Effects of bird seed dispersal on diversity of the invaded plants in several hedge types

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• 作者：Xinhua Li ; Xiaoming Yin ; Bing Xia ; Weilin Li ; Ya Li
• 关键词：tree hedges ; invaded plants ; seed dispersal ; birds ; seed sources ; disturbance ; Nanjing Botanical Garden Mem. Sun Yat-Sen ; community succession
• 刊名：Acta Ecologica Sinica
• 出版年：2006
• 出版时间：June 2006
• 年：2006
• 卷：26
• 期：6
• 页码：1657-1666
• 全文大小：289 K

文摘

The plants that invaded as weeds including woody weeds were surveyed in three hedge types, Euonymus japonicus(HEa), Viburnum awabuki (HV), and Deutzia scabra (HD), respectively, and two hedge types, Buxus microphylla var. sinica (HBa, HBb) cultivated in different habitats in Nanjing Botanical Garden Mem. Sun Yat-Sen (NBG), Nanjing of East China, from April 2001 to November 2002. Another hedge type, Euonymus japonicus (HEb) was also investigated as a contrast, cultivated in Nanjing Agricultural University (NAU), about 3 km away from NBG, between April and November 2003. In total, 1230 plant indi-viduals were found to have invaded these six hedge types, and were identified as belonging to 70 species in 57 genera and 42 fami-lies. Among these plants, 1047 individuals of 55 species were adapted for bird seed dispersal, and 161 individuals of 10 species were adapted for wind seed dispersal, but the seed dispersal mode of the other 22 individuals of five species was uncertain. Among the six hedge types, we found a significantly higher occurrence of bird-dispersed plant species than that of wind-dispersed species (t = 5.086, df = 10, P < 0.0001) or that of species with the unknown dispersal mode (t = 8.446, df = 10, P < 0.0001). However, the difference of occurrence between wind-dispersed species and species with the unknown dispersal mode was not significant (t = 1.977, df= 10, P = 0.076). The number of bird-dispersed plant species recorded in the five hedge types of NBG varied from 15 to 36, M ± SD = 25.6 ± 8.1, and the Shannon-Wiener indices were between 2.151 and 2.917, M ± SD = 2.671 ± 0.306. In contrast with NBG, only 12 species of bird-dispersed plants occurred in the hedge of NAU, with a lower Shannon-Wiener index of 1.679. As a result of cluster analysis, based on Bray-Curtis similarity indices of the invaded plant species adapted for bird seed dispersal, the similarity of species composition of bird-dispersed plants between hedges was influenced to a large extent by the surrounding habitat characteristics, e.g., locality, seed source diversity, distances from seed sources, seed dispersing birds, and frequency of human disturbance, rather than simply being dependent on the hedge tree species themselves. This research suggests that hedges could attract birds to utilize their interior shelter as habitats, and therefore, would have enhanced the deposition of bird-dispersed seeds, as well as have favored seed-ling survival under hedges. Consequently, avian seed dispersal has enriched the species composition of each of the six hedge types consisting of just a single tree species. Although survival and colonization of the migrated plants will inevitably cause some influ-ences on the aesthetic view of hedges, these invaded weeds or woody weeds could be managed and suppressed through regular arti-ficial pruning and by eradication. The results indicate the ecological significance of seed sources, bird seed dispersal, and shrub patches in promoting the successional development of woody vegetation.