黄河源区草地退化对土壤持水性影响的初步研究

Preliminary Study for the Influences of Grassland Degradation on Soil Water Retention in the Source Region of the Yellow River

在黄河源区草地退化严重的玛沁县军牧场地区,采用不同草地退化样地对比的方法,开展草地退化对土壤持水性影响研究。结果表明:①毛管持水量和饱和含水量在0～10 cm土层以无退化草地最大,极度退化草地最小,而在10～20 cm土层,两者在不同退化草地之间差异不明显,仍以极度退化草地最小,但两者在20～30 cm土层以轻度和重度退化草地较大,无退化和中度退化草地相对较小;②在土壤表层(0～10 cm),无退化草地的田间持水量远大于其他退化草地,轻度和重度退化草地田间持水量较大,极度退化草地最小,而在10 cm以下土层,田间持水量以轻度和重度退化草地较大,无退化和中度退化草地相对较小;③各土壤持水量与土壤理化性质关系密切,主要受容重、总碳、有机质和总氮这4个因素影响;④不同草地退化程度下地表覆被状况、植物根系生物量以及分布特征引起土壤容重、有机质等发生变化,可能是进一步导致土壤持水性差异的主要原因。研究可为区域草地退化对土壤水文生态效应影响提供科学依据。

The influences of grassland degradation on soil water retention were studied in the Jun- muchang region of Maqin County, where is in the source region of the Yellow River, and the grassland degradation in this area is very serious. The methods of quadrates comparing different grassland degradation degrees were chosen in this research. Some important conclusions were obtained from this study, which mainly contained four aspects as follows. 1 ） Capillary water capacity and saturated water content were the biggest in the nondegradated grassland with a soil depth of 0 - 10 cm but the smallest in the extremely degradated grassland. While the capillary water capacity and saturated water content had no significant differences for both cases in 10 -20 cm, and they were also the minimum in the extremely degradated grassland. However, the capillary water capacity and saturated water content in 20 -30 cm were larger in the slight and serious degradated grassland, and they were relatively low in the non and moderate degradated grassland. 2 ） The field water capacity in the non-degradated grassland was much bigger than other grassland with different degradated degrees in the 0 - 10 cm soil depth. The field water capacity was relatively large in the slight and serious degradated grassland, but it was the minimum in the extremely deg- radated grassland. The field water capacity was relatively large in the slight and serious ed grassland below a soil depth of 10 cm, and it was fairly low in the non and moderate degradat- degradat- ed grassland. 3 ） Soil water retention had a close relationship with soil physiochemical properties, and they were mainly affected by the bulk density, organic matter, total nitrogen and total carbon. 4） The landcover, biomass amount and distribution characteristics of plant roots with different grassland degradation degrees could induce the changes of bulk density, organic matter and so on, and would be possible to result in the changes of soil water retention. This research could provide the scientific basis for the study of the impacts of grassland vegetation degradation on soil hydrological and ecological effects.