抚育间伐对落叶松云冷杉混交林的影响

Effects of Thinning on Mixed Stands of Larix olgensis, Abies nephrolepis and Picea jazoensis

以15块人工落叶松纯林演化后形成的落叶松云冷杉混交林为对象,间伐后12年观测结果,研究间伐对林分和树木生长、树种组成、物种多样性及土壤等因子的影响。间伐强度分为2级:中度(平均为20%)和强度(平均为30%)。结果表明:间伐促进了保留木生长的显著增加,但不同间伐强度间无显著差异。林分及单木的直径、断面积和蓄积生长率均表现相同的趋势即随间伐强度的增加而增加。但间伐没有显著地增加12年间的总收获量。伐后对照样地表现为较高的枯损,枯死木主要是落叶松和阔叶树。林分进界株数严重不足,进界的主要树种是云冷杉、阔叶树和红松,以耐荫树种为主。从枯损和进界看,如果能对红松和阔叶树进行保护,这种林分很可能逐渐演化为阔叶红松林。建议对红松和阔叶树进行保护,使林分向阔叶红松林方向发展。各林分的树种组成在12年间基本没有发生变化,即间伐没有显著地改变林分的树种组成,目前的树种组成即落叶松、其他针叶树(云杉、冷杉和红松)和阔叶树组成比约为6∶3∶1可能是相对稳定的群落。20%和30%的间伐强度没有显著地改变林分的物种多样性、灌草生物量和土壤物理性质,间伐样地的物种多样性略有提高;间伐样地的土壤物理性质有所改善,总孔隙度和毛管孔隙度都大于对照;林下灌草生物量有所增加。

Experimental plots were established for thinning effects on stand and tree growth, tree species composition, species diversity and soil factors etc. in the mixed larch-spruce-fir stands which originated from planted larch pure forest by observations for 12 years after thinning. Experimental treatments included medium intensity thinning （average removal of 20% of the volume）, heavy intensity thinning（removal of 30% of the volume） and control. Results showed that thinning had a significant effect on residual stand growth, but there was no significant difference between medium and heavy thinning treatments. Periodical annual increment （PAl） of diameter, basal area and volume for both whole stand and individual trees showed similar trends,stands with heavy thinning treatments had the highest PAl, stands with medium thinning second, and unthinned stands the lowest. Thinning had no significant effects on total yield in 12 years after thinning. Stand development during the 12 years following thinning was characterized by high mortality in the unthinned stands, which occurred primarily for larch and broadleaved tree species. The number of ingrowth was very small in all stands, the ingrowth mainly occurred for shade-tolerant tree species such as Spruce, Fir, Korean Pine and broad-leaved tree species. It is recommended to reserve Korean Pine and broadleaved tree species for current mixed Larch-Spruce-Fir stands to develop towards deciduous Korean Pine forest. No significant differences were detected in tree species composition between thinning and unthinned stands, Therefore, the species composition of Larch, other conifer and broad-leaved tree species with the proportion of 6 ： 3 ： 1 maybe stable. Thinning stands with the thinning intensity of about 20% and 30% had no significant effects on species diversity, biomass of shrub and herb, and physical properties of soil. However, species diversity, the biomass of understory shrub and herb, and total porosity and capillary porosity of thinning stands were a little higher than those of control stands.