Abstract:
The standard plot method was used to study the distribution and biological cycling of 10 nutrient elements(N,P,K,Ca,Mg,Fe,Mn,Zn,Cu and B) in the 7-year-old(middle-age)
Acacia crassicarpa plantation.The results indicated that concentrations of the 10 nutrient elements in different organs of
A.crassicarpa plantation were in the order of leaves>bark>branch>root>stem. The contents of N were the highest,K and Ca the second,Mg and P the lowest for macro-elements,whereas Mn and Fe were the highest,B and Zn the second,and Cu the lowest for micro-elements.The nutrient storage of the plantation was 1 121.08 kg·hm
-2,of which overstorey of
A. crassicarpa trees stored 848.94 kg·hm
-2 accounting for 75.72%,forest floor 116.05 kg·hm
-2 account for 10.35%,and standing litter 156.08 kg·hm
-2 account for 13.92%.The amounts of nutrient elements in different parts of trees was in the order of stem>leaves>branch>bark>root.The amounts of annual uptake,retention and return of 10 elements in the plantation were 261.87,140.59 and 121.28 kg·hm
-2,respectively.The cycling coefficient and recycling period were 0.54 and 6.04. As was observed,the nutrient utilization efficiency in middle-aged
A. crassicarpa plantation was lower,but the return rate was higher and the turnover period was shorter,resulting in the recovery and maintenance of forestland fertilization.