Analysis On The Characteristics And Formation Mechanisms Of Breeding Bird Diversity In Inner Mongolia

As a key factor in maintaining the functioning and stability of the ecosystem,biodiversity is facing a serious threat from climate change and human activities.Inner Mongolia has a vast territory,great differences in hydrothermal conditions and diverse vegetation types,which is pregnant with rich and unique bird diversity.But at the same time it has also experienced severe climate change and human activities.Birds are sensitive to environmental changes,and their diversity composition characteristics are not only the result of long-term evolution but also a reflection of contemporary environmental changes.In addition to species diversity,phylogenetic diversity and functional diversity represent the evolutionary history and functional information of biological communities,respectively.The study of different dimensions of species diversity,phylogenetic diversity and functional diversity is helpful to better understand the distribution pattern and formation mechanism of bird diversity.However,so far,there is no in-depth study on the distribution pattern and multi-scale causes of bird diversity from the whole Inner Mongolia regional scale,such as paleoclimate change,contemporary climate,land use changes,interspecific relationships and so on.The study of land use changes and climate change on bird diversity pattern at a regional scale is of great significance for biodiversity conservation in Inner Mongolia.By combining species richness,phylogenetic and functional diversity,this thesis comprehensively discussed the distribution pattern and formation mechanism of breeding bird diversity at county scale in Inner Mongolia.And we also explored the differences of species richness,phylogenetic and functional ? diversity of breeding bird communities among different land use types and its relationship with climate in Inner Mongolia steppe.Additionally,we further analyzed the differences of beta diversity(homogenization)of bird communities in different land use types and its relationship with climatic distance.The main results are as follows:(1)Based on field investigations and collection of existing literatures,353 breeding bird species were recognized in Inner Mongolia according to the classification system of the Global Phylogeny of Birds,belonging to 173 Genera,56 Families and 21 Orders.Passeriformes and Charadriiformes are the dominant Orders,and the number of bird species accounts for 49.29% and 10.76% of all breeding birds,respectively.In the bird fauna,the northern type is dominant(76.20%),in which the Palaearctic type,Northeast type and Holarctic type constitute the main body,reflecting the Palaearctic characteristics of the bird fauna in Inner Mongolia.(2)At the county scale,with the increase of altitudinal range and plant species richness,bird species richness increases and the phylogenetic structure and functional structure tends to be overdispersed.Meanwhile,there are more bird species with more overdispersed phylogenetic structure and functional structure,fewer species with more clustered structure.Additionally,in regions with high temperature and low precipitation,bird communities have more clustered phylogenetic and functional structure.The above results show that local ecological factors such as habitat heterogeneity,biotic interaction and environmental filtering are the main drivers of the existing pattern of breeding bird diversity in Inner Mongolia.The results of structural equation model show that altitudinal range and mean annual temperature indirectly affect the species richness and phylogenetic diversity of birds through plant species richness,and mean annual temperature has a direct effect on the phylogenetic and functional diversity of birds.(3)There are significant differences in species richness,phylogenetic and functional ? diversity among different land use types in Inner Mongolia steppe.The species number of birds in natural grassland is significantly lower than that in woodland and is similar to that in farmland and village,but the composition of bird communities is significantly different.Bird communities in natural grassland have most clustered phylogenetic and functional structure and concentrated with species in recently evolutionary branches and species with larger body mass.The results of typical steppe and desert steppe subregions are similar to those of the whole steppe region,but there were no significant differences among land use types in meadow steppe subregions.There are no significant differences in the relationship between bird community ? diversity and climate variables among different land use types.(4)From grassland to woodland,farmland and village,the species,phylogenetic and functional similarity of bird communities increase with the influence of human activities,indicating that human activities not only homogenize the species composition of bird communities,but also homogenize the phylogenetic and functional diversity.At the same time,the climatic variables distance in natural grassland can better explain the species richness,phylogenetic and functional similarity of bird communities,it shows that human activities erase the relationship between ? diversity and climate distance.The results of meadow steppe and typical steppe subregions are consistent with those of the above steppe regions.The functional similarity of desert steppe subregion is also the lowest in natural grassland and increases significantly with the influence of human activities,but the species and phylogenetic similarity of birds in natural grassland are significantly higher than those in woodland and similar to those in farmland and village.In summary,the species richness,phylogenetic and functional diversity of breeding bird communities at the county scale in Inner Mongolia are mainly driven by local ecological factors,such as habitat heterogeneity,biotic interaction and environmental filtering.Land use changes may lead to changes in species composition,phylogenetic structure and functional structure of bird communities,accompanied by the decrease of species in recently envolutionary branches and the loss of larger birds.Land use changes have caused serious biotic homogenization of bird communities in Inner Mongolia steppe regions,especially in meadow steppe subregions and typical steppe subregions,that is,the loss of biodiversity.A study combined with different components(species diversity,phylogenetic diversity and functional diversity)and levels(?-diversity and ?-diversity)of biodiversity can understand the diversity distribution pattern and community structure comprehensively,so as to provide scientific reference for the protection of bird diversity in this region.