PARENT SESSION
Contributed Oral Session 66: Disturbance Ecology : Water, Wind, and Ice
Tuesday, August 9, 1:30 PM - 5:00 PM, Meeting Room 520 B, Level 5, Palais des congrès de Montréal
A method for modeling tree regeneration height growth after disturbance.
Fajvan, Mary Ann*,1, Barker Plotkin, Audrey2, Foster, David2, 1 USDA Forest Service, Morgantown, WV2 Harvard University, Petersham, MA
ABSTRACT- Studies aimed at quantifying the growth response of plant communities to disturbances frequently fail to adequately address the temporal component of the data. Analyses typically compare plant size or density attributes at specific times since disturbance without determining the actual growth response function. Height growth rates of permanently tagged tree seedlings were modeled during the first 10 years of cohort initiation following an experimental hurricane in central Massachusetts. Selected canopy trees in a second–growth, transition oak – northern hardwoods forest were pulled over with a winch in a 50 x 160 m area. Our height models considered the population dynamics of the recovering vegetation by adjusting for missing values and ingrowth at each measurement. Regeneration height growth did not follow the species–specific patterns anticipated if the disturbance had been stand–replacing. Instead, the temporal increase in shade from crown expansion and sprouting of residual trees prolonged cohort development and favored a wide suite of growth strategies. Red maple and white ash seedlings, and black cherry, white ash, black and yellow birch, paper birch and red oak seedlings and advance regeneration, exhibited increasing height growth rates for 3 years followed by either decreasing or unchanged rates as shading on the site increased. Only red maple and ash advance regeneration displayed increasing rates throughout the measurement period. After 10 years, black and yellow birch, and red maple are the most numerous species and compose the majority of the tallest regeneration whereas red oak, which dominated the original stand, are few and unlikely to emerge to the canopy of the new cohort. Our height modeling technique improves on previous efforts to document growth rate because the correlations between successive field measurements were accounted for. The technique allows scientists and managers to evaluate early cohort development after disturbance and predict a species future role in the forest community.
Key words: tree regeneration, hurricane, height growth, repeated measures