Graignic Noémie, Tremblay Francine, Bergeron Yves
Institut de Recherche sur les Forêts Université du Québec en Abitibi-Témiscamingue Rouyn-Noranda QC Canada.
Evol Appl. 2016 May 30;9(6):777-90. doi: 10.1111/eva.12384. eCollection 2016 Jul.
Selection cutting is a treatment that emulates tree-by-tree replacement for forests with uneven-age structures. It creates small openings in large areas and often generates a more homogenous forest structure (fewer large leaving trees and defective trees) that differs from old-growth forest. In this study, we evaluated whether this type of harvesting has an impact on genetic diversity of sugar maple (Acer saccharum Marshall). Genetic diversity among seedlings, saplings, and mature trees was compared between selection cut and old-growth forest stands in Québec, Canada. We found higher observed heterozygosity and a lower inbreeding coefficient in mature trees than in younger regeneration cohorts of both forest types. We detected a recent bottleneck in all stands undergoing selection cutting. Other genetic indices of diversity (allelic richness, observed and expected heterozygosity, and rare alleles) were similar between forest types. We concluded that the effect of selection cutting on the genetic diversity of sugar maple was recent and no evidence of genetic erosion was detectable in Québec stands after one harvest. However, the cumulative effect of recurring applications of selection cutting in bottlenecked stands could lead to fixation of deleterious alleles, and this highlights the need for adopting better forest management practices.
择伐是一种模拟对具有异龄结构的森林逐棵进行更新的处理方式。它在大面积区域创造小的林窗，并且常常形成一种与原始森林不同的、更为均匀的森林结构（大型留存木和缺陷木较少）。在本研究中，我们评估了这种采伐类型是否对糖枫（糖槭，Acer saccharum Marshall）的遗传多样性有影响。我们比较了加拿大魁北克择伐林分和原始林分中幼苗、幼树和成熟树木之间的遗传多样性。我们发现，与两种森林类型的较年轻更新群体相比，成熟树木具有更高的观察杂合度和更低的近交系数。我们在所有进行择伐的林分中检测到近期存在瓶颈效应。森林类型之间的其他遗传多样性指标（等位基因丰富度、观察和期望杂合度以及稀有等位基因）相似。我们得出结论，择伐对糖枫遗传多样性的影响是近期的，并且在魁北克林分经过一次采伐后未检测到遗传侵蚀的证据。然而，在瓶颈林分中反复进行择伐的累积效应可能导致有害等位基因的固定，这凸显了采用更好的森林管理实践的必要性。
