Soil microbes in urban ecosystems are affected by a variety of abiotic and biotic factors resulting from changes in land use. However, the influence of different types of land use on soil microbial properties and soil quality in urban areas remains largely unknown. Here, by comparing five types of land use: natural forest, park, agriculture, street green and roadside trees, we examined the effects of different land uses on soil microbial biomass and microbial functional diversity in Beijing, China. We found that soil properties varied with land uses in urban environments. Compared to natural forest, soil nutrients under the other four types of urban land use were markedly depleted, and accumulation of Cu, Zn, Pb and Cd was apparent. Importantly, under these four types of land use, there was less microbial biomass, but it had greater functional diversity, particularly in the roadside-tree soils. Furthermore, there were significant correlations between the microbial characteristics and physicochemical properties, such as organic matter, total nitrogen and total phosphorus (P < 0.05), suggesting that lack of nutrients was the major reason for the decrease in microbial biomass. In addition, the larger C/N ratio, Ni concentration and pool of organic matter together with a higher pH contributed to the increase in microbial functional diversity in urban soils. We concluded that different land uses have indirect effects on soil microbial biomass and microbial community functional diversity through their influence on soil physicochemical properties, especially nutrient availability and heavy metal content.

a b s t r a c tMuch of the world is experiencing fast urbanization. Many peri-urban open spaces, such as parks, forest, farmland, and wetlands, have been built over, which has resulted in a steep decline of ecosystem services at the municipal and regional levels. Using remote sensing, geography information system (GIS) technology and economic evaluation method for ecosystem services, the evolution of landscape spatial structure in 1991, 1996, 2001 and 2006 of Changzhou City, People's Republic of China, was obtained and the change of ecosystem services resulted from land use change was evaluated. Study results show a continuing expansion of urbanized areas and reduction in ecosystem services. Before 2001, farmland was the main type of land use, accounting for more than 53.3% of the total area within the broadlydrawn municipal boundaries. In 2006, farmland and built-up areas were the main land-use types. The built-up area increased by 122% from 1991 to 2006. From 1991 to 2001, the proportion of ecological land (farmland, forests, grasslands, and water-covered areas) within Changzhou's municipal boundaries decreased 24.1%. Based on the observed changes, the economic value of ecosystem services provided by Changzhou's ecological land decreased by 19.3% from 1991 to 2006 and the annual decrease ratio was approximately 1.3%. Conversion of farmland to other uses was responsible for the largest reduction in the value of ecosystem services, equal to 239.8 million RMB (equivalent to USD 37.8 million). Our research results were already adopted locally by Changzhou Municipal Bureau of Urban Planning and applied for Changzhou Mater Urban Planning. The current study can contribute not only to improvements in the Changzhou environment, but to the study of and improvements to other rapidly-urbanizing cities, as the rapid growth of urban areas is one of the most pronounced environmental trends of recent times.

No abstract