Analysis Of Soil Water Repellency Under Different Vegetation Types In Changwu Tableland

Soil water repellency is one of the indicators that describes the resistance of soil to water,and it has a significant impact on water infiltration in the Changwu Tableland.Analyzing the soil water repellency under different vegetation types in the Changwu Tableland can deepen our understanding of the reasons for differences in soil moisture conditions and their relationship with vegetation.Factors such as vegetation type,growth status,and root system structure can influence the water infiltration capacity of soil.Therefore,by assessing the soil water repellency under different vegetation types,we can comprehensively understand the regulatory role of vegetation in soil moisture and optimize vegetation types and layout to improve precipitation infiltration efficiency in the Changwu Tableland.In this study,five different vegetation types in the Changwu Tableland were selected,including Chinese pine,black locust,wolfberry,grassland,and farmland.The spatial distribution characteristics and differences of soil water repellency in both horizontal and vertical directions under different vegetation types were analyzed/evaluated,as well as the influence of soil properties on soil water repellency,including organic matter,total nitrogen,total phosphorus,available potassium,p H,aggregates,mechanical composition,and bulk density.Additionally,the study also examined the variation characteristics of soil water repellency under wet and dry environments.The analysis results are as follows:(1)There are differences in soil water repellency among different vegetation types.The soil water repellency of Chinese pine forest,black locust,wolfberry,and farmland is mostly mild or moderate,while the grassland exhibits only two types: hydrophilic and mildly waterrepellent.Soil water repellency mainly occurs in the surface layer at depths of 3-6 cm.Only soils under Chinese pine forest and black locust forest exhibit water repellency,while soils of all vegetation types lack water repellency at depths of 6-9 cm.(2)Different vegetation types cause significant differences in the physical and chemical properties of the soil,such as soil moisture content,total nitrogen content,organic matter content,water-stable aggregates content,and soil bulk density.Farmland and grassland have weak soil water repellency but higher nutrient content,while Chinese pine,black locust,and wolfberry exhibit stronger soil water repellency but lower nutrient content.Furthermore,the water-stable aggregates content and soil bulk density of farmland plots are significantly higher than other vegetation types,and the farmland soil has the highest clay content among soils with the same level of water repellency.(3)The response of soil physicochemical factors to in situ soil water repellency and potential soil water repellency varies.In situ water drop penetration time(WDPT)values are significantly negatively correlated with soil moisture content,water-stable aggregates content(R0.25),total phosphorus,available potassium,and p H,while potential WDPT values are only significantly negatively correlated with soil moisture content.(4)The WDPT values were determined for soil samples with different water repellency levels during the wetting and drying processes.During the wetting process,the WDPT values of most soil samples gradually increased with increasing soil moisture content,reached a certain peak,then decreased and increased in stages.During the drying process,the WDPT values of the soil samples initially decreased and then increased.The water repellency peak moisture content differs among soils under different vegetation and among soil samples with different water repellency levels.In summary,this study analyzed the spatial distribution characteristics and differences in soil water repellency under different vegetation types in the Changwu Tableland,as well as the variations in the influence of soil properties and moisture content on soil water repellency.These results provide important references for land use and management in the region.