Effects of Shading Treatments on the Growth of Pometia tomentosa Seedling
不同光照梯度的遮荫处理对绒毛番龙眼幼苗生长的影响

Pometia tomentosa is a dominant uppermost canopy tree species of vallyland forest in Xishuangbanna tropical seasonal rainforest,China. Under different light intensities such as 100% natural sunlight (NS), 37.3% NS, 15.5%NS, 4.2% NS, 1.6% NS, 0.6% NS in shade house, growth characteristics were studied in early development stage and established seedlings. Light was an important environmental factor for the growth of P. tomentosa seedlings. During the early growth stage of seedlings, basal stem diameter and paripinnate number were decreased with the increasing of shade, taproot length, root : shoot ratio, total dry weight and leaf area per seedling were maximal under 37.3% NS, specific leaf area (SLA) was increased with the increasing of shade, but the relative growth rate was declined. Seedlings grew fastest under 0.6% NS, suggesting that nutrients stored in seeds played an important role at the early growth stage. The treatment of 37.3% NS was best for established seedlings in seedling height, basal stem diameter, paripinnate number, rachis length, the maximum sub-leaflet number of individual paripinnate, leaf area per seedling, relative growth rate and net assimilation rate. Light intensity was positively correlated to total dry weight, and negatively to specific leaf area. The maximum of SLA was observed under 15.5% NS. The fluctuations of SLA and root : shoot ratio in developmental established seedlings may be responsible for light intensity and soil moisture.