Catastrophic Wind Disturbance Research Articles

Windstorm effects on herbaceous vegetation in temperate forest ecosystems: Changes in plant functional diversity and species trait values along a disturbance severity gradient

Catastrophic wind disturbance affects not only forest structure and regeneration, but also functional and compositional dynamics of the herbaceous layer. However, the issue of changes in functional diversity and functional trait values of the understory layer in response to wind disturbance has not been addressed so far. This study aims at investigating the patterns of variations in functional diversity, trait values and species richness of herbaceous species following wind disturbance.The study was carried out in the Piska Forest, a woodland complex in northern Poland, which was almost completely destroyed by a windstorm in 2002 and part of which was successively set aside to study the effects of natural disturbance on forest ecosystems. Vegetation surveys were conducted at 112 sample plots between 2014 and 2015. Four forest habitat types were identified and individually examined. The degree of disturbance severity was assessed as percentage of dead trees on all trees per surface unit. A set of twelve functional traits was assigned to the recorded species.Three functional diversity metrics (richness, evenness and divergence) were calculated based on the selected functional traits. We assessed the relationship between each of such metric and disturbance severity for each habitat type. The relationship between species richness and disturbance severity was also determined. We then estimated the relative importance of habitat type and disturbance severity on both functional diversity and species richness. Lastly, we examined the response of functional trait values to both disturbance severity and habitat type.Our results showed that wind disturbance effects on functional diversity are not univocal and that they strongly depend on habitat type. In fact, while in coniferous stands disturbance determined a decrease of functional divergence and left functional richness unaltered, in mixed-coniferous habitats it enhanced functional richness and did not affect functional divergence. In mixed-deciduous habitats, both functional richness and divergence decreased. In swamp habitats no major changes in functional diversity were observed. Changes in functional evenness were not significant. At the same time, disturbance significantly enhanced species richness in all forest habitats, but the coniferous one. It was not possible to clearly disentangle the relative contribution of disturbance and habitat type, since the two are strictly correlated. Out of the tested functional traits, only SLA, seed releasing height and share of stress-tolerant species exhibited significant response along the tested disturbance gradient. Most of the other traits reacted only to variations in the habitat type.

Resilience of a Fire-Maintained Pinus palustris Woodland to Catastrophic Wind Disturbance: 10 Year Results

Increased interest in ecosystem recovery and resilience has been driven by concerns over global change-induced shifts in forest disturbance regimes. In frequent-fire forests, catastrophic wind disturbances modify vegetation-fuels-fire feedbacks, and these alterations may shift species composition and stand structure to alternative states relative to pre-disturbance conditions. We established permanent inventory plots in a catastrophically wind-disturbed and fire-maintained Pinus palustris woodland in the Alabama Fall Line Hills to examine ecosystem recovery and model the successional and developmental trajectory of the stand through age 50 years. We found that sapling height was best explained by species. Species with the greatest mean heights likely utilized different regeneration mechanisms. The simulation model projected that at age 50 years, the stand would transition to be mixedwood and dominated by Quercus species, Pinus taeda, and P. palustris. The projected successional pathway is likely a function of residual stems that survived the catastrophic wind disturbance and modification of vegetation-fuels-fire feedbacks. Although silvicultural interventions will be required for this system to exhibit pre-disturbance species composition and structure, we contend that the ecosystem was still resilient to the catastrophic disturbance because similar silvicultural treatments were required to create and maintain the P. palustris woodland prior to the disturbance event.

