Study On The Coupling Relationship And Coordination Degree Between Structure And Function Of Different Types Of Pinus Massoniana Mixed Forests

Forest structure is the key factor to determine forest function,and complex forest structure regulates the whole forest ecosystem function.Pinus massoniana is a widely planted timber species in south China,but most of the current Masson pine plantations are mainly pure forests,with single forest phase,simple tree species structure,serious diseases and pests,and low ecological function.In order to explore the model of P.massoniana mixed forest with excellent structure and function,this study took P.massoniana and Cunninghamia lanceolata mixed forest,P.massoniana and Schima superba mixed forests and P.massoniana and Castanopsis carlesii mixed forests in Liping County of Qiandongnan Miao and Dong Autonomous Prefecture,Guizhou Province as the research object.Based on the spatial and non-spatial structure of the stand,the coupling relationship between the structure and the production function,the water conservation function and the soil fertility maintenance function was analyzed,and the coupling relationship model between the stand structure and different functions was built,and the coupling coordination degree between the three different functions of different types of mixed forests was analyzed by referring to the coupling coordination degree analysis method commonly used in software engineering.The degree of coupling coordination was evaluated,and some regulation strategies and suggestions were given for the multifunctional management scheme of P.massoniana mixed forest.The main conclusions are as follows:(1)The main indexes of affecting the stand production function are average DBH,average tree height,average height under branch,stand density index and mixed proportion;The coupling model of structure and production function of P.massoniana mixed forests was established.The production function index of pure P.massoniana forests was the highest,followed by P.massoniana and C.lanceolata mixed forests and P.massoniana and S.superba mixed forests.The mixed forests of P.massoniana and C.carlesii was the worst.(2)The main indexes affecting the coupling relationship between the stand structure and water conservation function were the average DBH,average tree height,stand density index,mixing ratio and other stand structure indexes,as well as the present stock of litter,the maximum water holding capacity of litter and the maximum water holding rate of litter.The coupling model of P.massoniana mixed forests structure and water conservation function was constructed.The water conservation function of different types of P.massoniana mixed forests was evaluated through the model.The results showed that the water conservation function of P.massoniana mixed with broadleaf tree was better than that of conifer and broad-leaved mixed forests and pure forests,and the P.massoniana × S Schima mixed forests was the best.(3)Soil organic matter,total nitrogen,available phosphorus,average tree height and mix ratio of stand were the main indexes affecting the coupling relationship between stand structure and soil fertility maintenance function.The coupling model of the structure and soil maintenance function of P.massoniana mixed forests was constructed.The soil maintenance function of different types of P.massoniana mixed forests was evaluated by the model.The soil maintenance function of P.massoniana mixed with broad-leaved tree was better than that of conifer and broad-leaved mixed forests and pure forests,and the comprehensive evaluation of P.massoniana pine and C.carlesii mixed forests was the highest.(4)The coupling coordination degree of production function,water conservation function and soil fertility maintenance function of 15 sample plots both were a barely coordination level,and the coupling coordination degree of the three functions of P.massoniana and C.carlesii mixed forests was the best.The coupling coordination degree between production function and water conservation function,production function and soil fertility maintenance function,water conservation function and soil fertility maintenance function were different in different stands,and the coordination degree between water conservation function and soil fertility maintenance function was the highest.Overall,the coupling coordination degree of different types of Pinus massoniana mixed forests showed: P.massoniana broad-leaved mixed forests> P.massoniana and C.lanceolata mixed forests> P.massoniana pure forests,and the mixed forests of P.massoniana and C.carlesii has the highest overall coordination degree among various functions.