间伐对华北土石山区油松林生长及其林下植被发育的影响

间伐是森林经营的主要措施之一,研究间伐对森林生态系统的影响对其可持续发展具有深远意义。对河北省木兰围场国有林场管理局北沟林场4块油松人工林样地分别进行46.6%,56.2%,67.1%的3个强度间伐以及对照处理,通过植被群落调查,研究不同间伐强度后油松林生长及其林下植被发育。结果表明:油松林分经不同强度抚育间伐后单木胸径、树高、冠幅和生物量均显著高于对照,且随间伐强度增大而增加,但单位面积蓄积量随间伐强度增大而减小;弱度、中度间伐能够增加林下植物种类,提高林下植物丰富度、多样性和均匀度指数,但是强度间伐后林下植物种类并不会增多,此现象符合"中度干扰假说";林分经不同强度间伐后,林下植被优势种各异;随着间伐强度的增大,林下植被生物量增加。综上,合理的间伐能够促进林分生长及其林下植被发育,研究区选择56.2%左右的间伐强度最优。

Effects of Thinning on the Growth and the Development of Undergrowth of Pinus tabulaeformis Plantation in Rocky Mountain Area of North China

Thinning is one of the main forest measures.Studying its effects on forest ecosystems is significant to the sustainable development of forest ecosystems.The effects of thinning intensity with four different treatments of 46.6%,56.2%,67.1% and 0(control group) on the undergrowth were carried out in the four Pinus tabulaeformis stands in Forest Bureau of Mulanweichang,Hebei Province.Through vegetation community investigation,the growth of forest and undergrowth vegetation after different intensities of thinning were studied.The results showed: the DBH,height,crown length and biomass of the tending group were significantly higher than those of the control group,and they increased with the thinning intensity,but stock volume of per unit area decreased with thinning intensity.Light,medium thinning could increase species,Gleason index,Shannon—Wiener index and Pielou index of the undergrowth vegetation,but the species of the undergrowth vegetation wouldn′t increase after heavy thinning.This phenomenon belonged to ’medium disturbance hypothesis’.The composition of dominant species of the four undergrowth vegetation varied after different intensities of thinning.The biomass of undergrowth vegetation increased with thinning intensity.All in all,reasonable thinning can promote the growth of forest and development of undergrowth vegetation.The reasonable thinning intensity of this study area should be about 56.2%.