Abstract Detail

Ecological Section

Chapman, Julia [1], McEwan, Ryan [1].

Changes in Relative Abundance and Spatial Distribution of Dominant Overstory Taxa in an Old-growth Forest Over 30 Years.

The temperate deciduous forests of eastern North America are subject to an array of ecosystem drivers including anthropogenic disturbance, gap dynamics, and both local and regional climate events. An ongoing “mesophication” trend has been observed in many of these forests where communities are shifting from oak dominance (Quercus spp.) to more mesophytic, shade-tolerant species (Acer spp.). Using a 30-year dataset (1979–2010) collected in an old-growth forest in southeastern Kentucky, we examined decadal patterns of distribution and relative abundance of dominant overstory taxa: oaks (Quercus spp.), maples (Acer spp.), hickories (Carya spp.), and beech (Fagus grandifolia). Overstory stem data were divided into three size classes, small (2.5–10 cm dbh), medium (10–25 cm dbh), and large (> 25 cm dbh), to assess regeneration patterns over time. The relative abundances (basal area and stem density) of large Quercus spp. and Carya spp. were consistent through time, but both taxa decreased in the small and medium size classes. The frequency of Quercus spp. and Carya spp. showed a similar trend with large stems consistently present, but small and medium stems occurring in fewer plots through time. On the contrary, small and medium Acer saccharum and Fagus grandifolia increased in relative abundance and frequency over the 30-year period. The spatial patterns of frequency within the three size classes suggested that Quercus species are persisting mainly as mature canopy trees with little recruitment in mesic areas of the study site, becoming more restricted to xeric ridgetop areas over time. Carya did not exhibit a strong spatial pattern but showed an overall lack of recruitment in smaller size classes. Mesophytic species (A. saccharum and F. grandifolia) appeared historically restricted to certain habitats (as evidenced by the clustered, limited distribution of mature trees) but small stems are recruiting across a broader area of the watershed. The differences in recruitment among dominant taxa at this old-growth site suggest a gradual, long-term shift toward a canopy dominated by mesophytic species, and we suspect that this change is occurring at a slower rate than other eastern North American forests that are experiencing more frequent and widespread canopy disturbances as a result of anthropogenic activity. This widespread “mesophication” trend in eastern deciduous forests is predicted to have important ecological and economic impacts, and understanding these changes in the context of multiple ecosystem drivers (fire, climate, human activity) is key for effective conservation and management.

1 - University of Dayton, Department of Biology, 300 College Park, SC 211, Dayton, OH, 45469, USA

Keywords:
old-growth
mesophication
Quercus
Acer saccharum
mesophytic species
eastern deciduous forest
Appalachia.

Presentation Type: Poster:Posters for Sections
Session: P
Location: Hall D/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 5:30 PM
Number: PEC010
Abstract ID:261
Candidate for Awards:None