Abstract:
The hemlock removal experiment at Harvard Forest contrasts differences in forest response to the removal of Tsuga canadensis due to the hemlock woolly adelgid and by pre-emptive salvage logging. Treatments include girdled plots to simulate damage caused by the adelgid, logged plots simulating a commercial logging operation, hemlock control plots, and hardwood control plots. This sub-study aims to better understand the effect the treatments have on the growth of overstory trees remaining in the plots through the use of diameter measurements and tree coring. Expected outcomes included variation in tree growth by species and plot treatment and that each species would show the most growth in the logged plot.
In the Valley block of plots, diameter at breast height was measured for each living tree in 2004 and 2009. Growth of Acer rubrum, Quercus rubra, Betula lenta, and Pinus strobus was examined among treatments. For lenta, and strobus, tree cores were sampled from ten trees in each plot to determine the annual growth by species.
Rubrum and lenta showed an increase in growth in the logged and girdled plots after hemlock removal whereas strobus and rubra showed little response to the treatments. The tree core samples showed similar increase in ring growth in the logged and girdled plots for lenta, while strobus showed the highest rate of growth in the girdled plot.
Overstory vegetation fills a fundamental role in forest structure and greatly contributes to forest regeneration. Through better understanding of overstory tree growth after hemlock removal, we can better forecast stand development after a disturbance.
