scholarly journals Effects of Cropland Conversion and Climate Change on Agrosystem Carbon Balance of China’s Dryland: A Typical Watershed Study

2018 ◽  
Vol 10 (12) ◽  
pp. 4508 ◽  
Author(s):  
Chaofan Li ◽  
Qifei Han ◽  
Geping Luo ◽  
Chengyi Zhao ◽  
Shoubo Li ◽  
...  
Keyword(s):  
Climate Change ◽  
Driving Forces ◽  
Arable Land ◽  
Northwest China ◽  
Mountain Lake ◽  
Agricultural Sustainability ◽  
Desert Grassland ◽  
Organic C ◽  
C Balance ◽  
C Cycle

Remarkable warm‒wet climate shifts and intensive cropland expansion strongly affected carbon (C) cycle and threaten agricultural sustainability in northwest China. In this study, we integrated a process-based ecosystem model and an empirical C bookkeeping model to investigate the coupled and isolated effects of arable land conversions and climate change (CLM) on regional C balance in a typical watershed of northwest China. Results revealed that the farmland area increased by 3367.31 km2 during 1979–2014. The combined effects of CLM with net cropland expansion enlarged the vegetation C (VEGC) and the soil organic C (SOC) stock by 2.83 and 11.83 Tg, respectively, and were strongest in 2008–2014. The conversions between desert grassland and cropland were the major driving forces for regional C balance. Cropland expansion shared equal effects on VEGC increase with CLM, but its effect on SOC increment was 53 times larger than CLM’s. VEGC was more responsive to CLM, whereas SOC gained more benefits from land management. The C sink from reclamation suffered from high water consumption and is facing great threats due to glaciers and mountain lake shrinking and groundwater overpumping. Water-saving irrigation techniques and environmentally friendly water use strategies are essential for local agricultural sustainability.

Carbon dioxide and methane fluxes from arctic mudboils

2010 ◽  
Vol 90 (3) ◽  
pp. 441-449 ◽  
Author(s):  
K S Wilson ◽  
E R Humphreys
Keyword(s):  
Climate Change ◽  
Carbon Dioxide ◽  
Vascular Plant ◽  
Organic Matter Content ◽  
Net Ecosystem Exchange ◽  
The Arctic ◽  
Plant Colonization ◽  
Patterned Ground ◽  
Organic C ◽  
C Balance

Climate change is expected to alter the Arctic’s carbon (C) balance and changes in these C-rich ecosystems may contribute to a positive feedback on global climate change. Low-center mudboils, a form of patterned ground in the Arctic, are distinct landforms in which the exchange of greenhouse gases between the atmosphere and soil has not been fully characterized, but which may have an important influence on the overall C balance of tundra ecosystems. Chamber systems were used to sample net ecosystem exchange of CO2 (NEE) and CO2 and CH4 effluxes along a 35-m transect intersecting two mudboils in a wet sedge fen in Canada’s Southern Arctic (lat. 64°52′N, long. 111°34′W) during the summer months in 2008. Mudboil features gave rise to dramatic variations in vegetation, soil temperature and thaw depth, and soil organic matter content along this transect. Variations in NEE were driven by variations in the amount of vascular vegetation, while CO2 and CH4 effluxes were remarkably similar among the two mudboil (CO2 effluxes: 1.1 ± 0.9 and 1.4 ± 0.7 µmol m-2 s-1; CH4 effluxes: 83.1 ± 189.4 and 23.1 ± 9.4 nmol m-2 s-1, ± 1 standard deviation) and the sedge fen (CO2 effluxes: 1.6 ± 0.7 mol m-2 s-1 ; CH4 effluxes: 28.0 ± 62.0 nmol m-2 s-1) sampling areas. Vegetation appeared to play an important role in limiting temporal variations in CH4 effluxes through plant mediated transport in both mudboil and sedge fen sampling areas. One of the mudboils had negligible vascular plant colonization presumably due to more active frost heave processes. The relatively high CO2 and CH4 efflux in this mudboil area was speculated to be a result of growth and decomposition of cryptogamic organisms, inflow of dissolved organic C, and warmer soil temperatures. Key words: Patterned ground, nonsorted circle, tundra, net ecosystem exchange, methane, carbon dioxide

scholarly journals Influence of climate change factors on carbon dynamics in northern forested peatlands

