马尾松林下栽植闽粤栲对生态系统养分循环的影响

Impact of Underplanting Castanopsis fi ssa on Nutrient Cycling in Pinus massoniana Stand

通过定位监测和取样分析,研究了马尾松林下栽植闽粤栲对生态系统养分循环的影响.结果表明:林木各组分养分含量排列顺序表现为叶>枝>皮>根>干.总体而言,在马尾松林下套种阔叶树后,除N、Ca元素外,各组分其它养分含量普遍高于纯林.土壤养分元素含量排列顺序为K>Mg>Ca>N>P,混交林土壤中N、P元素含量要高于纯林.马尾松混交林中,林木5种元素总量为3801.45kghm-2,比纯林高71.57%;养分元素的年净积累量为267.74kghm-2a-1,是纯林养分净积累量的2.30倍;养分总归还量为426.27kghm-2,是纯林的1.69倍.混交林养分利用系数为:N(0.14),P(0.10),K(0.49),Ca(0.16),Mg(0.20);周转时间(a)为:N(15.52),P(94.70),K(2.66),Ca(9.87),Mg(7.53).纯林养分利用系数为:N(0.13),P(0.06),K(0.31),Ca(0.16),Mg(0.20);周转时间(a)为:N(16.83),P(105.27),K(3.95),Ca(8.69),Mg(6.91).林下栽植阔叶树使林木的N、P、K元素的周转期缩短,养分利用系数增加.因此,将现有的马尾松纯林改造成混交林是解决目前马尾松纯林地力衰退的一个非常好的途径.

Based on field investigations and lab analyses, the impact of underplanting Castanopsisfissa on nutrient cycling was studied in Pinus massoniana stand. The results showed that the concentrations of nutrient elements in different parts of the forest trees differed and decreased in the order： needle〉branch〉bark〉root〉stem. Generally, the concentrations of K, Mg and P in the trees increased after C. fissa was underplanted in P. massoniana stand. The concentrations of the nutrient elements in soils ranked as K〉Mg〉Ca〉N〉P, with higher N and P contents in the mixed forest than in pure pine stand. Total nutrient storage of the trees in mixed forest was 3801.45 kg hm^-2, 71.57% higher than that in pure forest and the annual nutrient accumulation in the trees was estimated at 267.74 kg hm^-2.a^-1, approximately 2.30 times the amount of pure forest. The nutrient flux via litter and rainwater in mixed forest was estimated at 426.27 kg hm^-2, 1.69 times as much as that in pure forest. The nutrient utilization coefficient of the trees in mixed forest was 0.14, 0.10, 0.49, 0.16 and 0.20 for N, P, K, Ca and Mg, respectively, with nutrient recycling period of 15.52 a for N, 94.70 a for P, 2.66 a for K, 9.87 a for Ca and 7.53 a for Mg. In contrast, nutrient utilization coefficients in pure pine stand were estimated to be 0.13, 0.06, 0.31, 0.16, and 0.20 for N, P, K, Ca and Mg, respectively, with nutrient recycling period of 16.83 a for N, 105.27 a for P, 3.95 a for K, 8.69 a for Ca, and 6.91 a for Mg. The estimated parameters suggested that the planted hardwood species under the canopy of pine stand shortened the recycling period of the elements N, P and K, and improved nutrient utilization coefficient. Therefore, the change of pure pine stand into mixed plantation is an efficient way to reverse site degradation.