White-Tailed Deer and Balsam Woolly Adelgid Effects on Balsam Fir in Canaan Valley

Abstract

Abies balsamea (Balsam Fir) was historically abundant in parts of West Virginia, but it was drastically reduced by extensive logging around the turn of the 19th–20th centuries. More recently, intense herbivory by Odocoileus virginianus (White-tailed Deer) and an infestation of Adelges piceae (Balsam Woolly Adelgid), among other possible factors, have caused Balsam Fir to decline in the region. Understanding the impacts of White-tailed Deer and Balsam Woolly Adelgid is important for restoring Balsam Fir in Canaan Valley. On the Freeland Tract of the Canaan Valley National Wildlife Refuge, we surveyed the intensity of browsing on Balsam Fir and estimated deer population levels, while Refuge personnel assessed the intensity of the adelgid infestation. Even though estimates of deer density were significantly greater during 1999–2000 than in 2001–2002, the percent of buds browsed was similar during the two periods. During 2001–2002, browsing was more intense on Balsam Fir trees that were outside than on trees inside an exclosure. Deer had minimal to moderate impact on mature trees, but in many cases, they completely browsed all of the buds on trees <3.3 ft (1 m) tall. The proportion of trees infested by Balsam Woolly Adelgid rose by 17.4%—from 51.3% in 2000 to 68.7% in 2002. The average diameter at breast height of Balsam Firs heavily infested by adelgids was significantly larger than of those trees classified as moderate, light, or not infested. The Balsam Woolly Adelgid is of greater conservation concern than White-tailed Deer because some of the trees tallied in the first phase of our survey were already dead. Restoration efforts that involve the planting of seedlings should consider the impacts of deer on seedlings and the impacts of adelgids on mature trees.