长白山云冷杉针阔混交林幼苗幼树空间分布与关联性

Spatial distribution and association of seedlings and saplings in a spruce-fir forest in the Changbai Mountains area of northeastern China

【目的】幼苗幼树空间分布是影响森林群落动态变化的重要因素,对云冷杉不同苗高进行空间分布格局分析,并分别研究幼苗幼树与周围小径木和大径木的关联性,以探究云冷杉幼苗空间变化规律和空间结构对幼苗幼树的影响,提出促进云冷杉天然更新措施,为云冷杉林可持续经营提供理论依据。【方法】本研究于2017年8月在金沟岭林场设置长白山云冷杉针阔混交林标准地(0.36 hm^2),应用SADIE空间分析方法,分析了林分不同苗高级云冷杉的分布规律。【结果】云冷杉林分总体直径分布呈反"J"型;色木槭与冷杉直径分布呈增长型,云杉和红松为多峰波动曲线。林分内小径木聚集指数I_a>1,且随机化检验概率P_a<0.025,总体呈聚集分布;大径木P_a值为0.025~0.975,呈随机分布;随林木生长发育,林分空间分布由聚集逐渐趋于随机。冷杉作为主要树种之一,其小径木与大径木空间分布与林分总体空间分布相似;云杉呈随机分布;冷杉幼苗与冷杉大径木具有明显的空间关联性,并与云杉呈正相关,其幼苗具有较好的耐荫性;云杉幼苗总体呈空间分离或空间不相关,仅与冷杉大径木呈空间正相关性,云杉与冷杉为良好的伴生树种。苗高Ⅰ、Ⅱ、Ⅲ级冷杉幼苗空间关联性相似,苗高Ⅳ、Ⅴ级的幼树空间关联性相似;苗高Ⅰ、Ⅱ级云杉幼苗空间关联性相似。【结论】林分内,冷杉幼苗株数较多,与大多林木呈空间正相关,有利于冷杉的林下更新。云杉木材质量较好,作为主要目的树种,其大径木及幼苗株数较少,且幼苗幼树与小径木及大径木均呈空间分离,林下云杉更新状况较差,因此,在云杉幼苗时期采取适当的遮蔽措施,幼树时期进行采伐等经营措施,促进云杉幼苗生长,并通过对冷杉株数的合理控制,调整林分空间结构,为其释放生长空间,以增加云杉母树株数,提高产种能力及产量,促进云杉更新。

[Objective]Spatial distribution of seedlings and saplings is an important factor affecting the dynamic changes of forest communities.Spatial distribution of Picea jezoensis and Abies nephrolepis seedlings at different height levels was analyzed,and spatial association between their seedlings and surrounding small and large trees was studied in this paper to explore the spatial changes in a Picea jezoensis and Abies nephrolepis forest and to find the impact of spatial structure on Picea jezoensis and Abies nephrolepis seedlings.The measures were proposed for promoting natural regeneration,and theoretical basis was provided for the management plans in a Picea jezoensis and Abies nephrolepis forest.[Method]A sample plot of typical coniferous and broadleaved mixed forest with the area of 0.36 ha was set up in Jingouling Forest Farm,Jilin of northeastern China in August 2017.The SADIE spatial analysis method was used to analyze the spatial distribution of seedlings at different height levels.[Result]Within the forest stand,the diameter distribution showed an inverted"J"curve,the diameters of the Acer mono and Abies nephrolepis showed growth distribution pattern,and the diameter distribution of Picea jezoensis and Korean pine showed multi-peak fluctuation curves.The diameters of small trees in the forest stand showed an aggregate distribution with the aggregation index of I_a>1 and randomization test probability of P_a<0.025.The diameters of large trees were randomly distributed with P_a value between 0.025 and 0.975.The spatial distribution of forest stands changed from aggregation to randomization with the growth and development of forest trees.Since the Abies nephrolepis was one of the main tree species,its spatial distribution was similar to the overall spatial distribution in the forest stand.The diameters of Picea jezoensis had a random distribution.The locations of Abies nephrolepis seedlings had obvious spatial association with the locations of large Abies nephrolepis trees,and they were positively spatial associated with locations of all Picea jezoensis trees.Abies nephrolepis seedlings had good shade tolerance.The locations of Picea jezoensis seedlings generally showed spatial segregation or spatial irrelevance,which was only positively correlated with the locations of Abies nephrolepis trees,so Picea jezoensis and Abies nephrolepis are good companion species.The locations of Abies nephrolepis seedlings atⅠtoⅢheight levels had similar spatial associations,the locations of Abies nephrolepis seedlings atⅣandⅤheight levels had similar spatial associations,and the locations of Picea jezoensis seedlings atⅠandⅡheight levels had similar spatial associations.[Conclusion]Within the forest stand,the number of Abies nephrolepis seedlings is more than Picea jezoensis seedlings.Abies nephrolepis seedlings are positively spatial associated with the trees,which is beneficial to the regeneration of Abies nephrolepis.The quality of Picea jezoensis wood is good.As the main target species,the number of Picea jezoensis and its seedlings is small,and seedlings and saplings of Picea jezoensis show a separated spatial distribution with small trees and large trees.The regeneration status of Picea jezoensis under the forest is poor.As a result,appropriate shelter measures should be adopted for Picea jezoensis at the seedling stage,and management measures like cutting in the sapling period may be proposed to promote the growth of Picea jezoensis seedlings.In addition,the spatial structure of the stand could be adjusted for releasing the growth space of Picea jezoensis by appropriate controlled number of Abies nephrolepis in order to increase the number of Picea jezoensis mother trees.Then,seed production capacity will be improved,and the regeneration of Picea jezoensis will be promoted.