Effects Of Dispersal And Environment On Species Turnover Of Vascular Plants At Fine Scale In A Typical Grassland Community,Inner Mongolia P.R China

Understanding the patterns of species turnover is a key problem in community ecology.Species turnover(P-diversity)mediates other aspects of diversity,but still it has received less attention compared to a-diversity and ?-diversity.An experiment was carried out at a 10 m x 10m site in a typical steppe grassland community in East Ujimqin,Inner Mongolia,P.R China(45°31' N,116° 58' E and 8.39 m a.s.l.).The objectives of this research were to determine the effects of dispersal limitation(spatial distance)a stochastic process of neutral theory and environmental factors(environmental heterogeneity)from the niche theory on species turnover of vascular plants at fine scale;and also I explored the effect of analyzing size on determining species turnover.The absolute importance of both dispersal and environmental factor in determining species turnover were examined through measuring all the species composition found in the area of study.We also aimed to determine the importance of analyzing size;a 1 m2 quadrate and a 0.25 m2 quadrate were used during vegetation measurement.Then four different soil seamples were taken from each 1 m2 quadrat using a 7.5 cm diameter drill and analyzed for soil water content and total soil nitrogen.The data were analyzed using R free software where one sample t test in order to determine species turnover,linear regression for the effects of each spatial distance and environmental factor on species turnover.Lastly variation portioning was performed using vegan package software.The results showed that both spatial distance and environmental factors are generally important determinant of species turnover in this typical steppe grassland community.The species turnover was very significant,but inversely proportional to species richness and it was 0.54 and 0.42 on the scale of 0.25 m2 and 1 m2 respectively.Species turnover increased with an increase in log transformed spatial distance,but also species turnover increased with an increase of the total soil nitrogen content.Upon partitioning Log transformed spatial distance explained species turnover by 3%and 4%,environmental heterogeneity for(total soil nitrogen)explained about 10%and 9%of all fractions being from the scale of 0.25 m2 and 1 m2 respectively and negligible variation of water content.There were unexplained variation(residuals)of 89%and 88%respectively to our scale of consideration which represents other factors which were not considered in this study like Phosphorus,pH,and other demographic stochastic processes.These variations led us to conclude that species turnover were controlled by both dispersal and environmental factors but their effect varied with scale.Hence,for the better conservation process which needs to know the community structuring and diversity pattern formation,both dispersal and environmental factors should be considered.