| Since the Loess Plateau began to return the grain plots to forestry,the ecological environment has restored and soil erosion has significantly improved,vegetation plays a very important role in it.Vegetation growth is influenced by soil physical,chemical and biological properties as well as hydrothermal conditions.Wuqi County is located in the typical loess hilly-gully region.Because of the outstanding work after returning the grain plots to forestry,Wuqi County is known as "the first county".This article chooses the Wuqi County as the research area,selecting typical farmlands as control group.Choosing typical converted grasslands as plots which aspects are shady slope,sunny slope,semi-shady slope and semi-sunny slope.There are 8 landscape positions from top to bottom which means upper slope,middle slope,lower slope and bottom slope.Vegetation surveys are carried out and soil samples are collected on the sample plots.Calculating ? diversity of vegetation index,measuring soil physical and chemical properties.Analysis of the characteristics of vegetation restoration and soil physical and chemical properties under different topographic conditions,to explore the terrain effect on vegetation restoration and soil physical and chemical properties,in order to understand the effects mechanism of vegetation restoration and soil properties,to offer important support for the quantitative simulation of the influence of ecological environment factors on ecological restoration.The main conclusions of this article are as follows:(1)there are 30 species of common plants in the study area,including 10 families,24 genera,mainly Compositae,Leguminosae and Poaceae plants.The sunny slope's vegetation coverage and ? diversity of vegetation index are the best,while the shady slope's are the worst in the different aspects.Vegetation index showed the trend of lower slope> middle slope > upper slope >bottom slope.(2)The content of soil organic matter in semi-shady slope and semi-sunny slope are better than shady slope and sunny slope.While the content of soil total nitrogen in shady slope and sunny slope are better.There is a significant difference in soil nutrient content between 0-10 cm and 10-20 cm soil layers,and the soil nutrient content gradually decreased with the depth of soil layers.The soil bulk density,porosity and saturated water capacity of different aspects showed that semi-sunny slope,semi-shady slope better than shady slope,sunny slope and farmlands.The natural water content,capillary porosity and capillary water capacity showed shady slope,sunny slope better than semi-sunny slope,semi-shady slope and farmlands.The shady slope's soil particle composition is better than other five plots and the sunny slope's is the worst.Soil water-stable aggregate stability showed a trend that semi-sunny slope and semi-shady slope are better than sunny slope and shady slope.MWD of converted grasslands decreased gradually from the surface to the deep in different soil layers.(3)Above the gully edge,the properties showed a good trend in lower slope,while the upper slope is poor.The soil physical and chemical properties of soil in bottom slope which below the gully edge are not stable.(4)the growth status of surface vegetation is not consistent with the soil physical and chemical properties.Vegetation growth is subject to the comprehensive effect of topography,hydrothermal conditions and soil characteristics,although the changes of vegetation growth is intuitive,but it is more affected by the seasons.The improvement of soil physical and chemical properties is a long process.(5)In different topographic conditions,the physical and chemical properties of soil in converted grasslands are better than those in the farmlands,in the 0-20 cm soil layer,the physical and chemical properties of converted grasslands also showed obvious advantages.Grain for green project has made great contribution to improving soil properties,promoting ecological restoration and reducing soil erosion. |
PDF Full Text Request