Oak growth and acorn production in southern Appalachian mature forests and shelterwood with reserves regeneration harvests
Oaks (Quercus) are economically important, and their seed (acorns) are a valuable food for many animals. Thus, forest managers must consider potential tradeoffs between oak growth and acorn production. I used 13 years of dbh growth and 17 years of acorn trapping data on 195 trees of five common eastern oak species to compare stand-level growth and acorn production between closed canopy mature forest (M) and recent shelterwood with reserves regeneration harvests (SW) (BA 27.3 ± 1.7 m2/ha in M; 5.1 + 0.8 m2/ha in SW at study establishment). I also examined treatment differences in dbh growth, crown expansion, and acorns/m2 crown at the individual tree level, using a subset of paired (by species and dbh) trees. Despite five times more oak trees and oak BA in M, average annual total acorn production/ha was only double (58,199/ha in M) that in SW (27,298/ha), and was statistically greater in M than SW for total oaks and white oak. Stand- and paired individual tree-level analyses indicated that average acorns/m2 crown and dbh growth was approximately 70% greater in SW than M for total oaks. Crown area increases were greater in SW than M for total oak (66%) and northern red oak (74%), and crown areas in SW expanded disproportionately to increases in dbh alone. In mixed-oak southern Appalachian forests, silvicultural treatments retaining 20–40 mature oaks/ha with fully released crowns will likely yield 50–100% of acorns produced/ha in mature closed canopy stands, as acorn production by residual trees increases. Retention of multiple oak species will reduce the likelihood of stand-level crop failure, as acorn production differs among species and years.