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Many forest types globally have been subject to an increase in the frequency of, and area burnt by, high‐severity wildfire. Here we explore the role that previous disturbance has played in increasing the extent and severity of subsequent forest fires. We summarise evidence documenting and explaining the mechanisms underpinning a pulse of flammability that may follow disturbances such as fire, logging, clearing or windthrow (a process we term disturbance‐stimulated flammability). Disturbance sometimes initiates a short initial period of low flammability, but then drives an extended period of increased flammability as vegetation regrows. Our analysis initially focuses on well‐documented cases in Australia, but we also discuss where these pattens may apply elsewhere, including in the Northern Hemisphere. We outline the mechanisms by which disturbance drives flammability through disrupting the ecological controls that limit it in undisturbed forests. We then develop and test a conceptual model to aid prediction of woody vegetation communities where such patterns of disturbance‐stimulated flammability may occur. We discuss the interaction of ecological controls with climate change, which is driving larger and more severe fires. We also explore the current state of knowledge around the point where disturbed, fire‐prone stands are sufficiently widespread in landscapes that they may promote spatial contagion of high‐severity wildfire that overwhelms any reduction in fire spread offered by less‐flammable stands. We discuss how land managers might deal with the major challenges that changes in landscape cover and altered fire regimes may have created. This is especially pertinent in landscapes now dominated by extensive areas of young forest regenerating after logging, regrowing following broadscale fire including prescribed burning, or regenerating following agricultural land abandonment. Where disturbance is found to stimulate flammability, then key management actions should consider the long‐term benefits of: (i) limiting disturbance‐based management like logging or burning that creates young forests and triggers understorey development; (ii) protecting young forests from disturbances and assisting them to transition to an older, less‐flammable state; and (iii) reinforcing the fire‐inhibitory properties of older, less‐flammable stands through methods for rapid fire detection and suppression. [ABSTRACT FROM AUTHOR]

In a 2‐year field study conducted in the South‐Eastern Alps following a large windthrow disturbance, we tested a large‐scale use of a semiochemical push‐and‐pull strategy to protect susceptible Norway spruce edge trees from the European spruce bark beetle, Ips typographus (Coleoptera: Curculionidae, Scolytinae).Slot traps baited with aggregation pheromones ('pull') and three repellent semiochemicals ('push') were used in both years.In 2020, 26 windthrown areas were classified into three levels of infestation risk, and each was randomly assigned to one of three experimental protocols: eight push‐and‐pull sites; nine trap‐only sites and nine control sites. In 2021, the trials were repeated in 22 clear‐cuts of infested spruce forests, applying two protocols: 16 push–pull and 6 control sites. Fifty traps and 1500 repellent dispensers were used in 2020, and 26 traps and 1500 repellent dispensers were used in 2021.The push‐and‐pull technique performed well in post‐windthrow conditions (2020 trials), especially at high infestation risk, with significantly lower damage to forest edges when compared with untreated sites. The use of pheromone‐baited traps alone was not enough to avoid colonization of forest edges, especially in high‐risk sites.When the push‐and‐pull protocol was applied in clear‐cut areas (2021 trials), the technique was less effective and did not significantly reduce the number of infested trees along the forest edge. Possible interactions with climate conditions are also discussed. [ABSTRACT FROM AUTHOR]

Recent observations of tree regeneration failures following large and severe disturbances, particularly under warm and dry conditions, have raised concerns about the resilience of forest ecosystems and their recovery dynamics in the face of climate change. We investigated the recovery of temperate forests in Europe after large and severe disturbance events (i.e., resulting in more than 70% canopy loss in patches larger than 1 ha), with a range of one to five decades since the disturbance occurred. The study included 143 sites of different forest types and management practices that had experienced 28 disturbance events, including windthrow (132 sites), fire (six sites), and bark beetle outbreaks (five sites). We focused on assessing post‐disturbance tree density, structure, and composition as key indicators of forest resilience. We compared post‐disturbance height‐weighted densities with site‐specific pre‐disturbance densities to qualitatively assess the potential for structural and compositional recovery, overall and for dominant tree species, respectively. Additionally, we analyzed the ecological drivers of post‐windthrow tree density, such as forest management, topography, and post‐disturbance aridity, using a series of generalized additive models. The descriptive results show that European temperate forests have been resilient to past large and severe disturbances and concurrent climate conditions, albeit with lower resilience to high‐severity fire compared with other disturbance agents. Across sites and disturbance agents, the potential for structural recovery was greater than that of compositional recovery, with a large proportion of plots becoming dominated by early‐successional species after disturbance. The models showed that increasing elevation and salvage logging negatively affect post‐windthrow regeneration, particularly for late‐successional species, while pioneer species are negatively affected by increasing summer aridity. These findings provide a key baseline for assessing future recovery and resilience following the recent occurrence of widespread disturbance in the region and in anticipation of future conditions characterized by increasing heat and drought stress. [ABSTRACT FROM AUTHOR]

