摘要：
利用2a定位观测数据，本文对速生阶段的第2代杉木人工林内N、P、K、Ca、Mg5种养分元素的含量、积素、空间分布和生物循环进行了研究，结果表明：各组分养分含量排列顺序为草本层＞灌木层＞树叶＞树枝＞树皮＞树根＞树干。树枝中Ca的含量丰富，树皮中K的含量丰富。凋落物层养分元素含量低于树枝的树叶，反映了凋落时养分元素向林木体内迁移回收的现象。杉木富集N、P、Ca 3种元素。5种元素积累总量为854.65 kg·hm~(-2)，是第1代的1.5倍。第2代杉木生产1t干物质所需养分量为11.62kg，高于第1代，第2代杉木林将消耗更多的林地养分。林冠枝叶与树皮养分量占林木总积累量的75％，采伐利用应仅取走树干而在林地中留下其它部分，让其分解使 养分元素归还给土壤。草本层、灌木层与凋物层三者的养分积累量为88.13kg·hm~(-2)，是重要的养分库。第2代杉木中养分元素的年积累量为93.13kg·hm~(-2)a~(-1)，略高于第1代杉木林的养分年积累量。总归还量为89.49kg·hm~(-2)a~(-1)，其中凋落物归还17.46kg·hm~(-2)a~(-1)，略低于第1代，淋溶的养分量72.04kg·hm~(-2)a~(-1)，是凋落物的4倍多。吸收是为182.62kg·hm~(-2)a~(-1)。与第1代相比，第2代杉木林中土壤K、的含量高，而N、Ca、Mg3种养分元素含量比第1代低，这3种元素可能对杉木林的养分元素的动态和森林生产力有着较大的作用。第2代杉木林生物循环总的特征为养分利用效率较低，循环速度减慢，周转时间较长，不笪林地土壤养分的积累。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 liter 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~(-2)a~(-1), which was higher than that of the first generation. The nutrients absorption was up to 182.62 kg·hm~(-2)a~(-1) and nutrient return was 89.49 kg·hm~(-2)a~(-1), of which litter return and leaching return were 17.46, 72.04 kg·hm~(-2)a~(-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.