Effects of catastrophic wind disturbance on formation of forest patch mosaic structure on the western and southern slopes of Changbai Mountain

In the cold temperate zone of the western and southern slopes of the Changbai Mountain, Betula ermanii Cham. forest, Picea jezoensis (Siebold & Zucc.) Carrière forest, and mixed forests of B. ermanii and P. jezoensis are heterogeneously distributed in a mosaic of patches, and the reason for this formation is still unclear. In August 1986, a typhoon disturbed the forests on the western and southern slopes of Changbai Mountain, forming a large number of forest gaps. After more than 30 years of vegetation succession, vegetation patches in wind-stricken areas are obvious. To reveal the effects of catastrophic wind on the patch mosaic structure of these forests, a study was carried out in the cold temperate wind-stricken areas of the western and southern slopes of Changbai Mountain. Vegetation differences were classified according to the degree of vegetation damage by the catastrophic wind and the status of vegetation restoration was investigated, as well as the soil fertility was determined. The results show that the degree of forest damage caused by the catastrophic wind is not homogeneous, and there are significant differences in community composition and structure in the wind-stricken areas. After 30 years of restoration, some of the differences in damaged forests have been enhanced. The heterogeneity of vegetation in wind-stricken areas is due to both the difference in the degree of catastrophic wind damage and the differences in the succession of the damaged vegetation. There is a strong correlation between vegetation and soil fertility, and the variation in soil fertility strengthens the heterogeneity of vegetation in wind-stricken areas. Therefore, it can be inferred that several catastrophic wind disasters may occur in the history, which resulted in succession from shrub and herb to B. ermanii forest and then from B. ermanii forest to P. jezoensis forest on the western and southern slopes. This pattern of disturbance and succession formed the patch mosaic distribution pattern of the forests on Changbai Mountain.

Effects of catastrophic wind disturbance, salvage logging, and prescribed fire on fuel loading and composition in a Pinus palustris woodland

Feedbacks between forest vegetation, forest fuels, and fire are critical to the perpetuation of fire-dependent ecosystems. In Pinus palustris (longleaf pine) woodlands, low-intensity fires facilitate a positive feedback in which highly flammable Pinus needles produced by canopy trees sustain frequent fires. These frequent fires inhibit recruitment of more fire-sensitive species and facilitate P. palustris dominance. Although these relationships are recognized in frequent-fire forests, we do not understand how vegetation-fuels-fire feedbacks may be modified by catastrophic disturbances and subsequent salvage logging in these ecosystems. In this study, we sought to address how the composition of fuelbed components differed between mature, catastrophically wind-disturbed, and salvage-logged sites and how prescribed fire would differentially interact with these fuel complexes. Using a permanent plot network, we quantified total fuel loading and fuel loading by flammability group (seven categories based on flammability characteristics) across the three disturbance treatments before and after operational-scale prescribed fire. For total fuel loading, we found significant interactions between disturbance treatment and time relative to prescribed fire. The fuel complex of mature sites was relatively homogenous, dominated by Pinus needles. Fuels on wind-disturbed and salvaged sites had minor contributions from Pinus needles, but that was somewhat offset by increased contributions by early successional species that have flammability characteristics similar to Pinus needles. The prescribed fire reduced fuel loading across all treatments and homogenized the wind-disturbed and salvage-logged fuel complexes. Although salvage logging resulted in a disparate fuel assemblage, prescribed fire appeared to reduce dissimilarity with the naturally disturbed condition.

Microsite Influence on Woody Plant Regeneration in a Pinus palustris Woodland Following Catastrophic Disturbance

