Effects of Old-growth Riparian Forests on Adirondack Stream Systems
(Collaborators: William Keeton, University of Vermont; Former Graduate Student: Dana Warren)
Forested streams within the northeastern U.S. typically provide a source of cold, clean water, but many other aspects of the forested landscape also contribute to abundant fish populations. Wood in lakes and streams provides important fish habitat, yet human impacts on streamside forests throughout the northeastern U.S. have changed the role that wood formerly provided in aquatic systems. This research effort is focused on evaluating the structural attributes of scarce old-growth riparian forests within the Adirondack region to assess linkages between forest structure and in-stream habitat structure and associated biological processes.
This study was a collaborative effort between members of the Kraft lab group and a team led by William Keeton, Associate Professor of Forest Ecology and Sustainable Forestry at the Rubenstein School of Environment and Natural Resources, University of Vermont. From 2002 through 2006, we surveyed old-growth, mature, and young, mixed northern hardwood-conifer forests and associated streams within the Adirondacks. We identified structural attributes of old-growth hardwood-conifer riparian forests in the Adirondack Mountains of New York that influenced in-stream wood recruitment and dynamics along 1st and 2nd order streams. Sites were classified as mature forest (6 sites), mature with remnant old-growth trees (3 sites), and old-growth (10 sites). Forest structure was characterized over stream channels and at varying distances from each stream bank. Large logs, debris dams and pools were surveyed; a line-intercept method was used to measure wood volume in streams and on the riparian forest floor. In-stream wood volumes were significantly greater at old-growth sites (200 m3/ha) compared to mature sites (34 m3/ha) and were strongly influenced by the basal area of adjacent forests. In-stream large-log densities correlated strongly with debris-dam densities. AIC models that included large-log density, debris-dam density, boulder density, and bankfull width provided the most support for predicting pool density. A greater proportion of wood-formed pools was found at old-growth sites by comparison with mature sites that were dominated by boulder-formed pools. Our results show that old-growth riparian forests provide in-stream habitat features that have not been widely recognized in eastern North America, representing another potential benefit of riparian forest management upon in-stream processes.
For further information:
Keeton, W.S., C.E. Kraft and D.R. Warren. 2007. Structure and dynamics of old-growth riparian forests and effects on low order Adirondack stream habitats. Ecological Applications 17:852-868. [Link to Full article]
Warren, D.R. and C.E. Kraft. 2008. Dynamics of large wood in an eastern U.S. mountain stream. Forest Ecology and Management. 256:808-814.
Warren, D.R., W.S. Keeton, and C.E. Kraft. 2008. A comparison of line-intercept and census techniques for assessing large wood volume in streams. Hydrobiologia 598:123-130.
For images of accumulations of wood within streams in old-growth Adirondack forests, click here.