Decades of fire exclusion in the southern Appalachian Mountains, USA, has led to changing forest structure and species composition over time. Forest managers and scientists recognize this and are implementing silvicultural treatments to restore forest communities. In this study, conducted at the southern Appalachian Fire and Fire Surrogate Study site in Green River Game Land, North Carolina, USA, we assessed the effects of four fuel-reduction methods (burned four times, B; mechanical treatment two times, M; mechanical treatment two times plus burned four times, MB; and control, C) on the changes in understory community from pre-treatment to post-treatment years (2001 to 2016). We used non-metric multidimensional scaling (NMDS) to determine overall understory community heterogeneity, agglomerative hierarchical cluster analyses (AHCA) to determine finer-scale changes in understory community structure, and indicator species analyses (ISA) to identify the species that were associated with the different fuel reduction treatments over time. The NMDS ordination showed little separation between treatment polygons. The AHCA resulted in two main categories of understory species responses based on how treatment plots clustered together: (1) species apparently unaffected by the treatments (i.e., no treatment pattern present within cluster); and (2) species that responded to B, M, or MB treatments (i.e., pattern of treatment plots present within cluster). Nearly half (49.2%) of tree-species plots clustered based on treatments; 60% of shrub-species plots clustered based on treatments; and 64% of herbaceous-species plots clustered based on treatments. Many plots clustered similarly in response to fire-related treatments (B and MB). The ISA identified 11 total tree species: three in B, one in M, and seven in MB; six total shrub species: two in M, and four in MB, and 17 total herbaceous species or genera: one in C, and 16 in MB. Fire and fire surrogate treatments did not dramatically shift understory composition after 15 years. However, certain ruderal and early seral species responded positively to MB, which was the most intensive treatment. Modest understory community changes were also observed in B, suggestive of early signs of shifting composition toward a more open forest community after four burns.

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在美国南部阿巴拉契亚山脉，林下群落发生变化，以应对反复的火灾和火灾替代治疗

随着美国南部阿巴拉契亚山脉数十年的防火，导致森林结构和物种组成随时间变化。森林管理者和科学家认识到这一点，并正在实施造林措施以恢复森林群落。在本研究中，在美国北卡罗来纳州格林河游戏乐园的南部阿巴拉契亚火灾和火灾替代物研究现场进行了评估，我们评估了四种减少燃料消耗方法的效果（燃烧四次，B；机械处理两次，M；机械治疗两次，再烧四次，MB；对照C，从治疗前到治疗后（2001年至2016年）下层群落的变化。我们使用非度量多维标度（NMDS）来确定整体林下群落异质性，聚集层次聚类分析（AHCA）可以确定林下群落结构的更细微变化，指示剂种类分析（ISA）可以确定随时间推移与不同的减燃料方法相关的种类。NMDS排序显示处理多边形之间几乎没有分隔。根据处理地块如何聚集在一起，AHCA导致了林下物种响应的两个主要类别：（1）显然不受处理影响的物种（即，群集中不存在任何处理模式）；（2）对B，M或MB处理产生反应的物种（即簇中存在的处理地块的模式）。根据处理，将近一半（49.2％）的树种地块聚在一起；60％的灌木物种地块根据处理情况聚类；根据处理情况，有64％的草种地块成簇。许多地块对火灾相关处理（B和MB）的响应类似。ISA确定了11种树种：B中三种，M中一种，MB中七种；共有6种灌木物种：M中有2种，MB中有4种，共有17种草种或属：C中一种，MB中有16种。15年后，火灾和火灾替代治疗并没有显着改变下层组成。但是，某些属和早期的血清类物种对MB的反应是积极的，MB是最密集的治疗方法。在B区也观察到适度的林下群落变化，这表明在经历四次烧伤后，成分向更开放的森林群落转移的早期迹象。ISA确定了11种树种：B中三种，M中一种，MB中七种；共有6种灌木物种：M中有2种，MB中有4种，共有17种草种或属：C中一种，MB中有16种。15年后，火灾和火灾替代治疗并没有显着改变下层组成。但是，某些属和早期的血清类物种对MB的反应是积极的，MB是最密集的治疗方法。在B区也观察到适度的林下群落变化，这表明在经历四次烧伤后，成分向更开放的森林群落转移的早期迹象。ISA确定了11种树种：B中三种，M中一种，MB中七种；共有6种灌木物种：M中有2种，MB中有4种，共有17种草种或属：C中一种，MB中有16种。15年后，火灾和火灾替代治疗并没有显着改变下层组成。但是，某些属和早期的血清类物种对MB的反应是积极的，MB是最密集的治疗方法。在B区也观察到适度的林下群落变化，这表明在经历四次烧伤后，成分向更开放的森林群落转移的早期迹象。某些鱼和早期血清型物种对MB的反应良好，MB是最密集的治疗方法。在B区也观察到适度的林下群落变化，这表明在经历四次烧伤后，成分向更开放的森林群落转移的早期迹象。某些鱼和早期血清型物种对MB的反应良好，MB是最密集的治疗方法。在B区也观察到适度的林下群落变化，这表明在经历四次烧伤后，成分向更开放的森林群落转移的早期迹象。