Information and material biological legacies that persist after catastrophic forest disturbance collectively constitute the ecological memory of the system and may strongly influence future stand development. Catastrophic disturbances often result in an influx of coarse woody debris (CWD), and this material legacy may provide beneficial microsites that affect successional and structural developmental pathways. We examined how microenvironmental characteristics influence the regeneration of woody plants in a subtropical woodland that experienced a large influx of CWD from a catastrophic wind disturbance. Specifically, we asked (1) what microenvironmental factors best explain woody plant density, richness, and height in the regeneration layer and (2) does woody plant density, richness, and height benefit from the large influx of CWD to a degree that competition dynamics and succession may be modified? Data were collected in a Pinus palustris woodland that had experienced an EF3 tornado and was subjected to a four-year prescribed fire rotation. We documented live woody plants <5 cm diameter at breast height, soil, and site characteristics and tested for differences in seedling and sapling density, species richness, and height in relation to CWD proximity. We used a random forest machine learning algorithm to examine the influence of microenvironmental conditions on the characteristics of woody plants in the regeneration layer. Woody plant density and species richness were not significantly different by proximity to CWD, but plants near CWD were slightly taller than plants away from CWD. The best predictors of woody plant density, richness, and height were abiotic site characteristics including slope gradient and azimuth, organic matter depth and weight, and soil water content. Results indicated that the regeneration of woody plants in this P. palustris woodland was not strongly influenced by the influx of CWD, but by other biological legacies such as existing root networks and soil characteristics. Our study highlights the need to consider ecological memory in forest management decision-making after catastrophic disturbance. Information and material legacies shape recovery patterns, but, depending on the system, some legacies will be more influential on successional and developmental pathways than others.

Prescribed fire effects on Pinus palustris woodland development after catastrophic wind disturbance and salvage logging

Scientifically informed strategies to manage naturally disturbed forests are critical to support the sustained provisioning of ecosystem goods and services. In fire-adapted ecosystems, catastrophic canopy removal can disrupt surface fuel continuity and challenge the continued use of low-intensity prescribed fire. Although salvage logging is used globally after natural disturbance events, little information is available on how salvage logging interacts with subsequent use of prescribed fire. This study investigated the impacts of operational-scale prescribed fire on Pinus palustris (longleaf pine) stand development in areas differentially impacted by an April 2011 EF3 tornado and a subsequent salvage logging operation. Twenty 0.04-ha nested plots were systematically established in mature, wind-disturbed, and salvage-logged sites (n = 60) to measure seedlings, saplings, woody fuels, organic litter, and mineral soil before and after prescribed fire. Prescribed fire-induced fine fuel consumption, mineral soil exposure, and substantial sapling density reductions were observed throughout the treatment area. Prescribed fire effects were not apparently impacted by salvage logging, which did not alter the amount of fine fuels available for prescribed fire consumption. Despite overall sapling density reductions, fire-resistant P. palustris saplings exhibited increased densities on wind-disturbed and salvage-logged sites. Pinus palustris seedlings, however, exhibited marked post-fire reductions, which contrasted with a strong resprouting response observed among top-killed hardwood species. Concerning woody plant recovery, this study indicated that salvage logging was not detrimental to P. palustris stand development and that prescribed fire effectively enhanced recovery in unlogged and logged wind-disturbed sites.

Edge influence on composition and structure of a Pinus palustris woodland following catastrophic wind disturbance

Forest edges are an important legacy of natural and anthropogenic disturbances. Edges of intact forest fragments are influenced by adjacent non-forested ecosystems, resulting in compositional and structural differences at the edge and into the intact forest. Edge influence (EI) is the altered biotic and abiotic interactions that occur along the edge-to-interior gradient in disturbed forests. Few studies have analyzed natural disturbance created edges, particularly in woodland structures, which contain fewer trees per hectare and are typically less light-limited than forests. The goal of our study was to examine the EI of a tornado-created edge in a Pinus palustris Mill. (longleaf pine) woodland in Alabama. In 2011, an EF-3 tornado impacted a restored P. palustris woodland, resulting in a distinct edge. We installed transects perpendicular to the edge to quantify biotic and abiotic response variables and calculate the distance of EI. Reduced structural forest complexity and basal area (negative EI) were evident 70 m into the interior woodland. Ground flora richness and diversity experienced a positive EI, with higher richness and diversity at the edge. Results of this study add to our understanding of EI on woodland composition and structure and naturally created edges and may help guide natural disturbance based silvicultural systems.

