Fine root distribution pattern of different aged Leucaena leucocephala trees in debris flow source area in Jiangjia Gully,China

Fine root is critical to restrain soil erosion and its distribution pattern is of great influence on the restraining effects. This study studied the fine root biomass (B _r ) distribution of different aged Leucaena leucocephala (5, 10, 15 years) in debris flow source area in Jiangjia Gully by digging downward to the bottom at different distances to stem in three directions on slope. The results showed the B _r increased dramatically by 143% from 5 years to 10 years and then rose slowly by 38% from 10 years to 15 years. The B _r of 5 years was significantly asymmetric between uphill and alonghill directions, but there was little difference among directions for other ages, and a concentration trend appeared to exist in downhill and alonghill directions. Moreover, fine root (D≤1 mm) was significantly heavier than that of fine root (1mm<D≤2 mm), playing a leading role in the vertical distribution of the whole fine root, with a logarithmic or an exponential function. The results presented may shed light on fine root distribution pattern and evaluation of its effect on slope stability in debris flow source area.