长白山云冷杉针阔混交林不同林隙下幼苗幼树密度及空间分布

Density and spatial distribution of seedlings and saplings in different gap sizes of a spruce-fir mixed stand in Changbai Mountains,China

2019年8月在云冷杉针阔混交林样地(0.36 hm^2),对48个林隙及幼苗(0.2<更新高度RH<1 m)、幼树(RH≥1 m,胸径DBH<5 cm)进行调查,分析林隙大小(<20 m^2,小;20~50 m^2,中;50~120 m^2,大;>120 m^2,特大)对林隙内红松、鱼鳞云杉及冷杉幼苗幼树密度和生长指标(高、基径)的短期影响,并采用核密度估计法分析其空间分布规律。结果表明:云冷杉更新的密度通常随林隙增大而降低,仅对幼树影响显著,小林隙下云冷杉幼树密度分别为0.34和1.74株·m^-2,红松密度不受林隙大小的影响。林隙大小对冷杉幼苗幼树生长指标的影响最大,对红松影响最小,平均最大值多出现在大林隙。红松和云杉幼树的基径和树高最大值均分布在小、中、大林隙东北部,在特大林隙中转移至冠空隙西北部。小林隙有助于幼苗的建立和萌发,可通过择伐冷杉创造小林隙,随后扩大林隙面积(>50 m^2)促进幼树生长,需要持续监测来确定林隙大小对森林更新的长期影响。

In August 2019,we investigated natural regeneration(seedlings height between 0.2 m and 1 m;saplings≥1 m in height and<5 cm in DBH)inside canopy gaps(n=48)in a plot(0.36 hm2)established in a typical mixed spruce-fir conifer broadleaved stand.To examine the short-term effects of gap size(small<20 m2,medium 20-50 m2,large 50-120 m2,and extra large>120 m2)on the regeneration density and growth(height and ground diameter)of Korean pine(Pinus koraiensis),Ezo spruce(Picea jezoensis)and Khingan fir(Abies nephrolepis),the kernel density estimation was used to examine their spatial distribution within gaps.The results showed that spruce and fir regeneration density generally decreased with the increases of gap size(significant effect only on saplings).The density of spruce and fir saplings in small gaps was 0.34 and 1.74 trees·m-2,respectively.In contrast,the density of Korean pine was not affected by gap size.The effects of gap size on seedling and sapling growth were strongest in Khingan fir and weakest in Korean pine,with greater height and ground diameter in larger gaps.Within a given canopy gap,the Korean pine and Ezo spruce saplings in small,medium,and large gaps were taller and had larger DBH in the northeastern corner of the expanded gap than in other sections,whereas those in extra large gaps had the highest growth in the northwestern part of the core gap.Small gaps favoring seed germination and seedling establishment could be created through selective removal of Khingan fir,which should be expanded later to larger sizes(>50 m2)to enhance sapling growth.Further monitoring would be required to understand the long-term effects of gap size on natural regeneration of spruce-fir forest.