Study On Urban And Rural Environmental Gradients And Their Impact On Plant Biomass

Global Change refers to the worldwide changes driven by natural and anthropogenic factors, in the Earth’s environment, or the important regional environment association changes which may have strong impact on the present or future environment of human beings. Global Change includes global environmental change and global climate change. Researches on global change have great significance to the sustainable development of human society. Anthropogenic environmental control (FACE, OTC, etc), field inventory survey and model simulations are widely used among researches on terrestrial ecosystem response to Global Change. Recent studies showed that the spatial difference between urban and rural environmental gradients can substitute the time difference between Global Change. Therefore,by studying the growth of plants in urban and rural areas can reveal the plants’ response to Global ChangeIn our research, we monitored environmental factors among urban living area, urban forest and rural forest, compared their differences with Global Change. We also observed the growth difference of Cottonwood (Populus deltoides),Viburnum awabuki(Viburnum odoratissimum var:awabuki) and Rose Mallow(Hibiscus syriacus) in urban and rural forest sites, analyzed the various factors which may influence the growth of plants. The results showed that:The average annual temperature were 17.68℃ in urban living area,16.81℃ in urban forest and 15.89℃.in rural forest The temperature gradient in the urban-rural gradients wass consistent with the time spatial of the Global Change. The humidity showed a downtrend among urban living area, urban forest and rural forest, which were 70.79%,78.34%,16.87%, respectively. The max light intensity of three areas were 134012.091x in urban living area,108841.811x in urban forest, which was 11% lower than rural forest of 122080.521x.The average CO2 values were 449.26 nL/L in urban living area,413.75nL/L in urban forest and 424.37nL/L in rural forest. Statistical analysis indicated that significant difference existed between urban living area and urban forests during summer, and also occured among urban living area, urban forests and rural forests during autumn. Difference was not observed in spring or winter.The average annual O3 values were 13.96 nL/L in urban living area,19.95 nL/L in urban forest and 23.24 nL/L in rural forest. Urban living area was not different with urban forest in any seasons, but was significantly different with rural forest during spring, autumn and winter. O3 content of rural forest was higher than urban living area in each season, showing significant difference in spring and autumn. Estimated AOT40 aggregate-value of urban and rural forest were 0.968×10-6×h,1.259×10-6×h, no difference was observed between them.The leaf areas data indicated that plants grow in urban forest developed larger leaves than rural forest. In July, area of top leaf of urban forest was higher above rural forest at around 15.8cm2 without significant difference, while areas of middle and bottom leaves were significantly higher than rural forest at 17.8cm2 and 24.6cm2. In September, areas of top, upper and middle leaves were significantly higher than that in rural forest at 17.2cm2,16.4cm2 and 53.0cm2, respectively.The biomass data of plants in three sites showed that the plants in urban forest grew more rapidly than rural forest, and presented different growth rates among different species. The two years biomass of Cottonwood and V. awabuki in urban forest were 1.7 and 1.5 times of the rural forest, respectively, while Rose Mallow showed no significant difference between urban and rural forest.In our experiment, we found that not all the ecology factors in the urban-rural gradient changed consistenly with the Global Changes in time gradient. However, some important factors such as temperature and polluted air of city were demonstrated to change in the same way. Therefore, our experiment showed its value on the prediction of plant growth response to Global Change,and we comfirmed that urban space-for-time substitution experiments" were potentially feasible on Global Change study.