scholarly journals Simulation of Carbon Exchange from a Permafrost Peatland in the Great Hing’an Mountains Based on CoupModel

Atmosphere ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 44
Author(s):  
Yue Li ◽  
Zhongmei Wan ◽  
Li Sun

Climate change is accelerating its impact on northern ecosystems. Northern peatlands store a considerable amount of C, but their response to climate change remains highly uncertain. In order to explore the feedback of a peatland in the Great Hing’an Mountains to future climate change, we simulated the response of the overall net ecosystem exchange (NEE), ecosystem respiration (ER), and gross primary production (GPP) during 2020–2100 under three representative concentration pathways (RCP2.6, RCP6.0, and RCP8.5). Under the RCP2.6 and RCP6.0 scenarios, the carbon sink will increase slightly until 2100. Under the RCP8.5 scenario, the carbon sink will follow a trend of gradual decrease after 2053. These results show that when meteorological factors, especially temperature, reach a certain degree, the carbon source/sink of the peatland ecosystem will be converted. In general, although the peatland will remain a carbon sink until the end of the 21st century, carbon sinks will decrease under the influence of climate change. Our results indicate that in the case of future climate warming, with the growing seasons experiencing overall dryer and warmer environments and changes in vegetation communities, peatland NEE, ER, and GPP will increase and lead to the increase in ecosystem carbon accumulation.

2020 ◽  
Author(s):  
Aurelio Guevara-Escobar ◽  
Enrique González-Sosa ◽  
Mónica Cervantes-Jiménez ◽  
Humberto Suzán-Azpiri ◽  
Mónica Elisa Queijeiro-Bolaños ◽  
...  

Abstract. Vegetation fixes C in its biomass through photosynthesis or might release it into the atmosphere through respiration. Measurements of these fluxes would help us understand ecosystem functioning. The eddy covariance technique (EC) is widely used to measure the net ecosystem exchange of C (NEE) which is the balance between gross primary production (GPP) and ecosystem respiration (Reco). Orbital satellites such as MODIS can also provide estimates of GPP. In this study, we measured NEE with the EC in a scrub at Bernal in Mexico, and then partitioned into gross primary production (GPP-EC) and Reco using the recent R package Reddyproc. Measurements of GPP-EC were related to the estimates from the MODIS satellite provided in product MOD17A2H, which contains data of the gross primary productivity (GPP-MODIS). The Bernal site was a carbon sink despite it was an overgrazed site, the average NEE during fifteen months of 2017 and 2018 was −0.78 g C m−2 d−1 and the flux was negative in all measured months. The GPP-MODIS underestimated the ground data when representing the relation with a Theil-Sen regression: GPP-EC = 1.866 + 1.861 GPP-MODIS; an ordinary less squares regression had similar coefficients and the R2 was 0.6. Although cacti (CAM), legume shrubs (C3) and herbs (C3) had a similar vegetation index, the nighttime flux was characterized by positive NEE suggesting that the photosynthetic dark-cycle flux of cacti was lower than Reco. The discrepancy among the GPP flux estimates stresses the need to understand the limitations of EC and remote sensors, while incorporating complementary monitoring and modelling schemes of nighttime Reco, particularly in the presence of species with different photosynthetic cycles.


2016 ◽  
Author(s):  
Efrén López-Blanco ◽  
Magnus Lund ◽  
Mathew Williams ◽  
Mikkel P. Tamstorf ◽  
Andreas Westergaard-Nielsen ◽  
...  

