| Urbanization has been greatly accelerated by the economic growth in China.However,limited data are available for its effects on woody plant and bird species composition,diversity and soil properties,although both are important factors for urban green infrastructure and quality of life.Here,we analyzed spatial-temporal gradient data in Harbin city,China,to investigate the changes in the composition and diversity of woody plants and birds during urbanization.The number of woody plant families and genera planted in Harbin city increased by 9 and 17,respectively,from 1955 to 2014;there were 7 and 20 more families and 12 and 35 more genera in urban areas than in nature reserves and local forest farms,respectively.Over the past 60 years,the number of alien species increased 4-fold,while the percentage of tropical types increased by 11.4%.Temperature change played an important role in woody plants composition.The Shannon-Wiener index and the percentage of alien and tropical types at the plot scale in urban areas were much higher compared with local forest farms and farmland areas.Moreover,Shannon-Wiener index was higher in urban areas constructed in 1995 and 2005 than those in old urban areas constructed prior to 1945.Regression analysis indicated that the increase in the number of alien species and tropical types was significantly related with changes in plant species diversity.Along with changes in woody plant species diversity in urban areas,the number of omnivorous and forest birds in the 2010 s was increased by 14.1% and 23.4%,respectively,compared with the 1980 s,while the number of open-forest birds was decreased by 16.7%.Changes in bird species diversity may be related with the increase in woody plant species diversity,since plants provide habitat and food for birds,supporting their survival.Urbanization made Harbin soil slightly alkaline as well as total N,total P and SOM increased significantly except available N.In landscape scale,woody plants diversity was less affected by soil physical and chemical properties,while the woody plants richness and Margalef index were mainly affected by soil bulk density and EC in different ring roads.Shannon-Wiener and Pielou indexes were affected by pH,available N,available P,total P and SOM,while Pielou index was mainly affected by pH,available N and SOM in different settlement time areas.Harbin city has 66 common trees,belonging to 18 families and 34 genera in Harbin urban forest.The most common species was Populus alba ×P.berolinensi(13.5%),the most common genus was Populus(37.6%)and the most common family was Salicaceae(45.5%).According to 10/20/30 “rule of thumb”,which states municipal forests should comprise no more than 10% of any particular species,20% of any one genus or 30% of any single family otherwise urban forest will influence the stability of urban ecosystem,Harbin forest trees configuration were evaluated.Harbin forest trees configuration was reasonable at species level but not at the family and genus level based on the 10/20/30 “rule of thumb”.The primary reason was that single species,genus and family occupy absolute predominance in urban forest.To solve this problem,we should choose less Salicaceae but choose more other genus and families in the urban forest construction.Our results are useful for determining the optimal strategies and approaches for ecological construction in Harbin city... |
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