2006 ◽  
Vol 86 (Special Issue) ◽  
pp. 269-280 ◽  
Author(s):  
C. C. Trettin ◽  
R. Laiho ◽  
K. Minkkinen ◽  
J. Laine
Keyword(s):  
Climate Change ◽  
Organic Matter ◽  
Management Practices ◽  
Atmospheric Temperature ◽  
Soil C ◽  
Altered Hydrology ◽  
Biogeochemical Models ◽  
C Dynamics ◽  
C Balance ◽  
C Cycle

Peatlands are carbon-accumulating wetland ecosystems, developed through an imbalance among organic matter production and decomposition processes. Soil saturation is the principal cause of anoxic conditions that constrain organic matter decay. Accordingly, changes in the hydrologic regime will affect the carbon (C) dynamics in forested peatlands. Our objective is to review ecological studies and experiments on managed peatlands that provide a basis for assessing the effects of an altered hydrology on C dynamics. We conclude that climate change influences will be mediated primarily through the hydrologic cycle. A lower water table resulting from altered precipitation patterns and increased atmospheric temperature may be expected to decrease soil CH4 and increase CO2 emissions from the peat surface. Correspondingly, the C balance in forested peatlands is also sensitive to management and restoration prescriptions. Increases in soil CO2 efflux do not necessarily equate with net losses from the soil C pool. While the fundamentals of the C balance in peatlands are well-established, the combined affects of global change stressors and management practices are best considered using process-based biogeochemical models. Long-term studies are needed both for validation and to provide a framework for longitudinal assessments of the peatland C cycle. Key words: Peatland, carbon cycle, methane, forest, wetland.

scholarly journals Changes In Soil Properties Across A Hydrological Gradient In Saladas From Northeast Spain: Implications For Soil Carbon Stocks, CO2 Efflux And Microbial Communities In A Warming World.

2021 ◽  
Author(s):  
Andrew Thomas ◽  
Stephen Tooth ◽  
S. Lan ◽  
Thomas Holt ◽  
Ian Saunders ◽  
...  
Keyword(s):  
Climate Change ◽  
Microbial Communities ◽  
Soil Carbon ◽  
Soil Microbial Communities ◽  
Spatial And Temporal Variability ◽  
Co2 Efflux ◽  
Organic C ◽  
C Cycle ◽  
C Stocks ◽  
Warming World

Abstract Numerous permanent and temporary wetlands occur throughout the world’s drylands. Although characterised by diverse hydroperiods, these wetlands in drylands are typically hotspots of biological activity and productivity. The healthy functioning and possibly even existence of many wetlands in drylands, however, is threatened by desiccation resulting from a combination of climate change and human disturbance. Near Alcañiz in arid northeast Spain, three adjacent saladas (playas) with contrasting hydroperiods provide an opportunity to investigate how moisture availability affects their soil carbon (C) stocks, CO2 efflux, and microbial communities. Frequent inundation and/or near-permanent soil saturation supports the generation of organic C from a range of different sources. Soil inorganic C was greatest on the driest salada (3.8 %) compared to the wetter saladas (3.0 % and 2.1 %) owing to evaporative concentration and the reaction of CO2 with available Ca2+, Mg2+ and Na+ ions. CO2 efflux was greatest at intermediate moisture levels (142 mg CO2 m-2 hr-1), but the spatial and temporal variability in CO2 efflux on salada surfaces is very high, demonstrating the need for intensive sampling regimes to provide realistic estimates of their contribution to atmospheric CO2 exchanges. Different microbial community structures also characterise each salada. The saladas near Alcañiz, and many other similar features in northeast Spain, are renowned for their rare and threatened flora and fauna, yet their soil C cycle characteristics and soil microbial communities provide additional reasons to monitor the impacts of climate change and protect these vulnerable environments from further anthropogenic disturbances.

