The Spatial Distribution Pattern Of Korean Pine Trees And Association With Other Tree Species In Northeast China Along Latitudinal Gradient

Investigating spatial distribution and association of tree plant populations provide better insights into the dynamics and processes that shape the forest community.Korean pine(Pinus koraiensis)is one of the most important tree species in broadleaved Korean pine mixed forest,and little is known about the spatial point pattern and association between Korean pine and community-level woody species groups such as coniferous and deciduous trees at different developmental stages.Therefore,understanding the population structure of Korean Pine trees and the spatial relationship between this species and other tree species is vital to restore Korean Pine trees and maintain the crucial ecological functions of broadleaved Korean pine mixed forest in Northeastern China.This study investigated population structure of Korean pine trees and the spatial pattern of Korean pine(KP)trees,and then analyzed how the spatial associations among KP trees and between other tree species within community level vary with five different broadleaved Korean mixed forests in Northeast China.Five typical primary broadleaved Korean pine mixed forests along the latitudinal gradient in northeast China were selected as study sites,namely the Changbai Mountain(CBS),Muling(ML),Liangshui(LS),Fenglin(FL)and Shengshan(SS)National Nature Reserve.For the spatial distribution and intra-/inter-specific association analysis,plant trees were divided into three growth forms according to the attainable maximum height: canopy layer(H ≥ 20m),middle layer(H ≥ 5m)and shrub layer(H ≤ 5m).Likewise,each growth form was divided into different life history stages according to their DBH sizes.Uni-and bivariate pair correlation function and mark correlation function were applied to analyze the spatial distribution pattern and spatial association with the complete spatial randomness(CSR)null model and heterogeneous poison process(HPP)null model and antecedent null model.The DBH histogram of KP trees in Northeast China revealed that: KP trees in the CBS plot showed a unimodal-and bell-shaped distribution with a peak at the mature stage.In contrast,the ML and SS plots had exponentially descending distributions,and the LS and FL plots displayed bimodal shapes with two highest peaks at the sapling and mature stages.There were only 3 saplings(7.5 cm ≥ DBH)in CBS plot,representing the very poor regeneration process in CBS plot,while the other four plots exhibited moderate or expanding population structures.The different life stages of KP trees were significantly aggregated at 0-40 m scales under CSR null model,and the most of aggregation scales decreased to 10 m under HPP null model.Also,the aggregation scales decreased with increasing size classes.Positive or negative spatial associations were observed between different life stages of KP trees in different plots depending on the different life stages pairs.The interspecific spatial association of KP trees among different life stages revealed that saplings and juveniles(15 cm ≥DBH ≥ 7.5 cm)were positively correlated at scales of 0-40 m,while saplings and mature trees(70 cm ≥ DBH ≥ 15 cm)were randomly or negatively associated,and the mature and overmature trees(DBH ≥ 70 cm)exhibited non-or negative spatial association.Mark correlation function results demonstrated that the marks of KP trees(DBH)and distance tended to represent mutual inhibition at different scales for different plots.Life history stages of coniferous tree group(ND)showed positive spatial associations with KP sapling and juvenile trees at small scales within 0-10 m,while spatial independence or negative correlation to larger KP trees at greater scales.All broadleaved tree groups(BD1,BD2 and BD3)exhibited only slight positive association with KP trees at small scales,and dominant negative associations were observed at most of scales.We could not find any tendency and correlation between spatial point pattern characteristics and latitude,because the species composition,population structure and land use history,and environmental factors varied on different sites.Our results demonstrated that the site heterogeneity(canopy gaps,topography,soil condition etc.),limited seed dispersal and interspecific competitions characterize the spatial pattern of KP trees and community level spatial association KP trees and other tree species in Northeast China.The results of this study suggest that KP has strong interspecific competition with all life forms of broadleaved trees,which can limit the growth and survival of KP.While,positive associations were observed between lower height classes of KP and other coniferous trees at small scales.These can serve as the theoretical basis for management and restoration of broadleaved Korean pine mixed forests in Northeast China.