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近半个世纪前,中国西北干旱区人类大规模的水土开发活动使得流域下部的荒漠覆被土地转变成了人工绿洲,强烈的人类耕作活动使得人工绿洲土壤有机碳库发生了显著变化。以干旱区典型的三工河流域下部的人工绿洲为例,基于CENTURY模型,研究人工绿洲开发前后及农业管理模式变化对表层土壤有机碳库(0-20cm)的影响。CENTURY模型模拟结果表明:(1)研究区荒漠灌木林地开垦为人工绿洲后,在最初的2a土壤总有机碳(TOC)快速增加,随后呈逐渐下降的趋势;(2)研究区人工绿洲在被开发后50a的连续耕作下,平均土壤TOC呈先增后减再增的“N”型变化趋势,但最终土壤TOC超过了原始自然状态下的TOC,而且2008年土壤TOC比原始荒漠状态增加7.74%,说明研究区表层土壤有机碳总体呈“碳汇”趋势。尤其在研究区实施了免耕、秸秆粉碎还田、科学测土配方施肥等保护性耕作措施后,土壤固碳效应明显,这完全不同于热带森林、中国北部温带半干旱草原及非洲Savanna半干旱稀树草原开垦为耕地后土壤有机碳大量损失的结论。
Nearly half a century ago, man-made large-scale water and soil exploitation activities in the arid region of northwestern China turned the desertified land in the lower part of the basin into an artificial oasis, and intense human activities led to significant changes in the soil organic carbon pool in the artificial oasis. Taking a typical artificial oasis in the lower part of Sangong River basin as an example, this paper studies the influence of changes of artificial oasis on the surface soil organic carbon pool (0-20cm) based on the CENTURY model. The results of CENTURY model simulation showed that: (1) After the desert shrub land was reclaimed as an artificial oasis in the study area, TOC of the soil in the initial 2a increased rapidly and then decreased gradually; (2) In the study area, After continuous cultivation for 50 years after development, the average soil TOC showed the trend of “N” first increasing and then decreasing, but the TOC of the soil finally exceeded the original natural state TOC, and the TOC of soil in 2008 was higher than the original desert state An increase of 7.74%, indicating that the total surface organic carbon in the study area showed a “carbon sink” trend. Especially in the study area after the implementation of tillage, straw crushing and returning to fields, scientific soil testing and other conservation tillage measures, soil carbon sequestration effect is obvious, which is completely different from the tropical forests, temperate semiarid grassland in northern China and Africa Savanna semi-arid Conclusions are drawn from the massive loss of soil organic carbon after reclamation of savannah to arable land.