Interspecific variation in susceptibility to windthrow as a function of tree size and storm severity for northern temperate tree species

Abstract

Studies of wind disturbance regimes have been hampered by the lack of methods to quantify variation in both storm severity and the responses of tree species to winds of varying intensity. In this paper, we report the development of a new, empirical method of simultaneously estimating both local storm severity and the parameters of functions that define species-specific variation in susceptibility to windthrow as a function of storm severity and tree size. We test the method using data collected following a storm that struck the western Adirondack Mountains of New York in 1995. For intermediate-sized stems (e.g., 40 cm DBH), black cherry (Prunus serotina Ehrh.) and red spruce (Picea rubens Sarg.) showed the highest rates of windthrow across virtually all levels of storm severity, while yellow birch (Betula alleghaniensis Britt.) and sugar maple (Acer saccharum Marsh.) had the lowest rates of windthrow. For much of the range of storm severity, the probability of windthrow for the most susceptible species was at least twice as high as for the least susceptible species. Three of the species, yellow birch, red spruce, and beech (Fagus grandifolia Ehrh.), had significantly lower probability of windthrow at a given storm severity in old-growth stands than in second-growth stands. Our results suggest that the distinctive abundance of these three species in old-growth forests of the Adirondacks is due, at least in part, to their ability to survive the intermediate-scale disturbance events that appear to dominate the natural disturbance regime in this region.Résumé : L'étude des régimes de perturbation par le vent a été limitée par le manque de méthodes permettant de quantifier la variation dans la sévérité des tempêtes et la réaction des espèces arborescentes à des vents de différentes intensités. Dans cet article, les auteurs font état du développement d'une nouvelle méthode empirique permettant d'estimer simultanément la sévérité locale d'une tempête et les paramètres définissant les variations spécifiques de susceptibilité au chablis en fonction de la sévérité de la tempête et de la dimension des arbres. La méthode a été testée à l'aide de données recueillies après une tempête qui a frappé la partie ouest des monts Adirondacks, dans l'État de New York en 1995. Pour les tiges de dimension intermédiaire (i.e. dhp de 40 cm), le cerisier tardif (Prunus serotina Ehrh.) et l'épinette rouge (Picea rubens Sarg.) présentaient les plus forts taux de chablis pour à peu près tous les niveaux de sévérité de tempête, tandis que le bouleau jaune (Betula alleghaniensis Britt.) et l'érable à sucre (Acer saccharum Marsh.) avaient les plus faibles taux de chablis. Pour une bonne partie de la gamme de sévérité de tempête, la probabilité de chablis des essences les plus susceptibles était au moins le double de celle des essences les moins susceptibles. Pour une sévérité donnée de tempête, trois des espèces : le bouleau jaune, l'épinette rouge et le hêtre (Fagus grandifolia Ehrh.), présentaient des probabilités plus faibles de chablis dans ...

Long-Term Susceptibility of Even- and Uneven-Aged Northern Hardwood Stands to Partial Windthrow

“…As previously mentioned, the susceptibility to windthrow, viz., the loss of harvestable timber due to windthrow, was evaluated by coupling FVS, a deterministic distance-independent stand growth model, to stem windthrow probability equations developed from stands with variable structures that experienced a range of windstorm severities [16,17]. The coupling was straightforward, given that FVS provides the DBH of each tree within a stand over the whole simulation period, while stem susceptibility equations also use DBH to calculate stem windthrow probability.…”

“…Equations from both windthrow models differ from one another in their forms, in terms of both the manner in which S was calculated and the windstorm intensity range upon which they were based. For more details, readers are referred to Canham et al [16] and Nolet et al [17]. The rationale behind using two different windthrow models instead of just one, was to assess the robustness of our results.…”

“…We would expect this to be more important in uneven-aged than in even-aged stands because the domino effect (larger trees falling on smaller ones, [17]) is more likely to occur in uneven-aged stands. On the other hand, stem DBH was the main stem predictor of windthrow in both windthrow models we used [16,17]. Many studies (e.g., [13]) have reported that the height: diameter ratio (H:D ratio) is a more appropriate predictor than DBH for assessing stem windfirmness, with higher H:D ratios leading to diminished windfirmness.…”

“…Ideally, the analyses that were performed here should be based on H:D ratio equations or should incorporate tree height [30,31]. To our knowledge, equations similar to those of Canham and Nolet [16,17], providing windthrow probabilities as a function of wind severity and H:D ratio, are not available in the literature for North American hardwood species.…”

“…First, we take advantage of empirical windthrow equations that were developed by Canham et al [16] and by Nolet et al [17] for North American hardwood forests dominated by sugar maple (Acer saccharum Marshall). These two studies disentangled the effects of species, wind intensity and stem size on windthrow vulnerability and led to equations that predicted the windthrow probability for a stem of a given species that was exposed to a given wind intensity as a function of its DBH (diameter at breast height, 1.3 m).…”