Natural disturbance‐based management (NDBM) is hypothesized to maintain managed forest ecosystem integrity by reducing differences between natural and managed forests. The effectiveness of this approach often entails local comparisons of species composition or diversity for a variety of biota from managed and unmanaged forests. Understory vegetation is regularly the focus of such comparison because of its importance in nutrient cycling, forest regeneration, and for wildlife. However, larger scale comparisons between regions with distinct species assemblages may require a trait‐based approach to better understand understory responses to disturbance. We compared the long‐term effects of retention harvesting on understory vegetation in two large experimental study sites located in eastern and western regions of the Canadian boreal forest. These sites included the Sylviculture en Aménagement Forestier Ecosystémique (SAFE) experiment and the Ecosystem Management Emulating Natural Disturbance (EMEND) experiment, located in the eastern and western regions of Canada, respectively. EMEND and SAFE share common boreal understory species but have distinct tree communities, soils, and climate. Both experiments were designed to evaluate how increasing tree retention after harvest affects biodiversity. Here, we examined taxonomic richness, functional diversity, and functional composition (using community trait mean values) of understory plant communities, and also examine intraspecific trait variability (ITV) for five species common and abundant in both experiments. We observed the limited impacts of retention level on richness, functional diversity, and functional composition of understory plants 20 years postharvest. However, ITV of leaf morphological traits varied between retention levels within each experiment, depending on the species identity. Common species had different functional responses to retention level, showing species‐specific reactions to environmental variation. Our result suggests that understory plant communities in the boreal forest achieve resilience to disturbance both in terms of interspecific and intraspecific functional trait diversity. Such diversity may be key to maintaining understory biodiversity in the face of future disturbances and environmental change. Our results reveal the significance of ITV in plant communities for understanding responses to forest harvesting and the importance of choosing appropriate traits when studying species responses to the environment.

中文翻译：

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加拿大东部和西部林下植物对自然干扰管理的功能响应


假设基于自然扰动的管理（NDBM）通过减少天然林和管理森林之间的差异来维持管理森林生态系统的完整性。这种方法的有效性通常需要对管理和非管理森林的各种生物群的物种组成或多样性进行局部比较。林下植被通常是此类比较的焦点，因为它在养分循环、森林再生和野生动物方面非常重要。然而，具有不同物种组合的区域之间的更大规模比较可能需要基于性状的方法来更好地了解林下对干扰的反应。我们在位于加拿大北方森林东部和西部地区的两个大型实验研究地点比较了保留采伐对林下植被的长期影响。这些地点包括分别位于加拿大东部和西部地区的 Sylviculture en Aménagement Forestier Ecosystémique (SAFE) 实验和模拟自然扰动的生态系统管理 (EMEND) 实验。 EMEND 和 SAFE 拥有共同的北方林下物种，但具有不同的树木群落、土壤和气候。这两个实验的目的都是为了评估收获后增加树木保留率如何影响生物多样性。在这里，我们检查了林下植物群落的分类丰富度、功能多样性和功能组成（使用群落性状平均值），并检查了两个实验中常见且丰富的五个物种的种内性状变异性（ITV）。我们观察到保留水平对采后 20 年林下植物的丰富度、功能多样性和功能组成的影响有限。 然而，每个实验中叶形态性状的 ITV 在保留水平之间有所不同，具体取决于物种特性。常见物种对保留水平有不同的功能反应，显示出对环境变化的物种特异性反应。我们的结果表明，北方森林的林下植物群落在种间和种内功能性状多样性方面都实现了对干扰的恢复能力。这种多样性可能是面对未来干扰和环境变化时维持林下生物多样性的关键。我们的结果揭示了植物群落中 ITV 对于理解森林采伐反应的重要性，以及在研究物种对环境的反应时选择适当性状的重要性。