Effects of desertification on C and N storages in grassland ecosystem on Horqin sandy land
沙漠化对科尔沁沙质草地生态系统碳氮储量的影响

Sandy grassland is widespread in northern China,where desertification is very common because of overgrazing and estrepement.However,little is known about the effects of desertification on grassland C and N storages in this region.A field survey was conducted on Horqin sandy grassland,and desertification gradients were established to evaluate the effects of desertification on C and N storages in soil,plant,and litter.The results showed that desertification had deep effects on the contents and storages of grassland C and N.The C and N contents and storages in the grassland decreased significantly with increasing desertification degree.Comparing with those in un-desertified grassland,the C and N contents in lightly,moderately,heavily,and severely desertified grasslands decreased by 56.06% and 48.72%,78.43% and 74.36%,88.95% and 84.62%,and 91.64% and 84.62% in 0-100 cm soil layer,and by 8.61% and 6.43%,0.05% and 25.71%,2.58% and 27.14%,and 8.61% and 27.86% in plant components,respectively.Relevantly,the C and N storages decreased by 50.95% and 43.38%,75.19% and 71.04%,86.76% and 81.48%,and 91.17% and 83.17% in plant underground components in 0-100 cm soil layer,and by 25.08% and 27.62%,30.90% and 46.55%,73.84% and 80.62%,and 90.89% and 87.31% in plant aboveground components,respectively.In 2000,the total area of desertified grassland in Horqin sandy land was 30152.7 km2,and the C and N loss via desertification reached up to 107.53 and 9.97 Mt,respectively.Correlation analysis indicated that the decrease of soil C and N contents was mainly come from the decreased soil fine particles caused by wind erosion in the process of desertification,and the degradation of soil texture-and nutrient status led finally to the rapid decrease of C and N storages in plant biomass and litter.