A microburst windstorm in the Hubbard Brook forest

Figure 1. Spatial pattern of wind disturbance in the Hubbard Brook Experimental Forest (HBEF), NH resulting from a microburst storm on June 2, 2013. Above: position of the large blowdown ("epicenter") and the 600 ha storm impact area within the HBEF. Inset below: position and size of canopy gaps sampled along line transects in the intensive sampling area. Also shown are "wind rose" diagrams indicating the frequency of tree falls in different compass directions.

The natural disturbance regime of northern hardwood forests in New England is dominated by small gaps created by the death of one or a few canopy trees, favoring replacement by shade tolerant species like beech and sugar maple. However, occasionally large gaps are formed by severe windstorms which may favor shade intolerant species like cherry and birch. On 2 June 2013 a microburst windstorm associated with a strong cold front visited Hubbard Brook, causing widespread forest damage. We quantified the patterns of canopy disturbance resulting from this typical but rare blowdown event. Although numerous small gaps were created by the storm, most of the damaged area was associated with a few very large gaps, including a 5.2 ha gap in which 76% of the trees were severely damaged (see map). In this gap two-thirds of the damaged trees were uprooted and one-third were snapped off. Tree species of lower shade tolerance, including pin cherry, red maple and yellow birch were regenerating in the blowdown. Although storms of this intensity are infrequent in the region, our observations suggest that they play a significant role in maintaining intolerant tree species in the forest.

blowdown_0.pngBattles, J. J., Cleavitt, N. L., Saah, D. S., Poling, B. T., & Fahey, T. (2017). Ecological impact of a microburst windstorm in a northern hardwood forest. Canadian Journal of Forest Research. https://doi.org/10.1139/cjfr-2017-0206