Soil N dynamics as affected by different land use in Western and Southern China
Final Report Abstract
Soils with different degradation and rehabilitation status have been examined on the Loess Plateau of China. Accelerated soil erosion, mainly induced by land-use change from forest to agriculture, is the main process leading to soil degradation on the Loess Plateau. Actually only 12% of the Loess Plateau area is covered by forest. For successful re-vegetation of eroded sites it is crucial to supply plants adequately with nutrients. The rate of N mineralization, regulated by the soil microorganisms, is an important parameter that affects the amount of soil-N supplied to plants and thus plant growth. A successful re-vegetation of degraded soils, in turn, leads to the accumulation of soil organic matter and improves soil quality and stability. A land use gradient from bare soils without vegetation, soils under agricultural management, soils with six year old natural successional vegetation and soils under a 140 year old secondary forest has been investigated. Additionally, a sequence of increasing erosion intensity along a hill from top to down slope was included on bare and forest sites. Thus, the effects of a) land use and b) erosion intensity on i) nutrient turnover, ii) microbial biomass and iii) microbial community structure were assessed. Intensified soil erosion significantly decreased the contents of organic matter and microbial biomass in the soils. However, independent of erosion intensity N and C cycling rates were maintained in the bare plots. This might be explained by changes in the structure of the soil microbial community. Gross N mineralization and gross NH4 consumption rates were significantly highest in forest soils. Within the forest, after 140 years, nutrient contents, microbial activity parameters and the soil microbial community structure were similar, independent of former erosion intensity. Thus, these parameters developed into the same direction during 140 years of secondary forest growth. Even after six years of natural succession a partial re-establishment of soil properties toward forest conditions was detected.
Publications
- 2007. Impact of air-drying and rewetting on PLFA profiles of soil microbial communities. J. Plant Nutr. Soil Sci. 170,259-264
Hamer, U., Unger, M., Makeschin, F.
- 2008. Microbial activity and community structure in degraded soils on the Loess Plateau of China. J. Plant Nutr. Soil Sci.
Hamer, U., Makeschin, F., An, S., Zheng, F.