scholarly journals Separating the impacts of climate change and human activities on actual evapotranspiration in Aksu River Basin ecosystems, Northwest China

2018 ◽  
Vol 49 (6) ◽  
pp. 1740-1752 ◽  
Author(s):  
Peng Yang ◽  
Jun Xia ◽  
Chesheng Zhan ◽  
Xuejuan Chen ◽  
Yunfeng Qiao ◽  
...  
Keyword(s):  
Climate Change ◽  
Wind Speed ◽  
River Basin ◽  
Human Activity ◽  
Arable Land ◽  
Northwest China ◽  
Actual Evapotranspiration ◽  
Forest Land ◽  
Aksu River Basin ◽  
Impacts Of Climate Change

Abstract Separating the impacts of climate change and human activity on actual evapotranspiration (ET) is important for reducing comprehensive risk and improving the adaptability of water resource systems. In this study, the spatiotemporal distribution of actual ET in the Aksu River Basin, Northwest China, during the period 2000–2015 was evaluated using the Vegetation Interfaces Processes model and Moderate Resolution Imaging Spectroradiometer-Normalized Difference Vegetation Index. The impact of climate change and human activity on actual ET were separated and quantified. The results demonstrated that: (1) the annual pattern of actual ET per pixel exhibited the highest values for arable land (average 362.4 mm/a/pixel), followed by forest land and grassland (average of 159.6 and 142.8 mm/a/pixel, respectively). Significant increasing linear trends (p < 0.05) of 3.2 and 1.8 mm/a were detected in the arable land and forest land time series, respectively; (2) precipitation was the most significant of the selected climate factors (precipitation, average temperature, sunshine duration, and wind speed) for all ecosystems. The second most significant was wind speed; (3) human activity caused 89%, 98%, and 80% of the changes in actual ET of forest, grass, and arable land, respectively, while climate change caused 11%, 2%, and 20% of the changes in actual ET, in the Aksu River Basin during 2000–2015.

scholarly journals The sensitivity of carbon turnover in the Community Land Model to modified assumptions about soil processes

2014 ◽  
Vol 5 (1) ◽  
pp. 211-221 ◽  
Author(s):  
B. Foereid ◽  
D. S. Ward ◽  
N. Mahowald ◽  
E. Paterson ◽  
J. Lehmann
Keyword(s):  
Climate Change ◽  
Organic Matter ◽  
Temperature Sensitivity ◽  
Priming Effect ◽  
Data Set ◽  
Organic C ◽  
Community Land Model ◽  
Fresh Organic Matter ◽  
C Cycle ◽  
C Stocks

Abstract. Soil organic matter (SOM) is the largest store of organic carbon (C) in the biosphere, but the turnover of SOM is still incompletely understood and not well described in global C cycle models. Here we use the Community Land Model (CLM) and compare the output for soil organic C stocks (SOC) to estimates from a global data set. We also modify the assumptions about SOC turnover in two ways: (1) we assume distinct temperature sensitivities of SOC pools with different turnover time and (2) we assume a priming effect, such that the decomposition rate of native SOC increases in response to a supply of fresh organic matter. The standard model predicted the global distribution of SOC reasonably well in most areas, but it failed to predict the very high stocks of SOC at high latitudes. It also predicted too much SOC in areas with high plant productivity, such as tropical rainforests and some midlatitude areas. Total SOC at equilibrium was reduced by a small amount (<1% globally) when we assume that the temperature sensitivity of SOC decomposition is dependent on the turnover rate of the component pools. Including a priming effect reduced total global SOC more (6.6% globally) and led to decreased SOC in areas with high plant input (tropical and temperate forests), which were also the areas where the unmodified model overpredicted SOC (by about 40%). The model was then run with climate change prediction until 2100 for the standard and modified versions. Future simulations showed that differences between the standard and modified versions were maintained in a future with climate change (4–6 and 23–47 Pg difference in soil carbon between standard simulation and the modified simulation with temperature sensitivity and priming respectively). Although the relative changes are small, they are likely to be larger in a fully coupled simulation, and thus warrant future work.

