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Liu P, Barr AG, Zha T, Black TA, Jassal RS, Nesic Z, Helgason WD, Jia X, Tian Y. Re-assessment of the climatic controls on the carbon and water fluxes of a boreal aspen forest over 1996-2016: Changing sensitivity to long-term climatic conditions. Glob Chang Biol 2022; 28:4605-4619. [PMID: 35474386 DOI: 10.1111/gcb.16218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2021] [Accepted: 03/19/2022] [Indexed: 06/14/2023]
Abstract
Recent evidence suggests that the relationships between climate and boreal tree growth are generally non-stationary; however, it remains uncertain whether the relationships between climate and carbon (C) fluxes of boreal forests are stationary or have changed over recent decades. In this study, we used continuous eddy-covariance and microclimate data over 21 years (1996-2016) from a 100-year-old trembling aspen stand in central Saskatchewan, Canada to assess the relationships between climate and ecosystem C and water fluxes. Over the study period, the most striking climatic event was a severe, 3-year drought (2001-2003). Gross ecosystem production (GEP) showed larger interannual variability than ecosystem respiration (Re ) over 1996-2016, but Re was the dominant component contributing to the interannual variation in net ecosystem production (NEP) during post-drought years. The interannual variations in evapotranspiration (ET) and C fluxes were primarily driven by temperature and secondarily by water availability. Two-factor linear models combining precipitation and temperature performed well in explaining the interannual variation in C and water fluxes (R2 > .5). The temperature sensitivities of all three C fluxes (NEP, GEP and Re ) declined over the study period (p < .05), and, as a result, the phenological controls on annual NEP weakened. The decreasing temperature sensitivity of the C fluxes may reflect changes in forest structure, related to the over-maturity of the aspen stand at 100 years of age, and exacerbated by high tree mortality following the severe 2001-2003 drought. These results may provide an early warning signal of driver shift or even an abrupt status shift of aspen forest dynamics. They may also imply a universal weakening in the relationship between temperature and GEP as forests become over-mature, associated with the structural and compositional changes that accompany forest ageing.
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Affiliation(s)
- Peng Liu
- School of Soil and Water Conservation, Beijing Forestry University, Beijing, China
- Beijing Engineering Research Center of Soil and Water Conservation, Beijing Forestry University, Beijing, China
| | - Alan G Barr
- Global Institute for Water Security, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Tianshan Zha
- School of Soil and Water Conservation, Beijing Forestry University, Beijing, China
- Beijing Engineering Research Center of Soil and Water Conservation, Beijing Forestry University, Beijing, China
| | - T Andrew Black
- Biometeorology and Soil Physics Group, University of British Columbia, Vancouver, British Columbia, Canada
| | - Rachhpal S Jassal
- Biometeorology and Soil Physics Group, University of British Columbia, Vancouver, British Columbia, Canada
| | - Zoran Nesic
- Biometeorology and Soil Physics Group, University of British Columbia, Vancouver, British Columbia, Canada
| | - Warren D Helgason
- Chemical and Biological Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Xin Jia
- School of Soil and Water Conservation, Beijing Forestry University, Beijing, China
- Beijing Engineering Research Center of Soil and Water Conservation, Beijing Forestry University, Beijing, China
| | - Yun Tian
- School of Soil and Water Conservation, Beijing Forestry University, Beijing, China
- Beijing Engineering Research Center of Soil and Water Conservation, Beijing Forestry University, Beijing, China
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Briegel F, Lee SC, Black TA, Jassal RS, Christen A. Factors controlling long-term carbon dioxide exchange between a Douglas-fir stand and the atmosphere identified using an artificial neural network approach. Ecol Modell 2020. [DOI: 10.1016/j.ecolmodel.2020.109266] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Huang N, Wang L, Song XP, Black TA, Jassal RS, Myneni RB, Wu C, Wang L, Song W, Ji D, Yu S, Niu Z. Spatial and temporal variations in global soil respiration and their relationships with climate and land cover. Sci Adv 2020; 6:6/41/eabb8508. [PMID: 33028522 PMCID: PMC7541079 DOI: 10.1126/sciadv.abb8508] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 08/18/2020] [Indexed: 05/16/2023]
Abstract
Soil respiration (R s) represents the largest flux of CO2 from terrestrial ecosystems to the atmosphere, but its spatial and temporal changes as well as the driving forces are not well understood. We derived a product of annual global R s from 2000 to 2014 at 1 km by 1 km spatial resolution using remote sensing data and biome-specific statistical models. Different from the existing view that climate change dominated changes in R s, we showed that land-cover change played a more important role in regulating R s changes in temperate and boreal regions during 2000-2014. Significant changes in R s occurred more frequently in areas with significant changes in short vegetation cover (i.e., all vegetation shorter than 5 m in height) than in areas with significant climate change. These results contribute to our understanding of global R s patterns and highlight the importance of land-cover change in driving global and regional R s changes.
