【摘要】 砂仁 (Amomumvillosum)为耐荫多年生草本 ,喜生于雨林林窗中 ,果实药用。在西双版纳热带季节雨林下广泛种植。为了通过提高林下光照水平来促进砂仁生长、增加产量 ,种植地雨林下的灌木及草本被清除 ,约 6 0 %～70 %的乔木遭到疏伐 ,林冠盖度由 85 %～ 95 %降低到 5 5 %～ 6 0 % ,雨林受到严重干扰。对 3块原始热带季节雨林和3块受种植砂仁干扰雨林样地的净初级生产力 (NPP)进行了测定和比较 ,原始雨林NPP(平均值±SE)为 2 3 .47±2 .12t·hm-2 ·a-1,其中各层次的NPP分别为 :乔木层 2 2 .0 4± 2 .0 9t·hm-2 ·a-1、灌木层 0 .75± 0 .0 8t·hm-2 ·a-1、木质藤本 0 .43± 0 .0 5t·hm-2 ·a-1和草本层 0 .2 5± 0 .0 3t·hm-2 ·a-1。乔木层NPP分配为 :凋落量 11.75± 0 .5 4t·hm-2 ·a-1、倒木量 0 .6 2± 0 .2 1t·hm-2 ·a-1、叶虫食量 0 .6 6± 0 .0 5t·hm-2 ·a-1及生物量积累 9.0 1± 2 .70t·hm-2 ·a-1。与原始雨林相比 ,受干扰雨林的乔木层、灌木层、木质藤本以及群落总NPP分别降低 2 6 .1%、6 5 .7%、86 .1%和 2 2 .5 % ,但以砂仁为优势的草本NPP则增加 5 36 %。乔木层凋落量和生物量积累分别下降 2 5 .5 %和 5 3.4% ,倒木量增加35 6 %。研究结果表明 :西双版纳热带季节雨林的这种利用管?更多还原

【Abstract】 Xishuangbanna, located in south Yunnan, southwest China, is the northern border of the tropical zone. It maintains large areas of tropical rainforest called tropical seasonal rainforest. Like most tropical rainforests all over the world, these tropical seasonal rainforests are under high pressure of long_term disturbance caused by forest utilization. Amomum villosum, a shade_tolerant perennial herb, prefers to grow in forest gaps. It is one of the main cash crops of local people as its fruit is widely used in Chinese traditional medicine. It has been widely planted in tropical seasonal rainforest understorey in Xishuangbanna. To promote its growth and fruit yield by raising the light level of habitat, the forest shrub and herb layers are cleaned and about 60% 70% of trees are thinned. As a result, A. villosum planting has become the most serious disturbance to the tropical seasonal rainforest. Net primary productivity ( NPP ) is the primary element of nutrient cycling and energy flow within an ecosystem. It reflects the ability of a plant community to use natural resources. Most of the studies on forest NPP change after disturbance have focused on secondary forest, and few studies report the impact on NPP of forest canopy damage. This paper aims to determine the effect of A. villosum planting on forest NPP , and to study if that disturbance is the current most important limiting factor on NPP of the rainforest in Xishuangbanna. The study was carried out at Menglun, Xishuangbanna. Three primary seasonal rainforest sites and three disturbed rainforest sites with A. villosum plantation were chosen for the study and one 0.25 hm 2 plot was established at each site. All six study sites were distributed along ravines, within 21°55′ 21°59′N,101°08′ 101°13′E and at altitude of 650 800 m. Pometia tomentosa is the dominant tree species of the top tree layers at all research sites. At each plot, all trees and lianas with diameter at breast height ( DBH ) ≥5 cm were numbered and marked at breast height, and their DBH were measured annually. The biomass ( B ) and its annual increment ( ΔB ) of the research plots was estimated using the allometric regression equation relating tree mass to DBH of Xishuangbanna tropical rainforest. The amount of dead wood on all plots was recorded annually. At the same time, 20 litter fall traps were placed at each plot and litter was collected every half month. Leaf herbivory was measured by leaf samples and the total leaf herbivory ( G ) was estimated through annual leaf litterfall. The primary net productivity was calculated using the NPP equation NPP = ΔB+L+G, in which L is annual litterfall together with dead wood. The shrub and herb biomass were determined by the harvest method and their biomass increment was estimated by biomass divided by age. The biomass increment for shrub and herb was approximate to NPP . The results show that the annual mean NPP (mean±SE) of the primary rainforest is 23.47±2.12 t·hm -2 ·a -1 , with 22.04±2.09 t·hm -2 ·a -1 in the tree layer, 0.75±0.08 t·hm -2 ·a -1 in the shrub layer, 0.43±0.05 t·hm -2 ·a -1 in woody liana and 0.25±0.03 t·hm -2 ·a -1 in the herb layer. The allocation of NPP of the tree layer was: for litterfall, 11.75±0.54 t·hm -2 ·a -1 ; for tree fall, 0.62±0.21 t·hm -2 ·a -1 ; for leaf herbivory, 0.66±0.05 t·hm -2 ·a -1 ; and for biomass accumulation, 9.01±2.70 t·hm -2 ·a -1 . Compared to the primary rainforest, the NPP of the tree layer, shrub layer, woody liana and total community of the disturbed rainforest decreased 26.1%, 65.7%, 86.1% and 22.5% respectively, but the herb NPP increased 536% because of the dominance of A. villosum. Similarly, litterfall and biomass accumulation of the tree layer decreased 25.5% and 53.4% respectively. The tree fall increased 356% relative to the primary forest due to the change of microenvironment after disturb更多还原