Competitive success of natural oak regeneration in clearcuts during the stem exclusion stage

We sampled dominant and codominant regeneration oil 70 clearcuts, 21-35 years old, on the Hoosier National Forest in southern Indiana, USA, to evaluate influence of site variables oil the competitive success of natural oak (Quercus L.) over time. Collected data was compared with data collected oil these same sites 20 years prior. Regression tree analysis indicated aspect, natural I-C-ion, and oak abundance in preharvest stands had the greatest influence on competitive success (relative density, RD) of oak species in the latter sampling, which was then examined across sites as defined by these three variables. Oak RD increased across all mid- and some lower-slope positions, sites oil which oaks are expected to be replaced by faster growing species. Drought events between sampling periods apparently Contributed to a decline in RD and vigor of yellow-poplar (Liriodendron tulipifera L.), a major competitor for growing space. Stump sprouts contributed 45% of dominant oak sterns. Mean oak diameters were not significantly lower than those of other species groups, with the exception of yellow-poplar in younger stands and at mid-slope positions. Oak species drought tolerance, relative to more mesic species found on these sites, and the large proportion of oak stump sprouts likely contributed to oak competitive success.