Spatial Variation Of Plant Functional Traits And Its Correlation With The Environment At Different Spatial Scales In Karst Mixed Evergreen And Deciduous Forests,Guilin,China

The formation of plant community is a joint result of environmental factors,biological action and disturbances and other factors.In karst habitat,where conditions are harsh,its dominant process of community construction is an environmental screening process based on ecological niches.The trait-based community construction theory suggests that environmental factors has a multi-scale effect on the screening process of plant,which was screening by plants functional traits.Therefore,studying the spatial variation of plant functional traits and environmental factors and their scale associations is important for exploring the mechanisms of trait-based community construction.In this study,a 2 hm~2sample plot of mixed evergreen deciduous forest in the karst hills was set up at Niantianwei,Lingchuan County,Guilin.All woody plants with diameter at breast height≥1 cm in the sample plot were sampled in order to determine their functional traits including leaf area,specific leaf area,leaf dry matter content,leaf thickness,chlorophyll content,and branch density.The soil samples were collected from the plot for measuring the following ecological factor:total phosphorus,total nitrogen,p H value,alkali-hydrolyzable nitrogen,available phosphorus,water-soluble calcium,available potassium,organic matter,water content,as well as the environmental factors,such as slopes information based on altitude.Firstly,the variability and variation patterns of plant functional traits and environmental factors at different spatial scales were analyzed by means of geostatistical methods.The spatial autocorrelation and semi-variogram of the geostatistical method were used to analyse the variability and variation patterns of plant functional traits and environmental factors at different spatial scales.Secondly,we used Pearson correlation analysis and random forest regression models to quantify and analyze the relative importance of environmental factors on plant functional traits at different spatial scales so as to reveal the main environmental factors affecting the variation and distribution of plant functional traits.The main results and conclusions are as follows.（1）There are scale effects in the spatial variability of plant functional traits and environmental factors.The data obtained from the spatial autocorrelation and the semi-variogram showed that the spatial variability of plant functional traits was mainly at small scales（the greatest spatial variability of plant functional traits at the 5 m×5 m scale and the least spatial variability at the 100 m×100 m scale）.In contrast,the spatial variability of environmental factors increased as the scale expanded,with the least spatial variability at the 5 m×5 m scale.（2）Plant functional traits had different degrees of correlation with environmental factors at different spatial scales.At 5 m×5 m scale,plant functional traits and environmental factors had a poor correlation,but the correlation became stronger as the spatial scale increasing.The results indicate that the correlation between the two has a certain scale effect and a change pattern,in which the effect of the environment on plant functional traits gradually increases as the spatial scale increases,and and in the opposite direction,the effect on plant functional traits decreases.（3）By analyzing the correlation and the importance ranking of each environmental factor on plant functional traits at different spatial scales,the results showed that water-soluble calcium,organic matter,total nitrogen,total phosphorus,water content and altitude were the main factors affecting the variation and distribution of plant functional traits.These environmental factors influence and regulate plant functional traits through scale effects,and the relative importance of the factors on plant functional traits increases when the scale enlarges.In addition,within the scope of this study,the effects of environmental factors on plant functional traits increased significantly at 50 m×50 m scale.It indicated that in this scale,the environmental factors and plant functional traits has a stronger interaction,which could provide a scale reference for future investigations of plant-environment relationships in karst habitats.To sum up,by analyzing the correlation between the spatial variation of plant functional traits and the scale of environmental factors in mixed evergreen deciduous forests in karst hills of Guilin,this study provided preliminary insights into the environmental filtering and ecological niche differentiation that drive variation in plant functional traits.The results can not only provide some theoretical guidance for the study of plant functional traits in the region and the mechanisms of plant trait response to environmental change,but also offer a deeper perspective for future workers in related fields to understand the underlying mechanisms and processes of plant community construction,all of which will serve as a theoretical guide for community ecology development,vegetation restoration and ecological reconstruction in karst areas.