 20th and 21st centuries improved tree growth at low-elevation drought-sensitive sites. In contrast, at high-elevation PCAB sites, growth was mainly stimulated by recent warming. We propose that SN pollution should be considered in order to explain the steep increase in iWUE of conifers in the 20th century throughout Central Europe and other regions with a significant SN deposition history.
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Affiliation(s)
- Václav Treml
- Faculty of Science, Charles University, Prague, Czechia.
| | - Jan Tumajer
- Faculty of Science, Charles University, Prague, Czechia
| | | | | | - Miloš Rydval
- Faculty of Forestry and Wood Science, Czech University of Life Science, Prague, Czechia
| | - Vojtěch Čada
- Faculty of Forestry and Wood Science, Czech University of Life Science, Prague, Czechia
| | - Kerstin Treydte
- Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland
| | - Jiří Mašek
- Faculty of Science, Charles University, Prague, Czechia
| | | | | | - Miroslav Svoboda
- Faculty of Forestry and Wood Science, Czech University of Life Science, Prague, Czechia
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Manninen S, Zverev V, Kozlov MV. Foliar stable isotope ratios of carbon and nitrogen in boreal forest plants exposed to long-term pollution from the nickel-copper smelter at Monchegorsk, Russia. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:48880-48892. [PMID: 35199271 PMCID: PMC9252950 DOI: 10.1007/s11356-022-19261-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Accepted: 02/13/2022] [Indexed: 06/14/2023]
Abstract
Long-term exposure to primary air pollutants, such as sulphur dioxide (SO2) and nitrogen oxides (NOx), alters the structure and functions of forest ecosystems. Many biochemical and biogeochemical processes discriminate against the heavier isotopes in a mixture; thus, the values of δ13C and δ15N (i.e. the ratio of stable isotopes 13C to 12C and that of 15 N to 14 N, respectively) may give insights into changes in ecosystem processes and identify the immediate drivers of these changes. We studied sources of variation in the δ13C and δ15N values in the foliage of eight boreal forest C3 plants at 10 sites located at the distance of 1-40 km from the Monchegorsk nickel-copper smelter in Russia. From 1939‒2019, this smelter emitted over 14,000,000 metric tons (t) of SO2, 250,000 t of metals, primarily nickel and copper, and 140,000 t of NOx. The δ13C value in evergreen plants and the δ15N value in all plants increased near the smelter independently of the plant mycorrhizal type. We attribute the pollution-related increase in the foliar δ13C values of evergreen species mainly to direct effects of SO2 on stomatal conductance, in combination with pollution-related water stress, which jointly override the potential opposite effect of increasing ambient CO2 concentration on δ13C values. Stomatal uptake of NOx and root uptake of 15N-enriched organic N compounds and NH4+ may explain the increased foliar δ15N values and elevated foliar N concentrations, especially in the evergreen trees (Pinus sylvestris), close to Monchegorsk, where the soil inorganic N supply is reduced due to the impact of long-term SO2 and heavy metal emissions on plant biomass. We conclude that, despite the uncertainties in interpreting δ13C and δ15N responses to pollution, the Monchegorsk smelter has imposed and still imposes a great impact on C and N cycling in the surrounding N-limited subarctic forest ecosystems.
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Affiliation(s)
- Sirkku Manninen
- Faculty of Biological and Environmental Sciences, University of Helsinki, Viikinkaari 1, P.O. Box 65 , 00014, Helsinki, Finland
| | - Vitali Zverev
- Department of Biology, University of Turku, 20014, Turku, Finland
| | - Mikhail V Kozlov
- Department of Biology, University of Turku, 20014, Turku, Finland.
