A large fraction of the karst land has been degraded owing to intensive human disturbances, particularly agricultural activities in Southwest China.

One important characteristic of land degradation is losses of soil organic carbon (SOC) and other nutrients particularly nitrogen (N). 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.

Recently, a research team led by Dr. LI Dejun at the Institute of Subtropical Agriculture(ISA)Chinese Academy of Sciences investigated the characteristics of soil microbial communities in four agricultural land use types (e.g. maize-soybean, sugarcane, mulberry, and forage grass fields).

Through phospholipid fatty acid (PLFA) method, with mature forests included for comparison,the team found that 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.

Besides, the microbial community structure was not distinguished as much as the microbial abundance among the five land use types.

Moreover, soil organic carbon (SOC) was identified as the primary factor affecting both soil microbial abundance and structure.

The results 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.

This work was supported by the National Key Research and Development Program of China (2016YFC0502404), the National Key Basic Research Program of China (2015CB452703), the Strategic Priority

Research Program of Chinese Academy of Sciences (XDA13010302), and the National Natural Science Foundation of China (41877094).

The study entitled "Soil microbial community responses to forage grass cultivation in degraded karst soils, Southwest China" has been published in Land Degradation and Development. The details can be found at https://onlinelibrary.wiley.com/doi/10.1002/ldr.3188

Contact: LI Dejun

E-mail: dejunli@isa.ac.cn

Institute of Subtropical Agriculture, Chinese Academy of Sciences