Abstract. An improvement in our process-based understanding of carbon (C) exchange in the Arctic, and its climate sensitivity, is critically needed for understanding the response of tundra ecosystems to a changing climate. In this context, we analyzed the net ecosystem exchange (NEE) of CO2 in West Greenland tundra (64° N) across eight snow-free periods in eight consecutive years, and characterized the key processes of net ecosystem exchange, and its two main modulating components: gross primary production (GPP) and ecosystem respiration (Reco). Overall, the ecosystem acted as a consistent sink of CO2, accumulating −30 g C m−2 on average (range −17 to −41 g C m−2) during the years 2008–2015, except 2011 that was associated with a major pest outbreak. The results do not reveal a marked meteorological effect on the net CO2 uptake despite the high inter-annual variability in the timing of snowmelt, start and duration of the growing season. The ranges in annual GPP (−182 to −316 g C m−2) and Reco (144 to 279 g C m−2) were > 5 fold larger and they were also more variable (Coefficients of variation are 3.6 and 4.1 % respectively) than for NEE (0.7 %). GPP and Reco were sensitive to insolation and temperatures; and there was a tendency towards larger GPP and Reco during warmer and wetter years. The relative lack of sensitivity of NEE to climate was a result of the correlated meteorological response of GPP and Reco. During the 2011 anomalous year, the studied ecosystem released 41 g C m−2 as biological disturbance reduced GPP more strongly than Reco. With continued warming temperatures and longer growing seasons, tundra systems will increase rates of C cycling although shifts in sink strength will likely be triggered by factors such as biological disturbances, events that will challenge the forecast of upcoming C states.


2017 ◽  
Vol 14 (19) ◽  
pp. 4467-4483 ◽  
Author(s):  
Efrén López-Blanco ◽  
Magnus Lund ◽  
Mathew Williams ◽  
Mikkel P. Tamstorf ◽  
Andreas Westergaard-Nielsen ◽  
...  

Abstract. An improvement in our process-based understanding of carbon (C) exchange in the Arctic and its climate sensitivity is critically needed for understanding the response of tundra ecosystems to a changing climate. In this context, we analysed the net ecosystem exchange (NEE) of CO2 in West Greenland tundra (64° N) across eight snow-free periods in 8 consecutive years, and characterized the key processes of net ecosystem exchange and its two main modulating components: gross primary production (GPP) and ecosystem respiration (Reco). Overall, the ecosystem acted as a consistent sink of CO2, accumulating −30 g C m−2 on average (range of −17 to −41 g C m−2) during the years 2008–2015, except 2011 (source of 41 g C m−2), which was associated with a major pest outbreak. The results do not reveal a marked meteorological effect on the net CO2 uptake despite the high interannual variability in the timing of snowmelt and the start and duration of the growing season. The ranges in annual GPP (−182 to −316 g C m−2) and Reco (144 to 279 g C m−2) were  > 5 fold larger than the range in NEE. Gross fluxes were also more variable (coefficients of variation are 3.6 and 4.1 % respectively) than for NEE (0.7 %). GPP and Reco were sensitive to insolation and temperature, and there was a tendency towards larger GPP and Reco during warmer and wetter years. The relative lack of sensitivity of NEE to meteorology was a result of the correlated response of GPP and Reco. During the snow-free season of the anomalous year of 2011, a biological disturbance related to a larvae outbreak reduced GPP more strongly than Reco. With continued warming temperatures and longer growing seasons, tundra systems will increase rates of C cycling. However, shifts in sink strength will likely be triggered by factors such as biological disturbances, events that will challenge our forecasting of C states.


2020 ◽  
Author(s):  
Hongfei Xie ◽  
JUNFANG ZHAO ◽  
Jianyong Ma ◽  
Weixiong Yan

Abstract Background At present, global warming is an indisputable fact, and more and more attention has been paid to the impacts of climate warming on global ecological environments. Forests play increasing significant roles in regulating global carbon balance and mitigating climate change. Therefore, to understand the response mechanisms of the carbon budget of global forest ecosystems to future climate change, an improved version of the FORest ecosystem Carbon budget model for CHiNa (FORCCHN) and future Representative Concentration Pathway (RCP) scenario RCP4.5 and RCP8.5 were applied in this study.Results The global forest ecosystems will play a major role in the carbon sink under the future two climate change scenarios. In particular, the average carbon budget (namely the Net Ecosystem Productivity, NEP) of global forest ecosystems under RCP4.5 scenario was estimated to be 0.017 kg(C)·m− 2·yr− 1 from 2006 to 2100. The future carbon sink areas of global forest ecosystems will increase significantly. Under RCP4.5 and RCP8.5 climate scenarios, the carbon sink areas of global forest ecosystems during 2026–2100 would be significantly higher than those in 2006–2025, with increases of 83.16–87.26% and 23.53–29.70%, respectively. The impacts of future climate change on NEP of global forest ecosystems will significantly vary between different regions. The NEP of forests will be enhanced in the northern hemisphere and significantly weakened in the southern hemisphere under the future two climate change scenarios. The carbon sink regions of global forests will be mainly distributed in the middle and high latitudes of the northern hemisphere. In particular, the forests'NEP in northeastern and central Asia, northern Europe and western North America will increase by 40%~80%. However, the NEP of forests will decrease by 20%~40% in the most regions of the southern hemisphere. In northern South America and central Africa, the forests' NEP will be reduced by more than 40%.Conclusions The global forest ecosystems will play a major role in the carbon sink under the future two climate change scenarios. However, the NEP of forests will be enhanced in the northern hemisphere and significantly weakened in the southern hemisphere. In the future, in some areas of southern hemisphere, where the forests' NEP was predicted to be reduced, some measures for improving forest carbon sink, such as strengthening forest tending, enforcing prohibiting deforestation laws and scientific forest management, and so on, should be implemented to ensure immediate mitigation and adaptation to climate change.


