牧压梯度下高寒杂草类草甸土壤持水能力及影响因素分析

Analysis of the soil water-holding capacity in alpine forb meadow under grazing gradient and relevant influence factors

以祁连山南麓坡地夏季牧场高寒杂草类草甸为研究对象,进行了封育对照（CK,禁牧）、轻度放牧（LG）、中度放牧（MG）和重度放牧（HG）下土壤持水能力及影响因素的分析.结果表明：牧压梯度下0~10 cm层土壤最大持水量和毛管持水量均在LG最大,土壤自然贮水量LG略小于HG;而在10~20 cm和20~40 cm持水量均在HG最大,说明放牧对表层土壤的持水能力影响比深层更明显.0~10 cm层土壤容重随牧压强度增加而增大,较深层次土壤容重基本一致,表明放牧对较深层土壤容重造成的影响远小于表层.牧压梯度下植被地上地下生物量、枯落物、地表半腐殖质随放牧强度增大而减少;0~10 cm土壤有机质含量在MG最大,CK最小,10~20 cm和20~40 cm层土壤的有机质含量CK最大,说明不同土层有机质含量对牧压梯度的响应有所不同.土壤持水量与多种因素有关,主要受到地下生物量、有机质和容重等因素的影响,表明随放牧强度增大,践踏使土壤表面硬度增加,土壤空隙度减少,同时家畜过度采食使地面植被覆盖降低而增加土壤水分的蒸发.这些综合作用下引起放牧地土壤持水能力降低.

Soil water-holding capacities of the alpine forb meadow lying in the south slopes of the Qilian Mountains under different grazing intensities were analyzed. There are four grazing intensities, i. e. , banning grazing （CK）, light grazing （LG）, moderate grazing （MG） and heavy grazing （HG）. It is found that the maximal water-holding capacity and capillary water capacity are the maximum in LG, and natural water-holding capacity is the maximum in HG in the depth of 0 - 10 cm. Maximal water-holding capacity, capillary water capacity and natural water-holding capacity are the maximum in HG in the depth of 10 -20 cm and 20 -40 cm, indicating that the influence of grazing on soil water-holding is more evident in surface. Soil bulk density increases with grazing intensity in the depth of 0 -10 cm, while in deeper layer the soil bulk density is almost the same, indicating that the impact of grazing intensity on soil bulk density in deeper layer is much less than at the surface. Biomass, litter and humus decreases with grazing intensity. Organic matter is the maximum in MG and minimum in CK in the depth of 0 - 10 cm, and the maximum in CK within the depth of 10 -20 cm and 20 -40 cm, indicating that the response of organic matter to grazing intensity in different layers is not same. Soil water-holding capacity is related to various factors and is mainly influenced by belowground biomass, organic matter and soil bulk density. Cattle＇s trample leads to hardness increasing, porosity and vegetation cover decreasing, resulting in soil waterholding capacity decreases with grazing intensity.