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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. Forest managers have traditionally viewed the understory as primarily affecting forest regeneration or wildlife habitat, but the growing recognition of goods and services the understory provides (e.g., ecosystem function, ecological resiliency, non-timber forest products) has increased concerns about the impacts of forest management on understory diversity. We monitored response of understory diversity to microsite position and degree of ground-level disturbance within experimental gaps for 10 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 primary factor influencing species richness across all sites, but the patterns of diversity and evenness within gaps was site specific. Ground-disturbance was 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. The one exception was the sandy-skeletal site, which was still increasing in richness. Resource managers interested in protecting and enhancing understory species diversity need to consider underlying site, specifically soil type when planning silvicultural treatments, as the response of the understory community to disturbance can vary greatly with site.

This study was designed to answer questions about the patterns of understory diversity in managed forests of southern New England, and the factors that appear associated with those patterns. At the landscape-level, we used plot data to answer questions regarding the spatial distribution of forest understory plant species. Data from a combination of fixed area (understory vegetation) and variable radius (overstory trees) plot methods are combined with site variables for the analysis. Univariate and multivariate statistical methods are used to test for understory diversity relationships with overstory cover types and topography separately, and in combination. Analyses also test for relationships between specific understory species and cover types. In general the understory flora is dominated by four common clonal species that occur across the range of forest cover types: wild sarsaparilla ( Aralia nudicaulis L.), Canada mayflower ( Maianthemum candense Desf.), star flower ( Trientalis borealis Raf.), and partridgeberry ( Mitchella repens L.). Results also show that over story composition and structure can be used to assess understory species richness. Species richness follows a general trend among cover types of: hardwood ≥ regenerating forest, hardwood–pine, and pine ≥ mixed ≥ hardwood–hemlock > hemlock. Eastern hemlock ( Tsuga canadensis L. Carriere) and mountain laurel ( Kalmia latifolia L.) (which decreased in dominance from ridge to valley) both showed negative trends with understory species richness. Topographic position also appears associated with understory floristic patterns (particularly for the hardwood cover type), both in terms of species richness and compositional diversity which both increased from ridge, to midslope, to valley. However, overstory composition (covertype) appears to have a higher order influence on vegetation and mediates the role of topography. The results from this study provide foresters with a better understanding for maintaining floristic diversity and composition of the understory in managed forests.

Current interest in the conservation of biodiversity is generating a need for forest management and silvicultural techniques designed to maintain the integrity of ecosystems while satisfying society's need for timber resources. The conservation of forest understory plant communities should be a major emphasis of this effort as they contain the majority of plant diversity in most U.S. forests and play a significant role in many ecosystem functions. This article reviews the literature regarding plant responses to disturbance—most importantly changes in light environments—and applies that information to forest management. A comparison of developmental plasticity and rapid acclimation as response pathways is used to discuss plant level responses. At the landscape level, diversity models, silviculture treatments, and site characteristics are used to discuss changes in understory community composition following disturbance. Results of ongoing research on the effects of forest management on floristic patterns fo...

In many forests, advance regeneration represents an important ‘seedling bank’ for replacing overstory trees after canopy disturbance. However, long-term spatial and temporal dynamics of understory tree seedlings are poorly understood, particularly in topographically complex southern New England mixed-deciduous forests. From 1996 to 2005 we tracked the recruitment, growth and survival of seedlings of masting tree species across different topographic positions. Species included the largely valley associated sugar maple ( Acer saccharum ) and white ash ( Fraxinus americana ), the primarily ridge associated white oaks ( Quercus alba and Q. prinus ), and the site generalist red oaks ( Q. rubra and Q. velutina ) and red maple ( A. rubrum ). Four 1 m 2 circular plots were randomly established in nine different sites, which included three replicates of each topographic position (ridge, midslope and valley). Seedling recruits were tagged and measured annually. Densities varied largely between species, both over time and by topographic position. Ridge and midslope positions had similar patterns, with high densities of red oak (>200,000 seedlings/ha) declining over time, and other species generally fluctuating at much lower densities (