Effects of an experimental ice storm on forest canopy structure

Abstract

Intermediate disturbances are an important component of many forest disturbance regimes, with effects on canopy structure and related functions that are highly dependent on the nature and intensity of the perturbation. Ice storms are an important disturbance mechanism in temperate forests that often result in moderate-severity, diffuse canopy damage. However, it has not previously been possible to distinguish the specific effect of ice storm intensity (as ice accretion) from predisturbance stand characteristics and physiographic factors. In this study, we utilized a novel experimental ice storm treatment to evaluate the effects of variable ice accretion levels on forest canopy structure. Our results verified significant impacts of ice storm disturbance on near-term canopy structural reorganization. Canopy openness, light transmission, and complexity increased significantly relative to predisturbance baselines and undisturbed controls. We documented variable impacts with disturbance intensity, as significant canopy changes largely occurred with ice accretion levels of ≥12.7 mm. Repeated ice storm disturbance (two consecutive years) had marginal, rather than compounding, effects on forest canopy structure. Our findings are relevant to understanding how ice storms can affect near-term forest canopy structural reorganization and ecosystem processes and add to a growing base of knowledge on the effects of intermediate disturbances on canopy structure.

Experimental approach and initial forest response to a simulated ice storm experiment in a northern hardwood forest

“…The objectives of this paper are to (1) provide a detailed methodological approach for creating experimental ice storms, (2) discuss the efficacy of the design (i.e., our ability to create glaze ice on surfaces), (3) describe possible artifacts of the treatments, and (4) present results on the initial impact of these experimental storms on nutrient transfers in fine and coarse woody debris and tree canopy damage assessments. This work was conducted at the Hubbard Brook Experimental Forest (HBEF) in New Hampshire, builds on a feasibility study at the same site [17], and complements reporting by Fahey et al [28] on the response of forest canopy structure to these experimental perturbations. Fahey et al [28] detailed how experimental ice storms increased canopy openness, light transmission and complexity.…”

“…This work was conducted at the Hubbard Brook Experimental Forest (HBEF) in New Hampshire, builds on a feasibility study at the same site [17], and complements reporting by Fahey et al [28] on the response of forest canopy structure to these experimental perturbations. Fahey et al [28] detailed how experimental ice storms increased canopy openness, light transmission and complexity. Here, we describe the initial loss of wood and nutrients from the canopy that contributed to those changes in canopy structure.…”

The <i>fortedata</i> R package: open-science datasets from a manipulative experiment testing forest resilience

“…The magnitude, timing and duration of changes in the C cycle following disturbance vary among forests (Amiro et al 2010, Luo and Weng 2011, Coomes et al 2012, Hicke et al 2012, Gough et al 2013, Peters et al 2013, Vanderwel et al 2013, Flower and Gonzalez-Meler 2015Gu et al 2019). These responses may differ as a function of disturbance severity, type, and frequency along with the physical, structural, and biological properties of the affected ecosystem (Amiro et al, 2010;Williams et al, 2012;Scheuermann et al 2018;Rebane et al 2019;Fahey et al 2020;Atkins et al 2020a). Understanding which forest ecosystems are most vulnerable to disturbance and, conversely, what characteristics of an ecosystem confer C cycling stability, remains an important frontier crucial to forecasting changes in the terrestrial C sink in the face of rising global disturbance frequencies (Frelich and Reich, 1999;White and Jentsch, 2001;Johnstone et al 2010;.…”

“…Understanding which forest ecosystems are most vulnerable to disturbance and, conversely, what characteristics of an ecosystem confer C cycling stability, remains an important frontier crucial to forecasting changes in the terrestrial C sink in the face of rising global disturbance frequencies (Frelich and Reich, 1999;White and Jentsch, 2001;Johnstone et al 2010;. Large-scale manipulative experiments may be particularly useful to identify the C fluxes and drivers that determine ecosystem C balance following disturbance (Fahey et al, 2020;Gough et al, 2013;Shiels and González, 2014).…”

Multidimensional Structural Characterization is Required to Detect and Differentiate Among Moderate Disturbance Agents

“…2) due to agent-specific effects on canopy structure (Atkins et al 2018a;Fahey et al 2019a). We expected fire and ice storm damage to preferentially affect total leaf area, as well as area/density and canopy height as these pulse disturbances occur over acute time intervals often resulting in reductions in canopy leaf area and vegetation height throughout and across the canopy (Plotkin et al 2013, Cote et al 2014, Oldfield and Peterson 2019Fahey et al 2019b). We hypothesized that the other species-specific disturbances surveyed would primarily alter canopy traits such as arrangement, height, complexity, and openness ( Fig.…”