Abstract To inform biodiversity conservation efforts in managed forest landscapes, we explore if a topographic moisture index (depth-to-water, based on remotely-sensed (LIDAR) data) can provide insight into responses of understory vegetation to retention harvesting in the boreal mixedwood forests of northwestern Alberta, Canada. Sample plots were placed along the depth-to-water moisture gradient in three forest types: coniferous, mixedwood, and deciduous (broadleaf), and in four retention harvesting treatments: unharvested (control), 50% (dispersed green-tree) retention, 20% retention, and clearcut (2% retention). Understory diversity, abundance, and composition were assessed 15 years after harvest. Harvesting affected the relationships between understory variables and the depth-to-water index, with the effects differing between forest types. Coniferous stands showed the most dramatic responses to harvesting, in that most relationships between understory attributes and the depth-to-water index changed due to harvesting. For instance, harvested coniferous stands had higher diversity on wetter sites, rather than on drier sites as was seen in the unharvested stands. In mixedwood stands only the relationship between composition and depth-to-water was affected by harvesting. Broadleaf stands were intermediate; abundance and composition showed a significant depth-to-water by harvesting treatment interaction. Abundance and depth-to-water relationships were weaker in harvested, as compared to unharvested, broadleaf stands. Within each forest type, the effects of harvesting also varied along the depth-to-water gradient. In coniferous and mixedwood forest types, wetter sites were most sensitive to harvesting while in broadleaf stands drier sites were more sensitive. Our study shows that the depth-to-water index can be used to better understand and predict the response of understory vegetation to harvesting and can be useful for guiding the placement of retention.

中文翻译：

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地形水分指数解释了林下植被对保留采伐的反应

摘要 为了为受管理的森林景观中的生物多样性保护工作提供信息，我们探索了地形水分指数（深度到水，基于遥感（LIDAR）数据）是否可以深入了解林下植被对北方混材中保留采伐的反应加拿大艾伯塔省西北部的森林。样地沿三种森林类型的深度到水的水分梯度放置：针叶林、混交林和落叶林（阔叶林），并在四种保留采伐处理中放置：未收获（对照）、50%（分散的绿树）保留、 20% 的保留率和明确的（2% 保留率）。在收获后 15 年评估林下多样性、丰度和组成。采伐影响林下变量与水深指数之间的关系，影响因森林类型而异。针叶林对采伐的反应最为显着，因为林下属性与水深指数之间的大多数关系因采伐而发生变化。例如，收获的针叶林在较湿润的地点具有更高的多样性，而不是在未收获的林分中所见的干燥地点。在混材林中，只有成分和水深之间的关系受到采伐的影响。阔叶林是中间的；通过收获处理相互作用，丰度和组成显示出显着的水深。与未收获的阔叶林相比，收获的丰度和深度与水的关系较弱。在每种森林类型中，采伐的影响也随着深度到水的梯度而变化。在针叶林和混交林类型中，较潮湿的地点对收获最为敏感，而在阔叶林较干燥的地点则更为敏感。我们的研究表明，水深指数可用于更好地了解和预测林下植被对采伐的反应，并可用于指导保留的位置。