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Study On Soil Organic Carbon Stocks In National And Regional Scale Using GIS

Posted on:2005-04-12Degree:DoctorType:Dissertation
Country:ChinaCandidate:X L JieFull Text:PDF
GTID:1100360125461351Subject:Cartography and Geographic Information System
Abstract/Summary:PDF Full Text Request
Soil organic carbon (SOC) pool is an important factor in regional and global carbon cycle because it serves as a reservoir of large amounts of organic carbon. China play an important role in global carbon cycle for its large land area, the climatic variability, topographic complexity, natural ecosystem diversity, as well as human disturbance. Based on geographical information system (GIS) and soil organic carbon model (Denitrification-Decomposition model, DNDC), the national-scale SOC to the depths of 100cm and 20cm and regional-scale SOC of typical red soil regional were studied respectively. The objectives of present work are: a) to estimate total amounts of SOC in China by four approaches (including soil taxonomy, vegetation types, climate-soil-vegetation associations (CSV) and FAO-UNESCO soil subunit) and analyze the relationships by regression analyses between SOC and environmental variables, furthermore the spatial patterns of SOC in China were studied using two transects along the temperature/moisture gradient; b) to assess SOC pool and its annual change by linking the DNDC model with GIS in Yujiang county, Jiangxi province, a typical red soil area. The main research process and conclusions are as following:1. The estimates of soil organic carbon (SOC) stocks to the depths of 100cm and 20cm in China are: the soil taxonomy approach resulted in 84.4 Pg (lPg=1015g) and 27.4Pg; the vegetation types approach resulted in 69.4 Pg and 23.8Pg; the CSV approach resulted in 79.1 Pg and 26.6Pg; the FAO-UNESCO subunit approach resulted in 82.3 Pg and 26.7Pg. Although the soil taxonomy and FAO-UNESCO unit approaches resulted in similar totals, the soil taxonomy is more useful because FAO-UNESCO subunit did not take into account the regional differences in microclimate, parent material and land cover for soils of a particular subunit (Batjes 1996). The vegetation types approach did not give reliable estimates mainly for the unreliable area estimates, but the SOC density of each vegetation type is useful when evaluate the effects of vegetation changes on SOC.2. The amount of carbon varied significantly at different districts in China. Northeast China, the south and east of Qinghai-Tibet Plateau and southwest China had high carbon density. Tarim Basin, Caidam Basin, Junggar Basin and other desertification districts had low carbon density. This distribution showed an important climatic influence. Along the moisture gradient transect (North China, N 42), the trend of SOC is consistent with precipitation. Along the temperature gradient transect (Eastern China, E 110çš› 130?, the sequence of SOC is: north temperate zone> temperate zone> subtropical and tropical zone> south temperate zone, which mainly resulted from the integration effect of precipitation and temperature.3. The regression results of SOC against environmental variables demonstrate that generally SOC increases with increasing precipitation but decreases with increasing temperature, and elevation plays a positive effect on SOC. Furthermore, carbon accumulation in different areas depends .differently on different environmental variables, whose impact on SOC is becoming stronger when the research gets more specific. However, human activities reduce the influence of environmental variables on SOC.4. By integrating the .GIS database with DNDC model, the SOC stocks in the depths of 20cm of Yujiang County were estimated to be 3.52.109kg, and the average soil organic carbon density was 4.24 kg m-2.The sequence of the SOC densities of land uses is: irrigated paddy-rice> upland-rice > orchard > forests > vegetable land > cropland > grassland. The average SOC density of paddy soils and red soils are 5.51 kg m"2 and 3.05 kg m"2 respectively.:5. Unconsidering the effects of soil erosion, the annual variation of the SOC stocks of Yujiang County was +8.63107kg.Cropland and vegetable land lost 0.04 kg m"2 and 0.01 kg m'2 respectively whereas orchard, grassland and forests gained 0.54 kg m"2,0.21 kg m"2,and 0.17 kg m"2 respectively.
Keywords/Search Tags:soil organic carbon pool, spatial analysis, environmental variables, Denitrification-Decomposition model, G1S, Yujiang county
PDF Full Text Request
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