This study identifies 38 cases of windthrows in the Amazonia to explore the relationship between windthrows and the characteristics (storm passing time, cloud top temperature, and maximum precipitation) of mesoscale convective systems (MCSs) that produced them. Most of windthrow cases in this study occurred in August and September. The storm passing time is positively correlated with the size of windthrows. MCSs with colder cloud top temperature (with a mean at 206 K)—indicating deeper convection—resulted in large windthrows, while those with warm cloud top (with a mean above 230 K) resulted in relatively small windthrows except for windthrows in the western Amazonia. No significant relationship is found between maximum precipitation intensity and the area of windthrows. Plain Language Summary: Fan‐shaped dead forest patches were found over the entire Amazonia. These patches affect the role the Amazon forests played in the world's carbon cycle. Scientists found that frequent thunderstorms result in these dead forest patches, but how does the process happen? In this study, we explored the three characteristics of thunderstorms, including their passing over time, cloud top temperature, and associated precipitation, to identify their relationship with the size of the dead forests. We found that long‐lived thunderstorms with thicker and tall clouds, providing more power to the mesoscale convective systems, result in bigger sizes of dead forest patches. Moreover, forests in the western Amazonia are more vulnerable to thunderstorms than forests on the other parts of the Amazonia. Key Points: The storm passing time of mesoscale convective systems (MCSs) is positively correlated with the size of windthrowsMCSs with colder cloud top temperature are associated with larger size of windthrowsNo significant relationship is found between maximum precipitation intensity and the area of windthrows [ABSTRACT FROM AUTHOR]

On the basis of long‐term surveys of permanent plots and traps, we examined the communities of saproxylic beetles, fungi, herbs, and trees on an untreated 22 ha large beech forest windthrow and asked whether the results lend support to the intermediate disturbance hypothesis (IDH). We studied species richness and the similarity of community composition. Additionally, we grouped species by their frequency trend over time to successional model types to examine whether, corresponding to the IDH, the diversity of these groups explained peak richness at intermediate intervals after the disturbance. In line with the IDH, species richness showed a hump‐backed temporal course for alpha and gamma diversity. We found evidence for a linear succession directly after the disturbance. This, however, did not continue, and in all species groups, a partial recovery of the initial community was observed. In the case of fungi, herbs, and trees, but not for saproxylic beetles, alpha diversity was driven by the diversity of the successional model types. Our results underline that the mechanisms driving species richness after disturbances are more complex than the IDH suggests and that these mechanisms vary with species group. We assumed that, besides competition, legacy effects, facilitation, habitat heterogeneity, and random saturation of the species pool are important. In case of trees and herbs, we found indications for strong legacy and competition effects. For fungi and beetles, substrate heterogeneity and microclimate were assumed to be important. We concluded that disturbances contribute to increasing species richness not only by reducing the effectiveness of competitors but also by increasing the amount and diversity of resources, as well as their rate of change over time. [ABSTRACT FROM AUTHOR]

In order to assess how well ERA5 and IFS represent the real, observed wind speeds during storm I Aila i , Figure 7 shows the time series of maximum wind gust speed at two stations: Pietarsaari Kallan (Figure 7a) and Rauma Kylmäpihlaja (Figure 7b). Therefore, we can conclude that storm I Aila i had the strongest wind speeds and wind gusts out of all Septembers in the observation record in 2004-2020 and in ERA5 in the period 1979-2020. The dashed vertical line denotes the maximum wind speed or wind gust in the chosen dataset. gl Furthermore, when the maximum wind speeds in all marine and land stations in Finland (excluding mountainous stations which are located over 200 m above sea level) during the whole observational history are considered, no higher September wind speeds are found (not shown). The winds caused by storm I Aila i were analysed using wind speed and wind gust observations from FMI's weather stations located across Finland. [Extracted from the article]

