Research On Statistical Mechanism Of Species Richness Pattern For Woody Plants In China

The distribution pattern of plant species richness(SR)and the underlying mechanisms have been one of the important issues in ecology under the background of climate change,and also the key basis for global biodiversity conservation.China is one of the countries with the richest species diversity in the world,which has more than 10,000 species of woody plants,is an ideal laboratory of studying woody plant diversity patterns.In this paper,11405 species of Chinese woody plants from woody plant monographs were selected as the research objects.Based on the Worldclim global database,we explored the horizontal species richness pattern for Chinese woody plants at six scales(intervals of 50 km)from 50 km ×50 km to 300 km × 300 km and the underlying mechanism of hydrothermal climate impact by regression fitting and variance partitioning analyses.The main results were shown as follows:(1)At different scales,the species richness of woody plants in China showed a uniform decreased pattern with the increase of latitude.Quadratic function was the optimal model to describe the relationship between species richness and latitude,which explained 55.6-73.7%of the variation in species richness pattern of Chinese woody plant.With the increasing scale,the quadratic function had an upward trend in explaining the horizontal species richness pattern for woody plants in China.Therefore 300 km × 300 km was the best scale to study the horizontal species richness pattern for woody plants in China.(2)The species richness of woody plants was highest in Sichuan,Yunnan,Guizhou,Guangxi and Hainan in Hengduan Mountains,Southwest China.These areas were found to be the distribution centers of woody plants in China and needs reasonable protection in the future.The species richness of woody plants was lowest in Xinjiang,Tibet,Qinghai,Inner Mongolia and Northern Gansu in Western China,Heilongjiang,Jilin and Liaoning in Northern China as well as Shandong,Northern Jiangsu in Eastern China,which urgently needs priority protection in the future.(3)Climatic factors significantly affected the horizontal species richness pattern for woody plants in China.The species richness of woody plants in China showed an increasing trend with the increase of each climatic factor.The quadratic function was the optimal model to describe the relationship between species richness and actual evaporation and transpiration(AET),annual mean temperature(MAT)and minimum temperature in the coldest month(MTCM)of woody plants,which explained 76.7%,58.1%and 75.1%of the variation in species richness pattern of Chinese woody plant,respectively.The linear function was the optimal model to describe the relationship between species richness and annual precipitation(MAP),which explained 69.4%of the variation in species richness pattern of Chinese woody plant.The regression model SR=0.0014AET2+0.88AET-1.49MAP-11.27MAT2+4.35MTCM2+262.70MTCM+4118 was the optimal model to describe the relationship between species richness of woody plants and hydrothermal climate in China,which explained 89.6%of the variation in species richness pattern of Chinese woody plant.(4)The horizontal species richness pattern for woody plants in China supported the productivity hypothesis,the water-energy dynamic hypothesis and the freezing tolerance hypothesis,while not supported the metabolic theory of ecology in this study.In the water-energy dynamic hypothesis,the interaction of water and heat explained the largest part(56.8%)of the variation in species richness pattern for Chinese woody plants,while separate water or heat only explained very small part(12.5%and 1.3%,respective).This present study has systematically clarified the horizontal distribution pattern of species richness for the woody plants in China and its underlying statistical mechanism.This study provides theoretical basis for the biodiversity protection and sustainable development of woody plants in China,and also provides reference for prediction of plant species richness patterns in similar geographical or climatic environments worldwide.