放牧强度对典型草原积雪及融雪土壤水分的影响

Effects of grazing intensities on snow accumulation and soil water after snowmelt in a typical grassland

积雪是影响草原春季土壤水分的重要因素,积雪量主要受降雪量和积雪再分配影响。然而,很少有研究探讨放牧对积雪量及融雪后土壤水分的潜在影响。研究不同放牧强度对典型草原积雪量及春季融雪后土壤水分的影响及机制,为草原的合理利用与优化管理提供科学依据。基于锡林郭勒典型草原长期控制放牧试验平台,于2016年和2017年,对禁牧(G0)、轻度放牧(G0.75)、中度放牧(G1.50)、重度放牧(G2.25)、极重度放牧(G3.00)等5种放牧处理下的植被、积雪量和土壤水分进行测定。结果表明,随着放牧强度的增加,积雪量逐渐减少,并且2016年的平均积雪量比2017年高57.63%。具体而言,与禁牧处理相比,极重度放牧使2016年和2017年的积雪量减少了75.20%和74.53%。随着放牧强度的增加,春季土壤水分呈逐渐减少的趋势。2016年和2017年禁牧处理的春季土壤水分(0—40 cm)为14.91%和10.70%,是极重度放牧处理的1.5倍和1.4倍。土壤水分与植被特征(地上生物量和植被高度)和积雪(积雪量和积雪深度)呈显著正相关(P<0.05)。相比底层土壤,表层土壤(0—5 cm)水分对放牧的响应更敏感。结构方程模型结果显示,降雪量、植被和积雪对春季土壤水分具有显著的正作用。放牧通过去除植被,对草原积雪量和春季土壤水分有负作用。因此,为了获得更多的积雪量和春季土壤水分,土地管理者应考虑降低放牧强度或保留部分地块不放牧。

Snow accumulation is a critical factor influencing spring soil water dynamics in grassland ecosystems,with snow mass primarily affected by snowfall and redistribution processes.Nevertheless,there exists a paucity of research investigating the potential impacts of grazing on snow accumulation and subsequent soil water content during the spring thaw period.This study aims to elucidate the effects and underlying mechanisms of various grazing intensities on snow accumulation and the soil water content following snowmelt in spring in a representative grassland ecosystem.By doing so,it seeks to provide a scientific foundation for the rational utilization and optimal management of grasslands.Utilizing a long-term controlled grazing experimental setup established in the Xilingol grasslands,we quantified vegetation characteristics,snow accumulation,and soil water content under five grazing intensities,including ungrazed(G0),lightly grazed(G0.75),moderately grazed(G1.50),heavily grazed(G2.25),and extremely heavy grazed(G3.00)during 2016 and 2017.The results revealed a gradual reduction in snow mass with the increasing grazing intensity,with an average snow mass in 2016 being 57.63% higher compared to 2017.Specifically,extremely heavy grazing led to a substantial decrease in snow mass by 75.20% and 74.53% in 2016 and 2017,respectively,when compared to the ungrazed treatment.Soil water content tended to decrease gradually in the spring as grazing intensity increased.In the ungrazed treatment,spring soil water content(0—40 cm)measured 14.91% and 10.70% in 2016 and 2017,respectively,representing 1.5 and 1.4 times higher values than those observed in the extremely heavily grazed treatment.Our analysis indicated significant positive correlation between soil water content and vegetation characteristics(aboveground biomass and plant height),as well as snow accumulation metrics(snow mass and snow depth).The top soil layer(0—5 cm)water exhibited greater sensitivity to grazing compared to deeper soil layers.The results of structural equation modeling showed that snowfall,vegetation characteristics and snow accumulation had significant positive effect on spring soil water.Grazing activities exerted a detrimental effect on snow mass and spring soil water content by depleting vegetation cover.Hence,to obtain increased amounts of snow accumulation and spring soil water,land managers should consider to mitigate the grazing intensity or implementing ungrazed plots as management strategies.