天山北坡绿洲土壤养分对作物系统变化的响应

以天山北坡三工河流域下游绿洲作为研究区，通过对当地农作物轮作制度的调查和历史资料的分析，遴选6种主要作物组合系统，包括耐盐碱作物系统、粮食作物系统、瓜菜、经济作物-棉花、经济作物-葡萄、经济作物-啤酒花，并利用1982、1999和2003年土壤养分数据，分析干旱区绿洲土壤养分对农作物系统变化的响应.结果表明，研究区不同时期的土地政策和市场价格变化直接影响了作物系统由1年生作物向多年生作物的转变，而土壤有机质经历了先下降后上升的变化过程.1982—1999年其它作物系统向棉花的转变不利于土壤有机质的积累，而1999—2003粮食作物、棉花等向多年生作物的转变使得土壤有机质含量明显增加.三工河流域绿洲土壤总体表现为“碳汇”的过程，说明干旱区绿洲人工植被的变化有利于土壤碳的积累，土地利用呈现可持续发展的态势.

Dynamic change of soil organic matter under different cropping systems in the oasis of Tianshan Mountain northern slope.

Taking the oasis of lower Sangong River watershed in the Tianshan Mountain northern slope as study area,six kinds of cropping systems,including those of saline-alkaline tolerance crop,food crop,melon and vegetables,economic plants-cotton,economic plants-grape,and economic plants-hop,were selected based on the investigation of local cropping systems,and the dynamic change of soil organic matter under effects of these cropping systems was analyzed by using the laboratory data in 1982,1999 and 2003.The results showed that land policy and market price had a direct effect on the transformation from annuals cropping system to perennials cropping system,while soil organic matter(OM) content experienced a decline in 1982-1999 owing to the transformation from planting other crops to planting cotton,and a rise in 1999-2003 resulting from the conversion from planting food crops and cotton to planting perennial crops.On the whole,the soils in the oasis presented as a carbon sink,suggesting that the change of artificial vegetation in the oasis was helpful to the accumulation of soil OM,and beneficial to the sustainable use of farmland.