Abstract Single-tree selection silviculture management of northern hardwood forests relies on natural tree regeneration for long-term sustainability, yet current trends in tree regeneration and recruitment elicit concern. Low densities of economically valuable sugar maple (Acer saccharum Marsh.) in understories are often common, likely driven by many factors, including deer browsing, management-dictated stand structure, and site fertility/moisture regimes. However, landscape sugar maple regeneration patterns and relationships with underlying factors are largely unknown. We quantified associations of spatially varying factors with sugar maple regeneration using detailed vegetation and white-tailed deer winter fecal pellet surveys from 141 northern hardwood stands in Michigan, managed for decades with single-tree selection silviculture. We developed models of plot-level sugar maple regeneration counts for three key size classes as a function of plot- and stand-level predictors, including deer use, forest structure, and site quality. Among our 141 stands, sugar maple seedlings ( 137 cm tall and 2,500 small sugar maple sapling stems ha−1 and 35% of stands had > 1,000 large sapling stems ha−1. Based on our models, sapling densities negatively associated with deer use and were more abundant on medium than high quality sites. Across all size classes, negative associations with subcanopy trees and/or shrub densities suggest light limitation, whereas positive associations with sugar maple canopy trees > 25 cm DBH suggest persistent seed limitations. Overall, our study supports need for alternative forest and/or deer management strategies over much of the range of northern hardwood forests in Michigan to promote higher densities of large sugar maple regeneration for canopy recruitment. Medium quality sites with abundant large sugar maple canopy trees and low deer browsing pressure (for example, the deep snow region in the north western Upper Peninsula) are the exception; high sugar maple sapling densities suggest forests in this region are thriving under single-tree selection management.

中文翻译：

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糖槭（Acer saccharum）再生的复杂驱动因素揭示了北方硬木管理林长期可持续性的挑战

摘要 北方阔叶林的单树选择造林管理依赖于自然树木再生以实现长期可持续性，但目前树木再生和补充的趋势引起了关注。林下有经济价值的糖槭 (Acer saccharum Marsh.) 密度低通常很常见，这可能是由许多因素驱动的，包括鹿食、管理要求的林分结构和场地肥力/水分状况。然而，景观糖枫再生模式及其与潜在因素的关系在很大程度上是未知的。我们使用密歇根州 141 个北部硬木林分的详细植被和白尾鹿冬季粪便颗粒调查量化了空间变化因素与糖枫再生的关联，这些林分通过单树选择造林进行了数十年的管理。我们开发了三个关键尺寸等级的地块级糖枫再生计数模型，作为地块和林分级预测因子的函数，包括鹿的使用、森林结构和场地质量。在我们的 141 个林分中，糖槭树苗（137 厘米高和 2,500 个小糖枫树苗茎 ha−1 和 35% 的林分有 > 1,000 个大树苗茎 ha−1。根据我们的模型，树苗密度与鹿的使用和在中等质量的地点比高质量的地点更丰富。在所有大小级别中，与亚冠树和/或灌木密度的负相关表明光照限制，而与糖槭树冠 > 25 cm DBH 的正相关表明持续的种子限制。总体而言，我们的研究支持在密歇根州北部阔叶林的大部分范围内制定替代森林和/或鹿管理策略的必要性，以促进更高密度的大型糖枫再生以进行冠层补充。拥有大量大型糖枫树冠层和低鹿食压力的中等质量地点（例如，上半岛西北部的深雪区）是例外；高糖枫树树苗密度表明该地区的森林在单树选择管理下蓬勃发展。