Comparison of species diversity of plant communities in mountains of Beijing

In order to make clear the plant diversity of main forest communities and to protect plant diversity in mountains of Beijing, we compared plant diversities of main plant communities in Beijing based on results of extensive field investigations. Among the 12 forest community types, plant diversity in the herb layer is the highest, followed by that in the shrub layer and in the tree layer, with a significant difference between them. Seven forest community types have a mean number of plant species above 36, and 5 forest community types have such index between 30 and 36. Among the 12 forest community types, plant diversity of tree layer is the highest in the Form. Tilia amurensis, followed by the Form. Betula dahurica, Form. Juglans mandshurica, Form. Populus davidiana, Form. Betula platyphylla and Form. Carpinus turczaninowii; plant diversity of shrub layer is higher in Form. Populus davidiana, Form. Betula platyphylla, Form. Tilia amurensis and Form. Quercus variabilis than in other forms, and there are no significant differences in plant diversity of herb layer among the 12 forest community types. Plant diversity of herb layer is negatively correlated with that of shrub layer and tree layer, but not significantly. Plant diversity of herb layer is higher than that of shrub layer among the 8 shrub community types, and plant diversity of herb layer is correlated with that of shrub layer, but not significantly either. Amount of species in Form. Corylus heterophylla is the most among the 8 shrub community types, 39.54, followed by that of mixed-shrub, 36.94, and there are 4 shrub community types which have amounts of species above 30, i.e., Form. Corylus heterophylla, mixed-shrub, Form. Spiraea pubescens and Form. Prunus armeniaca var. ansu, and they are also the 4 shrub community types that have the greatest fluctuation in amount of species, over 30 species. There exist significant differences in plant diversity among the 8 shrub community types. Similarity index of species composition ranges from 030 to 060 in most forest communities, and there exist marked differences in similarity index of species among some forest communities. The similarity index of species composition is above 0.45 in most shrub communities, and highest between the Form. Spiraea pubescens and Form. Carpinus turczaninowii, that is 0.60, while lowest between the Form. Vitex negundo var. heterophylla and Form. Corylus heterophylla, only 0.39. Besides forest community and environment themselves, human interference is an important factor affecting species diversity of forest community, and should be taken into consideration.