Community Characteristics And Competition Relationship Of Form.Betula Ermanii At Different Altitudes

In order to investigate the community structure characteristics of Form.Betula ermanii at different altitudes.In the Heilongjiang Daxiagu National Nature Reserve,three fixed plots of Form.Betula ermanii with an area of 1 hm2 Were constructed along different gradients of altitude as the research object.According to preliminary statistics,there are 27 species of plants in the plot of 1 540 m above sea level,of which 5 species are trees.Betula ermanii and Picea jezoensis are dominant species;There are 30 species of plants in the 1 600 m altitude plot,of which there are 5 species of trees.Betula ermanii is the dominant species;There are 20 species of plants in the plot of 1 680 m above sea level,of which 4 species are trees.Betula ermanii and Picea jezoensis are dominant species;The diametral structure of stands at different elevations presented an inverted "J" type distribution.In order to study the competition relationship of Form.Betula ermanii at different altitudes,three plots were taken as the research object,and the fixed sample circle method was used to determine the competition range.The intraspecific and interspecific competition status of Form.Betula ermanii was analyzed using Hegyi competition index.The results showed that the intraspecific and interspecific competition intensity of Betula ermanii at 1540 m above sea level accounted for 34.78%and 65.22%of the total competition intensity,respectively.It indicates that the competitive pressure mainly comes from interspecies.The order of the intraspecific and interspecific competition intensity of Betula ermanii was:Betula ermanii>Picea jezoensis>Abies nephrolepis>Acer ukurunduense>Sorbus pohuashanensis.The intraspecific and interspecific competition intensity of Betula ermanii at 1 600 m altitude accounted for 61.72%and 38.28%of the total competition intensity,respectively.It indicates that the competitive pressure mainly comes from intraspecies.The order of the intraspecific and interspecific competition intensity of Betula ermanii was:Betula ermanii>Picea jezoensis>Acer ukurunduense>Sorbus pohuashanensis>Abies nephrolepis.The intraspeci fic and interspecific competition intensity of Betula ermanii at 1680m altitude accounted for 58.57%and 41.43%of the total competition intensity,respectively.It indicates that the competitive pressure mainly comes from intraspecies.The order of the intraspecific and interspecific competition intensity of Betula ermanii was:Betula ermanii>Picea jezoensis>Abies nephrolepis>Sorbus pohuashanensis.With the elevation increasing,the main competitive pressure of Betula ermanii changed from interspecific competition to intraspecific competition.The DBH of Betula ermanii at 1 540 m and 1 680 m above sea level had a power function relationship with the competitive intensity of the whole stand,associated tree species andBetula ermanii.With the increase of the chest diameter of the object,the three competitive intensities all decreased and finally tended to be stable.The model can predict the competition intensity within and between species.The DBH of Betula ermanii at 1 600 m above sea level has a power function relation with the competition intensity of the whole stand and the species of Betula ermanii,which can predict the competition intensity of Betula ermanii and the whole stand.However,the correlation between the competition intensity and the DBH of Betula ermanii is]ow,so the competition intensity between Betula ermanii and associated species cannot be predicted.This paper provides scientific basis for the species diversity maintenance mechanism,population competition research and reasonable management of Form.Betula ermanii in temperate regions of China.