Why Ice Storms Aren't Cool: New Research at Hubbard Brook Experimental Forest Targets Impacts of Extreme Winter Weather Events on Northern Hardwood Forest Ecosystems.

Ice storms are a common disturbance in north temperate and boreal forests worldwide. Current models suggest that the frequency and severity of ice storms may increase in the coming decades in response to changes in climate. Because of the stochastic nature of ice storms and difficulties in predicting their occurrence, most past investigations of the ecological effects of ice storms have been based on case studies following major storms. During the winters of 2016 and 2017, scientists at the Hubbard Brook Experimental Forest, NH took a novel approach and created a suite of experimental ice storms in a northern hardwood forest. The icing treatments included targets of 0, 6, 13, and 19 mm radial ice accretion sprayed in winter 2016 (to evaluate the impacts of different intensities of ice storms), and 13 mm sprayed again in winter 2017 (to evaluate impacts of consecutive ice storms). Measured ice accretion on wooden dowels suspended in the canopy showed that a gradient of ice accretion was achieved (6, 10, and 13 mm in 2016; 11 mm in 2017). The winter 2016 treatments resulted in a gradient of fine and coarse woody debris commensurate with the treatments (8, 33, 73, and 124 g C/m² fine woody debris and 5, 24, 133, and 685 g C/m² coarse woody debris for the 0, 6, 13 and 19 mm treatments, respectively, in the first year following icing (2016). Experimentally created gaps in the canopy resulted in increased variability in soil temperature and moisture. Surprisingly, impacts on total soil respiration were only modest (with depressed rates in the high ice treatments), and no treatment effects were observed for soil solution nutrient concentrations or microbial nitrogen dynamics during for the first year following icing (2016). Results provide new insights on the ecological impacts of these catastrophic winter storms.