A Study On Biodiversity Of Landscape Trees In Fuzhou Housing Estates

With urban development, landscape construction in residential area has been also changing. Landscape trees are not only the most important natural landscape element, but also a part of the urban forest system. Thus the significance of landscape trees is not only presented in the value of landscape, but also presented in the ecological function. In order to study the different status of landscape trees in residential areas and analyze the way urban development influence landscape trees in spatial and temporal dimension, this study investigated species composition and floristic diversity of landscape trees in 36 housing estates in Fuzhou.The results of the survey showed that there were 12694 trees belonged to 155 species,97 genera and 42 families. In species composition analysis, the housing estates were divided into 4 age groups, 64 species with 1837 trees were in group A (1995-2000). Group B (2001-2005), group C (2006-2010) and group D (2011-2015) contained 68,90 and 100 species with 1643,4543 and 4671 trees respectively. Besides, the housing estates were also divided into 3 location groups based on the relative location of the ring roads in the city,102 species with 4029 trees were in group 1 (within the second ring road). Group 2 (between the second and third ring road) and group 3 (outside the third ring road) contained 106 and 102 species with 4712 and 3953 trees respectively. And landscape trees in 3 location groups were considered uncorrelated after brief analysis. On contrast, landscape trees in early age groups showed lower variety, overwhelming dominant trees, species unbalanced. And those phenomena were improved in later age groups.The species were divided into 6 frequency groups.20 species with 7593 trees were in the Signature group. The Dominant, Common, Occasional, Rare and Solitary groups contained 17,18, 50,38 and 12 species with 2383,1233,1300,173 and 12 trees respectively. The giant dominant of Signature group in tree number demonstrated the obvious tendency in the selection of landscape trees.After the comparison with structure of landscape trees in 4 age groups, certain similarities bwtween group C and group D were indicated, and group B was more like a median between group A and group C. Therefore, it is to assume that the completition period of the housing estates in group B was a transition period of the structure of landscape trees, and that was probably caused by the change of tree selection. On the basis of that assumption, the analysis of tree selection in different age groups indicated that certain trees were gradually left out and another new were being chosen during this period.The landscape trees in Fuzhou showed lower biodiversity indexes, especially species richness, when compared to developed cities.The landscape trees in aged estates and relocation estates were with lower biodiversity than in other new estates.The AHP evaluation model consisted of Simpson biodiversity index, ornamental characters diversity, flowering season diversity, growth form diversity and landscape maintenance with different weights. The analysis on evaluation results indicated that the landscape trees in new estates showed higher ecological and ornamental value than in aged estates, and presented a growing trend in last 20 year which illustrated the emphasis of landscape designers and increasing quality demand of civil life.