Biogeochemical Cycling Characteristics of Nutrients in Acacia cincinnata Plantation

Standard plot method was used to study the contents, accumulation, distribution and biogeochemical cycling of five nutrient elements (N, P, K, Ca and Mg) in an 8-year-old Acacia cincinnata plantation in Nanning City of Guangxi. The results showed that nutrient contents in the leaves were the highest among those in different organs of A. cincinnata, with the lowest in the stems. The nutrient contents of N were the highest, followed by Ca and K, and those of Mg and P were the lowest. Total accumulation of these five elements in the plantation was 823.80 kg·hm^-2, of which arbor layer, shrub layer, herb layer and litter layer accounted for 64.86%, 20.59%, 5.20% and 9.35%, respectively. The amount of uptake, retention and return of the five elements in the plantation was 151.30, 88.48, and 66.82 kg·hm^-2·year^-1, respectively. The amount of retention of nutrients accounted for 55.84% of the uptake.The coefficient of the plantation was 0.56, and the cycling speed was: Mg＞Ca＞N＞K＞P.