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Affiliation(s)
- Ni Huang
- State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing Normal University, Beijing, China
| | - Li Wang
- State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing Normal University, Beijing, China.
| | - Xiao-Peng Song
- Department of Geosciences, Texas Tech University, Lubbock, TX, USA
| | - T Andrew Black
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC, Canada
| | - Rachhpal S Jassal
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC, Canada
| | - Ranga B Myneni
- Department of Earth and Environment, Boston University, Boston, MA, USA
| | - Chaoyang Wu
- The Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China
| | - Lei Wang
- State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing Normal University, Beijing, China
| | - Wanjuan Song
- State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing Normal University, Beijing, China
| | - Dabin Ji
- State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing Normal University, Beijing, China
| | - Shanshan Yu
- State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing Normal University, Beijing, China
| | - Zheng Niu
- State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing Normal University, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
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Liu P, Black TA, Jassal RS, Zha T, Nesic Z, Barr AG, Helgason WD, Jia X, Tian Y, Stephens JJ, Ma J. Divergent long-term trends and interannual variation in ecosystem resource use efficiencies of a southern boreal old black spruce forest 1999-2017. Glob Chang Biol 2019; 25:3056-3069. [PMID: 31055880 DOI: 10.1111/gcb.14674] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Revised: 04/23/2019] [Accepted: 04/25/2019] [Indexed: 05/14/2023]
Abstract
Long-term trends in ecosystem resource use efficiencies (RUEs) and their controlling factors are key pieces of information for understanding how an ecosystem responds to climate change. We used continuous eddy covariance and microclimate data over the period 1999-2017 from a 120-year-old black spruce stand in central Saskatchewan, Canada, to assess interannual variability, long-term trends, and key controlling factors of gross ecosystem production (GEP) and the RUEs of carbon (CUE = net primary production [NPP]/GEP), light (LUE = GEP/absorbed photosynthetic radiation [APAR]), and water (WUE = GEP/evapotranspiration [E]). At this site, annual GEP has shown an increasing trend over the 19 years (p < 0.01), which may be attributed to rising atmospheric CO2 concentration. Interannual variability in GEP, aside from its increasing trend, was most strongly related to spring temperatures. Associated with the significant increase in annual GEP were relatively small changes in NPP, APAR, and E, so that annual CUE showed a decreasing trend and annual LUE and WUE showed increasing trends over the 19 years. The long-term trends in the RUEs were related to the increasing CO2 concentration. Further analysis of detrended RUEs showed that their interannual variation was impacted most strongly by air temperature. Two-factor linear models combining CO2 concentration and air temperature performed well (R2 ~0.60) in simulating annual RUEs. LUE and WUE were positively correlated both annually and seasonally, while LUE and CUE were mostly negatively correlated. Our results showed divergent long-term trends among CUE, LUE, and WUE and highlighted the need to account for the combined effects of climatic controls and the 'CO2 fertilization effect' on long-term variations in RUEs. Since most RUE-based models rely primarily on one resource limitation, the observed patterns of relative change among the three RUEs may have important implications for RUE-based modeling of C fluxes.
