Marlyse Duguid, Yale School of Forestry & Environmental Studies, (Presenter)


The forest understory contains the majority of vascular plant diversity in eastern temperate forests, and its diversity, composition, and dynamics contribute directly to ecosystem function. While managers have traditionally viewed the understory as affecting forest regeneration or wildlife, there is increasing concern about impacts of management on understory diversity, and a growing recognition of the range of goods and services it provides In this study we monitored response of understory diversity to microsite position and degree of ground-level disturbance within experimental gaps for ten years. We did this at four sites with distinct soil types and topographic positions of a glacial geology in Southern New England that were categorized as i) mesic, ii) mid-slope, iii) outwash, and iv) sandy-skeletal. We analyzed differences in patterns of species richness, Shannon diversity, and evenness across sites and through time. Understory species richness was generally enhanced by gap formation. Gap position was the most important factor influencing species richness across all sites, but the patterns of diversity and evenness were site specific. Ground-disturbance was more influential on drier sandy sites, and more pronounced earlier in the experiment. Temporal differences were also evident across sites, with richness stabilizing at all sites 10 years after gap creation, with the exception of the sandy-skeletal site, which was still increasing. Resource managers who are interested in protecting and enhancing understory species diversity need to consider site when planning silvicultural treatments, as the response of the understory community to disturbance can vary greatly with site.