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Curzon, Miranda Thomas

Natural Resources

2008

MS

Recent research suggests that canopy gap dynamics in temperate, late-successional riparian forests may influence organic matter recruitment and the light environment over streams. However, controls on gap dynamics specific to riparian forests are poorly understood in the northern forest region of eastern North America. I hypothesized that gaps would be larger and more frequent closer to streams. I also expected riparian landforms and the varied exposure to wind associated with them to influence patterns of canopy gap openings. The 4 study sites lie in old growth hemlock-northem hardwood forest along low order streams in Adirondack Park, NY. All gaps within four 6-9 ha plots were mapped and characterized based on the number of gapmakers, expanded gap area, slope, and aspect. I recorded the species, decay stage, orientation, DBH, and type of damage (snap, uproot, standing dead) for each gapmaker. The spatial distribution of gaps was assessed using Ripley's K. Relationships between topography and gap characteristics were examined using spatial autocorrelation, ANOVA, chi-squared goodness-of-fit tests, and regression. The total area in expanded gaps ranged from 28.3 - 47.6%. Gaps in all sites had random spatial distributions at scales less than 25 m and clustered distributions between 63-122 m. Spatial autocorrelation occurred in the distribution of canopy gap size In all sites (p=O). Aspect and distance from stream did not significantly predict gap size, but convergent and divergent landforms significantly influenced species distribution, gap fraction, and type of damage for gapmakers. Results suggest an interaction between low order riparian landforms and gap distribution in late-successional forests, creating a continuously heterogeneous pattern of canopy openings along stream reaches.