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Affiliation(s)
- Peng Liu
- Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, China
- Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, China
- Biometeorology and Soil Physics Group, University of British Columbia, Vancouver, BC, Canada
| | - T Andrew Black
- Biometeorology and Soil Physics Group, University of British Columbia, Vancouver, BC, Canada
| | - Rachhpal S Jassal
- Biometeorology and Soil Physics Group, University of British Columbia, Vancouver, BC, Canada
| | - Tianshan Zha
- Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, China
- Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, China
| | - Zoran Nesic
- Biometeorology and Soil Physics Group, University of British Columbia, Vancouver, BC, Canada
| | - Alan G Barr
- Climate Research Division, Environment and Climate Change Canada, Saskatoon, SK, Canada
- Global Institute for Water Security, University of Saskatchewan, Saskatoon, SK, Canada
| | - Warren D Helgason
- Chemical and Biological Engineering, University of Saskatchewan, Saskatoon, SK, Canada
| | - Xin Jia
- Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, China
- Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, China
| | - Yun Tian
- Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, China
- Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, China
| | - Jilmarie J Stephens
- Biometeorology and Soil Physics Group, University of British Columbia, Vancouver, BC, Canada
| | - Jingyong Ma
- Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, China
- Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, China
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Hawthorne I, Johnson MS, Jassal RS, Black TA, Grant NJ, Smukler SM. Application of biochar and nitrogen influences fluxes of CO 2, CH 4 and N 2O in a forest soil. J Environ Manage 2017; 192:203-214. [PMID: 28161628 DOI: 10.1016/j.jenvman.2016.12.066] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Revised: 12/16/2016] [Accepted: 12/27/2016] [Indexed: 06/06/2023]
Abstract
Nitrogen (N) fertilization of forests for increasing carbon sequestration and wood volume is expected to influence soil greenhouse gas (GHG) emissions, especially to increase N2O emissions. As biochar application is known to affect soil GHG emissions, we investigated the effect of biochar application, with and without N fertilization, to a forest soil on GHG emissions in a controlled laboratory study. We found that biochar application at high (10%) application rates increased CO2 and N2O emissions when applied without urea-N fertilizer. At both low (1%) and high biochar (10%) application rates CH4 consumption was reduced when applied without urea-N fertilizer. Biochar application with urea-N fertilization did not increase CO2 emissions compared to biochar amended soil without fertilizer. In terms of CO2-eq, the net change in GHG emissions was mainly controlled by CO2 emissions, regardless of treatment, with CH4 and N2O together accounting for less than 1.5% of the total emissions.
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Affiliation(s)
- Iain Hawthorne
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, Canada.
| | - Mark S Johnson
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, Canada; Institute for Resources, Environment and Sustainability, University of British Columbia, Vancouver, Canada
| | - Rachhpal S Jassal
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, Canada
| | - T Andrew Black
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, Canada
| | - Nicholas J Grant
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, Canada
| | - Sean M Smukler
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, Canada
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Bhatti JS, Jassal RS. Long term aboveground litterfall production in boreal jack pine ( Pinus banksiana) and black spruce ( Picea mariana) stands along the Boreal Forest Transect Case Study in western central Canada. Écoscience 2015. [DOI: 10.2980/21-(3-4)-3699] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Jagtar S. Bhatti
- Canadian Forest Service, Northern Forestry Centre, 5320 122 Street, Edmonton, Alberta T6H 3S5, Canada,
| | - Rachhpal S. Jassal
- Biometeorology and Soil Physics Group, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
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Jassal RS, Johnson MS, Molodovskaya M, Black TA, Jollymore A, Sveinson K. Nitrogen enrichment potential of biochar in relation to pyrolysis temperature and feedstock quality. J Environ Manage 2015; 152:140-144. [PMID: 25621388 DOI: 10.1016/j.jenvman.2015.01.021] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Revised: 01/11/2015] [Accepted: 01/16/2015] [Indexed: 06/04/2023]
Abstract
Nitrogen (N) enrichment of biochar from both inorganic and organic waste N sources has the potential to add economic and environmental value through its use as a slow release N fertilizer. We investigated the sorption of N by, and its release from, biochar made at pyrolysis temperatures of 400, 500 and 600 °C from three feedstocks: poultry litter (PL with a carbon (C) to N ratio (C:N) of 14), softwood chips of spruce-pine-fir (SPF with a C:N of 470), and a 50:50 mixture of PL and SPF (PL/SPF). The prepared biochars were enriched with ammonium nitrate (AN) and urea ammonium nitrate (UAN). PL biochars had the lowest C content (50-56% C), but the highest pH (9.3-9.9), electrical conductivity (EC, 780-960 dS m(-1)), cation exchange capacity (CEC, 40-46 cmol kg(-1)), and N content (3.3-4.5%). While N content and hydrogen (H) to C atomic ratio (H:C) decreased with increasing pyrolysis temperature irrespective of the feedstock used, both pH and EC slightly increased with pyrolysis temperature for all feedstocks. The PL and SPF biochars showed similar H:C and also similar N sorption and N release at all pyrolysis temperatures. These biochars sorbed up to 5% N by mass, irrespective of the source of N. However, PL/SPF biochar performed poorly in sorbing N from either AN or UAN. Biochar H:C was found to be unrelated to N sorption rates, suggesting that physical adsorption on active surfaces was the main mechanism of N sorption in these biochars. There were minor differences between N sorbed from NO3-N and NH4-N among different biochars. Very small amounts of sorbed N (0.2-0.4 mg N g(-1) biochar) was released when extracted with 1 M KCl solution, indicating that the retained N was strongly held in complex bonds, more so for NH4-N because the release of NO3-N was 3-4 times greater than that of NH4-N. NH4-N sorption far exceeded the effective CEC of the biochars, thereby suggesting that most of the sorption may be due to physical entrapment of NH4(+) in biochar pores. The results of this study suggest that biochar can be used to remove excess N from poultry and dairy manure and be a good mitigation option for reducing N leaching and gaseous losses.
