Effects of thinning on microsites and natural regeneration in a Larix olgensis plantation in mountainous regions of eastern Liaoning Province, China

In order to understand the effects of thinning on microsite conditions and natural regeneration in the larch plantation, thinning experiment was conducted in a 40-year-old Larix olgensis plantation in Qingyuan County in eastern Liaoning Province, China in 2003-2004 Five thinning treatments （0%, 10.2%, 19.8%, 29.7% and 40.3% thinned） were designed on the same site. After thinning, canopy openness and the microsite conditions such as photosynthetic photon flux density （PPFD）, soil moisture content, and soil temperature were measured in one growing season. Meanwhile, the investigation of natural regeneration was conducted at the end of the growing season. The results showed that the canopy openness increased with the increase of thinning intensities. PPFD and soil temperature and soil moisture content in different soil layers were positively relative with canopy openness after thinning. The richness of regenerating tree species did not significantly increase （p=0.30） after one growing season since thinning, but the regeneration density and frequency of tree species increased significantly （p〈0.05）. In addition, the number of regenerating tree species increased, and the increment was correlated with the characteristics of iudividual tree species. The increasing percentage of regenerating seedlings of the shade-intolerant tree species was more than that of shade-tolerant tree species. Among the investigated regeneration species, the biggest response of seedling emergency to the canopy openness was Phellodendron amurense. This paper confirmed the following conclusions： after thinning, the variety of regenerating tree species was correlative with the characteristics of regenerating tree species, and the distribution of unthinned trees and the site conditions in the investigated larch plantation were the additional factors influencing, the regeneration.

以便理解在落叶松种植园在微地点条件和自然新生上变瘦的效果，变瘦的实验在东方辽宁省在 Qingyuan 县在 40-year-oldLarix olgensis 种植园被进行，在 2003-20 的中国(14。Fivethinning 处理(0% ， 10.2% ， 19.8% ， 29.7% 和 40.3% 变瘦) 在一样的地点上被设计。在变瘦以后，象光合的光子流动密度(PPFD ) 那样的华盖坦诚和微地点条件，土壤含水量，和土壤温度在一生长期被测量。同时，自然新生的调查在生长期的结束被进行。结果证明华盖坦诚随变瘦的 intensities.PPFD 和土壤温度的增加增加了，在不同土壤层的土壤含水量与在变瘦以后的华盖坦诚是确实相对的。改革树种类的丰富显著地没增加(p = 0.30 ) 自从变瘦，而是新生，在一生长期以后，树种类的密度和频率显著地增加了(p < 0.05 ) 。另外，改革树种类的数字增加了，并且增长与单个树种类的特征被相关。改革 shade-intoleranttree 种类的幼苗的增加的百分比多于阴影容忍的树种类的。在调查新生种类之中，到华盖坦诚的幼苗紧急情况的最大的反应是 Phellodendronamurense。这篇论文证实了下列结论：在变瘦以后，改革树种类的变化是有在调查落叶松种植园改革 unthinned 树和地点条件的树种类，和分发的特征的关联词是影响新生的另外的因素。