Evaluating the ecological impacts of salvage logging: can natural and anthropogenic disturbances promote coexistence?
Evaluating the ecological impacts of salvage logging: can natural and anthropogenic disturbances promote coexistence?
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评估抢救性伐木的生态影响：自然和人为干扰能否促进共存？
作者：
A. Royo;C. Peterson;J. Stanovick;W. Carson
风吹后的抢救性伐木在全世界森林中都很常见，尽管这种做法通常被认为不利于森林恢复。由于抢救会砍伐树木、压碎幼苗并压实土壤，许多人警告说这种做法可能会延迟演替、抑制多样性并改变组成。在这里，在风吹后 8 年多的时间里，我们通过实验评估了抢救如何影响宾夕法尼亚州东部落叶林 11 个间隙的树木演替，其中每个间隙被分为抢救和对照（未抢救）两半。我们的差距大小和风力严重程度各不相同，我们明确考虑了这种变化以及打捞造成的土壤扰动（即松土）的变化，以便我们的结果具有普遍性。抢救性伐木对树木的演替影响有限且短暂。随着时间的推移，在抢救和未抢救的地区，随着个体长成树苗，幼苗的丰富度和密度也同样下降。抢救对演替的主要影响发生在抢救松化的土壤上。在这里，抢救导致树苗丰度、丰富度和多样性下降 41% 至 82%，但这些差异在 5 年内基本消失。此外，我们还记录了风抛严重程度和划痕之间的相互作用。具体来说，低强度的风吹和松土结合增强了耐荫和耐啃食物种（Acer pensylvanicum、Fagus grandifolia）的优势。相比之下，严重的风吹和松土作用一起使快速生长的先锋树（Prunus pensylvanica）的密度和非树木植被覆盖率分别降低了 75% 和 26%。这种减少使两种中期演替树种（红枫和李）的补充量分别增加了 2 倍和 3 倍。因此，我们的研究结果表明，抢救创造了新的微场所并减少了竞争性植被，从而促进了重要硬木的建立并促进了树种共存。我们的结果，加上对 27 项已发表的风抛后抢救研究的评估，表明短期研究可能高估了抢救对再生的影响。我们的结论是，抢救的生态成本和效益取决于树冠和土壤扰动严重程度的变化以及评估影响的时间尺度。因此，我们的研究结果与抢救不可避免地破坏植物多样性的观点不一致。相反，我们建议抢救可以促进树种在不同环境下的共存。
Salvage logging following windthrow is common throughout forests worldwide even though the practice is often considered inimical to forest recovery. Because salvaging removes trees, crushes seedlings, and compacts soils, many warn this practice may delay succession, suppress diversity, and alter composition. Here, over 8 yr following windthrow, we experimentally evaluate how salvaging affects tree succession across 11 gaps in Eastern deciduous forests of Pennsylvania, wherein each gap was divided into salvaged and control (unsalvaged) halves. Our gaps vary in size and windthrow severity, and we explicitly account for this variation as well as variation in soil disturbance (i.e., scarification) resulting from salvaging so that our results would be generalizable. Salvage logging had modest and ephemeral impacts on tree succession. Seedling richness and density declined similarly over time in both salvaged and unsalvaged areas as individuals grew into saplings. The primary impact of salvaging on succession occurred where salvaging scarified soils. Here, salvaging caused 41 to 82% declines in sapling abundance, richness, and diversity, but these differences largely disappeared within 5 yr. Additionally, we documented interactions between windthrow severity and scarification. Specifically, low-severity windthrow and scarification combined reinforced dominance by shade-tolerant and browse-tolerant species (Acer pensylvanicum, Fagus grandifolia). In contrast, high windthrow severity and scarification together reduced the density of a fast-growing pioneer tree (Prunus pensylvanica) and non-tree vegetation cover by 75% and 26%, respectively. This reduction enhanced the recruitment of two mid-successional tree species, Acer rubrum and Prunus serotina, by 2 and 3-fold, respectively. Thus, our findings demonstrate that salvaging creates novel microsites and mitigates competing vegetation, thereby enhancing establishment of important hardwoods and promoting tree species coexistence. Our results, coupled with an assessment of 27 published post-windthrow salvage studies, suggest short-term studies may overestimate the impact of salvaging on regeneration. We conclude that the ecological costs and benefits of salvaging depend upon the variation in canopy and soil disturbance severity as well as the timescale at which effects are evaluated. Thus, our findings are inconsistent with the view that salvaging inexorably undermines plant diversity; rather we suggest salvaging can promote tree species coexistence within various contexts.