Abstract:

The contents, accumulation and distribution as well as biological cycles of 9 nutrient elements (N, P, K, Ca, Mg, Cu, Fe, Zn, Mn) were studied in four 16-year-old experimental Slash Pine plantations with different density at Lufeng Mountain Forestry Farm in Guangxi Autonomous Region.The results indicated as follows:the total nutrient elements accumulation of various Slash Pine stands amounted to 1273.83~1615.88kg/hm², of which stem occupied about 60 %.The nutrient retention accounted for 111.46~133.39kg/hm²·a, which is higher than that of either Chinese fir or Masson pine plantation.The nutrient return equalled to 90.43~105.09kg/hm²·a.Nutrient elements' turnover period is long while cycling rate is lower.The net production per ton needs 13.19~14.81kg nutrient.Obviously, the nutrient cycles mechanism of Slash Pine is characterized by high nutrient use efficiency with low cycling rate, so in management of Slash Pine plantation, the relation between forest utilization and forest land tending must be dealt with rationally in order to prevent forest land degrading.Of different density plantations, the 3200 tree/hm² one possessed the greatest net productivity, the largest amount of nutrient accumulation and uptake, as well as the highest nutrient use efficiency.

Key words: Slash Pine, Nutrient cycling, Nutrient use effciency, Density effect