Effects Of Vegetation Succession Caused By Invasion Of Pine Wood Nematode On Bird Community

This study examines changes in avian community composition and diversity associated with the loss of China Pine (Pinus massoniana) resulting from pine wood nematode infestations, with particular emphasis on habitat structure and bird-habitat relations. In May and June 2004, and January 2005, the study was conducted in Xiangshan County and Tiantong National Forest Park in Ningbo, Zhejiang Province of China. In the study areas, four habitat types were identified: mature forest of China pine(type â…  a and b, undisturbed and disturbed by logging respectively), evergreen broad-leaved coppices of 5 years old after pine wood nematode infestations(type â…¡), evergreen broad-leaved forest of 12 years old after pine wood nematode infestations(type â…¢), evergreen broad-leaved forest of about 40 years old(type IV). Birds surveys were conducted by point count. The major results are as follows.1. A total of 31 bird species were recorded during breeding season. The numbers of species of breeding birds in each habitat type were 23(type â… ), 14(type â…¡), 22(type â…¢) and 20(type â…£). Taking one with another, type â…  (a) presented by far the richest community (in term of species richness, diversity, evenness and abundance), followed by two early seral stages of evergreen broad-leaved forest (type â…¡ ,â…¢) (in the two habitats inter-stand differences were not significant), and type â…£. There was little differences between type â…  (a) and each early seral stage in bird species richness, diversity, evenness and abundance. Bird species richness and diversity showed significant differences between type IV and each of other habitat types, and evenness differed between type â…£and each early seral stage. The four habitat types did not differ in bird abundance significantly. In winter, a total of 18 bird species were recorded. The numbers of species recorded in each habitat type were 16 (type â… ), 8(type â…¡), 17(type â…¢) and 15(type â…£). Type â…  (a) also presented relatively the richest bird community. The three types of evergreen broad-leaved forest did not differ significantly in bird richness, evenness and abundance, whereas bird diversity wassignificantly greater in type III than the others.2. Analyses of bird guild showed that bird abundance of 6 guilds varied significantly among the four habitat types. Low-foliage insectivores were most common in type I (a) and type II ,and little differences existed in the former two. Abundance of mid-canopy insectivores differed between type IV and each of two early serai habitat types, and little differences existed in the latter two. Abundance of low and medium-canopy plantivores show no significant differences between type I (a) and type IV, but significant differences existed between the former two and type II. Abundance of medium and high-canopy plantivores show little differences between type III and type IV, but significant differences existed between the former two and type II. Abundance of understory omnivores, various height insectivores, understory nesters, canopy nesters and cavity nesters did not differ among the four habitat types, whereas all above-metioned guilds were relatively more common in type I .3. Comparisons of bird assemblages in disturbed and relatively undisturbed stands of China pine by logging showed that bird species diversity, richness abundances of low-foliage insectivores, low and medium-canopy plantivores and understory nesters declined significantly and bird abundance decreased sharply in disturbed stands. It meant that understory gleaners and understory nesters were more sensitive to the disturbance of logging.4.The four habitat types showed significant differences with regard to vegetation structure. Only these variables such as DBH, percentage of edge occurrence, understory species richness and diversity did not differed significantly among these habitat types. On the stand level, the understory of type I was well-developed and supported the richest floral communities.5. Stepwise multiple regression analysis showed that bird species diversity, richness, evenness, abundance of low-foliage insectivores, mid-canopy insectivores and low and medium-canopy plantivores were all negatively correlated to PCI (stand age). Bird evenness was also positively correlated to understory species richness, and abundance of low-foliage insectivores to the occurrence of edge. Abundance of low and medium-canopy plantivores was also negatively correlated to PC2(structuralheterogeneity), and positively to understory species richness. Abundance of medium and high-canopy plantivores and cavity nesters were positively correlated to PCI. It meant that stand age was important predictor of bird community composition.On summary, the results suggest that local forest bird communities composition would not be changed significantly and bird species diversity would not decline because of the rapid increase in understory vegetation that included large numbers of seedlings and saplings of arbor species when China pine forests are destroyed as a result of pine wood nematode infestations. Early serai evergreen broad-leaved forests are very important for birds. In our study area, evergreen broad-leaved forests lack vertical heterogeneity and floral diversity. To improve bird species diversity in evergreen broad-leaved forests following the death of pine forests resulting from pine wood nematode infestations, we suggest that, when coping with infested pine forests by pine wood nematode, some reasonable and effective measures are required to increase habitat vertical heterogeneity and floral diversity.