Study On Regeneration Rules Of A Natural Coniferous(Tsuga Chinensis Var.Tchekiangensis)and Broadleaf Mixed Forest In Jiangxi Wuyishan

To explore the biotic and abiotic factors affecting natural regeneration of T.chinensis primordial forest,a natural coniferous and broadleaf mixed forest was set as research plot in the core region of Jiangxi Wuyishan.The regeneration characteristics,population dynamics,niche characteristics of main populations and the effects of different micro-topographic habitats on seedlings regeneration were studied in this paper.The results showed that:（1）In permanent plot,there were 910 individuals of T.chinensis,whose importance value was 59.32%.Only 38 seedlings of T.chinensis（DBH<5cm）existed in permanent plot,and showed a contagious spatial distribution.T.chinensis seedlings were at disadvantage in regeneration layer,which rank was the 16th.But its population was still a kind of stable expanding population.Survival curve of T.chinensis was between Deevey-I and Deevey-II,and mortality rate and vanish rate curve trends were basically consistent.After different years of age class,the number of T.chinensis individuals varied and fluctuated in various directions.（2）The species with the largest niche breath in tree layer were T.chinensis(B_L=0.9378,B_SW=2.2702)and Cyclobalanopsis glauca(B_L=0.9393,B_SW=2.2700),while Enkianthus chinensis(B_L=0.7401,B_SW=1.9718)and Clethra cavaleriei(B_L=0.6865,B_SW=2.0905)had the least niche breath.The shrub with the largest niche breath in regeneration layer was Eurya saxicola(B_L=0.9121,B_SW=2.2548).The specie with the largest niche breath in herb layer was Fargesia spathacea(B_L=0.9134,B_SW=22.2553).The niche breath of T.chinensis seedlings in regeneration layer was apparently below that in tree layer,which demonstrated the disadvantage of seedlings in regeneration.Niche overlap analysis indicated that the competition between T.chinensis and C.glauca was the most intense in tree layer,E.saxicola and F.spathacea had high intensity competition to seedlings of T.chinensis,which led to a great influence on seedlings recruitment.（3）The micro-topography of sample plot were divided into four categories:steep slope,valley,ridge and gentle slope.The average DBH and diversity indexes were the highest in the steep slope,followed by the valley.In the 4 types of micro-topography,the forest canopy structure was similar,but the under-forest structure was slightly different.And the valley was thought as the micro-topography with the highest soil element content.The total amount of seedlings and T.chinensis seedlings in regeneration layer were the most in ridge,whereas the number of seedlings and T.chinensis seedlings in valley were less than half of those in ridge.The slow slope was the second choice for the seedlings growth of T.chinensis.Altitude and convexity showed the extreme significant positive correlation（P<0.01）with the number of seedlings in regeneration layer,and slope showed an extreme significant negative correlation（P<0.001）with the number of seedlings.Among the terrain factors,altitude and convexity had significant effects on seedling recruitment of T.chinensis.According to the comprehensive analysis,the ability of resources utilization of T.chinensis seedlings was poor,but its population still belonged to a kind of stable expanding population.The high intensity competition between E.saxicola,F.spathacea and T.chinensis was the main biological factor affecting its natural regeneration.Tree species composition,stand density light and so on in different micro-topography categories have certain influence on seedlings recruitment of T.chinensis.In order to maintain the stability of primary forest and improve the management measures of T.chinensis,the quantity of E.saxicola and F.spathacea populations are supposed to be properly regulated.