Species And Functional Diversity Of Wintering Bird In Potatso National Park,Southwestern China

Understanding the supproting mechanism of biodiversity is important in ecological research,exploring the relationship between different aspect of biodiversity in different typical habitats and the driving mechanism of community assemblage is conducive to the overall development of biodiversity conservation and species coexistence theory.In this study,it attended to survey the bird species diversity of Bita Lake-Shudu Lake region of Potatso National Park,and investigate the species/functional trait diversity pattern and the underlying mechanism of the wintering bird communities of this region.Bird transect surveys were conducted in eight transects with a total of 17 km long from August 2021 to July 2022,and 24 infrared cameras were set up from November 2021 to October 2022 to obtain bird species diversity in this region.From November 2021 to March 2022,we surveyed bird composition of 30 wintering bird communities belongs to four habitat types:plateau lakes,alpine meadows,mixed broad-leaved and coniferous forests,and coniferous forests in Bita Lake-Shudu Lake region of Potatso National Park.Three species diversity indices were calculated: Shannon-Weiner diversity index,Simpson dominance index and Pielou’s evenness index;based on fifteen bird functional traits to access four functional diversity indices,including the functional richness(FRic),functional evenness(FEve),functional divergence(FDiv)and functional dispersion(FDis),we analyzed the relationship between species diversity and functional diversity of wintering bird community.Null model of the functional richness and mean nearest neighbor functional distance(MNND)was constructed to access the standardized effect size of the them.The results are as follows:(1)A total of 114 bird species belonging to 13 orders and 42 families were recorded in Bita Lake-Shudu Lake region of Potatso National Park,including 74 new wild observation records of this region.Our results provided the latest data support for the subsequent species protection and management of the park.(2)The four habitat types held different bird species composition,with overlap between the two forest habitat types.Species richness of alpine meadow was the highest(n=27).The larger-billed crow(Corvus macrorhynchos)with the widest feeding niches was recorded in all the four habitats,indicating that the bird species with the varied feeding charactersitics hold large distribution range.Simpson index and Pielou’s index were the highest in the mixed forest.The functional evenness(FEve),functional divergence(FDiv)and functional dispersion(FDis)of bird communities in mixed conifer forest were higher than those in other habitats.The Shannon index of bird community in alpine meadow was higher than that in other habitats,and Pielou’s evenness index was the lowest.(3)Functional richness and Shannon diversity index were significantly positively correlated with species richness(P < 0.05),functional divergence was negatively correlated with species richness(P < 0.05).Shannon diversity index and Simpson index were positively correlated(P < 0.05).Pielou’s evenness index was positively correlated with functional dispersion and functional evenness,and negatively correlated with functional richness(P <0.05).The relationship between functional diversity index and species diversity index can be positive,negative or not correlated.The relationship between species diversity and functional diversity was different in different habitat type.These patterns indicate that species richness information should be considered in the calculation of community functional diversity and its construction,and also confirm that species diversity and functional diversity indicate the characteristics of different aspects of biodiversity.(4)The functional space volume of bird communities in the four habitats increased with the increase of species richness,and the mean nearest neighbor functional distance decreased with the increase of species richness,that is,the degree of aggregation of species in functional space increased,but the rate of increase of functional space and the degree of accumulation of species in functional space decreased with the increase of species richness.It indicates that the increase of functional space and the degree of aggregation of species in space are restricted.(5)Based on the unconstrained null model analysis,it is found that the observed functional space is usually smaller than the expected value and the functional volume is limited under the premise of given species richness.It is also detected that most of the observed values of the average nearest adjacent functional distance are less than the expected value.Based on the constraint null model analysis,it is found that in the constrained functional space,the observed value of the mean nearest neighbor functional distance is greater than the expected value,which is in sharp contrast with the unconstrained null model.Environmental filtering limited the increase of the functional space of the wintering bird community in this region,and made the species more closely grouped in the functional space.At the same time,limiting similarity can prevent excessive accumulation of species.This indicates that birds suitable for survival are filtered into the community through layers of environment,which makes the functional traits of birds in the community converge.Therefore,similarity among bird species intensifies competition and leads to competitive exclusion,and thus promotes species coexistence through niche differentiation.To sum up,species are usually "added" to the existing functional space of the community.Environmental filtering screens species with high fitness into the community,while species with similar ecological niches co-exist in the community through the limiting similarity effect,that is,strong limiting similarity effect can occur in the functional space constrained by abiotic environment.(6)Plateau lakes and alpine meadows were the main wintering sites for birds in this region,and 16 winter bird species only appeared in these two habitats.The migration of wintering birds significantly expanded the functional space of the wintering bird community,but significantly reduced the mean nearest neighbor functional distance of species in the functional space.The results showed that the original community had left a gap in the niche,but the winter birds occupied and used the available empty functional space,which made the community more tightly packed and stable during the wintering period.