The effect of climate change on the richness distribution pattern of oaks (Quercus L.) in China.

Increased concentration of greenhouse gases in the air is acknowledged as one of the main reason for observed global climatic change. This phenomenon significantly affects the species geographical distribution, and changes their richness distribution pattern. Oak (Quercus L.) is an important component of forests in China, and it has significant ecological value. Based on the distribution data of 35 species and 19 bioclimatic variables, the potential richness distribution of Quercus L. in China was predicted using the MaxEnt model under present climatic conditions and three different emission scenarios in the years 2050 and 2070 with six General Circulation Models (GCMs). The results revealed that Quercus L. at present was primarily distributed in the mountainous areas of southwestern China. The simulations indicated that climate change could affect the spatial pattern of the richness distribution, and if climate change intensified, its impact would gradually increase. As temperatures rise, the distribution of Quercus L. was predicted to be concentrated, and suitable areas of certain species would contract. These species may migrate to high altitudes or high latitudes. The high percentage of species lost is the reason for the higher turnover values in the mountainous areas, while other regions are mostly be influenced by the high percentage of species gained associated with the northward shift of species. Predicting changes in the richness distribution pattern of Quercus L. as a result of climate change can help us understand the biogeography of Quercus L. and enact conservation strategies to minimize the impacts of climate change.

Altitudinal Patterns of Species Diversity and Phylogenetic Diversity across Temperate Mountain Forests of Northern China.

The spatial patterns of biodiversity and their underlying mechanisms have been an active area of research for a long time. In this study, a total of 63 samples (20m × 30m) were systematically established along elevation gradients on Mount Tai and Mount Lao, China. We explored altitudinal patterns of plant diversity in the two mountain systems. In order to understand the mechanisms driving current diversity patterns, we used phylogenetic approaches to detect the spatial patterns of phylogenetic diversity and phylogenetic structure along two elevation gradients. We found that total species richness had a monotonically decreasing pattern and tree richness had a unimodal pattern along the elevation gradients in the two study areas. However, altitudinal patterns in shrub richness and herbs richness were not consistent on the two mountains. At low elevation, anthropogenic disturbances contributed to the increase of plant diversity, especially for shrubs and herbs in understory layers, which are more sensitive to changes in microenvironment. The phylogenetic structure of plant communities exhibited an inverted hump-shaped pattern along the elevation gradient on Mount Tai, which demonstrates that environmental filtering is the main driver of plant community assembly at high and low elevations and inter-specific competition may be the main driver of plant community assembly in the middle elevations. However, the phylogenetic structure of plant communities did not display a clear pattern on Mount Lao where the climate is milder. Phylogenetic beta diversity and species beta diversity consistently increased with increasing altitudinal divergence in the two study areas. However, the altitudinal patterns of species richness did not completely mirror phylogenetic diversity patterns. Conservation areas should be selected taking into consideration the preservation of high species richness, while maximizing phylogenetic diversity to improve the potential for diversification in the future.