Kroll Andrew J, Springford Aaron, Verschuyl Jake
Weyerhaeuser, 785 N 42nd Street, Springfield, Oregon, 97478, USA.
Weyerhaeuser, 220 Occidental Avenue S, Seattle, Washington, 98104, USA.
Ecol Appl. 2020 Oct;30(7):e02148. doi: 10.1002/eap.2148. Epub 2020 May 26.
Reductions in management intensity are often proposed to support a broader range of beneficial ecosystem responses than traditional management approaches. However, few studies evaluate ecosystem responses across approaches. Also, managers lack information about how species traits mediate responses across management approaches, a potentially substantial source of spatial and temporal variation in population and community responses that if ignored may hinder effectiveness of management programs. We used data collected over eight years from a manipulative experiment to test how four forest management strategies influenced avian community composition and wood production. After harvesting, we evaluated responses to three levels of plant cover suppression (Light, Moderate, and Intensive herbicide applications) in relation to a control without herbicide. We predicted the Moderate and Intensive treatments would exert strong negative effects on leaf-gleaning insectivores, including species of conservation concern due to long-term population declines. However, given high forest productivity, we expected temporal duration of effects to be short. Richness of leaf-gleaning bird species was reduced by 20-50% during the first four years post-harvest (when herbicide treatments were on-going), but the effect size declined over the next four years once treatments were completed (13-20% reduction). Effect sizes were substantially smaller for the non-leaf-gleaner group during years 1-4 (19-27%) and disappeared during years 5-8 (2-3%). However, in our final year of observation, we did find an average of five fewer non-leaf-gleaner species on Light vs. Control units. In the last two years of observation, turnover probabilities for the leaf-gleaner species remained higher on all treatments compared to the Control (0.11-0.21), indicating that new species continued to colonize treatments. Planted conifers were 40-44% taller and 74-81% larger in diameter in the Moderate and Intensive treatments compared to the Control, leading to substantial gains in wood biomass. Current practices provided more balance between two ecosystem responses, avian diversity and wood production, compared to less intensive alternatives. When short-term negative effects occur, the spatial distribution of harvesting and regeneration regionally indicates that habitat is often available locally to support leaf-gleaning and non-leaf-gleaning bird populations while releasing other portions of the region for high priority conservation objectives including late-successional forest reserves.
与传统管理方法相比，人们常常建议降低管理强度，以支持更广泛的有益生态系统响应。然而，很少有研究评估不同管理方法下的生态系统响应。此外，管理者缺乏关于物种特性如何介导不同管理方法下的响应的信息，这是种群和群落响应中时空变异的一个潜在重要来源，如果被忽视，可能会阻碍管理计划的有效性。我们利用从一项操纵实验中收集的八年数据，来测试四种森林管理策略如何影响鸟类群落组成和木材产量。采伐后，我们评估了与不使用除草剂的对照相比，三种植物覆盖抑制水平（轻度、中度和重度除草剂施用）的响应。我们预测，中度和重度处理会对食叶昆虫食性鸟类产生强烈的负面影响，包括因长期种群数量下降而受到保护关注的物种。然而，鉴于森林生产力较高，我们预计影响的持续时间会很短。采伐后的头四年（除草剂处理进行期间），食叶鸟类物种丰富度降低了20%-50%，但处理完成后的接下来四年里，效应大小下降（降低了13%-20%）。在第1-4年，非食叶鸟类组的效应大小要小得多（19%-27%），在第5-8年消失（2%-3%）。然而，在我们观察的最后一年，我们确实发现，与对照单元相比，轻度处理单元上的非食叶鸟类物种平均少了五种。在观察的最后两年，与对照相比，所有处理下食叶鸟类物种的周转概率仍然更高（0.11-0.21），这表明新物种继续在处理区域定居。与对照相比，中度和重度处理下种植的针叶树高40%-44%，直径大74%-81%，导致木材生物量大幅增加。与强度较低的替代方法相比，当前的做法在鸟类多样性和木材产量这两种生态系统响应之间提供了更多平衡。当出现短期负面影响时，区域内采伐和更新的空间分布表明，当地通常有栖息地来支持食叶和非食叶鸟类种群，同时为包括晚期演替森林保护区在内的高优先级保护目标释放该区域的其他部分。
