普达措国家公园越冬期鸟类群落功能空间及驱动机制

Functional Trait Space and the Driving Mechanism of Wintering Bird Community in Potatso National Park,Southwestern China

解析群落中生物多样性维持的决定因素是生态学研究的一个重要目标。为了获得普达措国家公园碧塔海-属都湖片区鸟类物种多样性,2021年8月至2022年7月,设置8条总长17km的鸟类调查样线,并于2021年11月至2022年10月在片区24个位点布设红外相机进行辅助调查。为了重点研究越冬期鸟类群落功能多样性格局及其驱动机制,2021年11月至2022年3月,对碧塔海-属都湖片区内高原湖泊、高山草甸、针阔混交林和针叶林4种生境共30个样点进行了越冬期鸟类群落的调查。利用15个鸟类功能性状计算群落功能丰富度(FRic)和平均最近邻接功能距离(MNND),并构建零模型,探讨环境过滤和极限相似性作用对越冬期鸟类群落构建的相对重要性。结果表明,本研究在普达措国家公园碧塔海-属都湖片区共记录13目42科114种鸟类,与该区域前期野外记录相比新增了74个野外记录鸟种。该片区不同生境类型的鸟类物种组成差异明显,针阔混交林和针叶林物种组成相似,但未完全重合。在该区域高原湖泊和高山草甸越冬的16种鸟类显著扩大了越冬期鸟类群落的功能空间,但同时显著减小了功能空间中物种的平均最近邻接功能距离。4种生境鸟类群落功能空间随物种丰富度增加而增大,但零模型分析发现功能空间的观察值总体上小于期望值;功能空间中物种间平均最近邻接功能距离随物种丰富度增加变得更近,限制性零模型分析结果显示,其观察值整体趋势上大于期望值。综上,本研究更新了对普达措国家公园鸟类物种多样性的认知,可为该区域鸟类保护和管理提供最新数据支持。越冬鸟的迁入使片区越冬期鸟类群落在功能结构上更紧凑、更稳定;群落功能多样性研究结果表明,环境过滤限制了该区域越冬期鸟类群落功能空间随物种丰富度的增大,同时极限相似性对物种在功能空间中的分布起着重要作用,即环境过滤和极限相似性对片区越冬期鸟类群落的构建过程具有双重重要性。

[Objectives]The determinant of biodiversity maintenance of natural communities is important in ecological research.In this study,we aim to survey the bird species diversity of Bita Lake-Shudu Lake region of Potatso National Park,and further explore the functional trait diversity pattern and the underlying mechanism of the wintering bird communities of this region.[Methods]We used line transect method in this study from August 2021 to July 2022.Specifically,eight transects with a total of 17 km long were selected in Bita Lake-Shudu Lake region of Potatso National Park.Besides,we set up twenty-four infrared cameras 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 coniferous and broad-leaved forests,and coniferous forests in the region(Fig.1 and Appendix 1).We selected 15 functional traits of bird in the database(Appendix 5),including four morphological traits(mass,beak width,wing length,tail length)(Appendix 2),six traits of diet(vertebrate,invertebrate,scavenger,nectar&fruit,seed,plant),and five traits of foraging strata(canopy or aerial,midhigh,understory,ground,water).Based on bird functional traits,functional richness(FRic)is used to measure the volume of functional space,and mean nearest neighbor functional distance(MNND)is used to measure species distribution in functional space,then use“Picante”package in R to build unconstrained null model and constrained null model by using“independentswap”method.The standardized effect size(SES)generated by the null model was used to infer the dominant drive mechanism of wintering bird community assembly.Finally,the paired t-test was used to compare whether the functional richness(FRic)and mean nearest neighbor functional distance(MNND)of the community were significantly different before and after the removal of wintering birds,and then combined with the null model results to explore the influence of wintering bird community on the functional structure.[Results]A total of 114 bird species belong to 13 orders,42 families were recorded,74 birds have been added to the previous field record of this region(Appendix 6).Five and fourteen species were listed as National Class I(Appendix 7)and II protection bird in China respectively.The four habitat types held different bird species composition,with overlap for the two forest habitat types(Fig.2),however,there is no complete overlap in the survey points.Sixteen wintering birds recorded in plateau lakes and alpine meadows significantly expanded the functional trait space of the community(P<0.05),meanwhile significantly reduced the mean nearest neighbor functional distance(P<0.05)between species in the functional space(Fig.4).The functional richness of the wintering bird community increased with the increase of species richness(Fig.3),but the null model analysis found that the observed functional richness was generally smaller than expected(Fig.5),that is,the functional space increased with the increase of species richness,but its increase was limited by environmental filtering.The mean nearest neighbor functional distance of species in functional space became closer with the increase of species richness(Fig.3),while the constrained null model showed that the standardized effect size was almost greater than zero(Fig.6),in other words,with the increase of species richness,species are packed more closely in the functional space,but limited by the effect of limiting similarity,species will not gather indefinitely.[Conclusion]This study updated field records of bird species of the Bita Lake-Shudu Lake region of Potatso National Park,which can provide a new data basis for the conservation and management of bird diversity in the region.The migration of wintering birds filled the gap of niche and made the functional structure of wintering bird community more compact and stable.More importantly,our results showed that the functional space of the wintering bird communities was constrained by environmental filtering,meanwhile,the distribution of bird within the functional trait space was affected by the limiting similarity,that is,environmental filtering and limiting similarity are doubly important for wintering bird community assembly.