A windthrow disturbance alters the functioning and structure of a forest ecosystem and causes substantial economic losses., A 10-year pitfall study of carabid assemblages (Coleoptera, Carabidae) was carried out in pine stands disturbed by windthrow (Pisz Forest, North Poland) in the first year after the disturbance, with different classes of severity: severely disturbed stands (canopy cover up to 30%), moderately disturbed stands (canopy cover of 40-60%) and least disturbed stands (canopy cover of 70-90%)., Based on the number of carabid species and their ecological traits, I confirmed the hypothesis that the amplitude of changes in carabid assemblages inhabiting severely and moderately disturbed stands would be greater than in the least disturbed stands. Variation in carabid assemblages was also linked to soil pH and to carbon and nitrogen content in the soil., The study confirmed my hypothesis regarding the delayed replacement of late successional carabid fauna by early successional fauna, which was linked to the broken pines lying on the soil, allowing late successional fauna to survive in the first few years after the windthrow., The principal response curve analysis identified three phases of post-disturbance succession in carabid assemblages: (i) slight changes in the number of species and their ecological traits, lasting for 4 years; (ii) 'rapid' changes, lasting for 3 years, involving an increase in the number of species and rapid replacement of late successional carabid fauna by early successional fauna; and (iii) the slow recovery of late carabid successional fauna. [ABSTRACT FROM AUTHOR]

Results from a newly available empirical maximum gust speed model were evaluated for their predictive power of forest storm damage caused by the high-impact winter storm 'Lothar' in the German federal state of Baden-Wuerttemberg. In this state, Lothar was the most severe storm event of the last decades, causing nearly 30 million m3 of damaged timber. By applying a least squares boosting procedure, daily maximum gust speed values measured at 28 meteorological stations were used to empirically model highly resolved (50 × 50 m) near-surface gust speed fields associated with Lothar. Gust speed was modelled using terrain- and roughness-related variables as predictors. The modelled gust speed fields were then used as input to an empirical forest storm damage model. To build the damage model, the machine learning method random forests was applied. Results from this study demonstrate that the empirically modelled maximum gust speed field associated with Lothar was the most important predictor variable for forest storm damage at the landscape scale. Modelled maximum gust speed was nearly twice as important as all other available predictor variables. The medians of classified proportions of storm-damaged timber quasi-linearly increased with increasing maximum gust speed. [ABSTRACT FROM AUTHOR]

Wind is the major abiotic disturbance in New Zealand's planted forests, but little is known about how the risk of wind damage may be affected by future climate change. We linked a mechanistic wind damage model (Forest GALES) to an empirical growth model for radiata pine ( Pinus radiata D. Don) and a process-based growth model ( cenw) to predict the risk of wind damage under different future emissions scenarios and assumptions about the future wind climate. The cenw model was used to estimate site productivity for constant CO2 concentration at 1990 values and for assumed increases in CO2 concentration from current values to those expected during 2040 and 2090 under the B1 (low), A1B (mid-range) and A2 (high) emission scenarios. Stand development was modelled for different levels of site productivity, contrasting silvicultural regimes and sites across New Zealand. The risk of wind damage was predicted for each regime and emission scenario combination using the Forest GALES model. The sensitivity to changes in the intensity of the future wind climate was also examined. Results showed that increased tree growth rates under the different emissions scenarios had the greatest impact on the risk of wind damage. The increase in risk was greatest for stands growing at high stand density under the A2 emissions scenario with increased CO2 concentration. The increased productivity under this scenario resulted in increased tree height, without a corresponding increase in diameter, leading to more slender trees that were predicted to be at greater risk from wind damage. The risk of wind damage was further increased by the modest increases in the extreme wind climate that are predicted to occur. These results have implications for the development of silvicultural regimes that are resilient to climate change and also indicate that future productivity gains may be offset by greater losses from disturbances. [ABSTRACT FROM AUTHOR]

