川西高山森林生态系统林下生物量及其随林窗的变化特征

作为森林生态系统的重要组成部分,林下植被及其残体的分布受到林冠层的影响,但迄今有关林窗对林下植被和残体生物量的影响尚无研究报道.于2013 年8 月2 日至20 日,以海拔3 600 m 的川西岷江冷杉原始林林下植被为研究对象,根据区域内的坡向和林分组成等因素设置3 个100 m×100 m 的典型样地,调查其生物量及其随林窗的变化特征.在每个样地内选择3 个大林窗,在林窗、林缘和林下分别设置3 个20 m×20 m 的样方,调查粗木质残体长度或高度、大小头直径、枯立木记录胸径、腐烂等级等;在林窗、林缘和林下分别设置3 个5 m×5 m 的样方,采用“收获法”收集样方内直径在2.5-10 cm之间的细木质残体和灌木生物量;在林窗、林缘和林下分别设置3 个1 m×1 m 的样方来调查凋落物储量和草本生物量;在1m×1 m 的样方内随机选择1 个20 cm×20 cm 的小样方来调查地被植物生物量.结果表明,（1）川西高山森林生态系统总生物量为72.75 t·hm^-2,其中林下生物量为67.92 t·hm^-2,占生态系统生物量的95.17%.活体植被以灌木为主,其生物量为9.81t·hm^-2;残体部分以粗木质残体为主,其储量为53.00 t·hm^-2;（2）林窗对灌木、草本、地被植物的影响各不相同,且不同物种的灌木生物量表现出不同的分布规律;草本生物量表现出明显的“边缘效应”,在林缘显著高于林下;林窗和林缘的地被植物生物量相对较低;（3）粗木质残体储量从林下到林窗呈现减小的趋势,但总体储量仍然较大,林窗和林缘的细木质残体储量高于林下.这些结果为认识高山森林生态系统林下生物量及其格局,以及林窗在森林生态系统的重要作用提供了基础理论依据.

Understory biomass and its characteristics as affected by forest gap in the alpine forest ecosystem in west Sichuan

Understory vegetation and its debris, as an important component in the forest ecosystem, can be greatly affected by forestcanopy. As yet, little information has been available on the effects of forest gaps on understory plant and its debris biomass. In orderto understand the changes of understory plant and its debris biomass as affected by forest gaps, therefore, three 100 m×100 m plotswere sampled in a Minjiang fir （Abies faxoniana） primary forest ecosystem around 3 600 m altitude in western Sichuan in August,2013. Coarse woody debris with length/height, basic diameter, diameter at breast height and decay class were investigated in each ofthree 20 m×20 m sampling quadrats in forest gap center, gap edge and closed canopy, respectively. Fine woody debris and shrubbiomass were investigated in each of three 5 m×5 m sampling quadrats in forest gap, gap edge and closed canopy, respectively.Moreover, non-woody litter and herb biomass were harvested in each of three 1 m×1 m sampling quadrats in forest gap, forest edgeand closed canopy, respectively. Each of 20 cm×20 cm sampling quadrat was randomly selected to harvest groundcover vegetationbiomass in the above 1 m×1 m quadrat. The results indicated that： （1） the total biomass was 72.75 t·hm^-2 in the sampled alpine forestecosystem, and understory biomass was 67.92 t·hm^-2 which accounted for 95.17% of the total biomass in whole ecosystem. Shrubbiomass was 9.81 t·hm^-2 and occupied the majority proportion of living vegetation, but coarse woody debris biomass was 53.00t·hm^-2 and occupied the majority of dead debris. （2） Shrub, herb and groundcover vegetation biomass showed different responses toforest gap. Shrub biomass was significantly higher in forest edge than that in closed canopy, although the biomass of groundcovervegetation was relatively lower in forest gap and forest edge compared with that in closed canopy. （3） Coarse woody debris biomassshowed a decrease tendency from closed canopy to gap center, but the storage of fine woody debri