Correlations among stand ages and forest strata in mixed-oak forests of southeastern Ohio

Abstract

Many models of landscape ecosystem development, as well as of forest stand dynamics, are based upon spatial and temporal changes in the species composition and structure of various forest strata. However, few document the interrelationships among forest strata, or the response of different strata to alterations of natural disturbance regimes. To examine how relationships among forest strata varied with stand age, we sampled a chronosequence (five age classes) of 21 second-growth (70 to 149 years old) and old-growth (≥150 years old) mixed-oak stands from a single ecosystem type within the ecological classification system framework for the Wayne National Forest. All woody stems were measured by dbh and species, and classified into these strata by lifeform: (1) canopy (dominant, codominant, and intermediate crown classes); (2) saplings (stems < 10 cm dbh, but > 1.37 m tall with canopy potential); (3) subcanopy (stems < 10 cm dbh, but > 1.37 m tall without canopy potential); and (4) seedlings (stems < 1.37 m tall with canopy potential). Canonical correspondence analysis (CCA) was used to summarize the compositional variation in each strata by age class. Canonical correlation analysis was then used to examine the interrelatedness among forest strata using CCA axis scores. CCA ordinations revealed several trends, primarily that site differences and stand age were important factors constraining the development of various forest strata. Although there was no significant correlation between the canopy and sapling strata, there was strong correlation between the canopy and seedling strata, as well as between the sapling and seedling strata. These canopy, sapling, and seedling strata also were strongly correlated with their canonical variables, suggesting that each is responding to similar gradients. We suggest that the natural disturbance regimes of the study area have been altered, and as a result, the compositions of the mixed-oak stands in southeastern Ohio are responding to these modifications. Whereas a primary landform effect regulating landscape ecosystem and stand development prior to European settlement was likely the spatial pattern of surface fires, the effect of landform on the frequency and spatial geometry of these surface fires has diminished with fire suppression efforts.

Citation

Goebel, P. Charles; Hix, David M. 1997. Correlations among stand ages and forest strata in mixed-oak forests of southeastern Ohio. In: Pallardy, Stephen G.; Cecich, Robert A.; Garrett, H. Gene; Johnson, Paul S., eds. Proceedings of the 11th Central Hardwood Forest Conference; Gen. Tech. Rep. NC-188. St. Paul, MN: U.S. Department of Agriculture, Forest Service, North Central Forest Experiment Station: 269-282