Long-term effects of salvage logging after a catastrophic wind disturbance on forest structure in northern Japan

Many reports on the effects of conventional salvage logging—the removal of fallen and damaged trees after a catastrophic windthrow—on subsequent forest restoration have focused on short-term results occurring over less than 20 years; however, this time scale is inadequate, especially for boreal forests, because of the time required for tree growth. Here, we examine the long-term effects of salvage logging after a catastrophic windthrow event in 1954 on the resilience of a boreal forest by assessing the continuous recruitment of coniferous trees, dominance of typical coniferous tree species, and potential for future recruitment. We targeted two regions with different proportions of coniferous trees that were subject to three disturbance and management histories: windthrow (WT: fallen trees left intact), windthrow and salvage (WT+SL: salvage logged after the windthrow), and old growth (OG: not affected by the windthrow). In both regions, past salvaging has had serious negative impacts on the continuous recruitment of coniferous trees and potential for future recruitment. Negative impacts on the dominance of typical coniferous tree species were only observed in mixed forests. Our results suggest that in comparison to the coniferous forest, the mixed forest was less resilient, i.e.; the capability of a forest to maintain its identity as assessed by the dominance and recruitment of typical conifer species after wind disturbance and salvage logging. We found that salvage logging could affect forest structure, even 60 years later, by destroying advanced growth, including potential mother trees, and nursery beds for seedlings of typical conifer tree species.

Editorial

Natural disturbances alter the biophysical conditions of ecosystems, influencing patterns of structure, composition, and successional dynamics. Following high severity natural disturbance in forest ecosystems, land-managers sometimes employ salvage harvesting to harvest trees killed or damaged by the disturbance agent. Despite its widespread practice, the effects of salvage harvesting on many ecosystem functions and species assemblages are still poorly understood. This study presents the first attempt to document and analyze the effects of salvage harvesting on macrofungal communities following catastrophic wind disturbance. On 27 April 2011, an EF3 tornado damaged forest stands within the Oakmulgee Ranger District of the Talladega National Forest in west-central Alabama, USA. Following the event, portions of some stands were subject to salvage harvesting. In 2016, we established three treatments, undisturbed, tornado disturbed, and salvage harvested, in stands that were dominated by Pinus palustris P. Miller prior to the 2011 disturbance events. Throughout the sample period, 546 occurrences of 84 macrofungal species were recorded. Tornado disturbed areas hosted the highest macrofungal species richness overall. Undisturbed areas hosted the highest species richness for ectomycorrhizal macrofungi. Salvage harvested areas had reduced species richness for both saprotrophic and ectomycorrhizal macrofungi compared to tornado disturbed plots. Non-metric multidimensional scaling ordination and permutational multivariate analysis of variance indicated that all three treatments differed in macrofungal community composition. The results indicated that salvage harvesting following catastrophic wind disturbance has the capacity to reduce macrofungal species richness and fruiting abundance. The reduction in deadwood volume and alterations to the ectomycorrhizal-associating plant community documented at salvage harvested sites is likely responsible for the observed differences in macrofungal fruiting patterns. The implications of reduced macrofungal richness in the early stages of forest development following catastrophic disturbance should be subject to long-term studies.

Effects of wind disturbance and salvage harvesting on macrofungal communities in a Pinus woodland

