Many fire-dependent forests have experienced significant declines in species, structural, and functional diversity. These changes are attributed in part to traditional management approaches that were dominated by even-aged regeneration methods such as clearcutting. Variable retention harvesting (VRH) is an ecologically based forestry practice that involves retention of some mature overstory trees and other biological structures in the postharvest stand to emulate the effects of natural disturbance events. In this study, we examined the effect of a VRH treatment on recruitment of historically dominant pine species and understory vegetation two- and six years after its implementation in a naturally regenerated mixed pine forest in the Upper Peninsula of Michigan, USA. We found greater regeneration of red pine (Pinus resinosa L.) and eastern white pine (Pinus strobus L.) in VRH stands compared to the unharvested controls. Although red pine recruitment was very low during the first 2 years, both species increased significantly from year two to year six. Recruitment responses for the two species did not differ significantly between the aggregated and dispersed retention treatments. We also found high recruitment of deciduous tree species, consisting primarily of sprouts, and red pine exhibited a negative correlation with these sprouts. Treatment, time, and the interaction of treatment and time were significant factors in red pine recruitment. Time had a strong effect on the understory vegetation, with significant decreases in shrubs and ferns over time. The results suggest that VRH enhanced recruitment of red pine and eastern white pine and that this recruitment increased with time. We identify competition from sprouts and unfavorable seedbed conditions as the main factors that limited recruitment of red pine during the first 2 years. To reduce competing vegetation and improve seedbed conditions, we suggest following the VRH with a prescribed fire, mechanically removing sprouts, and implementing herbicide treatments. At a time when changes in global climate exacerbates the effects of traditional drivers of forest degradation, and with the need to maintain biodiversity, new ecologically based forest practices such VRH have the potential to facilitate regeneration of native trees and enhance the resilience of many fire-dependent forests.

中文翻译：

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混交林中主要松树物种的更新模式表明可变保留采伐具有积极作用，随着时间的推移招募增加

许多依赖火种的森林的物种，结构和功能多样性都大大下降。这些变化部分归因于传统的管理方法，而传统的管理方法主要由成熟的再生方法（例如清除方式）主导。可变保留采伐（VRH）是一种基于生态的林业实践，涉及保留一些成熟的树皮和其他生物结构，以模仿采伐后的林分。在这项研究中，我们研究了VRH处理在美国密歇根州上半岛的天然再生混交林中实施后的两年和六年对募集历史上占优势的松树物种和林下植被的影响。我们发现赤松（Pinus resinosa L. ）和VRH林中的东部白松（Pinus strobus L.）与未收获的对照相比。尽管在最初的两年中红松的募集量很低，但是从第二年到第六年这两种物种都显着增加。在聚集和分散保留处理之间，这两个物种的招聘反应没有显着差异。我们还发现落叶树种（主要由新芽组成）的高招募，赤松与这些新芽表现出负相关。处理，时间以及处理与时间的相互作用是赤松募集的重要因素。时间对地下植被的影响很大，灌木和蕨类植物随时间的推移而显着减少。结果表明，VRH增强了红松和东部白松的募集，并且该募集随时间增加。我们将发芽和不利的苗床条件确定为竞争的主要因素，这是限制头2年红松募集的主要因素。为了减少竞争性植被并改善苗床条件，我们建议在VRH之后使用规定的火种，机械去除芽苗并实施除草剂处理。在全球气候变化加剧了传统的森林退化驱动因素的影响以及维护生物多样性的必要性之时，基于生态的新森林实践（例如VRH）有可能促进本地树木的再生并增强许多火源的复原力，依赖的森林。我们将发芽和不利的苗床条件确定为竞争的主要因素，这是限制头2年红松募集的主要因素。为了减少竞争性植被并改善苗床条件，我们建议在VRH之后使用规定的火种，机械去除芽苗并实施除草剂处理。在全球气候变化加剧了传统的森林退化驱动因素的影响以及维护生物多样性的必要性之时，基于生态的新森林实践（例如VRH）有可能促进本地树木的再生并增强许多火源的复原力，依赖的森林。我们将发芽和不利的苗床条件确定为竞争的主要因素，这是限制头2年红松募集的主要因素。为了减少竞争性植被并改善苗床条件，我们建议在VRH之后使用规定的火种，机械去除芽苗并实施除草剂处理。在全球气候变化加剧了传统的森林退化驱动因素的影响以及维护生物多样性的必要性之时，基于生态的新森林实践（例如VRH）有可能促进本地树木的再生并增强许多火源的复原力，依赖的森林。我们建议使用规定的火力跟随VRH，机械去除芽苗并实施除草剂处理。在全球气候变化加剧了传统的森林退化驱动因素的影响以及维护生物多样性的必要性之时，基于生态的新森林实践（例如VRH）有可能促进本地树木的再生并增强许多火源的复原力，依赖的森林。我们建议使用规定的火力跟随VRH，机械去除芽苗并实施除草剂处理。在全球气候变化加剧了传统的森林退化驱动因素的影响以及维护生物多样性的必要性之时，基于生态的新森林实践（例如VRH）有可能促进本地树木的再生并增强许多火源的复原力，依赖的森林。