【摘要】 研究了高山草地土壤有机碳、氮含量以及土壤团聚体稳定性随开垦年限而变化的动力学过程.与未开垦草地土壤相比较,开垦导致的土壤总有机碳在开垦最初的5 a内迅速降低了17%,此后降低速度趋于减缓,至开垦约70 a时降低了34%.不同粒径组分的有机碳降低的时间尺度不同,粗组分(particulate)有机碳在开垦后的5 a内显著降低,而矿物结合态(mineral-associated)有机碳则最早在开垦33 a以后开始降低.在亚高山草地开垦过程中土壤氮含量的降低与有机碳的降低具有相似的趋势;土壤团聚体稳定性的降低主要在开垦开始的5 a之内,其后以至开垦33 a以上团聚体的稳定性基本保持稳定.除机械扰动的破坏作用之外,土壤粗组分有机碳含量的降低是开垦耕种导致的土壤团聚体稳定性降低的主要原因之一.更多还原

【Abstract】 The dynamics of soil organic C,N and aggregate stability in sub-alpine grassland soil along a chronosequence of cultivation were investigated.Compared with uncultivated grassland soil,cultivation decreased total soil organic C concentration by 17 % within foremost five-years after cropping commenced and by 35 % up to 70 years of cultivation.Cultivation-induced reduction in particulate organic C mainly occurred in initial five-years,whereas mineral-associated organic C fraction began to show a significant decline at the year 33 after cultivation commenced.This indicated that different particle-size organic C fractions decreased on different time-scales when grassland soil was experienced cultivation in a sub-alpine environment.Decrease in soil total N concentration showed similar trend with total soil organic C.The soil disaggregation mainly happened in the first five years after cultivation started and thereafter soil aggregate stability was maintained.It was suggested that a rapid decrease in particulate organic C fraction be mainly responsible for the degradation in soil aggregate stability during the course of cultivation,in addition to tillage disruption.更多还原