沙漠化对科尔沁沙质草地生态系统碳氮储量的影响

Effects of desertification on C and N storages in grassland ecosystem on Horqin sandy land

通过野外调查,研究了沙漠化对科尔沁沙质草地生态系统碳、氮储量的影响.结果表明:沙漠化对草地碳、氮含量和储量具有显著影响,随着草地沙漠化的进程,草地碳、氮含量和储量明显下降.与非沙漠化草地相比,轻度、中度、重度和严重沙漠化草地0～100cm深土壤有机碳和全氮含量分别下降了56.06%和48.72%、78.43%和74.36%、88.95%和84.62%、91.64%和84.62%,植物组分中的碳、氮含量分别下降了8.61%和6.43%、0.05%和25.71%、2.58%和27.14%、8.61%和27.86%;轻度、中度、重度和严重沙漠化草地地上植物组分中的碳、氮储量分别下降了25.08%和27.62%、30.90%和46.55%、73.84%和80.62%、90.89%和87.31%,0～100cm深地下植物组分中碳和全氮储量分别下降了50.95%和43.38%、75.19%和71.04%、86.76%和81.48%、91.17%和83.17%.2000年科尔沁沙地沙漠化草地总面积为30152.7km2,因沙漠化损失的碳、氮总储量高达107.53和9.97Mt.草地碳、氮含量的下降主要源于风蚀过程中土壤细颗粒的损失.土壤的粗化和贫瘠化最终导致了植物和凋落物中碳、氮储量的明显下降.

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 km^2, 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.