Effects Of Potentilla Fruticosa L. On Spatial Heterogeneity Of Soil C,N And P In Alpine-Cold Grassland Of Northwest Sichuan

The Alpine Grassland in Northwest Sichuan is situated on the eastern edge of the Qinghai-Tibet Plateau and is the largest plateau peat marsh wetland in the world.It is also an important water conservation area of the Yangtze River and Yellow River in China.Its ecological health is of great significance to the ecological environment of the whole country and even the world.However,in recent years,by the reason of global climate change and human activities,alpine grassland has began to degrade in the Qinghai-Tibet Plateau,among which grassland shrubbery is one of the manifestations of grassland degradation.1 Potentilla fruticosa L.shrubs grow widely in the alpine grassland of Northwest Sichuan,and have become common shrubs in this area.Grassland shrubbing often leads to changes in ecosystem structure and function,and even leads to land degradation and desertification.Shrubs and grasslands affect the spatial distribution and cycling of soil organic carbon and other nutrients by affecting the ecological environment,thus enhancing the heterogeneity of soil properties.Discussing the relationship between the process of grassland shrubbing and the spatial heterogeneity of soil properties will help to reveal the mechanism of grassland degradation caused by shrubbing,and provide theoretical basis for effectively curbing the expansion of shrubs and slowing down land degradation.However,the current studies on the effects of shrubs on soil spatial heterogeneity are mainly concentrated in the arid and semi-arid agro-pastoral ecotone,while there are few reports on shrubs in the alpine grassland of Northwest Sichuan.At present,the research on Potentilla fruticosa L.mainly focuses on its growth and distribution,especially on the effect of shrubs on soil fertility of Alpine Grassland in Northwest Sichuan.Therefore,it is necessary to study the effect of Potentilla fruticosa L.shrub on soil spatial heterogeneity in Alpine Grassland in Northwest Sichuan.Taking the alpine grassland of Northwest Sichuan as the research object,the soil samples of 0-10 cm,10-20 cm,10-20 cm,20-30 cm,30-40 cm,40-60 cm,60-80 cm and80-100 cm were collected by setting soil sampling points inside,edge and outside the shrubs.The soil physical and chemical properties of Potentilla fruticosa L.shrubs on alpine grassland in Northwest Sichuan were studied by laboratory analysis.And the influence of soil C,N,P spatial quality.The results show that:?1?Soil water content?SWC?decreased gradually from inside to outside of shrubs,while soil bulk density?BD?and pH increased gradually.There were significant differences in BD,SWC and pH between inner and outer shrubs in 0-40cm soil layers?P<0.05?,and the spatial heterogeneity of BD,SWC and pH was the strongest in 0-10cm soil layers.With the increase of soil depth,BD,SWC and pH at all sampling locations showed a downward trend,and the differences in the interior,edge and exterior of shrubs below 40cm were not significant?P>0.05?.The heterogeneity of BD,SWC and pH of larger shrubs and smaller shrubs was stronger at the same sampling location.?2?Soil organic carbon?SOC?,calcium-bound organic carbon?Ca-SOC?,humic acid carbon?HAC?,Fulvic Acid Carbon?FAC?and humin Carbon?HMC?showed a gradual downward trend from shrub to shrub.There were significant differences in SOC,Ca-SOC,HAC,FAC and HMC between inside and outside shrubs in 0-60cm soil layers?P<0.05?,among which SOC,Ca-SOC,HAC,FAC and HMC had the strongest spatial heterogeneity in 0-10cm soil layers.In particular,iron-aluminum bound organic carbon?Fe-?Al?-SOC?increased significantly both inside and outside the shrubs in 0-20cm soil layers?P<0.05?,and decreased gradually from inside to outside of the shrubs in the soil layers below 20cm.SOC,Ca-SOC,Fe-?Al?-SOC,HAC,FAC and HMC all showed a downward trend with the increase of soil depth.There was no significant difference in the internal,marginal and external of shrubs below 60cm?P>0.05?.The heterogeneity of SOC,Ca-SOC,Fe-?Al?-SOC,HAC,FAC and HMC in the same sampling location of larger shrubs and smaller shrubs was stronger.?3?Total Nitrogen?TN?,Ammonium Nitrogen?NH₄⁺-N?and Nitrate Nitrogen?NO₃-N?showed a gradual downward trend in all soil layers from inside to outside of shrubs.There were significant differences in TN,NH₄⁺-N and NO₃-N between inner and outer shrubs in 0-40cm soil layers?P<0.05?.The spatial heterogeneity of TN,NH⁴⁺-N and NO₃-N was the strongest in 0-10cm soil layers.TN,NH₄⁺-N and NO₃-N decreased with the increase of soil depth,but there was no significant difference between the interior,edge and exterior of each soil layer below 40cm?P>0.05?.The heterogeneity of TN,NH₄⁺-N and NO₃-N in the same sampling location was stronger in the larger shrubs and smaller shrubs.?4?Total Phosphorus?TP?and Available Phosphorus?AP?decreased gradually in0-30cm soil layers and increased gradually in 30-100cm soil layers.The spatial heterogeneity of TP and AP was the strongest in 0-10cm soil layer?P<0.01?.With the increase of soil depth,both TP and AP showed a downward trend,and there was no clear change rule in the interior,edge and exterior of each soil layer.Large shrubs and small shrubs at the same sampling location caused more heterogeneous changes in TP and AP.?5?The larger increase of SOC leads to stronger heterogeneity of C/N and C/P,while N/P is more stable.The differences of C/N and C/P in horizontal and vertical directions were significant in 0-60 cm locations?P<0.05?,but not significant in locations below 60 cm?P>0.05?.There was no significant change of N/P in different soil layers.The heterogeneity of C/N and C/P in the same sampling position of larger shrubs and smaller shrubs was stronger,and the effect on N/P was not obvious.