Microbial activity and community structure in degraded soils on the Loess Plateau of China

• Published in: Journal of plant nutrition and soil science 2009-02, Vol.172 (1), p.118-126
• Main Authors: Hamer, Ute, Makeschin, Franz, An, Shaoshan, Zheng, Fenli
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biochemistry and biology; Biological and medical sciences; calcareous soil; Chemical, physicochemical, biochemical and biological properties; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; gross N mineralization; microbial biomass; Microbiology; Physics, chemistry, biochemistry and biology of agricultural and forest soils; PLFA; soil erosion; Soil erosion, conservation, land management and development; Soil science; Soil-plant relationships. Soil fertility; Soil-plant relationships. Soil fertility. Fertilization. Amendments; SOM mineralization
• ISSN: 1436-8730; 1522-2624
• DOI: 10.1002/jpln.200700340

Soil erosion is the main process leading to soil degradation on the Loess Plateau of China. The effects of soil-erosion intensity (sheet, rill, and gully erosion) and different land use (140 y-old secondary forest site, 16 y-old bare site, 6 y-old succession site, and 43 y-old arable site) on gross and net N mineralization, soil organic-carbon (SOC) turnover, the size and structure of the soil microbial community (phospholipid fatty acid analysis) were assessed. Erosion intensity in the bare plot increased from top slope (sheet erosion) to down slope (gully erosion). The more severe the soil erosion the stronger was the decline of SOC, total N, and microbial biomass (MB). The MBC/SOC ratio decreased whereas the metabolic quotient (qCO₂) increased. Differences in nutrient turnover in the different erosion zones of the bare plot were not significant. The microbial community changed towards less Gram negative bacteria and relative more fungi in the gully-erosion zone. In forest soils, qCO₂ and the MBC/SOC ratio demonstrate a higher substrate-use efficiency of the microbial biomass than in bare soils. Gross N mineralization and gross NH$ _4^+ $ consumption clearly indicated a higher microbial activity in forest than in bare soils. Arable land use shifted the soil microbial community towards a higher relative abundance of fungi and a lower one of actinomycetes. During 6 y of natural succession on former bare plots, soil nutrient content and turnover as well as microbial biomass and structure developed towards forest conditions.