Dynamics Of Spatial Pattern And Its Environmental Interpretation Of Saplings In Broad-leaved Korean Pine Forest In The Lesser Khingan Mountains

In order to understand the trend of community succession and discuss the biological mechanism of community adaptation to environmental change in broad-leaved korean pine forest,and also provide scientific basis for long-term monitoring of forest community dynamics,maintaining community structure,restoring community biodiversity and rational management,in the study,a typical broad-leaved korean pine plot in the Lesser Khingan mountains was selected as the research object.The dynamic changes of sapling species diversity and spatial pattern were analyzed in 2010,2015 and 2020,and the spatial distribution pattern of dominant saplings in 2010,2015 and 2020 was analyzed.The relationship between environmental variables and spatial distribution of three dominant saplings in 2020 was also analyzed.The results are as follows:In the three surveys,the number of tree species was 20,but the number of individuals increased first and then decreased.The composition of dominant species in saplings remained unchanged.At a spatial scale of 200m×200m,Shannon-Wiener diversity index and Simpson dominance index firstly decreased and then increased with the increase of time,while Pielou evenness index continued to increase.With the increase of time,the average DBH of both small trees and big trees increased,and the average DBH of saplings decreased significantly in2020.The average DBH of all trees in the plots were 15.11 cm,15.58 cm and 15.60 cm at different survey years.The spatial distribution pattern of saplings in the three surveys was similar,which showed aggregation distribution at small scale.With the increasing of the scale,the spatial pattern of the saplings changed to random distribution or uniform distribution.In the three surveys,the spatial correlations of saplings and small trees were positive correlated at small scales.With the increase of the scale,the correlation weakened and became no correlation,but there was a partial negative correlation at medium scale and large scale.There was no correlation or positive correlation between saplings and big trees on most scales,but there was still a negative correlation at small and medium scales.In different survey years,Acer mono,Abies fabri and Acer ukurunduense of saplings were distributed anywhere in the plot.The spatial correlations between Acer mono and Abies fabri,Acer mono and Acer ukurunduense,and Abies fabri and Acer ukurunduense were uncorrelated at most scales,and there were occasional positive and negative correlations at the sapling stage.The environmental variables showed significant positive spatial correlation at medium and small scales.Acer mono,Abies fabri and Acer ukurunduense also showed significant positive spatial correlation at medium and small scales.At the community level,pure environmental variables had poor explanatory ability(1.75%),pure wide-scale spatial variables and pure micro-scale spatial variables had strong explanatory ability.The part that can’t be explained by environmental variables and spatial variables was higher(64.38%).At the population level,environmental variables had a poor ability to explain the spatial distribution of dominant tree species,which can explain 3.22%、0.97% and 2.35% of Acer mono,Abies fabri and Acer ukurunduense at the sapling stage.The pure wide-scale spatial variables and the pure micro-scale spatial variables accounted for a high proportion of Acer mono,Abies fabri and Acer ukurunduense,In addition,environmental variables and spatial variables accounted for a high proportion of unexplained.Succession was at a relatively stable stage.Saplings and small trees compete little and depend on each other in small scale,while upper trees compete strongly for resources in medium scale and large scale.Saplings and large trees compete less on the whole.There was no obvious spatial heterogeneity,and competition among species was not obvious.Saplings were concentrated around their mother trees,and soil p H and total phosphorus were important factors for community establishment.The land surface may be disturbed frequently,and the spatial distribution pattern of the population does not correspond well with the soil conditions,and the environmental factors with certain spatial structure have certain influence on the spatial distribution of the population.