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Affiliation(s)
- Rachhpal S Jassal
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, Canada.
| | - Mark S Johnson
- Institute for Resources, Environment and Sustainability, University of British Columbia, Vancouver, Canada; Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, Canada
| | - Marina Molodovskaya
- Institute for Resources, Environment and Sustainability, University of British Columbia, Vancouver, Canada
| | - T Andrew Black
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, Canada
| | - Ashlee Jollymore
- Institute for Resources, Environment and Sustainability, University of British Columbia, Vancouver, Canada
| | - Kelly Sveinson
- Department of Chemistry, Langara College, Vancouver, Canada
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Vargas R, Baldocchi DD, Allen MF, Bahn M, Black TA, Collins SL, Yuste JC, Hirano T, Jassal RS, Pumpanen J, Tang J. Looking deeper into the soil: biophysical controls and seasonal lags of soil CO2 production and efflux. Ecol Appl 2010; 20:1569-1582. [PMID: 20945760 DOI: 10.1890/09-0693.1] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We seek to understand how biophysical factors such as soil temperature (Ts), soil moisture (theta), and gross primary production (GPP) influence CO2 fluxes across terrestrial ecosystems. Recent advancements in automated measurements and remote-sensing approaches have provided time series in which lags and relationships among variables can be explored. The purpose of this study is to present new applications of continuous measurements of soil CO2 efflux (F0) and soil CO2 concentrations measurements. Here we explore how variation in Ts, theta, and GPP (derived from NASA's moderate-resolution imaging spectroradiometer [MODIS]) influence F0 and soil CO2 production (Ps). We focused on seasonal variation and used continuous measurements at a daily timescale across four vegetation types at 13 study sites to quantify: (1) differences in seasonal lags between soil CO2 fluxes and Ts, theta, and GPP and (2) interactions and relationships between CO2 fluxes with Ts, theta, and GPP. Mean annual Ts did not explain annual F0 and Ps among vegetation types, but GPP explained 73% and 30% of the variation, respectively. We found evidence that lags between soil CO2 fluxes and Ts or GPP provide insights into the role of plant phenology and information relevant about possible timing of controls of autotrophic and heterotrophic processes. The influences of biophysical factors that regulate daily F0 and Ps are different among vegetation types, but GPP is a dominant variable for explaining soil CO2 fluxes. The emergence of long-term automated soil CO2 flux measurement networks provides a unique opportunity for extended investigations into F0 and Ps processes in the near future.
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Affiliation(s)
- Rodrigo Vargas
- Department of Environmental Science, Policy, and Management, 137 Mulford Hall, University of California, Berkeley, California 94720, USA.