Abstract Natural disturbances alter the biophysical conditions of ecosystems, influencing patterns of structure, composition, and successional dynamics. Following high severity natural disturbance in forest ecosystems, land-managers sometimes employ salvage harvesting to harvest trees killed or damaged by the disturbance agent. Despite its widespread practice, the effects of salvage harvesting on many ecosystem functions and species assemblages are still poorly understood. This study presents the first attempt to document and analyze the effects of salvage harvesting on macrofungal communities following catastrophic wind disturbance. On 27 April 2011, an EF3 tornado damaged forest stands within the Oakmulgee Ranger District of the Talladega National Forest in west-central Alabama, USA. Following the event, portions of some stands were subject to salvage harvesting. In 2016, we established three treatments, undisturbed, tornado disturbed, and salvage harvested, in stands that were dominated by Pinus palustris P. Miller prior to the 2011 disturbance events. Throughout the sample period, 546 occurrences of 84 macrofungal species were recorded. Tornado disturbed areas hosted the highest macrofungal species richness overall. Undisturbed areas hosted the highest species richness for ectomycorrhizal macrofungi. Salvage harvested areas had reduced species richness for both saprotrophic and ectomycorrhizal macrofungi compared to tornado disturbed plots. Non-metric multidimensional scaling ordination and permutational multivariate analysis of variance indicated that all three treatments differed in macrofungal community composition. The results indicated that salvage harvesting following catastrophic wind disturbance has the capacity to reduce macrofungal species richness and fruiting abundance. The reduction in deadwood volume and alterations to the ectomycorrhizal-associating plant community documented at salvage harvested sites is likely responsible for the observed differences in macrofungal fruiting patterns. The implications of reduced macrofungal richness in the early stages of forest development following catastrophic disturbance should be subject to long-term studies.

Landscape-scale consequences of differential tree mortality from catastrophic wind disturbance in the Amazon.

Wind disturbance can create large forest blowdowns, which greatly reduces live biomass and adds uncertainty to the strength of the Amazon carbon sink. Observational studies from within the central Amazon have quantified blowdown size and estimated total mortality but have not determined which trees are most likely to die from a catastrophic wind disturbance. Also, the impact of spatial dependence upon tree mortality from wind disturbance has seldom been quantified, which is important because wind disturbance often kills clusters of trees due to large treefalls killing surrounding neighbors. We examine (1) the causes of differential mortality between adult trees from a 300-ha blowdown event in the Peruvian region of the northwestern Amazon, (2) how accounting for spatial dependence affects mortality predictions, and (3) how incorporating both differential mortality and spatial dependence affect the landscape level estimation of necromass produced from the blowdown. Standard regression and spatial regression models were used to estimate how stem diameter, wood density, elevation, and a satellite-derived disturbance metric influenced the probability of tree death from the blowdown event. The model parameters regarding tree characteristics, topography, and spatial autocorrelation of the field data were then used to determine the consequences of non-random mortality for landscape production of necromass through a simulation model. Tree mortality was highly non-random within the blowdown, where tree mortality rates were highest for trees that were large, had low wood density, and were located at high elevation. Of the differential mortality models, the non-spatial models overpredicted necromass, whereas the spatial model slightly underpredicted necromass. When parameterized from the same field data, the spatial regression model with differential mortality estimated only 7.5% more dead trees across the entire blowdown than the random mortality model, yet it estimated 51% greater necromass. We suggest that predictions of forest carbon loss from wind disturbance are sensitive to not only the underlying spatial dependence of observations, but also the biological differences between individuals that promote differential levels of mortality.

Factors Affecting Tropical Tree Damage and Survival after Catastrophic Wind Disturbance

AbstractThe structure and dynamics of cyclone‐prone tropical forests are driven in part by variation in tree species resistance to and survival after wind‐induced structural damage. We determined the factors associated with tree damage and 3‐yr survival following Category 5 Cyclone Olaf on the Polynesian island of Ta'u, American Samoa. Despite sustaining a high rate of severe damage (34.6% of all trees snapped, 23.0% uprooted), system resilience was high with 74.3 percent stem survival overall and an annual mortality rate of 7.9 percent compared with 2.1 percent in nearby undisturbed late successional forest. Three‐yr survival rate of trees sustaining severe damage was 63.1 percent, compared to about 89 percent for trees sustaining only branch loss or defoliation. Three‐yr survival differed according to damage type, 78.5 percent after snapping vs. 38.4 percent after uprooting. Species differed widely in resistance to and survival after snapping and uprooting. Several species and individual traits were associated with the probability of snapping or uprooting; however, wood density was the only species trait consistently, and negatively, associated with the probability of sustaining either damage type. Survival after snapping was negatively associated with the proportion of the tree snapped off, which was determined by individual tree architecture. Species growth rate was negatively associated with survival after uprooting, indicating the importance of shade tolerance for survival after uprooting. Thus, whereas species traits seemed to exclusively underpin resistance to and survival after uprooting, they only partly accounted for snapping resistance, and did not determine the intensity of snap damage or survival after snapping. Our results highlight the importance of considering each damage type separately when considering ecological trade‐offs.

