In North American conifer forests, a variety of federally initiated thinning programs are implemented to restore pre-European settlement forest structures, but these changes may impact ecosystem function via impacts on sensitive biotic communities. Across the wildland–urban interface of the Front Range region of Colorado, agencies associated with the Collaborative Forest Landscape Restoration Program (CFLRP) have implemented thinning treatments across thousands of hectares of ponderosa pine forest; here we leverage these treatments as an experimental framework to examine thinning effects on a pollinator community. We measured variation in forest structure and sampled bee community assemblages using multiple methods (trapping and netting) to compare bee biodiversity and patterns of floral visitation by bees (bee–flower networks) between mechanically thinned stands that were 3–10 years after treatment and nonthinned stands. Three key findings emerged: (1) Native bee abundance, richness, and diversity were 120%, 53%, and 37% greater, respectively, in thinned stands. In addition, nestedness, richness, and abundance of bee–flower interactions were all substantially higher in thinned stands, and there was increased functional redundancy in bee assemblages after thinning. (2) Structural equation modeling indicated that variation in temperature and floral abundance were mediated by canopy openness and correlated with bee richness and abundance, thereby indirectly driving variation in bee–flower interactions. (3) Four floral species (Penstemon virens, Cerastium arvense, Erysimum capitatum, and Geranium caespitosum) were identified as key connectors in bee–flower interaction networks, though these were not necessarily the most abundant flowering plants. Our analyses indicate that native bee α-diversity and bee–flower interactions positively responded to thinning treatments, and these effects were indirectly driven by canopy removal. We conclude that CFLRP treatments have conservation value for native bee communities. Further monitoring is warranted to evaluate the longevity of these effects.

中文翻译：

---

森林恢复处理通过花和温度介导的效应间接使授粉网络多样化

在北美针叶林中，实施了各种联邦政府发起的间伐计划，以恢复欧洲人定居之前的森林结构，但这些变化可能会通过影响敏感的生物群落来影响生态系统功能。在科罗拉多州弗兰特山脉地区的荒地与城市交界处，与森林景观合作恢复计划 (CFLRP) 相关的机构已经对数千公顷的黄松林实施了间伐处理；在这里，我们利用这些处理作为实验框架来检查对传粉昆虫群落的稀疏影响。我们使用多种方法（诱捕和网捕）测量了森林结构的变化，并对蜜蜂群落组合进行了采样，以比较处理后 3-10 年的机械间伐林分和非间伐林分之间的蜜蜂生物多样性和蜜蜂的花卉访问模式（蜂花网络）。站立。得出了三个关键发现：(1) 在疏伐林中，本地蜜蜂的丰度、丰富度和多样性分别增加了 120%、53% 和 37%。此外，在间伐林分中，蜂花相互作用的嵌套性、丰富度和丰度都显着更高，并且间伐后蜜蜂组合的功能冗余增加。(2)结构方程模型表明，温度和花卉丰度的变化是由冠层开放度介导的，并与蜜蜂的丰富度和丰度相关，从而间接驱动蜂花相互作用的变化。(3) 四种花卉物种（Penstemon virens、Cerastium arvense、Erysimum headum和Geranium caespitosum）被确定为蜂花相互作用网络中的关键连接器，尽管它们不一定是最丰富的开花植物。我们的分析表明，本地蜜蜂的α多样性和蜂花相互作用对间伐处理有积极的反应，而这些影响是由冠层去除间接驱动的。我们得出的结论是，CFLRP 处理对本地蜜蜂群落具有保护价值。需要进一步监测以评估这些影响的持续时间。