The Dynamics Study Of Understory Plants Diversity And Soil Environment During The Transformation Of Pinus Massoniana Forest

At present,the secondary pure Pinus massoniana forest is a type of forest that urgently needs to be transformed,and Cinnamomum camphora is one of the ideal tree species for P.massoniana forest transformation in sub-tropical regions.In order to improve the study on the transformation of P.massoniana forest to C.camphora forest and guide the transformation of P.massoniana forest in practice,four communities at different stages of the transformation of P.massoniana forest to C.camphora forest were selected to study the understory plant diversity,soil environment and the relationship between understory plant diversity and soil environment.This study aims to reveal the dynamic response characteristics and response mechanism of understory plant community during the transformation from P.massoniana to C.camphora forest.The results showed that:1.With the progress of forest transformation,the number of species and the species diversity of understory plants indicated a trend of increasing first and then decreasing,the comprehensive ranking of species diversity of undergrowth in each period was as follows: middle stage of transformed community > early stage of transformed community > late stage of transformed community > untransformed community;The species composition and species diversity of herb layer plants varied more than that of shrub layer plants.2.With the progress of forest transformation,the number of species and the diversity of functional traits of understory plants indicated a trend of increasing first and then decreasing,among them,the functional diversity in the early and middle stages of the transformation is relatively high,while that in other periods is relatively low;In the process of transformation,the variation trend of functional traits and diversity of “light response traits” and “reproductive traits” of understory plants was similar,but the former was more sensitive to the forest transformation than the latter;In addition,the functional diversity of“soil-related traits”was highly correlated with the stand density of the tree layer.3.With the progress of forest transformation,the soil nutrient environment has generally improved,but the content of nitrogen and phosphorus indicated a trend of decreasing.The diversity of soil bacteria was as follows: middle stage of transformed community> late stage of transformed community> untransformed community> early stage of transformed community.4.The species diversity of undergrowth shrub layer plants was positively correlated with soil water content and negatively correlated with available nitrogen;The species diversity of herbaceous layer plants was significantly correlated with soil available potassium,pH,total nitrogen and available phosphorus.There was a significant correlation between the functional diversity of undergrowth plants and the available nitrogen,organic matter,water content,and total phosphorus of soil.To sum up,compared with each period of forest reconstruction,the forest reconstruction effect is the best in the middle stage of transformed community.The transformation from P.massoniana forest to C.camphora forest accelerated the succession of the community,increased the diversity of undergrowth plants,and improved the soil environment and the diversity of soil bacteria.However,in the late period of forest reconstruction,the tree layer seriously interfered with the light resources under the forest,and the soil showed nitrogen deficiency,which might be related to the high planting density of C.camphora.In the practice of transformation from P.massoniana forest to C.camphora forest,we should adjust the appropriate afforestation density based on the overall situation of the forest and advocate the transformation mode of mixed forest.The tree species with higher nutrient return of litters can be the preferred choice of mixed planting,so as to increase the nitrogen content in the soil and promote the good operation of nutrient circulation in forest system.This study provides a theoretical reference for the transformation of P.massoniana forest,protection of undergrowth plant diversity,improving the soil site conditions,improving the sustainable management and management of forest.