2019 ◽  
Vol 11 (22) ◽  
pp. 6376 ◽  
Author(s):  
Guangcun Hao ◽  
Zhongmin Hu ◽  
Qun Guo ◽  
Kai Di ◽  
Shenggong Li

Over the past 50 years, rainfall events have made significant alterations to environments due to global warming. The grasslands in arid and semi-arid regions are extremely sensitive to variations in rainfall patterns, which are considered to significantly affect ecosystem functions. In this study, an experiment with varying rainfall sizes and frequencies (0 mm, 2 mm, 5 mm, 10 mm, 20 mm, and 40 mm) was conducted during growing seasons in typical grasslands, to study the effect of changes in rainfall regime on net ecosystem exchange (NEE). Our results indicated that NEE exhibited nonlinear responses to rainfall treatments, and reached its peak under 20 mm in middle growing season. Further, the component fluxes of both NEE (i.e., gross primary productivity (GPP)) and ecosystem respiration (ER) illustrated nonlinear responses to treatment gradient, with peak values at 20 mm and 5 mm, respectively. Based on five-year eddy flux measurements, further analyses demonstrated that GPP and ER increased with increasing soil moisture, and net ecosystem carbon uptake (-1*NEE) was significantly stimulated due to a more enhanced GPP than ER, when soil moisture was above 8%. Additionally, we found that the response of root biomass was different from that of carbon fluxes to changes in rainfall patterns. Overall, these findings highlight the importance of both changes in rainfall regimes in controlling ecosystem C exchange and investigation of the potential threshold for ecosystem function shifts, which are crucial to further understand C cycles in grasslands.


2014 ◽  
Vol 11 (15) ◽  
pp. 4271-4288 ◽  
Author(s):  
J. B. Fisher ◽  
M. Sikka ◽  
W. C. Oechel ◽  
D. N. Huntzinger ◽  
J. R. Melton ◽  
...  

Abstract. Climate change is leading to a disproportionately large warming in the high northern latitudes, but the magnitude and sign of the future carbon balance of the Arctic are highly uncertain. Using 40 terrestrial biosphere models for the Alaskan Arctic from four recent model intercomparison projects – NACP (North American Carbon Program) site and regional syntheses, TRENDY (Trends in net land atmosphere carbon exchanges), and WETCHIMP (Wetland and Wetland CH4 Inter-comparison of Models Project) – we provide a baseline of terrestrial carbon cycle uncertainty, defined as the multi-model standard deviation (σ) for each quantity that follows. Mean annual absolute uncertainty was largest for soil carbon (14.0 ± 9.2 kg C m−2), then gross primary production (GPP) (0.22 ± 0.50 kg C m−2 yr−1), ecosystem respiration (Re) (0.23 ± 0.38 kg C m−2 yr−1), net primary production (NPP) (0.14 ± 0.33 kg C m−2 yr−1), autotrophic respiration (Ra) (0.09 ± 0.20 kg C m−2 yr−1), heterotrophic respiration (Rh) (0.14 ± 0.20 kg C m−2 yr−1), net ecosystem exchange (NEE) (−0.01 ± 0.19 kg C m−2 yr−1), and CH4 flux (2.52 ± 4.02 g CH4 m−2 yr−1). There were no consistent spatial patterns in the larger Alaskan Arctic and boreal regional carbon stocks and fluxes, with some models showing NEE for Alaska as a strong carbon sink, others as a strong carbon source, while still others as carbon neutral. Finally, AmeriFlux data are used at two sites in the Alaskan Arctic to evaluate the regional patterns; observed seasonal NEE was captured within multi-model uncertainty. This assessment of carbon cycle uncertainties may be used as a baseline for the improvement of experimental and modeling activities, as well as a reference for future trajectories in carbon cycling with climate change in the Alaskan Arctic and larger boreal region.