Annual and seasonal dynamics of ectomycorrhizal fungi colonizing white pine (Pinus strobus) seedlings following catastrophic windthrow in northern Georgia, USA

The effect of wind disturbance on ectomycorrhizal fungal (EMF) communities in forests remains largely uninvestigated. We monitored EMF colonizing Pinus strobus L. seedlings in an oak–pine forest in northern Georgia, USA, after catastrophic wind disturbance. Over three years, we sampled naturally regenerating P. strobus seedlings across three growing seasons in the windthrow area and an adjacent undisturbed forest, identifying 53 unique EMF taxa using molecular techniques. The diversity of EMF colonizing seedlings in the undisturbed forest was consistently greater than in the windthrow area. Although the EMF compositional similarity between EMF in the gap and in the undisturbed forest was low throughout the study, many EMF taxa colonized seedlings in both the gap and the undisturbed forest. Seasonal differences in EMF composition and diversity were pronounced in the undisturbed forest, with diversity increasing from spring to fall. In contrast, EMF composition and diversity were relatively constant throughout seasons in the windthrow gap. We hypothesize that the extent of host community mortality and the extent of EMF host community regeneration following disturbance drive both EMF species composition and community dynamics. However, this hypothesis warrants further study.

Forest damage and recovery from catastrophic wind

The literature on the effects of catastrophic wind disturbance (windstorms, gales, cyclones, hurricanes, tornadoes) on forest vegetation is reviewed to examine factors controlling the severity of damage and the dynamics of recovery. Wind damage has been quantified in a variety of ways that lead to differing conclusions regarding severity of disturbance. Measuring damage as structural loss (percent stems damaged) and as compositional loss (percent stems dead) is suggested as a standard for quantifying severity. Catastrophic wind produces a range of gaps from the size caused by individual treefalls to much larger areas. The spatial pattern of damage is influenced by both biotic and abiotic factors. Biotic factors that influence severity of damage include stem size, species, stand conditions (canopy structure, density), and the presence of pathogens. Abiotic factors that influence severity of damage include the intensity of the wind, previous disturbance, topography, and soil characteristics. Recovery from catastrophic wind disturbance follows one of four paths: regrowth, recruitment, release, or repression. The path of recovery for a given site is controlled both by the severity of disturbance and by environmental gradients of resources. Recovery is influenced also by frequency of wind disturbance, which varies across geographical regions. To develop robust theories regarding catastrophic wind disturbance, the relative roles of different abiotic and biotic factors in controlling the patterns of severity of damage must be determined. These patterns of severity and environmental gradients must then be tied to long-term dynamics of recovery.

Catastrophic wind disturbance in an old-growth hemlock–hardwood forest, Wisconsin

On 4 July 1977, the Flambeau River Hemlock–Hardwood Scientific Area (Sawyer County, WI) was leveled by a downburst of hurricane-force winds. This paper documents preblowdown and postblowdown composition in a 61-ha portion of a state Scientific Area. Total stand basal area after the blowdown was reduced to 6% of prestorm levels. Total seedling density increased greatly following the blowdown, especially that of Betula alleghaniensis Britt. Acer saccharum Marsh, continued to dominate the relatively unaffected sapling layer. A dense shrub layer of Sambucus pubens Michx. developed. Such massive blowdowns do not appear uncommon in northern Wisconsin. Implications for forest regeneration and structure are discussed.