Preliminary five-year dominance probabilities for oak seedlings and stump sprouts by ecological province in Pennsylvania

Background/Question/Methods Previous research in several areas of the eastern United States has produced guidelines for adequacy of oak regeneration based on the size and numbers of advanced oak regeneration and the potential contribution of stump sprouts. The basis of these guidelines is the performance of the advanced regeneration stems and stump sprouts at some point, usually 5 or 10 years, after final removal cut. The probability of survival and of dominance at that point is correlated with the preharvest size and vigor of the advanced regeneration or stump. A study was designed to obtain this information with the following objectives: 1) to determine the survival and dominance probabilities of oak advanced regeneration and stump sprouts for 5 and 10 years after final removal cuts and 2) to determine if these probabilities vary significantly by site factors such as slope position and aspect and by ecological classification systems. We have 32 timber sales on eleven Pennsylvania state forests, as well as Collins Pine property, representing 6,235 tagged seedlings and 1,776 tagged stumps spread across four ecological sections. Data on survival, growth, sprouting, and competitive status have been collected for 19 of the stands at five years postharvest.

Results/Conclusions Preliminary results show that 75% of the advance regeneration is still alive. The larger the initial size of the seedling, the larger the 5-year old stem and the higher its dominance probability. Heights at five years for the largest group of seedlings are on pace to match Schnur’s site index curves for eastern oak forests. Stump sprouts show considerably higher mortality with an average of only 34% survival at five years. Heights at five years for stump sprouts show similar values across ecological sections but some oaks species do better in specific areas. For example, scarlet oak was the tallest species in the Northern Ridge Valley and the Northern Unglaciated Allegheny Plateau ecological sections but not the Northern Glaciated Allegheny Plateau nor the Blue Ridge Mountains sections. At five years, 70 to 80% of the stump sprouts were competitive with other vegetation. The tallest stump sprouts came from trees smaller than 25 cm diameter. This data will provide forest managers with the information needed to determine the future composition and sustainability of regenerated forests.