| Soil is an important carrier of nutrients and water,and its spatial distribution will directly affect the growth and distribution of vegetation.In the degraded ecosystem,soil physical and chemical properties are the limiting factor of vegetation restoration.In order to found the variation and influencing factors of soil water and organic matter in the degraded red soil area.In 2016,we conducted a field-based experiment of a 25-years vegetation sites in the degraded red soil area of Taihe County,Jiangxi Province,and we selected two methods and four vegetation types(Pinus elliottii forest,Liquidambar formosana forest,Pinus elliottii × Liquidambar formosana mixed forest and control natural restoration).The results of soil moisture status in different vegetation type was compare with that of in 2005.In addition,the distribution of soil moisture and organic matter which influence by topographic factors was analyzed in a 3 km2 study area.We also using geostatistics and GIS techniques to analysis the spatial variability and Kriging interpolation of soil moisture and organic matter.And combine with quantitative theory to discusse the mainly reason of spatial distribution.The results shows that:(1)The soil moisture content of this study area was maintained at 12.50%-14.91%,and shows medium degree of discrete.The soil moisture content was higher in the lower soil layer than surface layer in the early stage of vegetation restoration,while,it was exactly the opposite after accomplish of restoration.Form the result of geostatistical analysis,we can know that the mainly factors which affect the spatial variability of soil moisture in this study area were structural composition.And the structural manifestations of distribution are generally expressed as Liquidambar formosana forest > Pinus elliottii × Liquidambar formosana mixed forest > Pinus elliottii forest > control natural restoration.(2)Soil organic matter content in this study area was about 16.17 to 26.38 g/kg.The soil modification effect of Pinus elliottii ×Liquidambar formosana mixed forest shows the best in all three vegetation restoration types,However,it shows the worst of that in Pinus elliottii forest.Generally,the soil modification effect of broadleaf forest was better than coniferous forest.The spatial distribution characteristics of soil organic matter under different vegetation conditions are quite different,and vegetation factors are the mainly factors that affecting the distribution of organic matter.(3)The soil moisture content and organic matter content was decreased with slope increase in this study area.And the soil moisture and organic matter content was higher in uphill of shady slope than that of sunny slope.Due to the greater human disturbance(e.g.dead organic matter collection)in lower slope position that lead the organic nutrients release to soil are more likely to decreased,which results shows that the organic matter increased with altitude increasing.Based on the characteristics of all topographical factors,the simple topographical factor has a greater impact on soil moisture content,while,the composite topographical factor impacts smaller.However,the topographical factors effect of organic matter content was shows opposite with soil moisture content,which the curvature of plane and profile are more likely to affected organic matter content variation.(4)The spatial variability of soil moisture and organic matter content has some common point in the sample block and regional scales.On both scales,the autocorrelation of soil moisture and organic matter content was range from a few meters to tens of meters.Meanwhile,the autocorrelation ability were varied by different scales.It shows a moderate degree of spatial autocorrelation on the sample block scales,while the regional scales shows a strong spatial autocorrelation.Further,the variation degree of spatial autocorrelation was varied by regional scales.(5)Under the combine effect of vegetation factors and topographic factors,the soil moisture content and organic matter content shows a large difference of distribution.In the hilly of degraded red soil region,the soil moisture content was higher in the broad-leaved forest with lower elevation,lower,gentle and shady slope.While,the soil organic matter content was higher in the broad-leaved forest with high elevation,shady slope,larger plane curvature and lower profile curvature.The vegetation restoration types selects of broad-leaved forest,or coniferous and broad-leaved mixed forest was beneficial to the improve of soil physical and chemical properties in the process of vegetation restoration in the degraded red soil area. |
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