ECOLOGICAL RESTORATION OF FIRE-MAINTAINED OAK WOODLANDS IN MASSACHUSETTS
BRIAN HOLT HAWTHORNE, B.A., WESLEYAN UNIVERSITY M.S., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Professor William A. Patterson III
This study describes the results of a factorial experiment involving three levels of overstory thinning (none, moderate, heavy) and two levels of prescribed burning (no burn, burn) in three replicated blocks of upland oak forest in Pelham, Massachusetts to reproduce qualities of the fire-maintained oak woodlands that are thought to have existed in southern New England prior to European settlement. The primary aspects studied were overstory structure, soft mast (berry) production, and understory openness. A reference site in Worcester, MA exhibits an open understory maintained by frequent burning and supports a unique natural community of flora and fauna. Overstory thinning was completed in January 2001, and understory burning in June 2001. Two growing seasons after treatments, burning reduced the cover of understory shrubs (p=0.0002). There was a significant interaction (p=0.011) between the treatments with regards to tree species in the understory. Overall, thinning increased the cover of tree species in the understory (p=0.002), and burning decreased the cover of tree species for all but the moderate thinning treatment (p=0.04). The number of understory species browsed by wildlife was increased by both the thinning (p<0.0001) and burning (p=0.026) treatments. Neither treatment significantly affected overall species diversity of vegetation. Thinning increased production of soft mast (p=0.001) and increased available light to the shrub-level understory (p<0.0001). Stem density, flower production, and berry production of Vaccinium angustifolium were highly correlated with available light (p<0.0001). Prescribed burning increased understory visibility in the year following application (p=0.008). Horizontal foliar density (HFD) increased linearly with distance (p<0.001) and decreased with height above ground (p<0.001). The combined results suggest that the combination of overstory thinning and understory burning is a promising method to create woodland openings that meet wildlife, aesthetic, and recreation goals for public and private landowners, while restoring a rare natural community to the Massachusetts landscape.