scholarly journals Organic carbon stocks in Mediterranean soil types under different land uses (Southern Spain)

2012 ◽  
Vol 4 (2) ◽  
pp. 1095-1128 ◽  
Author(s):  
M. Muñoz-Rojas ◽  
A. Jordán ◽  
L. M. Zavala ◽  
D. De la Rosa ◽  
S. K. Abd-Elmabod ◽  
...  
Keyword(s):  
Climate Change ◽  
Land Use ◽  
Arable Land ◽  
C Sequestration ◽  
Organic C ◽  
Soil C ◽  
Digital Elevation ◽  
Mediterranean Systems ◽  
Mitigate Climate Change ◽  
Land Use And Management

Abstract. Soil C sequestration through changes in land use and management is one of the sustainable and long-term strategies to mitigate climate change. This research explores and quantifies the role of soil and land use as determinants of the ability of soils to store C along Mediterranean systems. Detailed studies of soil organic C (SOC) dynamics are necessary in order to identify factors determining fluctuations and intensity of changes. In this study, SOC contents from different soil and land use types have been investigated in Andalusia (S Spain). We have used soil information from different databases, as well as land use digital maps, climate databases and digital elevation models. The average SOC content for each soil control section (0–25, 25–50 and 50–75 cm) was determined and SOC stocks were calculated for each combination of soil and land use type, using soil and land cover maps. The total organic C stock in soils of Andalusia is 415 Tg for the upper 75 cm, with average values ranging from 15.9 Mg C ha−1 (Solonchaks under "arable land") to 107.6 Mg C ha−1 (Fluvisols from "wetlands"). Up to 55% of SOC accumulates in the top 25 cm of soil (229.7 Tg). This research constitutes a preliminary assessment for modelling SOC stock under scenarios of land use and climate change.

scholarly journals Organic carbon stocks in Mediterranean soil types under different land uses (Southern Spain)

Solid Earth ◽  
2012 ◽  
Vol 3 (2) ◽  
pp. 375-386 ◽  
Author(s):  
M. Muñoz-Rojas ◽  
A. Jordán ◽  
L. M. Zavala ◽  
D. De la Rosa ◽  
S. K. Abd-Elmabod ◽  
...  
Keyword(s):  
Climate Change ◽  
Land Use ◽  
Arable Land ◽  
C Sequestration ◽  
Southern Spain ◽  
Organic C ◽  
Soil C ◽  
C Stocks ◽  
Mediterranean Systems ◽  
Land Use And Management

Abstract. Soil C sequestration through changes in land use and management is one of the sustainable and long-term strategies to mitigate climate change. This research explores and quantifies the role of soil and land use as determinants of the ability of soils to store C along Mediterranean systems. Detailed studies of soil organic C (SOC) dynamics are necessary in order to identify factors determining fluctuations and intensity of changes. In this study, SOC contents from different soil and land use types have been investigated in Andalusia (Southern Spain). We have used soil information from different databases, as well as land use digital maps, climate databases and digital elevation models. The average SOC content for each soil control section (0–25, 25–50 and 50–75 cm) was determined and SOC stocks were calculated for each combination of soil and land use type, using soil and land cover maps. The total organic C stocks in soils of Andalusia is 415 Tg for the upper 75 cm, with average values ranging from 15.9 Mg C ha−1 (Solonchaks under "arable land") to 107.6 Mg C ha−1 (Fluvisols from "wetlands"). Up to 55% of SOC accumulates in the top 25 cm of soil (229.7 Tg). This research constitutes a preliminary assessment for modelling SOC stock under scenarios of land use and climate change.

scholarly journals Effects of model assumptions for soil processes on carbon turnover in the earth system

