PARENT SESSION
Oral Session #44: Disturbance ecology of forests: Animals, wind, gaps, edges. Presiding: S. Archer.
Wednesday, August 8, 2001. 8:00 AM to 11:45 AM. Hall of Ideas G.

Disturbance regimes of old-growth and second-growth hemlock-hardwood forests in Adirondack Park.

ZIEGLER, SUSY¹, ¹

ABSTRACT- Ten old-growth and 6 post-fire second-growth hemlock-hardwood forests in northern Adirondack Park, New York, were studied: (1) to analyze the spatial and temporal patterns of the natural disturbance regime of this forest type; and (2) to compare the dynamics of old growth and surrounding second growth. Procedures for data collection and analysis were adapted from methodology developed by C.G. Lorimer and L.E. Frelich in similar forests of the Upper Midwest. Nearly 725 increment cores of canopy trees were analyzed for evidence of gap origin and date of canopy accession. Rapid early growth and growth releases were assumed to correspond with canopy-disturbance events. The proportion of exposed crown area removed by disturbance was estimated from the diameter of each tree with high growth rates. The average rate of natural disturbance (i.e. in old growth forests) for all plots and decades of the 130-year period from 1850 to 1979 is 4.4–5.2% (moderate and conservative estimates, respectively) of the total canopy per decade. The average canopy-tree residence time is 192 to 225 years. The decadal rate of canopy turnover for the 50-year period from 1930 to 1979 is statistically comparable in old growth (3.1–4.5%) and second growth (3.6–4.2%). The impact of logging-related fires is still evident to the trained eye, but Adirondack second growth is wild to the casual observer because it appears to be characterized primarily by natural processes.

KEY WORDS: disturbance, hemlock-hardwood, old growth, Adirondack Park