PARENT SESSION
Contributed Oral Session 79: Forest Ecology: Communities, Species Richness, and Coarse Woody Debris
Wednesday, August 10, 8:00 AM - 11:30 AM, Meeting Room 518 A, Level 5, Palais des congrès de Montréal

Structure of old-growth riparian forests and effects on stream habitats, Adirondack Mountains, New York.

Keeton, William^*,1, Kraft, Clifford², Warren, Dana ², Millward, Andrew², ¹ University of Vermont, Burlington, Vermont² Cornell University, Ithaca, New York

ABSTRACT- Relationships between riparian forest structure and freshwater stream habitats are poorly understood in the northeastern U.S., particularly in relation to forest stand development. Our research has a) described structural attributes associated with old-growth riparian forests; and b) assessed linkages between these characteristics and indicators of in-stream habitat structure. Indicators included coarse woody debris, debris dams, plunge pools, and variations in canopy structure over stream channels. The study focused on northern hardwood-conifer forests in the Adirondack Mountains of New York. We sampled a total of 19 sites along 1st and 2nd order stream reaches. Sites were classified as mature forest (6 sites), mature with scattered remnant old-growth trees (3 sites), and old-growth (10 sites). Forest structure was sampled over channels and at varying distances from each bank. Canopy architecture was measured using Leaf Area Index meters, laser rangefinders, hemispheric photography, and stem-mapping. In-stream features were surveyed using high-precision GPS units. Data were examined using ANOVA, linear regression, multivariate analyses, 3-dimensional visualization, and spatial analyses of in-stream structure. Mean in-stream CWD volumes were significantly (= 0.05) higher at old-growth sites (200 m3/ha) compared to mature sites (34 m3/ha) or mature sites with remnant trees (126 m3/ha). Volumes were strongly correlated with the basal area of adjacent forests. Large log density, rather than CWD volume itself, was highly predictive of in-stream pool density. There was a higher proportion of CWD-formed pools relative to boulder-formed pools at old-growth sites as compared to mature sites. Multivariate analyses supported our hypothesis of an interaction between forest structure and site-specific geomorphology. LAI was significantly more variable spatially over old-growth streams due to canopy gaps. Heterogeneous light environments may increase primary productivity in endogenous streams while also maintaining high allochthonous inputs and cool, shaded conditions. Old-growth riparian forests provide in-stream habitat characteristics that are much less prevalent in younger systems, signaling a possible benefit of late-successional riparian forest restoration and conservation.

Key words: old-growth, riparian, coarse woody debris, stream habitat