Impact of soil scarification on the composition of regeneration and species diversity in an oak shelterwood

Abstract

This study was conducted in a fenced 1-yr-old 70-acre mixed-oak shelterwood to determine the impact of soil scarification on species composition and the production of oak regeneration from abundant northern red oak (Quercus rubra L.) acorns. In October 1993, seven replicates were established and randomly divided into control and scarified plots. Pretreatment sampling showed that control and scarified treatments had statistically similar numbers of advance regeneration in various species categories (including total seedlings - 4,085/acre) as well as similar numbers of acorns (48,463/acre). Species composition was dominated by red maple (Acer rubrum L.) (45%), followed by oaks (27%), acceptable low value species (24%), and other desirable hardwoods (4%) with 14 tree species found in each treatment. Plots were lightly scarified using a brush rake-equipped crawler dozer in an attempt to incorporate acorns into the soil (scarification seeding) after dissemination but prior to leaf fall. One year later, the number of seedlings in scarified plots (16,870/acre) was significantly greater than that in control plots (9,614/acre). The number of seedlings increased for all species categories in control plots and for all but red maple in scarified plots. Species composition shifted as a result of treatments with the result that scarified plots totaled significantly more northern red oak (11,596/acre) and fewer red maples (1,106/acre) compared to control plots (1,002/acre, and 3,973/acre, respectively). Composition of other desirable hardwoods (4% of total) and low value species (15% and 11%, respectively) were similar for control and scarified plots. Based on the Shannon-Weiner index, species diversity of the tree seedling community slightly increased from 1.73 to 1.81 in control plots, in part, reflecting more balanced numbers of red maple and oaks. Species diversity in scarified plots decreased from 1.96 to 1.30 reflecting the greatly increased dominance of northern red oak. This decrease occurred in scarified plots despite an increased tree species richness and increased numbers of seedlings in 13 of 15 species suggesting that care must be taken when interpreting diversity values relative to regeneration success. Results show that soil scarification scheduled with recently disseminated acorns prior to leaf fall can significantly improve species composition of seedling regeneration by decreasing red maple and increasing oak seedlings.

Citation

Zaczek, James J.; Harding, Joseph; Welfley, James. 1997. Impact of soil scarification on the composition of regeneration and species diversity in an oak shelterwood. 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: 341-348