Wednesday, August 4, 2010
Exhibit Hall A, David L Lawrence Convention Center
Background/Question/Methods The Zoar Valley Canyon of western New York State’s 6th order Cattaraugus Creek contains one of the largest tracts of old-growth riparian broadleaf forest in the East. The present study aimed to catalogue tree species distributions on undisturbed and heretofore unexplored 50 – 130-m high 20 – 50° forested slopes that line much of the canyon. In addition to assessing the influence of slope angle, elevation, and aspect (north vs. south) on tree species composition, we are evaluating these canyon slopes and also fluvial terraces as potential colonizer sources to primary successional floodplains within the canyon. Canyon slope trees were surveyed by using clinometers and laser range finders to determine elevation above or below safe vantage points. Trees were indentified to species and classified as: 1) understory, 2) mid-story, 3) canopy, or 4) emergent.
Results/Conclusions North and south-facing slopes differed markedly in that upper-elevation south-facing slopes supported xeric communities dominated by Quercus rubra, Q. prinus, and Pinus resinosa, whereas north-facing slopes supported mesic species (Acer saccharum, Fagus grandifolia, Tsuga canadensis, Fraxinus american, Liriodendron tulipifera) across their entire vertical profiles. Tsuga canadensis was notably more abundant on mesic north-facing slopes (especially at upper elevations where terrain is steep and erosional) than on fluvial terraces below. Xeric canopies were reduced to <10 m in height (although trees could be very old; e.g. 165 years for a 20-cm diameter Q. prinus), compared to the often >30-m height of mesic slope canopies, and >40-m on terraces. Site distribution in non-metric multidimensional scaling ordination suggested xeric slope communities play no role in floodplain colonization, but that mesic slopes and old-growth forested terraces have important though variable influences on vegetation initiation on nascent floodplains.
Results/Conclusions North and south-facing slopes differed markedly in that upper-elevation south-facing slopes supported xeric communities dominated by Quercus rubra, Q. prinus, and Pinus resinosa, whereas north-facing slopes supported mesic species (Acer saccharum, Fagus grandifolia, Tsuga canadensis, Fraxinus american, Liriodendron tulipifera) across their entire vertical profiles. Tsuga canadensis was notably more abundant on mesic north-facing slopes (especially at upper elevations where terrain is steep and erosional) than on fluvial terraces below. Xeric canopies were reduced to <10 m in height (although trees could be very old; e.g. 165 years for a 20-cm diameter Q. prinus), compared to the often >30-m height of mesic slope canopies, and >40-m on terraces. Site distribution in non-metric multidimensional scaling ordination suggested xeric slope communities play no role in floodplain colonization, but that mesic slopes and old-growth forested terraces have important though variable influences on vegetation initiation on nascent floodplains.
