Runkle, James R. (Department of Biological Sciences, Wright State University, Dayton, OH 45435). Twenty-four years of change in an old Tsuga canadensis woods affected by beech bark disease. J. Torrey Bot. Soc. 132: 483–491. 2005.—Long-term studies are necessary to determine how various environmental and anthropogenic factors influence the rates of forest change. To study such changes a 2.02 ha permanent plot in the stand of Tsuga canadensis established about 1800 and located north of Lincoln Pond in the Edmund Niles Huyck Preserve, Rensselaerville, NY, was established in 1978 and resurveyed in 1986, 1994, and 2002. The species, stem diameter, injury type and location (nearest 0.1 m) for all living and dead stems ≥ 1 m tall were recorded. Overall, the stand decreased in density and increased in basal area, with similar proportional changes in each time interval. Tsuga canadensis, by far the most important species, increased its relative density and basal area, as did Quercus rubra. Fagus grandifolia decreased in both. Overall mortality rates decreased from 2.4 % to 2.1% to 1.7 %/yr during the three time intervals, primarily because of the decrease in density of small stems. Mortality rates of individual size classes and species were similar for all three time intervals. Minimum mortality rates occurred for stems newly reaching the canopy (11–30 cm dbh). Quercus rubra and Tsuga had low mortality rates and Fagus and Fraxinus americana high mortality for all time intervals. Previously described long-term trends (beginning with data from 1940) continued. The number of stems < 10 cm dbh decreased while the number of stems ≥ 25 cm dbh and total basal area increased. Deer browsing may be implicated in the decrease of small stems, which seems too continuous for climatic fluctuations to be responsible. The impact of beech bark disease is still apparent. Although the rate of Fagus decline has diminished in recent years, Fagus mortality is still higher than other species, especially for large stems. Snag densities, formation rates and deterioration rates remained nearly constant for stems ≥ 11 cm dbh, supplying that resource consistently for organisms requiring it.