Abstract:

Based on the data observed for 2 years at Huitong Located Ecology Station, the concentrations, accumulation, distribution and biological cycling of 5 nutrient elements (N, P, K, Ca, Mg) were studied in the second rotation Chinese fir plantation at fast-growing stage. The nutrient concentration of different component was in the order as: herb> shrub> leaf> branch> bark> root> stem. The branch contained higher Ca and the bark had more K. Nutrient concentration of litter was lower than that of Chinese fir trees. This result shows that there was nutrient transferal from leaf and branch to stem when litter was produced. The total nutrient accumulation accounted for 854.65 kg·hm^-2. The fact that producing 1 tone biomass in the second generation plantation needed higher amount nutrient than that in the first generation indicates the second generation exhausts more nutrient from soil. The annual nutrient retention reached 93.13 kg·hm^-2a^-1, which was higher than that of the first generation. The nutrients absorption was up to 182.62 kg·hm^-2a^-1 and nutrient return was 89.49 kg·hm^-2a^-1, of which litter return and leaching return were 17.46,72.04 kg·hm^-2a^-1, respectively. In contrast to the first generation, the nutrient cycling mechanism of the second rotation Chinese fir is characterized by lower nutrient use efficiency, slower recycling rate and long recycling period.

Key words: Second rotation Chinese fir plantation, Fast-growing stage, Nutrient elements, Distribution, Biological cycling