黄土丘陵沟壑区不同降水年型下土壤水分动态

Dynamic changes of soil moisture in loess hilly and gully region under effects of different yearly precipitation patterns.

采用定位监测法,对黄土丘陵沟壑区不同降水年型下旱农坡地、刺槐林、沙棘灌丛和白羊草地土壤水分的时空变化规律进行了分析.结果表明,降水年型对研究区不同植被类型土壤水分的季节变化和剖面垂直变化均有一定影响.旱农坡地平水年土壤水分的季节变化平缓;枯水年雨季前土壤水分缓慢减小,雨季后显著增加;丰水年则整体增加,且雨季后增加明显.刺槐林、沙棘灌丛和白羊草地平水年土壤水分的季节变化表现为整体降低;枯水年沙棘灌丛土壤水分先减后增,刺槐林与白羊草地呈"W"型曲线变化,两个最低值均出现在6月和8月;丰水年沙棘灌丛和刺槐林土壤水分的季节变化呈"V"型,白羊草地的波动较大,最低值出现在8月.旱农坡地枯水年的土壤水分活跃层和次活跃层深度较平水年下移,丰水年次活跃层消失;丰水年和枯水年,刺槐林和白羊草地土壤水分活跃层深度均较平水年下移,沙棘灌丛则上移.

Based on field determinations, the dynamic changes of soil moisture in dry farmland, Robinia pseudoacacia forestland, Hippophae shrubland and Bothriochloa ischaemum grassland in loess hilly and gully region under effects of different yearly precipitation patterns were analyzed. The results showed that yearly precipitation pattern had definite effects on the seasonal variation and profile distribution of soil moisture. In normal year, soil moisture in dry farmland had a gentle seasonal variation; in dry year, it decreased slowly before rainy season but increased markedly after rainy season; while in rainy year, it had an overall increase and the increment was remarkable after rainy season. The soil moisture in R. psendoacacia forestland, Hippophae shrubland, and B. ischaemun grassland decreased as a whole in normal year. In dry year, soil moisture in Hippophae shrubland decreased first and increased then, while that in R. psendoacacia forestland and B. ischaemun grassland varied in ＂W＂ type, with the minimum in June and August. In rainy year, the seasonal variation of soil moisture in R. psendoacacia forestland and Hippophae shrubland presented ＂V＂ type, and that in B. ischaemu grassland fluctuated markedly, with the minimum in August. In dry farmland, the active and sub-active layers of soil moisture were deeper in dry year than in normal year, and the sub-active layer disappeared in rainy year. In R. psendoacacia forestland and B. ischaemu mal year; grassland, the active layer of soil moisture was deeper in dry and rainy years than in norwhile in Hippophae shrubland, this active laver was shallower in dry and rainy years than in normal year.