The Study On Plant Diversity Of Remnant Grassland Patches In The Agro-pastoral Ecotone Of Inner Mongolia

Habitat fragmentation is the mean cause of biodiversity loss,and the driving factors of biodiversity in fragmented habitats are complex and diverse.Therefore,the pattern and maintenance mechanism of biodiversity in fragmented habitats had become a hot issue in ecological research.As an important ecological security barrier in China,the agro-pastoral ecotone in northern China has experienced an intense process of habitat fragmentation in the past two decades and formed many remnant grassland patches.It is of great significance to find out the diversity pattern and influencing factors of these remnant grassland patches to protect and restore biodiversity in this area.This study investigated the Tabu River basin located as a studied area in the agro-pastoral ecotone in Inner Mongolia.The plant diversity pattern of 82 remnant grassland patches was investigated from three dimensions: species,phylogeny,and functional traits.After determining the appropriate buffer radius for patch plant diversity,we further discussed the impacts of patch characteristics,landscape characteristics,and environmental characteristics on patch plant diversity.The main conclusions are as follows:(1)A total of 172 vascular plants belonging to 44 families and 109 genera were investigated in the study area.The phylogenetic relationship between Saussurea amara and S.japonica is the closest,and the phylogenetic relationship between Ephedra sinica and Psilotum nudum is the farthest.The varying degree of different functional traits is other,the coefficient of variation of leaf dry matter content is the highest,and the leaf carbon content is the lowest.(2)Pearson correlation analysis showed that when the buffer radius is 150 m,the correlation between grassland area ratio and plant species richness,phylogenetic richness,and functional richness of remnant grassland patches is the strongest,which indicated that 150 m is the appropriate buffer radius for predicting plant richness of remnant grassland patches.(3)Synchronous autoregressive analysis shows that the remnant grassland patch area had a significant positive effect on species richness,phylogenetic richness,and functional richness of the patch.The proportion of grassland area in the buffer zone with a radius of 150 m also had a significant positive effect on species richness and phylogenetic richness of patch plants but has no significant relationship with the functional richness of patch plants.(4)Random forest analysis showed that the relative importance of patch area and patch isolation to species richness,phylogenetic richness,and functional richness of patch plants in the remnant grassland was very high,which indicated that patch area and patch isolation were the two main factors affecting the diversity of patch plants in the remnant grassland.The above results showed that the island biogeography theory could predict well plant species richness,phylogenetic richness,and functional richness of remnant grassland patches in the agro-pastoral ecotone of Inner Mongolia.Therefore,this study suggests that large and highly connected patches should be protected for the construction of nature reserves which can improve the effectiveness of biodiversity conservation.Meanwhile,the grassland habitat in a certain range around the remnant grassland patches can not be ignored.