中文摘要：

对桂西北喀斯特峰丛洼地中耕地和退耕牧草地不同深度的土壤水分进行了1年的定位观测,采用时间序列分析法研究了降雨对土壤储水量的动态影响.结果显示,两种类型土壤表层（0～10 cm）和亚表层（10～20 cm）土壤水分含量较低但波动强烈,越到底层含水量越稳定（牧草地60～80 cm层除外）;土壤储水量具有明显的季节变化特征,旱季储水量的波动较雨季更显著,而且牧草地的剖面土壤储水量较耕地高8.5%.一般采样前1 d或2 d的降水对表层和亚表层土壤储水量的影响最大,随着土层加深,耕地在采样前3 d,牧草地在前6 d的降水对土壤储水量仍有一定影响且一般以3 d为一个波动周期.剖面土壤储水动态及其与降水序列的相关关系显示退耕还草后能延缓降雨入渗和地面蒸发,有助于喀斯特退化生态系统的土壤水分保蓄和植被恢复.

英文摘要：

In the peak-cluster depression area of karst region at northwest Guangxi province, soil moisture at different layers in cropland and grassland was observed for one year （from May 2004 to May 2005）. The soil moisture storage dynamics and its response mechanism to precipitation were studied through time series analysis. The results showed that the surface （0-10 cm） and subsurface （10-20 cm） soil moisture was low but changed violently which may be influenced by precipitation in dry season, evaporation and transpiration, root absorption and so on. Soil moisture became more stable along with the soil depth （excluding 60-80 cm soil layer in grassland）, but the soil moisture in grassland showed greater variability than that in cropland in the same layer. The soil moisture storage also changed with seasons, which was mainly influenced by precipitation, vegetation coverage, bulk density and micro-physiognomy, and the changes were more violent in dry season than in wet season. Moreover the total soil moisture storage in grassland was 8.5% higher than that in cropland. In general, the surface and subsurface soil moisture storage was mainly influenced by the precipitation two or three days before sampling. Beneath the subsurface layer, the soil moisture storage in cropland was also influenced to some extent by the precipitation three days before sampling, but six days of grassland. And the influences generally behaved with three-day-cycle. The soil moisture storage dynamics and its correlations with the precipitation showed that the ＂grain-for-green＂ could improve the soil physical properties, increase the vegetation coverage and delay the infiltration of precipitation and soil surface evaporation, which was helpful to conserve soil moisture and increase the vegetation restoration process in the karst degenerative ecosystems.