Response Of Spatial Distribution Of Trees To Slope Micro-topography In Loess Area Of North Shaanxi Province, Northwest China

Traditional planting design method ignores the impact of slope micro-topography on growth of trees, so according to the micro-habitat conditions and Spatial distribution pattern of existing natural trees to deploy reasonable structure configuration of trees is one of the major scientific problem in in loess area, Northwest China. The purpose of our research was to analyze the coupling between gully、 collapse、platform and other micro-topography with spatial distribution of exising tree stand, which can provide base for near-natural vegetation restoration and soil and water conservation trees、shrub mixed structure configuration. Based on the investigaition data of the vegetations in Sandaochuan valley in Wuqi County of Shaanxi Province, to analyse the effect of slope micro-topography on spatial distribution of trees by using the spatial analysis tools in Arcgis 9.3 software,Ripley’s K function and 5 indexs of main populaitons of natural recovery trees community of saptial distribution. It can reveal the distribution and habitat of micro-topography,as well can study response of spatial distribution of trees to slope micro-topography in loess area of north Shaanxi Province,Northwest China. The results showed that:(1) Shallow gully and scarps are mainly distributed in the upper slope, gully and collapse are mainly distributed in the middle slope, platform is mainly distributed in the down slope. Gully, collapse, platform and other five micro-topography maximum area accounts for 30.34% in undisturbed slope area, the minimum is 15.94%, the average is 23.59%.(2) In woodland,the soil moisture of platform is the best, scarp soil moisture is the worst, the soil moisture conditions of gully and collapse are very close; the soil structure and water retention of gully is best performance, the plantfrom and collapse have highly soil moisture but its soil structure and water retention are worse. The gully and platform have better available nutrients of soil, but scarp and collapse are very poor, platform has the best full nutrients of soil, but scarp and collapse are very poor, gully has the highest organic matter content, but the collapse is the wores.(3) Slope has more impact on the maximum aggregate radius and spatial distribution of species population, but slope has less affected to largest aggregate strength of Populus hopeiensis and Populus simonii,as well the slope has great affected to largest aggregate strength of Ulmus pumila、Prunus sibirica、Robinia pseudoacacia. At different slop, scal has a large difference to Populus hopeiensis、 Populus simonii、Ulmus pumila、Primus sibirica、Robinia pseudoacacia when their spatial distribution from aggregate to random change;Aspect have a greaterimpact on species association of forest stand, sunny slope made the species association of forest stand more variously and complexly.(4) All types of micro-topography account for 21.03% in undisturbed slope area, but the number of trees on micro-topography account for 51.21% of the total number of plot, The distribution of trees has significant difference with micro-topography (P<0.01), Trees were mainly distributed in various type of micro-topographyvarious.(5) Trees were showed aggregated distribution at gully and platform, but was showed random distribution at collapse and scrap; Various of trees in different micro-topography displayed very significant difference, Ulmus pumila、Populus simonii、Primus sibirica were aggregated distribution at gully; Populus hopeiensis were aggregated distribution at gully and platform, Robinia pseudoacacia was aggregated distribution at platform.(6) Various type of Slop micro-topography soil moisture and its microhabitat have significant effects on the spatial distribution of trees. We should maintain the long term point of configuration trees planted in near-natural vegetation restoration according to various types of slope micro-topography habitat and spatial distribution of trees.Therefore, Populus hopeiensis、Populus simonii、Ulmus pumila and other trees could be planted on gully, Populus hopeiensis、Robinia pseudoacacia could be planted on platform, like Populus hopeiensis、Populus simonii thoese trees could be planted on scrap.