Spatial and temporal variation in the response of understory vegetation to disturbance in a central Appalachian oak forest

SMALL, C.J. AND B.C. MCCARTHY (Department of Environmental and Plant Biology, Ohio University, Athens, Ohio 45701). Spatial and Temporal Variation in the Response of Understory Vegetation to Disturbance in a Central Appalachian Oak Forest. J. Torrey Bot. 129: 136-153. 2002.-Understory vegetation in stand-initiating (7 year clearcuts) and understory-reinitiating (> 125 year mature second-growth) oak-dominated forest stands in southeastern Ohio was examined relative to topographic aspect, micro-environmental conditions, and sampling season to explore patterns of understory dynamics and stand development following management disturbance. Plots were established on upper and lower slopes across a range of aspect positions and sampled in spring and summer to capture topographic and seasonal changes in herb layer dynamics. Micro-site light, temperature, and physical soil properties differed significantly with stand age whereas fertility and moisture varied with aspect. Species richness was greater in clearcut than mature forest stands, associated with greater resource availability and spatial heterogeneity. Herb richness and abundance were greater on NWand SE-facing slopes and lower slope positions, corresponding to greater soil moisture and fertility. Greater frequencies of non-native species were also found in resource rich, clearcut plots. Canonical correspondence analysis showed stand age, aspect, and fertility to strongly influence herb layer composition. Non-metric multidimensional scaling showed compositional divergence of spring vs. summer and clearcut vs. mature forest herb samples. Composition of clearcuts and mature forests differed markedly in June, suggesting that management influences may be more pronounced in summer herb communities. Most studies of understory dynamics in eastern forests fail to account for spatial and temporal variations in site and vegetation characteristics, however, understory disturbance response appears strongly linked to these ecosystem properties. A better understanding of these factors is needed to fully understand the effects of forest management on herb layer communities in our eastern forests.