The Spatial Heterogeneity Of Soil Properties And Its Influence On Distribution Pattern Of Seedling Community In The Montane Region Of Eastern Liaoning Province

In this study,in order to capture the spatial heterogeneity of soil chemical properties,we collected 192 soil samples and obtained 8 soil chemical properties in a 4 hm2 secondary forest plot in the montane region of eastern Liaoning Province,which were p H,organic matter,total N,available N,total P,available P,total K and available K.With the seedlings census data of the plot,we used the semivariogram and kriging to explore the spatial heterogeneity and used the principal component analysis and generalized additive model to analyze the correlation between seedlings of different species and the main soil factors,and used variation partitioning to assess the influence of soil factors on the distribution pattern of tree seedling community in the plot.The main conclusions were as follows:1.The soil was slightly acidic;the variation of p H was weak,while the variation of organic matter,total N,total P,total K,available N,available P and available K was moderate;Spherical model fitted best for soil p H,exponential model fitted best for other soil chemical properties;soil available K,p H and organic matter showed moderate spatial autocorrelation,while other soil chemical properties showed strong spatial autocorrelation;p H showed a relatively uniform distribution pattern,while other chemical properties' distribution patterns were similar,high in east but low in west.Seedlings distribution and soil temperature may be the main factors of producing the spatial distribution of soil chemical properties in the montane region of eastern Liaoning Province.2.Pearson correlation analysis results showed that p H had no significant correlation with available P and available K,organic matter also had no significant correlation with total K,while there were significant positive correlation between other soil chemical properties,up to 0.963.The principal component analysis(PCA)of 8 soil chemical properties showed that the first three principal components represented 67.9%,15.3% and 7.6%,and cumulative contribution rate was 90.8%.The GAM fitting results showed that the correlation between the distribution patterns of seedlings of different tree species and the three main soil components were different,and the deviations D2 explained by model were 0.03%-65.45%.Except for Juglans mandshurica,tree seedlings of nine species had significant correlation with PC1,Syringa amurensis,Fraxinus mandshurica and Bothrocaryum controversum also had significant correlation with PC2,while Juglans mandshurica only had significant correlation with PC2.These results indicated that the main soil chemical properties affected the distribution pattern of tree seedlings and these differences proved the existence of niche theory in the montane region of eastern Liaoning Province.3.We used the variation partitioning method to assess the relative contribution of soil heterogeneity and space on the community composition across several scales(for quadrats with a resolution of 5m,10 m and 20m)in the plot.The variance partitioning results showed that community composition changed with the quadrat variation,and the variation of soil factor decreased with the increase of quadrat.To some extent the soil and spatial factors could explain the variation of the community composition and species richness,and the larger the quadrats,the more proportion explained.For soil and space,the total explained proportion of richness variation was 80.86%,which was larger than that of the community composition(47.66%).With the increase of quadrat,the proportion of soil and space that have spatial structure which explained community composition and species richness increased significantly.On the 20 m×20 m quadrat level,under three different PCNM scales,for soil and PCNM variables,the proportion of total explanation on community composition were 28.91%,20.22% and 28.91% respectively,and the explained proportion of soil variable(9.78%)was unchanged.Under three PCNM variable group scales,the explained proportions of the spatial factor were 27.1%,8.76% and 2.92% respectively,and the total explained proportion of spatial factor decreased with the decrease of PCNM variable group scales.In the montane region of eastern Liaoning Province,both soil and spatial factors influenced on the tree seedling community,which indicated that species coexistence was not maintained by one mechanism,but were determined by the niche theory and the neutral theory.