Montoro Girona Miguel, Lussier Jean-Martin, Morin Hubert, Thiffault Nelson
Ecology Restoration Group, Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences (SLU), Umeå, Sweden.
Département des Sciences Fondamentales, Université du Québec à Chicoutimi, Saguenay, QC, Canada.
Front Plant Sci. 2018 Aug 17;9:1145. doi: 10.3389/fpls.2018.01145. eCollection 2018.
Forest regeneration is a key element in achieving sustainable forest management. Partial harvest methods have been used extensively in temperate broadleaf and mixedwood ecosystems to promote regeneration on poorly stocked sites and to maintain forest composition and productivity. However, their effectiveness in promoting conifer establishment has yet to be demonstrated in unmanaged boreal forests, especially those dominated by black spruce ( (Mill.) BSP) where constraints for regeneration differ from those found in more meridional regions. We aimed to evaluate conifer seedling density and dimensions, 10 years after the onset of a gradient of silvicultural treatments varying in harvesting intensities, and to identify the critical factors driving the regeneration process. Study blocks of even-aged black spruce stands in the eastern Canadian boreal forest were submitted to three variants of shelterwood harvesting: a seed-tree harvest, a clear-cut and an untreated control. Shelterwood and seed-tree harvesting were combined with spot scarification to promote regeneration. Shelterwood and seed-tree harvesting produced a density of conifer regeneration sufficient to maintain forest productivity, but they did not promote seedling growth. Black spruce was the predominant species in terms of regeneration density, with proportions 3-5× higher than that for balsam fir ( (L.) Mill.). Ten years after treatment, seed-origin black spruce seedlings were abundant in skidding trails, while layers dominated the residual strips. Balsam fir density was not influenced by treatment nor by tree position relative to skidding trails. Balsam fir and black spruce had different responses to treatment in terms of height and diameter, the former exhibiting a better growth performance and larger diameter in the residual strips. Spot scarification created micro-sites that had a significant impact on the regeneration process. Overall, our results support that shelterwood and seed-tree harvesting combined with scarification enable adequate regeneration in black spruce stands, confirming these treatments as viable silvicultural alternatives to clear-cutting when required by sustainable forest management objectives.
森林更新是实现可持续森林管理的关键要素。择伐方法已在温带阔叶林和混交林生态系统中广泛应用，以促进立木蓄积量低的林分更新，并维持森林组成和生产力。然而，在未经营的北方森林中，尤其是以黑云杉（(Mill.) BSP）为主的森林中，其促进针叶树定植的有效性尚未得到证实，在这些森林中，更新的限制因素与更靠南的地区不同。我们旨在评估不同采伐强度的一系列营林措施实施10年后针叶树幼苗的密度和尺寸，并确定驱动更新过程的关键因素。在加拿大东部北方森林中，对同龄黑云杉林分的研究样地进行了三种渐伐采伐方式：保留母树采伐、皆伐和未处理对照。渐伐和保留母树采伐结合局部松土以促进更新。渐伐和保留母树采伐产生了足以维持森林生产力的针叶树更新密度，但并未促进幼苗生长。就更新密度而言，黑云杉是优势种，其比例比香脂冷杉（(L.) Mill.）高3至5倍。处理10年后，种子来源的黑云杉幼苗在集材道上大量出现，而分层幼苗则在残留带上占主导。香脂冷杉密度不受处理方式或相对于集材道的树木位置影响。香脂冷杉和黑云杉在树高和直径方面对处理的反应不同，前者在残留带上表现出更好的生长性能和更大的直径。局部松土创造了对更新过程有重大影响的微生境。总体而言，我们的结果支持渐伐和保留母树采伐结合松土能够在黑云杉林分中实现充分更新，证实了这些处理方式是可持续森林管理目标要求时替代皆伐的可行营林选择。
