The impacts of accelerated erosion on soil nutrient loss and microbial quantity following deforestation in the Ziwuling area

This paper quantitative analyzed changes of soil nutrient and soil microbial quantity on different slope positions in a shallow gully catchment with bare-fallow land after 15 a of deforestation.Research results showed that following 15yr of deforestation,accelerated soil erosion was severe and erosion intensity reached 159.7 t /(hm2a),which was more thousands times greater than those in the forested land prior to deforestation.Due to severe soil loss,topsoil organic C,total N,available P and soil microbial quantity greatly decreased.As compared to the forest land prior to deforestation,soil total N,organic C,available P and soil microbial quantity reduced by 37.9%～82.6%,42.7%～86.4%,24.2%～80.3%,and 31.8%～92.0%,respectively.As slope length increased on hillslope in a shallow gully catchment with bare-fallow land,soil total N,organic C,available P and soil microbial quantity markedly tended to decrease;soil nutrient contents in gully channels were greatly higher than those in gully slope.The spatial distribution in soil nutrient loss intensity and soil microbial quantity reduction rate was responded to soil erosion pattern and intensity in shallow gully catchments.After 15 yr of deforestation,the sequence of soil nutrient loss rate was total N organic C available P;the order of soil microbial quantity reduction rate was fungibacterium actinomyces.