In 2021,the Hainan Tropical Rainforest National Park was established,within which the operations of certain plantation forests were discontinued,the natural succession was happened,and the understory vegeta-tion is exceptionally abundant.In the report,60 sample squares(10 m × 10 m)were designated in the Acacia mangium forest,while 53 sample squares of the same size were designated in the Eucalyptus robusta forest.The findings are as follows:(1)The A.mangium forest harbors a total of 109 families,312 genera,and 530 species of vascular plants in the understory,whereas the eucalyptus forest encompasses 96 families,302 genera,and 445 species.(2)The canonical correspondence analysis(CCA)was performed,and the eigenvalues of Axis 1 and Axis 2 were determined to be 0.4954 and 0.3954,respectively,accounting for 58％of the total eigenvalues(1.5341),which elucidate the relationship between the understory plant communities and environmental fac-tors.When annual precipitation,mean annual temperature,elevation,mean daily temperature variation were used as individual explanatory variable,the depression exhibited significant effects(P＜0.05).(3)As the ele-vation increased,both the Shannon-Wiener and Simpson indices initially rose and then declined.Similarly,the Shannon-Wiener index,species richness,Simpson index,and species richness showed an initial increase fol-lowed by a decrease with increasing depression.With the increase of average annual temperature,the Shannon-Wiener index,Simpson index,and species richness all exhibited an initial increase followed by a decrease.The Shannon-Wiener index,Simpson index,and species richness decreased with increasing annual precipitation.
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万方数据
