Driving factors of understory species diversity layers in forest on the northeastern Qinghai Province

Objectives The Qinghai-Tibet Plateau is one of the most sensitive regions to global climate change. The northeastern part of Qinghai Province is an important distribution area of forests on the Qinghai-Tibet Plateau. To explore the biotic and abiotic driving factors of the understory species diversity on the northeast of the Qinghai Province, and provide a scientific basis for species diversity protection and forest management under climate change.

Methods Based on the field survey data of understory species diversity of 29 tree quadrats, 116 shrub quadrats and 116 herb quadrats in the northeast of the Qinghai-Tibet Plateau, the relationships between Understory diversity and biotic (stand structure), abiotic factors (including climate, topography and soil) were analyzed by the generalized linear model (GLS).

Result The main results were showed that (1) The species composition of forest community in northeast Qinghai Province is single, mostly pure forest, and the species diversity is mainly contributed by understory vegetation. A total of 108 species of vascular plants belonging to 89 genera and 44 families were found in 29 quadrats. Rosaceae, Caprifoliaceae and Berberidaceae were the main species. The diversity of herbaceous species was significantly higher than that of shrub species (P < 0.001). (2) Climate and stand structure were the most important driving factors, accounting for 34.9% and 26.2% respectively. (3)The key driving factors of species diversity of shrub layer and herb layer are different. The species diversity of shrub layer is mainly affected by stand structure (44.0%), and the species diversity of herb layer is mainly affected by abiotic factors such as edaphic (28.8%) and climate (28.2%).

Conclusion There are differences in the driving mechanisms of species diversity between understory shrub layer vegetation and herbaceous layer vegetation in northeastern Qinghai province. The feedback mechanisms of species at different levels should be fully considered in the process of biodiversity conservation and forest management of forest vegetation community in this region.