| Urban plants are important components in urban ecosystem,and the evaluation of plant functional diversity based on functional traits is one of the hotspots in ecological research.Based on the investigation data of 200 green space sites in the built-up area of Shenzhen,this paper analyzed the composition of plant species,functional traits,community composition,species diversity and functional diversity about urban plants,which can provide important reference for urban plant diversity research and urban green space management.The species diversity analysis selected species richness index,Shannon-Wiener index and Pielou's evenness index.About functional traits,a total of 12 functional traits were selected,including plant height,growth form,plants thorns,colored-leaf plants,leaf texture,leaf hairs,leaf compoundness,root system type,flowering period,fruiting period,fruit type and species source.The functional diversity analysis used three indices,including functional richness index FDp,functional evenness index FEve and Rao's quadratic entropy index.In addition,this paper assumed that the three groups of landscape elements,including roads,facilities and water,had important effects on the functional diversity of urban plants,and to demonstrated it.The results showed:(1)There were 722 plant species belonging to 124 families and 440 genera recorded in random selection investigation of urban plants in the built-up area of Shenzhen.The dominant families with 40 or more species were Leguminosae,Gramineae,Euphorbiaceae and Compositae,and the dominant genera with 10 or more species were Ficus and Euphorbia.The phenomenon of dominant families in urban green space was obvious.The ratio of trees,shrubs,herbs and vines was 5: 4: 7: 1,the ratio of evergreen trees to deciduous trees was 11: 4,the ratio of evergreen shrubs to deciduous shrubs was 18: 5,the ratio of annual or biennial herbs to perennial herbs was 5: 8;the specie number of herbaceous vines was equivalent to that of woody vines.The proportion of exotic species was 44.04%,and the exotic species from foreign countries accounted for 68.87% of exotic species.Road green space and park green space were the types of green space with a higher proportion of exotic species.Tree was the growth form with the highest proportion of exotic species.The analysis of dominant plants in the built-up area showed that dominant herb species of all types of green space were highly similar.(2)No-thorn plant,non-colored-leaf plant,single leaf,taproot system,flowering from June to August,dried fruit,fruiting from September to November and glabrous or hairless leaf accounted for a high proportion in their respective functional traits.(3)The TWINSPAN classification result showed that urban tree-shrub community could be divided into 41 groups and herb community could be divided into 54 groups.There were 9 tree-shrub groups involved ?10 plots,and 15 herb groups involved ?30 plots.The classification result showed that wasteland was significantly different from others.The functional orientation and human management of green space affected the composition of urban plants communities.And urban landscape paid more attention to trees and shrubs.(4)The species richness index and Shannon-Wiener index of the overall plant community were dominated by park green space,followed by residential green space and square green space.The Pielou's evenness index of square green space had a slight advantage,followed by park green space and residential green space.The species diversities of these three types of green space were relatively high,which may be related to their wide service objects.The higher species diversity of trees appeared in park green space and square green space,which were open to the public and put more emphasis on trees.For shrubs,there was no significant difference in the species richness index and Pielou's evenness index of different types of green space.And the higher Shannon-Wiener index appeared in road green space,which may be due to its functional orientation.The species diversity of herbs in square green space was relatively high.(5)The functional richness index FDp and Rao's quadratic entropy index of the overall plant community were dominated by park green space and residential green space,and perhaps because of their high ornamental requirements.There was no significant difference in the functional evenness index FEve of different types of green space.The higher functional diversity of trees appeared in park green space and square green space,which put more emphasis on tree traits.About shrubs,the higher FDp index appeared in park green space and road green space,and there were no particularly prominent types of green space in terms of the FEve index and Rao's quadratic entropy index.Like the overall plant community,the higher FDp index and Rao's quadratic entropy index of herbs appeared in residential green space and park green space,and there was no significant difference in the FEve index of different types of green space.(6)The distribution of the landscape elements showed that the concrete type accounted for the highest proportion of road pavement,the curve type was the most common road alignment,and the road type was dominated by sidewalks;the most common type of facility was for entrance;the proportion of water elements was small.The distribution of plant functional diversity near the landscape elements showed that,the functional diversities of plants near wooden and(pebble)stone paving roads,curved roads,the sidewalks + road green spaces + single lanes and the sidewalk roads were relatively high.In terms of the facility types,the functional diversity of plants near the rest facilities was higher.The plants near small man-made water and pool,ditch,and artificial regular revetments had higher functional diversities.(7)The result of the demonstration found that the three landscape elements had a certain effect on the urban plant functional diversity,but the degree of effect was less important than in the hypothesis.The three landscape elements totally explained 21.66% of the functional diversity of urban plants,and road was the key factor group.The explanations to the functional diversities of trees,shrubs,and herbs were 20.31%,23.95% and 15.71% respectively.The key factor groups were water,road and road respectively.The plant functional diversity was affected more by the independent rather than the joint effect of the landscape elements.Compared with trees and shrubs,the functional diversity of herbs was less affected by three landscape elements. |
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