2021 ◽  
Vol 18 (2) ◽  
pp. 367-392
Author(s):  
Aurelio Guevara-Escobar ◽  
Enrique González-Sosa ◽  
Mónica Cervantes-Jiménez ◽  
Humberto Suzán-Azpiri ◽  
Mónica Elisa Queijeiro-Bolaños ◽  
...  

Abstract. Arid and semiarid ecosystems contain relatively high species diversity and are subject to intense use, in particular extensive cattle grazing, which has favored the expansion and encroachment of perennial thorny shrubs into the grasslands, thus decreasing the value of the rangeland. However, these environments have been shown to positively impact global carbon dynamics. Machine learning and remote sensing have enhanced our knowledge about carbon dynamics, but they need to be further developed and adapted to particular analysis. We measured the net ecosystem exchange (NEE) of C with the eddy covariance (EC) method and estimated gross primary production (GPP) in a thorny scrub at Bernal in Mexico. We tested the agreement between EC estimates and remotely sensed GPP estimates from the Moderate Resolution Imaging Spectroradiometer (MODIS), and also with two alternative modeling methods: ordinary-least-squares (OLS) regression and ensembles of machine learning algorithms (EMLs). The variables used as predictors were MODIS spectral bands, vegetation indices and products, and gridded environmental variables. The Bernal site was a carbon sink even though it was overgrazed, the average NEE during 15 months of 2017 and 2018 was −0.78 gCm-2d-1, and the flux was negative or neutral during the measured months. The probability of agreement (θs) represented the agreement between observed and estimated values of GPP across the range of measurement. According to the mean value of θs, agreement was higher for the EML (0.6) followed by OLS (0.5) and then MODIS (0.24). This graphic metric was more informative than r2 (0.98, 0.67, 0.58, respectively) to evaluate the model performance. This was particularly true for MODIS because the maximum θs of 4.3 was for measurements of 0.8 gCm-2d-1 and then decreased steadily below 1 θs for measurements above 6.5 gCm-2d-1 for this scrub vegetation. In the case of EML and OLS, the θs was stable across the range of measurement. We used an EML for the Ameriflux site US-SRM, which is similar in vegetation and climate, to predict GPP at Bernal, but θs was low (0.16), indicating the local specificity of this model. Although cacti were an important component of the vegetation, the nighttime flux was characterized by positive NEE, suggesting that the photosynthetic dark-cycle flux of cacti was lower than ecosystem respiration. The discrepancy between MODIS and EC GPP estimates stresses the need to understand the limitations of both methods.


2014 ◽  
Vol 11 (2) ◽  
pp. 2887-2932 ◽  
Author(s):  
J. B. Fisher ◽  
M. Sikka ◽  
W. C. Oechel ◽  
D. N. Huntzinger ◽  
J. R. Melton ◽  
...  

