Bird Diversity,Distribution Pattern And The Underlying Mechanisms In An Urbanized Mosaic Landscape,Huaxi University Areas,Guizhou Province

Habitat fragmentation is a direct cause of biodiversity.But it is not well known about the effects of fragmentation at different study scales and whether the relevant theories apply in urbanized mosaic landscape.In order to explore the mechanisms underlying species diversity and community distribution in heterogeneous habitat fragments,this study used the line-transect method to investigate birds in 30 patches of fragmented woodlands in Huaxi University Area,Guizhou Province during the bird breeding season(March to August)from 2020 to 2022.Our work focused on answering the following questions:(1)bird diversity and the species-area relationship of bird communities;(2)effects of geographical characteristics and habitat diversity on bird species richness;(3)factors regulating bird assemblages,so as to assess the impact of habitat fragmentation on bird communities at patch and landscape scales and to examine the effects of island biogeography theory,landscape ecology theory and metapopulation theory accounting for community distribution in fragmented habitats,and,thus,to improve the theoretical basis for landscape planning,habitat restoration and species conservation.We recorded a total of 106 bird species during 14-rounds surveys which belonging to 12 orders and 41 families.After excluding occasional species,winter residents,passage migrants and high-flying birds,there were 83 species.The results are as follows:(1)Species-area relationship:By constructing four key species-area regression models,we found that the best model was the left-horizontal with one-threshold model(AICc=188.36),and the next best model was the linear model(AICc=189.95).The best model showed that above the area threshold of 1.00 hm~2,species-area relationship was consistent with the area effect proposed by island biogeography theory.However,species richness did not change significantly with area below the area threshold of 1.00 hm~2,suggesting a possible small island effect.(2)Effects of geographical characteristics and habitat diversity on bird species richness:We constructed the linear regression model of bird species richness and geographic characteristics and habitat diversity(the number of habitat types).The results showed a significantly positive correlation between species richness and patch area(P<0.001),and habitat diversity(P<0.001),but negative correlation between species richness and perimeter-area ratio(PAR,P<0.01).There was no significant correlation of species richness with isolation(P>0.05).(3)Factors regulating bird assemblages:The RLQ analysis(R-mode linked to Q-mode analysis)results showed that the first two RLQ axes accounted for 83.97%and 13.79%of total co-variation between geographic characteristics,habitat diversity of patches and bird species functional traits mediated by bird assemblage composition.The results of the fourth-corner analysis further revealed that apart from the positive correlation between PAR and body size(P=0.03,P adjusted=0.49),isolation and territoriality(P=0.04,P adjusted=0.49),there was no obvious correlation between species functional traits and geographic characteristics and habitat diversity.In addition,the procrustes analysis results showed that habitat composition had a significant correlation with bird assemblage composition(M~2=0.7510,r=0.4990,P<0.001).This study revealed that bird species richness in the fragmented woodlands of Huaxi University Area was regulated by area,but there may exist small island effect.In addition,species richness was positively correlated with habitat diversity,and marginal effects had a negative impact on species diversity.However,the geographical characteristics of patches and species functional traits have little influences on bird assemblage composition.Although habitat diversity did not significantly affect bird assemblage composition,there was a significant correlation between bird assemblage composition and habitat composition.Our findings suggest that island biogeography theory,landscape ecology theory and metapopulation theory may jointly account for species community distribution in heterogeneous fragmented habitats.Our results have important implications for sustainable landscape planning and habitat restoration.For example,protecting patches with large areas or high heterogeneity,promoting heterogeneous habitats by creating greenbelts and increasing plant diversity and habitat composition complexity in urban green space should be emphasized in the process of urban planning,construction and development,to contribute to the local pool of species and favor meta-community persistence.