Study On Spatial Distribution Characteristics Of Soil Organic Carbon Reservoir In Tibet

This paper studied on spatial distribution characteristics of soil organic carbon reservoir in Tibet. The research area is on the southeast of China, about 120.5×10⁴km², taking 12.5% of the whole country's area including Qamdo, Naqu, Linzhi, Shannan, Zigaze, Lhasa and Ali. According to 2,607 soil profiles and 1:2,000,000 digital soil map, reckoned the soil organic carbon pool(SOCP) by the popular soil type method, analyzed the spatial distributing characteristics of Tibet soil organic carbon density (SOCD) and its storage, and also analyzed the effect factors of the Tibet SOCP primarily.The comprehensive and exact datum of soil organic matter and gravel is the basis to count the SOCD and SOCR veraciously. Whereas the obviously regional change of SOCD and high gravel content, the count made soil gravel calibration by area as soil subgroup a unit. The average SOCD of soil surface layer(0²0cm)and whole profile in all Tibet taken by the method mentioned before are separately 4.27kg m^-2 and 7.48kg m^-2, which is lower than the global average (5kg m^-2 in surface layer and 12.1kg m^-2 in whole profile), also is lower than the national average(5.7kg m^-2 in natural surface layer, 3kg m^-2 in plough layer, 8.0-10.5 kg m^-2 in whole profile), is one of the soil low carbon density area in China. This result is lower than that in literature, but is more fit the fact.SOCD in different soil types changed a lot, taking zonal soil which is more than 95% of the area for example. The SOCD (kg m^-2) changed in this order: Ferro-allitic soils (29.2) > Eluvial soils (16.6) > Alpine meadow soils (12.2) > Semi-eluvial soils (9.2) > Alpine steppe soils (3.7) > Frigid frozen soils (1.6) and Alpine desert soils (1.3). Meanwhile, the proportion which surface layer (0²0cm) SOCD in the whole profile's is above 50% mostly, 57% in average. It reflected that SOCP is in instability.SOCD of Tibet soil has unique horizontal distribution, which decreasing gradually from southeast to northwest. So it can be divided into 4 carbon density zones as high( I ), medium (II), low (III), extra-low ones (IV), the average SOCD is respective 21 kg m^-2,10 kg m^-2,4...