Variation of soil microbial community abundance and structure has great implications for soil fertility and nutrient cycling. A better understanding of soil microbial community dynamics under different land use types is undoubtedly needed in order to develop sustainable land use schemes. The current study aimed to assess how soil microbial community changed after replacement of maize–soybean crop by sugarcane, mulberry, or forage grass crop in a karst area of Southwest China. Mature forests were included for comparison. Phospholipid fatty acid (PLFA) method was used to characterize soil microbial community abundance and structure. The abundances of total PLFAs and PLFAs of bacteria, fungi, actinomycetes, and arbuscular mycorrhizal fungi were significantly increased in the forage grass field but not in the sugarcane and mulberry fields relative to the maize–soybean field. Total PLFAs' abundance in the forage grass field was increased by 81% compared with that in the maize–soybean field but was about 52% lower than that in the forest. The microbial community structure was not distinguished as much as the microbial abundance among the five land use types. Soil organic carbon (SOC) was identified as the primary factor affecting both soil microbial abundance and structure. Soil microbial community abundance was positively correlated with SOC, but the ratios of fungal to bacterial PLFAs and Gram‐positive to Gram‐negative bacterial PLFAs were negatively correlated with SOC. Our findings suggest that the replacement of the maize–soybean rotation system by forage grass cultivation has the potential to improve soil fertility in the karst region, Southwest China.

中文翻译：

---

西南喀斯特退化土壤中土壤微生物群落对牧草生长的响应

土壤微生物群落丰度和结构的变化对土壤肥力和养分循环具有重要意义。毫无疑问，需要更好地了解不同土地利用类型下的土壤微生物群落动态，以制定可持续的土地利用计划。当前的研究旨在评估在西南喀斯特地区用甘蔗，桑树或牧草替代玉米-大豆作物后，土壤微生物群落的变化。比较包括成熟森林。磷脂脂肪酸（PLFA）方法用于表征土壤微生物群落的丰度和结构。细菌，真菌，放线菌，与玉米-大豆田相比，牧草田和丛枝菌根真菌显着增加，但甘蔗和桑树田没有增加。与玉米-大豆田相比，牧草田的总PLFA丰度增加了81％，但比森林低了约52％。在五种土地利用类型中，微生物群落结构的区别不如微生物丰富。土壤有机碳（SOC）被认为是影响土壤微生物丰度和结构的主要因素。土壤微生物群落的丰度与SOC呈正相关，但真菌与细菌的PLFA比值和革兰氏阳性与革兰氏阴性细菌的PLFA比值与SOC呈负相关。