云雾山自然保护区环境因素对土壤水分空间分布的影响

Impacts of environmental factors on spatial distribution of soil moisture of grassland in Yunwu Mountain

选取黄土高原云雾山自然保护区天然草地,研究分析了地形因素、植被类型、降雨和封育措施对土壤水分的影响,研究结果表明:在0～100cm土壤,单点季节平均土壤含水量的空间变化主要受坡向、坡位、群落类型和封育措施的影响;在深层土壤100～300cm,相对海拔、坡位、坡向、群落类型和封育措施在控制土壤水分的再分布中具有重要作用。不同的环境因素对土壤水分空间分布影响的季节变化存在明显差异,坡度、相对海拔、坡位与土壤湿度的关系依赖于前期降雨量,土壤湿度和坡度、海拔、坡位和封育措施的相关性一般随前期降雨的增加而增大。群落类型对土壤湿度的影响与群落盖度和蒸腾速率有关,在植被盖度差异较大的5月份和蒸腾速率差异较大的7月份影响显著。坡向对土壤湿度的影响依赖于太阳辐射的变化,在太阳辐射较强烈的7月份差异显著。由于长期自然封育,草地覆盖度不断增加,其蓄水保水能力增强,对土壤水分的调节能力得到提高,从而能在一定程度上改善土壤水分条件。

This article analyzed the effect of topography attributes,vegetation type,rainfall and enclosing on the soil moisture in grassland of the Yunwu Mountain.Results showed that the environmental attributes play controlling roles in the spatial distribution of grassland soil moisture.However,the contribution of these environmental indices varies with soil depth.The dominant controls on spatial variability of the time-averaged soil moisture changed from aspect,hill-slope position,community types and enclosing in the soil depth of 0-100cm to relative elevation,hill-slope position,aspect and enclosing for deeper soil layer of 100-300cm.The dynamic behavior of influences of different environmental indices on the layer-averaged soil moisture depends on several factors.In general,the correlation of soil moisture with slope gradient,elevation,slope position and enclosing showed a more significant increase following a greater amount of antecedent precipitation.It was observed that the influence of community types on soil moisture corresponds to the difference in community coverage and transpiration,with a stronger influence in May and July when have a greater difference in vegetation.The influence of aspect depends on solar irradiation,and is significant in July having intense solar irradiation.Being enclosed for a long time,the grassland coverage gradually increased,and water holding ability is boosted up,thus vegetation accommodation ability and redistribution ability for soil water are improved.Therefore,naturally enclosed grassland controls effectively soil water transport from air to vegetation and to soil,thus improves grassland hydrologic cycle.