PARENT SESSION
Poster Session #30: Disturbance Ecology II.
Tuesday, August 6. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC
162
Surprisingly big changes in an old-growth Ohio beech-maple stand after 24 years.
Runkle, James*,1, 1 james.runkle@wright.edu, Dayton, OH
ABSTRACT- The extent to which old-growth forests are in a "steady state" is unknown and likely varies. In 1976-1977 I studied three old-growth forests, which have been resampled several times, most recently in 1990-1991. Two were discussed at last year's ESA meeting. The southern Appalachian sites have remained nearly at equilibrium in species composition and stand structure. The Tionesta site (Pennsylvania) has undergone larger changes, partly due to the increase of beech bark disease. This paper will discuss changes in my third major site, Hueston Woods, Ohio, dominated by maple (Acer saccharum) and beech (Fagus grandifolia). I sampled the small vegetation associated with treefall gaps every four years from 1977-2001. I sampled canopy trees at fixed points in 1977, 1991, 1997, and 2001. Altogether in 2001 I sampled 36 gaps, 102 points, and 578 trees. Vegetation within gaps changed gradually toward fewer (after an initial increase) and larger stems. However, although no major disturbance events or disease outbreaks have occurred, the canopy of this site has changed much more than the southern Appalachians and about the same amount as the Tionesta site with decreases of 12% in tree density and 8% in basal area. The importance value (average of relative density and relative basal area) for maple has increased 12% and that of beech has decreased 15% over the 24 yr. The density of snags has stayed more constant at 11-15/ha. Some of these changes are being driven not by recent events but by events of the last century. Maple and beech have changed their size class distributions. Maple has many small canopy stems and a few large ones. The growth of these smaller stems, with their inherently low mortality, led to increases in maple's importance in the stand. Beech has fewer small canopy stems and more large ones. As these large stems reach their species-specific maximum size and suffer the high mortality rates of those sizes, the percent of beech in the stand decreases and overall mortality rates are high. The disequilibrium in size classes may be due to historical events in the 1800s or to gradual changes in environmental conditions (e.g. long-term weather trends). The legacy of those past events is the presently large changes in the stand.
KEY WORDS: Acer saccharum , Fagus grandifolia , Hueston woods, old-growth forest