Abstract:

A study on the internal nutrients transfer and cycling of the above-ground parts in the 15-years-old loblolly pine (Pinus teada L.)plantation,located in Xiashu forest farm,Jiangsu Province,was carried out.The results obtained were as followed:(1)The internal transfer of nutrients (N,P,K and Mg)in needle was more than in branch or in bole,which played the most important role in the internal transfer of nutrients in the above-ground parts,and the transfer ratios of N,P,K and Mg in the above-ground parts were 44.9 %,34.5 %,20.8 % and 30.7 %,respectively.(2)The nutrient return of N,P,K Ca and Mg were 55.78,6.13,26.70,70.79 and 20.30 kg·hm^-2·a^-1,which were 36.67 %,44.65 %,55.30 %,78.02 % and 42.84 % of the nutrients requirement,separately,and the soil depletion of N,P,K,Ca and Mg were 22.48,2.13,4.64,26.98 and 11.64kg·hm^-2·a^-1,which were 23.99 %,22.76 %,11.84 %,24.32 % and 33.10 % of the nutrients uptake,respectively.(3)The nutrients availability in this plantation was higher than that in Chinese fir plantation and Oak forest in this region,but the loblolly pine plantation is still in the stage of nutrients depletion.

Key words: Loblolly pine plantation, Nutrient elements, The internal transfer and cycling