Research On Temporal And Spatial Dynamics Of Xianghai Wetland Bird Diversity

We undertook point counts of birds in the Xianghai National Wetland Nature Reserve in Northeastern China, and used remote sensing and geographic information system technologies to study the effect of landscape types and climate change to bird diversity from patch scale to muti-scales.1. Using a backward linear regression model, we found that there was a negative relationship between bird diversity indices and farmland. Presence of water and marsh was negatively associated with Evenness, Richness, whereas positively associated with Shannon-wiener index. We also found the negative effects of distance to roads on Evenness and Shannon-wiener index.2. Using remote sensing and geographic information system technologies to map land cover types, we linked cover types to avian species Richness, Evenness, and Shannon-wiener index. With the stepwise linear regression model and regressions of proportions of cover types at different spatial scales, we noted that measures of avian diversity were positively influenced by the presence of open water, farmland, and alkaline marsh, while negatively by human settlement. Notably, some relationships were apparentonly when scale was considered.3. We linked landscape scales to avian species Richness, Evenness, and Shannon-wiener index for cover types at different proportions of cover types, and find:(1) Both high and low proportions of alkaline marshes reduce the heterogeneity of the habitat that is prerequisite for water bird’s survival, and middle proportions should be maintained to sustain avian biodiversity. The soil of the Songnen Plain is naturally prone to alkalinisation, but the availability of alkaline marshes and open waters to the avian assemblage will inevitably diminish if the increase of upstream water offtaking from the Huolin River continues;(2) Allowing a small proportion of the reserve in a distributed pattern to continue to be used for farming of crops contributes to the maintenance of avian diversity, and the farmland proportions should be controlled by a certain threshold in habitat management of the nature reserve in the future;(3) Significant effects of scale on three biodiversity indices occurred at the high proportion of open water in the landscape composition. In spring, a high proportion of open water in the landscape resulted in species that were less disparate in numbers, although it did not attract a greater range of species. Conversely, in autumn, high proportions of open water in the landscape detracted from the number of species, the species were more disparate in numbers, and diversity was lower.4. We also studied the effects of vegetation index (normalized difference vegetation index, NDVI) and climate factors on bird diversity. Our results revealed that abundant precipitation would increase the bird diversity while temperature showed different utility to diversity index in different seasons. Warm temperature may shift bird migration to an earlier time, cousing drought at the same time, which may lead to the shrink of open water areas and the decline of vegetation cover, and threating habits like swamps and shallow waters, which are essential for a lot of waterfowls.