PARENT SESSION
Oral Session # 86: Invasive Species VII: Forests.
Presiding: C Huebner
Thursday, August 7. 1:30 PM to 5:00 PM, SITCC Meeting Room 204.
Southern pine beetle impacts on the ecosystem dynamics of a white pine watershed.
Kloeppel, Brian*,1, Mazzarelli, Lisa1, Swank, Wayne2, Vose, James2, Wentworth, Thomas 3, 1 University of Georgia;, Otto, NC, USA2 USDA Forest Service;, Otto, NC, USA3 North Carolina State University;, Raleigh, NC, USA
ABSTRACT- Southern pine beetle (Dendroctonus frontalis) most commonly affects loblolly, slash, and longleaf pine forests in the southern United States. However, the recent (1998 to 2002) drought conditions in the southern Appalachians including a 17% reduction in precipitation and a 34% reduction in stream flow have predisposed white pine (Pinus strobus) trees to attack by southern pine beetle. Several tree mortality pockets (> 2 ha each) in the white pine watersheds (1 and 17) at Coweeta Hydrologic Laboratory in North Carolina provide a great opportunity to study the southern pine beetle and its effects on white pine watersheds. Therefore, the following treatments were imposed. A treatment including cutting and removal of the dead and infested trees was conducted in watershed 17 in October 2001. The infested areas in watershed 1 remain untreated and the beetle- and non-beetle impacted areas in watershed 1 were investigated further in this study. We evaluated the changes in resource availability in beetle vs. non-beetle infested areas including changes in light, soil water availability, and soil and litter temperature. We found that in beetle-infested areas available light increased 27 %, available soil water increased 13 %, mean soil temperature increased 0.9 C, but mean litter temperature was not significantly different vs. non-beetle infested areas. Forest floor mass increased significantly (P < 0.05) after beetle-impact. In addition, after 15 months in the field, white pine foliage decomposition exhibited a trend toward increased decomposition in the beetle-impacted areas, but the difference was not significant. The response to beetle-infestation was most dramatic in the seedling and herbaceous layers. Seedling density increased two-fold and seedling height was four times greater in beetle vs. non-beetle infested plots. Herbaceous diversity was 30 % greater in beetle vs. non-beetle-infested areas. Overall, the likely long-term impact on white pine watersheds will be a dramatic species change from nearly pure white pine forest stands to mixed hardwood and white pine forests. This study also suggests some of the ecosystem properties to measure to evaluate the impact of the exotic insect, hemlock woolly adelgid, that is now impacting southern Appalachian hemlock trees.
Key words: southern pine beetle, seedling dynamics, Pinus strobus, litter decomposition