Study on Vascular Plant Diversity and Their Dispersal Mechanisms on the Vertical Surfaces of nanjing Ming Dynasty City Wall
|School||Nanjing Agricultural College|
|Keywords||Nanjing Ming Dynasty City Wall Vertical wall surface Vascular plant Species diversity Dispersal mechanism|
Nanjing Ming Dynasty City Wall is the largest and well preserved city wall with long history all over the world. This paper reported the diversity of vascular plants on the vertical surfaces of Nanjing Ming Dynasty City Wall, and analyzed dispersal mechanisms of these colonized plants. The aim of this study was to provide scientific data for the maintenance and management of Nanjing Ming Dynasty City Wall, and also offer some practical and theoretic references for plant dispersal ecology.From September 2007 to November 2009, we selected six typical patches of city walls for field survey, including Qianhu、Qingliang gate、Shence gate、Taicheng、Shizishan、Zhonghua gate patches of Ming dynasty city wall. Ten quadrats were sampled to survey all the vascular plant species and its individual number for each of the 6 patches of city walls, and every quadrat consisted of a surface area of 10 m long along the wall base upwards to top of the city wall. A total of 60 quadrats were investigated and the main results are listed as follows.(1) In total,101 vascular plant species were found on the vertical wall surfaces, belonging to 88 genera and 55 families with 11134 plant individuals. Ferns consisted of 3 species, belonging to 3 genera and 3 families, with 2335 individuals. Flowering plants consisted of 98 species, belonging to 85 genera and 52 families, with 8799 individuals; Species number of each of the 6 wall patches varied from 30 to 71, M±SD=49.33±16.23, their Shannon-Wiener indices were between 2.84 and 3.669, M±SD=3.23±0.33. There were 71 plant species on the Taicheng city wall, with a higher Shannon-Wiener index of 3.669, both ranked first among these wall patches. However, only 30 plant species occurred on the Qingliang gate city wall, with the lowest Shannon-Wiener index just of 2.84. Ficus pumila and Campsis radicans becomed the dominant species on Qianhu patch; F. pumila and Broussonetia papyrifera were the dominant species on Qingliang gate patch; B. papyrifera and Polygonum multiflorum becomed the dominant species on Zhonghua gate patch; dominant species were not obvious on the other three pathes. (2) Among the 101 species on the wall surfaces,3549 individuals of 48 species were adapted to animal seed dispersal,4498 individuals of 26 species were adapted to wind seed dispersal, but the seed dispersal mode of the other 3039 individuals of 26 species was uncertain. These wall plants were mainly originated from both wild and cultivated plants around the city wall, their propagules, such as fruits, seeds or spores had been dispersed by animals or some physical agents to the gaps or cracks between the bricks or stones on vertical surface of wall, and have germinated and colonized on the wall.(3) Higher plant diversity appeared on those wall patches with larger gaps between bricks or stones, a higher degree of weathering, and adequate water supply, even some large trees have survived for a long time on vertical surfaces of the city walls. Consequently, we suggest that these gaps or cracks should be repaired or sealed in time, in order to effectively prevent the propagules from arriving and colonizing the gaps、cracks or cavity on city walls. The results also indicated the important ecological significances of seed sources, seed dispersal in promoting the successional development of plant communities.