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Savard MM, Martineau C, Laganière J, Bégin C, Marion J, Smirnoff A, Stefani F, Bergeron J, Rheault K, Paré D, Séguin A. Nitrogen isotopes in the soil-to-tree continuum - Tree rings express the soil biogeochemistry of boreal forests exposed to moderate airborne emissions. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 780:146581. [PMID: 33774298 DOI: 10.1016/j.scitotenv.2021.146581] [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: 01/11/2021] [Revised: 03/15/2021] [Accepted: 03/15/2021] [Indexed: 06/12/2023]
Abstract
Anthropogenic N emissions represent a potential threat for forest ecosystems, and environmental indicators that provide insight into the changing forest N cycle are needed. Tree ring N isotopic ratios (δ15N) appear as a contentious choice for this role as the exact mechanisms behind tree-ring δ15N changes seldom benefit from a scrutiny of the soil-to-tree N continuum. This study integrates the results from the analysis of soil chemistry, soil microbiome genomics, and δ15N values of soil N compounds, roots, ectomycorrhizal (EcM) fungi and recent tree rings of thirteen white spruce trees sampled in five stands, from two regions exposed to moderate anthropogenic N emissions (3.9 to 8.1 kg/ha/y) with distinctive δ15N signals. Our results reveal that airborne anthropogenic N with distinct δ15N signals may directly modify the NO3- δ15N values in surface soils, but not the ones of NH4+, the preferred N form of the studied trees. Hence, the tree-ring δ15N values reflect specific soil N conditions and assimilation modes by trees. Along with a wide tree-ring δ15N range, we report differences in: soil nutrient content and N transformation rates; δ15N values of NH4+, total dissolved N (TDN) and EcM mantle enveloping the root tips; and bacterial and fungal community structures. We combine EcM mantle and root δ15N values with fungal identification to infer that hydrophobic EcM fungi transfer N from the dissolved organic N (DON) pool to roots under acidic conditions, and hydrophilic EcM fungi transfer various N forms to roots, which also assimilate N directly under less acidic conditions. Despite the complexities of soil biogeochemical properties and processes identified in the studied sites, in the end, the tree-ring δ15N averages inversely correlate with soil pH and anthropogenic N inputs, confirming white spruce tree-ring δ15N values as a suitable indicator for environmental research on forest N cycling.
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Affiliation(s)
- Martine M Savard
- Geological Survey of Canada, Natural Resources Canada, 490 rue de la Couronne, Québec, QC G1K 9A9, Canada.
| | - Christine Martineau
- Canadian Forest Service, Laurentian Forestry Centre, 1055 rue du P.E.P.S., Stn. Sainte-Foy, P.O. Box 10380, Québec, QC G1V 4C7, Canada
| | - Jérôme Laganière
- Canadian Forest Service, Laurentian Forestry Centre, 1055 rue du P.E.P.S., Stn. Sainte-Foy, P.O. Box 10380, Québec, QC G1V 4C7, Canada
| | - Christian Bégin
- Geological Survey of Canada, Natural Resources Canada, 490 rue de la Couronne, Québec, QC G1K 9A9, Canada
| | - Joëlle Marion
- Geological Survey of Canada, Natural Resources Canada, 490 rue de la Couronne, Québec, QC G1K 9A9, Canada
| | - Anna Smirnoff
- Geological Survey of Canada, Natural Resources Canada, 490 rue de la Couronne, Québec, QC G1K 9A9, Canada
| | - Franck Stefani
- Agriculture and Agri-Food Canada, 960 Avenue Carling, Ottawa, ON K1A 0C6, Canada
| | - Jade Bergeron
- Geological Survey of Canada, Natural Resources Canada, 490 rue de la Couronne, Québec, QC G1K 9A9, Canada
| | - Karelle Rheault
- Canadian Forest Service, Laurentian Forestry Centre, 1055 rue du P.E.P.S., Stn. Sainte-Foy, P.O. Box 10380, Québec, QC G1V 4C7, Canada
| | - David Paré
- Canadian Forest Service, Laurentian Forestry Centre, 1055 rue du P.E.P.S., Stn. Sainte-Foy, P.O. Box 10380, Québec, QC G1V 4C7, Canada
| | - Armand Séguin
- Canadian Forest Service, Laurentian Forestry Centre, 1055 rue du P.E.P.S., Stn. Sainte-Foy, P.O. Box 10380, Québec, QC G1V 4C7, Canada
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