Understory Plant Species Diversity And Its Influencing Factors In Betula Platyphylla Natural Forest At Different Latitudes In The Greater Khingan Mountains

Betula platyphylla(Betula platyphylla Suk.)forest is one of the most common broad-leaved tree species in the Greater Khingan Mountains.It has attracted much attention from researchers because of its vast area.Nowadays,with a series of environmental problems such as climate warming,species migration or invasion is not uncommon,and species composition and species diversity will change significantly.Existing studies have shown that the studies on the variation of species diversity of the Betula platyphylla natural forest with latitude in the Greater Khingan Mountains,on the understory plants of the Betula platyphylla forest,especially on the influencing factors of species diversity in the Betula platyphylla natural forest understory in the Greater Khingan Mountains need to be clarified.In this experiment,the Greater Khingan Mountains forest area was taken as the research object,and the changes in understory plant species diversity of Betula platyphylla forest in different latitudes were analyzed by field investigation and sampling combined with the method of laboratory experiment analysis.This experiment aimed to explore the changing trend and influencing factors of understory plant species diversity of Betula platyphylla forest in different latitudes.It provides a theoretical basis for the management of the Greater Khingan Mountains forest area.The main results are as follows:(1)A total of 99 species of understory plants were counted in the Betula platyphylla natural forest in the Greater Khingan Mountains,among which 28 species of shrub plants belonged to 13 families and 19 genera,and Rosaceae Juss.and Ericaceae Juss.were mainly typical families.There were71 species of herb plants belonging to 51 genera and 23 families,mainly Asteraceae Bercht.& J.Presl and Rosaceae Juss..The niche width of each species changed with the change of importance value,and the number of species increased first and then decreased with latitude.(2)The Shannon-Wiener index of a Betula platyphylla natural forest in the Greater Khingan Mountains increased first,then decreased with increasing latitude,and reached the peak value in the Genhe primary forest(49.78°N).In terms of β diversity,the Jaccard index value of the herb layer was significantly higher than that of the shrub layer(0.21 VS 0.08)and reached the peak value near Beijicun(53.46°)and Wuma Nature Reserve(52.81°N).However,there was no apparent convergence between plant communities.(3)Annual precipitation and soil nitrate nitrogen content had significant effects on the species diversity of understory plants in the shrub layer and herb layer(P < 0.05).(4)The redundancy analysis and stepwise regression analysis results showed that the main environmental factors affecting species diversity in the understory shrub layer were soil total phosphorus content and precipitation.In contrast,the main factors affecting species diversity in the herb layer were soil total nitrogen content and nitrate nitrogen content.