随着城镇化的推进，中原农业区大量的农业用地转变为城市用地，受城市化过程中人为活动的强烈影响，与城市化有关的土壤质量问题日益突出。而土壤质量与土壤微生物密切相关，后者对环境变化比较敏感，它能够较早地指示生态系统功能的变化，并反映出土壤的质量和健康状况。因此，研究土地利用方式的变化对土壤微生物的影响是评价土壤环境质量的重要指标。以“中部崛起”六省中城镇化率增长最快的地区之---河南省商丘市为例，采用以空间梯度代替时间顺序的方法，以城市建成区、城市外围的郊区及农田为研究对象，分别测定不同城市化水平下土壤微生物的数量和组成，研究土壤由农业用地转变为城市用地过程中，土壤微生物群落结构的变化。以城市中心为起点，分别在东、南、西、北四个方向上取样，在同一方向上沿城区-郊区-农田梯度上进行取样。采用平板涂抹计数法测定土壤中细菌、真菌、放线菌的数量。结果表明，农田、郊区和城市土壤微生物总数分别为14.68×106 cfu·g-1、8.19×106 cfu·g-1和10.99×106 cfu·g-1，即城市化使土壤中微生物总数量减少；同时，土壤微生物的组成和比例结构也发生变化，其中，城市建成区土壤中细菌和真菌所占微生物总数的比例高于郊区和农村，而放线菌在农村占的比例高于城市建成区和郊区。城市建成区不同用地类型下土壤微生物总数的变化趋势为公园>校园>居住区>道路，其中，细菌占微生物总数的比例在公园土壤中最大，而放线菌和真菌则相反，二者占微生物总数的比例在道路土壤中最大，在公园土壤中比例最小。土壤微生物数量和组成的这些变化反映出土地由农业用地转变为城市用地过程中，土壤质量和健康状况及生态系统功能的变化，可以为评价土壤环境质量及土壤管理提供参考依据。%The farmland has been gradually transformed into urban land in central China during the process of the booming urbanization. The problems of soil quality accompanied by urbanization become worse due to the anthropogenic influence. Soil microbes correlate closely with soil quality, and these microbes are sensitive to changing environment, which could indicate the variations of ecosystemfunction. In this respects, they could be chosen as indices to reflect the conditions of soil quality and health. In this work, Shangqiu city, one of the most rapid urbanization cities in central China, was chosen for the analysis the effect of urbanization on the community structure of soil microorganism. For this purpose, three urbanization levels (i.e., city center, suburb and farmland) were identified firstly to indicate various stages of urbanization, soil samples were collected across four orthogonal directions (i.e., east, south, west and north) from city center to farmland at each urbanization level, then the amount of cultivable soil bacteria, fungi and actinomycetes was investigated by using standard dilution plate count method. The results showed that the total number of microorganism decreased with an increasing urbanization level, where the values was 14.68×106 cfu·g-1 in farmland, 8.19×106 cfu·g-1 in suburband and 10.99×106 cfu·g-1in city center, respectively. Additionally, the composition and the ratio of each component of soil microorganism also changed during the process of urbanization. More specifically, ration of soil bacteria and fungi in city center was higher than those in suburb and farmland soil, opposite to what were observed in actinomycetes. Regarding different land use types in built-up area, total number of soil microorganism showed an overall decrease in the order of park >campus>residential area>roadside. Ratio of soil bacteria was highest in park soil than other three land use types, opposite to what were observed in actinomycetes and fungi. Our results suggested a shift in soil microorganism from farmland to urban land during the process of urbanization, which may have important recommendation for the management of soil quality and health.
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