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Arevalo CBM, Bhatti JS, Chang SX, Jassal RS, Sidders D. Soil respiration in four different land use systems in north central Alberta, Canada. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2009jg001006] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Krishnan P, Black TA, Jassal RS, Chen B, Nesic Z. Interannual variability of the carbon balance of three different-aged Douglas-fir stands in the Pacific Northwest. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008jg000912] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Cai T, Black A, Jassal RS, Morgenstern K, Nesic Z. Incorporating diffuse photosynthetically active radiation in a single-leaf model of canopy photosynthesis for a 56-year-old Douglas-fir forest. Int J Biometeorol 2009; 53:135-148. [PMID: 19132410 DOI: 10.1007/s00484-008-0196-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2007] [Revised: 11/02/2008] [Accepted: 11/10/2008] [Indexed: 05/27/2023]
Abstract
A simple top-down model of canopy photosynthesis (P) was developed and tested in this study. The model (referred to as the Q(e)-MM model) is P = alphaQ (e) P (max)/(alphaQ ( e ) + P (max)), alpha and P (max) are quantum-use efficiency and potential P, respectively. Q (e) is given by Q (d) (0) + kQ (b) (0), where Q (d) (0) and Q (b) (0) are the diffuse and direct photosynthetically active radiation (PAR) incident on the canopy, respectively. Q (e) can be considered to be the effective incident PAR contributing to P and k is a measure of the contribution of Q (b) (0) to Q (e). When k = 1, the Q(e)-MM model becomes the regular Michaelis-Menten type model of P (referred to as the MM model). A major objective of this study was to determine how well the Q(e)-MM model could estimate P of a 56-year-old coastal Douglas-fir stand. To this end, we parameterized the Q(e)-MM model using five and half years of eddy-covariance measurements of CO(2) flux above the Douglas-fir stand. The Q(e)-MM model, with the incorporation of a function of air temperature, accounted for 74% of the variance in over 34,000 half-hourly P measurements. P estimated using the Q(e)-MM model had no systematic errors with respect to Q (d) (0). Although the Q(e)-MM model has only one more parameter than the MM model, it accounted for 30% more variance in P than the latter when total incident PAR exceeded 900 micromol m(-2) s(-1). On average, k was found to be 0.22. We show that this small value of k reflects the significant effect of the scattering of the solar beam and the fraction of light-limited sunlit leaves. We also show that the success of the Q(e)-MM model was due to the fact that a large fraction of the sunlit leaves were light-limited as a result of their orientation to the solar beam.
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Affiliation(s)
- Tiebo Cai
- University of British Columbia, Vancouver, Canada.
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Jassal RS, Black TA, Chen B, Roy R, Nesic Z, Spittlehouse DL, Trofymow JA. N2O emissions and carbon sequestration in a nitrogen-fertilized Douglas fir stand. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2008jg000764] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Rachhpal S. Jassal
- Biometeorology and Soil Physics Group; University of British Columbia; Vancouver, British Columbia Canada
| | - T. Andrew Black
- Biometeorology and Soil Physics Group; University of British Columbia; Vancouver, British Columbia Canada
| | - Baozhang Chen
- Biometeorology and Soil Physics Group; University of British Columbia; Vancouver, British Columbia Canada
| | - Real Roy
- Department of Biology; University of Victoria; Victoria, British Columbia Canada
| | - Zoran Nesic
- Biometeorology and Soil Physics Group; University of British Columbia; Vancouver, British Columbia Canada
| | - D. L. Spittlehouse
- Research Branch; Ministry of Forests and Range; Victoria, British Columbia Canada
| | - J. A. Trofymow
- Canadian Forest Service; Natural Resources Canada; Victoria, British Columbia Canada
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Hilker T, Coops NC, Schwalm CR, Jassal RS, Black TA, Krishnan P. Effects of mutual shading of tree crowns on prediction of photosynthetic light-use efficiency in a coastal Douglas-fir forest. Tree Physiol 2008; 28:825-834. [PMID: 18381263 DOI: 10.1093/treephys/28.6.825] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Gross primary production (GPP) is often expressed as the product of absorbed photosynthetically active radiation and the efficiency (epsilon) with which a plant community uses absorbed radiation in biomass production. Light-use efficiency is affected by environmental stresses, and varies diurnally and seasonally. Uncertainty about epsilon can be a serious limitation when modeling GPP. An important determinant of epsilon is the amount and type of solar radiation incident on a canopy, because an abundance of light can trigger a photo-protective reaction, diminishing GPP. The radiation regime in a forest canopy is determined by the predominant sky conditions and by mutual shading of tree crowns. Shading effects, producing shifts in the amount of incident direct and diffuse solar radiation, have been largely ignored, however, because they depend on forest structure and are difficult to measure. We describe a new approach for estimating changes in mutual canopy shading throughout the day and year based on a canopy structure model derived from light detection and ranging (LiDAR). Proportions of canopy shading were then combined with eddy covariance data to assess the explanatory power for variance in epsilon by regression tree analysis over half-hourly, daily and weekly time scales. The approach explained between 75 and 97% of variance in epsilon, representing an increase of between 5 and 16% compared with models driven solely by meteorological variables.
