Nutrient amounts of a Pinus massoniana plantation on various slope positions.

摘要

A study was made of the biomass and nutrient levels of a 30-yr-old Pinus massoniana (masson pine) plantation, and of the nutrients supplied to the soil by litterfall, on upper, middle and lower slope sites at Fuzhou, in Fujian Province, China. The total biomass accumulation (pines + understorey + A0 soil horizon) on the upper slope was 82 t/ha, and that on the middle and lower slopes was 2.4 and 2.9X greater, respectively. Data on accumulated nutrient (N, P, K, Ca and Mg) amounts are tabulated forthe pines, the understorey, and the A0 horizon, and 4 soil depths (0-10, 10-20, 20-30 and 40-50 cm) for each slope position; data on C content are also given for the A0 horizon and the different soil depths. The understorey biomass made up 11-17% of theabove-ground biomass of the pines, and as shown by its nutrient contents, plays an important role in nutrient circulation. Usually, after clear felling a masson pine plantation, the organic matter left on the ground is burned. In this study, the total amounts of organic matter left on ground after clear felling (sum of pine leaves and branches, understorey organic matter, and A0 horizon) were 21.5, 46.4, 59.8 t/ha on the upper, middle, lower slopes, respectively; N contents of these components were 187,400, 460 kg/ha, respectively. These figures indicate that large amounts of nitrogen will be lost after clear felling and burning for site preparation. If clear felling is repeated in short rotations, it is also a concern that Mg would not circulate smoothly in the ecosystem.