2013 ◽  
Vol 4 (2) ◽  
pp. 1091-1116
Author(s):  
B. Foereid ◽  
D. S. Ward ◽  
N. Mahowald ◽  
E. Paterson ◽  
J. Lehmann
Keyword(s):  
Climate Change ◽  
Organic Matter ◽  
Temperature Sensitivity ◽  
Priming Effect ◽  
Tropical Rain Forests ◽  
Data Set ◽  
Organic C ◽  
Community Land Model ◽  
Fresh Organic Matter ◽  
C Cycle

Abstract. Soil organic matter (SOM) is the largest store of organic carbon (C) in the biosphere, but still the turnover of SOM is incompletely understood and not well described in global C cycle models. Here we use the Community Land Model (CLM) and compare the output for soil organic C (SOC) to estimates from a global data set. We also modify the assumptions about SOM turnover in two ways: (1) we assume distinct temperature sensitivities of SOC pools with different turnover time and (2) we assume a priming effect, such that decomposition rate of native SOM increases in response to a supply of fresh organic matter. The standard model predicted the global distribution of SOM reasonably well in most areas, but it failed to predict the very high stocks of SOM at high latitudes. It also predicted somewhat too much SOC in areas with high plant productivity, such as tropical rain forests and some mid-latitude areas. Assuming that the temperature sensitivity of SOC decomposition is dependent on the turnover rate of component pools reduced total SOC at equilibrium by a relatively small amount (<1% globally). Including a priming effect reduced total global SOC more (6.6% globally) and tended to decrease SOC most in areas with high plant input (tropical and temperate forests), which were also the areas where the unmodified model overpredicted SOC (by about 40%). The model was then run with climate change prediction for the standard and modified versions. Future simulations showed that differences between the standard and modified versions were maintained in a future with climate change (4–6 and 23–47 Pg difference in soil carbon between standard simulation and the modified with temperature sensitivity and priming respectively).

scholarly journals Dynamics of soil organic carbon in the steppes of Russia and Kazakhstan under past and future climate and land use

2021 ◽  
Vol 21 (3) ◽  
Author(s):  
Susanne Rolinski ◽  
Alexander V. Prishchepov ◽  
Georg Guggenberger ◽  
Norbert Bischoff ◽  
Irina Kurganova ◽  
...  
Keyword(s):  
Climate Change ◽  
Land Use ◽  
Organic Carbon ◽  
Land Use Change ◽  
Soil Organic Carbon ◽  
Arable Land ◽  
Future Climate ◽  
Future Climate Change ◽  
Climate Scenarios ◽  
The Impact

AbstractChanges in land use and climate are the main drivers of change in soil organic matter contents. We investigated the impact of the largest policy-induced land conversion to arable land, the Virgin Lands Campaign (VLC), from 1954 to 1963, of the massive cropland abandonment after 1990 and of climate change on soil organic carbon (SOC) stocks in steppes of Russia and Kazakhstan. We simulated carbon budgets from the pre-VLC period (1900) until 2100 using a dynamic vegetation model to assess the impacts of observed land-use change as well as future climate and land-use change scenarios. The simulations suggest for the entire VLC region (266 million hectares) that the historic cropland expansion resulted in emissions of 1.6⋅ 1015 g (= 1.6 Pg) carbon between 1950 and 1965 compared to 0.6 Pg in a scenario without the expansion. From 1990 to 2100, climate change alone is projected to cause emissions of about 1.8 (± 1.1) Pg carbon. Hypothetical recultivation of the cropland that has been abandoned after the fall of the Soviet Union until 2050 may cause emissions of 3.5 (± 0.9) Pg carbon until 2100, whereas the abandonment of all cropland until 2050 would lead to sequestration of 1.8 (± 1.2) Pg carbon. For the climate scenarios based on SRES (Special Report on Emission Scenarios) emission pathways, SOC declined only moderately for constant land use but substantially with further cropland expansion. The variation of SOC in response to the climate scenarios was smaller than that in response to the land-use scenarios. This suggests that the effects of land-use change on SOC dynamics may become as relevant as those of future climate change in the Eurasian steppes.

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