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Affiliation(s)
- Thomas Hilker
- Faculty of Forest Resources Management, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada.
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Gaumont-Guay D, Black TA, Barr AG, Jassal RS, Nesic Z. Biophysical controls on rhizospheric and heterotrophic components of soil respiration in a boreal black spruce stand. Tree Physiol 2008; 28:161-171. [PMID: 18055427 DOI: 10.1093/treephys/28.2.161] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
We conducted a root-exclusion experiment in a 125-year-old boreal black spruce (Picea mariana (Mill.) BSP) stand in 2004 to quantify the physical and biological controls on temporal dynamics of the rhizospheric (R(r)) and heterotrophic (R(h)) components of soil respiration (R(s)). Annual R(r), R(h) and estimated moss respiration were 285, 269 and 57 g C m(-2) year(-1), respectively, which accounted for 47, 44 and 9% of R(s) (611 g C m(-2) year(-1)), respectively. A gradual transition from R(h)-dominated (winter, spring and fall) to R(r)-dominated (summer) respiration was observed during the year. Soil thawing in spring and the subsequent increase in soil water content (theta) induced a small and sustained increase in R(h) but had no effect on R(r). During the remainder of the growing season, no effect of theta was observed on either component of R(s). Both components increased exponentially with soil temperature (T(s)) during the growing season, but R(r) showed greater temperature sensitivity than R(h) (Q(10) of 4.0 and 3.0, respectively). Temperature-normalized variations in R(r) were highly correlated with eddy covariance estimates of gross ecosystem photosynthesis, and the correlation was greatest when R(r) was lagged by 24 days. Within diurnal cycles, variations in T(s) were highly coupled to variations in R(h) but were significantly decoupled from R(r). The patterns observed at both time scales strongly suggest that the flow of photosynthates to the rhizosphere is a key driver of belowground respiration processes but that photosynthate supply may control these processes in several ways.
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Affiliation(s)
- David Gaumont-Guay
- Biometeorology and Soil Physics Group, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
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Black TA, Gaumont-Guay D, Jassal RS, Amiro BD, Jarvis PG, Gower ST, Kelliher FM, Dunn A, Wofsy SC. Measurement of CO2 exchange between Boreal forest and the atmosphere. SEB Exp Biol Ser 2005:151-85. [PMID: 17633035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
The Boreal forest is the world's second largest forested biome occupying the circumpolar region between 50 degrees N and 70 degrees N. This heterogeneous biome stores about 25% of all terrestrial carbon. We have reviewed EC measurements of CO2 exchange between the atmosphere and Boreal forests, and assessed progress in understanding the controlling processes. We have assessed net ecosystem productivity, the net balance between net primary productivity and heterotrophic respiration, measured using the EC method, for 38 Boreal forest sites. Gross ecosystem productivity has been estimated by adding day-time EC-measured CO2 fluxes to respiration estimated from night-time relationships between respiration and temperature. Maximum midday values of gross ecosystem productivity vary from 33 pmol m(-2) s(-1) for aspen to 6 micromol m(-2) s(-1) for larch stands. Long-term EC flux measurements, ongoing at nine Boreal sites, have shown the strong impact of spring weather and growing season water balance on annual net ecosystem productivity. Estimation of net biome production, incorporating the effects of disturbance resulting from forest fires and logging, has progressed significantly in recent years. After disturbance, summer measurements in Boreal chronosequences suggest that it takes about 10 years before growing season carbon uptake offsets the decomposition emissions. Small-scale exchange rate measurements using chambers and manipulative experiments such as stem girdling and soil heating help to understand the processes and mechanisms playing major roles in the carbon balance of terrestrial ecosystems. Aircraft EC flux measurements, convective boundary layer carbon budgets, and (13)C/12C changes in the atmosphere play an important role in validating estimates of regional carbon exchange based on scaled up EC measurements. Atmospheric inverse models are an important approach to studying regional and global carbon balance but need further improvement to yield reliable quantitative results.
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Affiliation(s)
- T Andrew Black
- Department of Agricultural Sciences, University of British Columbia, Vancouver, Canada
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