Using Geographical Variation Of Water And Energy To Explain The Spatial Distribution Patterns Of Pteridophyta Of China

Pteridophyta(fern)is also known as the fern plant.It is not only the higher spore plant,but also the original vascular plant.Fern is considered to be a transitional plant group between bryophyte and gymnosperm.There are about twelve thousand species of fern all over the world,but more than 2600 species of fern have been found in China.So China is the country which has most kinds of pteridophyta in the world.Pteridophyta plays a vital role in the growth and development of forests.Fern can be used as an indicator of soil and climate as well because of their high sensitivity to the natural conditions.Hundreds of hypothese have been put forward to explain the mechanism of species diversity patterns on large scale.In these hypothese,the energy hypothese were the most talked-about,and the water-energy dynamic hypothesis is one of them.Its main idea is that the species diversity patterns of large scale is codetermined by water and energy.In this study,our aim is to quantify the geographical variation about the relative importance of water and energy on the species richness of Pteridophyta,and to test the Hawkins' conjecture.Then,we examine the interaction between water and energy available to the impact of the patterns of pteridophyta species richness.Our species distribution data is from the list of pteridophyta species in the National Nature Reserve of China,and we have analyzed 48 national nature reserves in total.There are 476 species of ferns in the Jinfo Mountain State Nature Reserve in Chongqing,which is the largest protected area with ferns.The climate data is from the website of WorldClimate dataset,and we choose 19 variables of biological and climatic.The 19 variables are derived from monthly temperature and precipitation,including 11 energy variables and 8 water variables.These variables represent annual trends,seasonal and extreme or restrictive environmental factors.In order to eliminate the multicollinearity between climate variables,we use principal component analysis to extract the principal components.Then,we do the geographically weighted regression analysis separately for the relationship betweenpteridophyta richness and water and energy and evaluate the spatial variation of the relationship between richness-energy and richness-water.Finally,we verify whether the distribution of ferns is determined by the interaction between water and energy,and find the water and energy combinations where the fern has most species richness.The results of this study have shown that the distribution of ferns in China is uneven,and the number of species in each nature reserve is quite different.As a whole,the number of ferns in south is higher than that in north,and there are many species in the warm and humid areas,while the number of species in the arid areas is less.The the influence of water and energy factors on the diversity of fern plants will change with the distribution gradient of available water and energy.Both of them have showed a trend of increasing interpretation with latitude,but the influence of energy on the whole country was obviously weaker than that of water.The relative influence of water and energy on the richness of pteridophyta has showed an obvious difference along with latitude.The difference was opposite of the Hawkins' hypothesis that energy was the most important factor at the low latitudes,while water played an obvious dominant role at the high latitudes.It also indicated that the distribution pattern of ferns in China was different from the pattern of Hawkins'.Furthermore,the interaction between water and energy availability had a significant effect on regional-scale oak diversity–water relationships,but had little effect on oak diversity–energy relationships.When water and energy were at higher level,the species richness of pteridophyta was the highest.And at this time,the statistical effect of local climate on richness was also in the lowest in these areas.In dry and cold ambient,ferns have the lowest species richness,and the local climate has the greatest impact on species richness.