| As an important part of the forest,saplings affect the spatial pattern change and development trend of the forest in the future.Exploring the characteristics of sapling structure is of great significance for understanding the process of forest community construction and providing a theoretical basis for forest succession law.Based on the investigation of 2 1hm~2 plots in Cenwanglaoshan Nature Reserve,this study analyzed the composition,structure,functional traits,and relative growth rate of DBH of dominant species saplings.This study received the following conclusions:(1)In terms of sapling species composition,the statistical arrangement of saplings in the two plots showed that the dominant saplings were mainly concentrated in Lauraceae,Fagaceae,and Theaceae.Generally,these species could adapt to the shady environment well,and the population regeneration was good,and could continuously replenish the population individuals to maintain the dominant position.The study of the two plots must have an altitudinal gradient instead of a continuous plot,but from two 1 hm~2 plot of the spatial distribution pattern of dominant saplings,interspecific association and plant functional traits can be seen under the elevation gradient community update the tree species with similar laws,it can be seen that the strategy of growing the growth and update of forests in the Cenwanglaoshan nature reserve has a certain similarity.(2)Through the point pattern analysis of the dominant saplings in two plots,it can be found that most saplings are in 0-25 meter-scale was clustered distribution,only a Laurocerasus spinulosa,Litsea pseudoelongata,and Neolitsea aurata as well as the plot b Machilus leptophylla,Lithocarpus megalophyllus and Ficus erecta population in 0-25 meter-scale generally presented as a random distribution.The relationship between the dominant saplings by the coupling coefficient is found that the relationship between two types of advantages has similar patterns.That is,the logarithm of the positive link is more negatively coupled to the logarithm,but the negative intensity is greater than the intensity of the positive joint,under may be on the space environment and nutrition of saplings(especially light)needs are similar,but as light under forest resources are relatively scarce,these saplings of interference competition to compete for limited resources.(3)The functional traits of the dominant saplings in the two cases of Cenwanglaoshan evergreen and deciduous broad-leaved mixed forest,showing similar laws and can divide two growth strategies according to functional traits.The first category is the"speculative"group,and the individual leaf of the saplings are relatively thin,and there are a larger specific leaf area and leaf nutrient content and smaller leaf dry matter content.Faster growth of this class,ability to use energy resources more,but less individual.The second category is the"pastime"group,such individual leaves are relatively thick,more tolerant,can resist a more harsh environment,and a large number of saplings,but the individual growth is slow.(4)By comparing the biomass allocation of sapling’s twigs in the current year,it was found that the twig biomass of"speculative"saplings would be more used to support the construction of saplings."Pastime"saplings,in which the biomass of the twigs is devoted more to maintaining leaf growth.The results showed that the strategy adopted by saplings in response to environmental stress was to make use of the high phenotypic plasticity of their branches and leaves to achieve the optimal allocation of branch and leaf resources.(5)The two dominant species in the forest in the DBH of the relative growth of saplings and species of a comprehensive assessment of key relationships,and found that the content of the leaf dry matter,the leaf water content,the leaf C content,and the leaf P content are the relatives of the saplings.These plant functional traits a more appropriate as a key to indicate changes in rates of growth of forest characters.With the higher DBH of the relative growth of saplings are mainly of a thin leaf"speculative"group,the DBH of relative growth rates were mainly influenced by leaf C content and leaf water content.Saplings with a smaller DBH relative growth rate are mainly the"pastime"group,and their relative growth rate is mainly affected by leaf dry matter content,leaf water content,and leaf P.(6)The saplings of the dominant species in the two plots showed similar spatial distribution patterns,which were related to the functional traits of saplings.The saplings of"speculative"were mostly distributed randomly,and the biomass of saplings was more used to support the extension of saplings.The"pastime"saplings all showed an aggregation distribution pattern,and the biomass of saplings’twigs would be more used to maintain the growth of sapling leaves.Response to similar environmental reasons may be that different species will choose a different trait,its final distribution pattern is both the result of the long-term interaction.(7)In this study,the interspecific correlation of saplings of dominant species with similar leaf functional traits was negative,while the interspecific correlation of saplings of dominant species with different leaf functional traits was positive.Therefore,using plant functional traits to replace the spatial distribution pattern of species and interspecific correlation,we can make a more reasonable explanation for the formation mechanism of the sapling structure. |