Abstract. Climate change is leading to a disproportionately large warming in the high northern latitudes, but the magnitude and sign of the future carbon balance of the Arctic are highly uncertain. Using 40 terrestrial biosphere models for Alaska, we provide a baseline of terrestrial carbon cycle structural and parametric uncertainty, defined as the multi-model standard deviation (σ) against the mean (x) for each quantity. Mean annual uncertainty (σ/x) was largest for net ecosystem exchange (NEE) (−0.01± 0.19 kg C m−2 yr−1), then net primary production (NPP) (0.14 ± 0.33 kg C m−2 yr−1), autotrophic respiration (Ra) (0.09 ± 0.20 kg C m−2 yr−1), gross primary production (GPP) (0.22 ± 0.50 kg C m−2 yr−1), ecosystem respiration (Re) (0.23 ± 0.38 kg C m−2 yr−1), CH4 flux (2.52 ± 4.02 g CH4 m−2 yr−1), heterotrophic respiration (Rh) (0.14 ± 0.20 kg C m−2 yr−1), and soil carbon (14.0± 9.2 kg C m−2). The spatial patterns in regional carbon stocks and fluxes varied widely with some models showing NEE for Alaska as a strong carbon sink, others as a strong carbon source, while still others as carbon neutral. Additionally, a feedback (i.e., sensitivity) analysis was conducted of 20th century NEE to CO2 fertilization (β) and climate (γ), which showed that uncertainty in γ was 2x larger than that of β, with neither indicating that the Alaskan Arctic is shifting towards a certain net carbon sink or source. Finally, AmeriFlux data are used at two sites in the Alaskan Arctic to evaluate the regional patterns; observed seasonal NEE was captured within multi-model uncertainty. This assessment of carbon cycle uncertainties may be used as a baseline for the improvement of experimental and modeling activities, as well as a reference for future trajectories in carbon cycling with climate change in the Alaskan Arctic.


2017 ◽  
Vol 39 (4) ◽  
pp. 387 ◽  
Author(s):  
Xiaoni Liu ◽  
Baisen Zhang ◽  
Beverley Henry ◽  
Jinglan Zhang ◽  
Peter Grace

The study investigated the impact of historical and future climate changes on potential natural vegetation (PNV) types and net primary productivity (NPP) in Australia, using the Comprehensive and Sequential Classification System model and the Miami model coupled with climate of the 1931–70 and 1971–2010 periods and the projected climate in 2050. Twenty-eight vegetation classes were classified based on the key climate indicators with four of them being the major vegetation classes corresponding to Australian rangelands and accounting for 75% of total land area. There was a substantial shift in areas of vegetation classes from the 1931–70 period to the 1971–2010 period due to the increased rainfall over large areas across Australia. The modelling projected a range of changes in vegetation classes for 2050 depending on the climate-change scenario used. Many vegetation classes with more intense land use (e.g. steppe and forest) were projected to decrease in 2050, which may have significant impact on the grazing industry and biodiversity conservation. By 2050, NPP was projected to increase in central and northern Australia and to decrease in southern and eastern coastal areas and was projected to be higher on average than that of the 1931–70 period. The vegetation classes approximately corresponding to Australian rangelands mostly had increased NPP projections compared with the 1931–70 period. Although actual response will partially depend on human management activities, fire and extreme events, the projected increase in average NPP in 2050 indicates that Australian vegetation, particularly the rangeland vegetation, will likely be a net carbon sink rather than a carbon source by 2050, with the exception of a ‘warm-dry’ scenario.


2018 ◽  
Vol 40 (2) ◽  
pp. 167 ◽  
Author(s):  
Guozheng Hu ◽  
Zhiqiang Wan ◽  
Yali Chen ◽  
Luomeng Chao ◽  
Qingzhu Gao ◽  
...  

A randomised block experiment was conducted to study the response of plant community characteristics (biomass, density and diversity) and ecosystem carbon exchange processes to warming, increased precipitation and their combination on Stipa steppe in Inner Mongolia. Increased precipitation enhanced the effect that warming had in promoting community diversity and biomass. Increased precipitation directly increased net ecosystem exchange and gross ecosystem productivity, although ecosystem respiration and soil respiration also increased. However, warming did not have a significant effect on net ecosystem exchange and gross ecosystem productivity, whereas ecosystem respiration and soil respiration were significantly decreased by warming. All carbon flux processes had a significantly positive correlation with soil moisture. However, the carbon sequestration processes, gross ecosystem productivity and net ecosystem exchange, were significantly negatively correlated with temperature, contrary to carbon emission processes, soil respiration and ecosystem respiration. Results suggest that Stipa steppe may be benefited by future climate change, as the predicted precipitation is increasing with warming in Inner Mongolia. However, it is hard to predict the feedback of Stipa steppe to climate, because of the uncertainty in magnitude and temporal dynamics of climate change. To reveal the mechanism of the observed responses, further studies are suggested in this region on the effects of altered climate variables on plant species interactions, soil organic carbon composition, soil extracellular enzyme activity, microbial biomass and microbial respiration.


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