Paper No. JAWRA-10-0130-P of the Journal of the American Water Resources Association (JAWRA). Discussions are open until six months from print publication.
Effects of Eastern Hemlock Decline on Large Wood Loads in Streams of the Appalachian Mountains
Article first published online: 17 NOV 2011
© 2011 American Water Resources Association
JAWRA Journal of the American Water Resources Association
Volume 48, Issue 2, pages 266–276, April 2012
How to Cite
Evans, D. M., Dolloff, C. A., Aust, W. M. and Villamagna, A. M. (2012), Effects of Eastern Hemlock Decline on Large Wood Loads in Streams of the Appalachian Mountains. JAWRA Journal of the American Water Resources Association, 48: 266–276. doi: 10.1111/j.1752-1688.2011.00610.x
- Issue published online: 4 APR 2012
- Article first published online: 17 NOV 2011
- Received August 4, 2010; accepted August 31, 2011.
- large wood;
- riparian ecology;
- environmental impacts;
- Adelges tsugae;
- Tsuga canadensis.)
Evans, Daniel M., C. Andrew Dolloff, W. Michael Aust, and Amy M. Villamagna, 2012. Effects of Eastern Hemlock Decline on Large Wood Loads in Streams of the Appalachian Mountains. Journal of the American Water Resources Association (JAWRA) 48(2): 266-276. DOI: 10.1111/j.1752-1688.2011.00610.x
Abstract: Eastern hemlock (Tsuga canadensis), a foundation species important to riparian forests of the Appalachian Mountains, is in decline due to the hemlock woolly adelgid (HWA) (Adelges tsugae). The effect of this insect on large wood (LW) production and recruitment to streams is largely unknown. We measured LW load, riparian forest composition, and T. canadensis health in 47 streams from Maine to Alabama and developed a conceptual model that frames the expected forest stand and instream LW response to the disturbance caused by HWA. In stands with HWA, 24.3% of the overstory T. canadensis basal area was stressed and 7.5% was dead, whereas only 3.0% was stressed and 2.0% was dead in stands without HWA. Mean T. canadensis effective LW load was 0.20 m3/100 m2 in streams with adjacent stands infested by HWA, almost three times higher than in streams flowing through uninfested stands (p = 0.048). Higher frequencies of LW were found at streams with HWA present and there was a positive association between the percent of dead T. canadensis and T. canadensis LW load (ρ = 0.4468; p = <0.0001). Greater total LW loads were associated with higher stream gradients, lesser bankfull widths, and streams at lower latitudes. Our research supports the hypothesis that HWA infestation of T. canadensis in riparian forest stands has increased LW loads in streams. This episodic disturbance to the riparian forest overstory may have lasting impacts on aquatic ecosystem structure and function.