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.
LIU Zu-genZHU Jiao-junHU Li-leWANG He-xinMAO Zhi-hongLI Xiu-fenZHANG Li-jun
One of the most important and frequently studied variable in forests and the most basic element in governing transport processes of airflow is wind speed. The study of wind profile, defined as the change of wind velocity with height, and wind ve-locity are important because of tree physiological and developmental responses. Generally, wind profiles above the ground or at a canopy surface follow classical logarithm law, but wind profiles in a single tree and in a forest stand are not logarithmic. This paper summarizes the results of wind profile studies within a single tree, in a forest stand, above the forest canopy and in a forest area from recent research in a coastal pine forest. The results demonstrate that: 1) wind profiles with in a single conifer tree crown showed an exponential function with height, 2) wind profiles in forest stands were able to be expressed by attenuation coefficient of wind, 3) wind profiles over a forest canopy could be determined using profile parameters (friction velocity, rough-ness length and displacement), and 4) for a forest area, the extreme wind speed could be predicted reasonably using the methods developed for the design of buildings. More research will be required to demonstrate: 1) relationships between wind profiles and tree or stand characteristics, 2) the simple methods for predicting wind profile parameters, and 3) the applications of wind profile in studies of tree physiology, forest ecology and management, and the detail ecological effects of wind on tree growth.