Islands formed upstream of mega hydroelectric dams are excellent experimental landscapes to assess the impacts of habitat fragmentation on biodiversity. We examined the effects of plot-, patch- and landscape-scale variables on the patterns of floristic diversity across 34 forest islands that had experienced 26 years of isolation since the creation of the 4437 km2 Balbina Hydroelectric Reservoir of central Brazilian Amazonia. In addition, three undisturbed continuous forest sites in neighbouring mainland areas were also sampled across a comparable elevational gradient., We identified all live trees ≥10 cm DBH at species level within a total of 87 quarter-hectare forest plots and conducted a comprehensive compilation of functional attributes of each tree species. We then examined species-area relationships ( SARs) and the additional effects of patch and landscape-scale metrics on patterns of tree assemblage heterogeneity, both in terms of taxonomic and functional diversity., Despite a clearly positive SAR, edge-mediated forest disturbance was the single most important driver of species composition and abundance within islands. Our results suggest that non-random floristic transitions within island plots followed a predictable pattern, with different life-history traits either penalizing or rewarding local persistence of different functional groups. Distance to edges mediated the probability of tree mortality induced by windfalls and episodic surface fires, clearly resulting in faster species turnover and unidirectional changes in guild structure within small islands where light-wooded fast-growing pioneers largely replaced heavy-wooded species of the old-growth flora., Synthesis. Following a simultaneous 26-year post-isolation history, we disentangle the effects of habitat loss and insularization on tree assemblages within a large set of Amazonian 'true' forest islands, of variable sizes, sharing a uniform open-water matrix. Area effects are expressed via a response to edge effects, with trees in smaller islands being more vulnerable to edge-related surface fires and wind-throws. Additionally, forest edge effects can be a powerful driver of non-random floristic transitions across islands within the Balbina archipelago via a process of rapid pioneer proliferation, drastically affecting both the taxonomic and functional composition of insular tree communities. Finally, our results indicate that detrimental effects of forest fragmentation induced by hydroelectric dams are considerably stronger than those of forest patches embedded within a terrestrial vegetation matrix. [ABSTRACT FROM AUTHOR]

Questions How does windthrow influence plant diversity and composition as well as regeneration and microsite characteristics? What are the consequences of post-windthrow salvage logging on these key attributes? Location Eastern black spruce-moss forest, Quebec, Canada. Methods A total of 92 plots were sampled, each with a radius of 11.28 m; 49 of these plots were salvaged while 43 were unsalvaged. Regeneration density, plant diversity and seedbeds were characterized. We tested the effect of microtopography and windthrow severity on species richness and Shannon diversity index for salvaged and unsalvaged windthrows using a mixed model. Partial redundancy analysis ( RDA) determined which environmental and stand characteristics were most important in explaining differences in plant species and forest floor types among the treatments. The effects of treatments (salvaged and unsalvaged windthrows), microtopography attributes, windthrow severity and regeneration species on seedling and sapling abundance were tested using a linear mixed model. Results Salvaged windthrow, with a large proportion of skid trails, dead mosses and Sphagnum, had a lower degree of seedbed heterogeneity. Also, some understorey species present in the unsalvaged ecosystem were absent from the salvaged windthrow. Sphagnum and other moss species were clearly associated with the unsalvaged treatment. White birches were positively associated with mound microtopography in the unsalvaged windthrow. Conclusion From an ecosystem-based forest management perspective, natural post-windthrow understorey conditions and microsite heterogeneity can be in part maintained in salvaged cut blocks by incorporating retention patches that include downed and standing dead wood and living trees of diverse sizes. These steps should favour plant regeneration and augment diversity for salvage logging after wind disturbance. [ABSTRACT FROM AUTHOR]

Windthrows in spruce forests provide a prime substrate for the population build-up of bark beetles. Until now, no information has been available on the population development of associated parasitoids., The development of bark beetle and parasitoid populations was monitored on cleared and uncleared windthrow areas for 4 years, corresponding to the second to fifth growing seasons after the storm., The population level of both groups quickly increased synchronously from the second to the third season, and gradually declined thereafter until the fifth growing season. The parasitoids showed no time lag., At the species level, the same pattern was found for the pest Ips typographus (L.) and its specific parasitoid Dinotiscus eupterus (Walk.)., During the 4 years under study, a succession of different bark beetle and parasitoid species was found., Bark beetles and parasitoids were more abundant on uncleared windthrow areas than on cleared areas, whereas predatory beetles generally preferred the adjacent forest., Once the deteriorated phloem quality precludes further bark beetle development, no more bark beetle-relevant parasitoids are produced in windthrows. [ABSTRACT FROM AUTHOR]

* Premise of study: New Caledonia commonly experiences cyclones, so trees there are expected to have enhanced wood traits and trunk allometry that confer resistance to wind damage. We ask whether there is evidence of a trade-off between these traits and growth rate among species. * Methods: Wood traits, including density, microfibril angle (MFA), and modulus of elasticity (MOE), ratio of tree height to stem diameter, and growth rate were investigated in mature trees of 15 co-occurring canopy species in a New Caledonian rainforest. * Key results: In contrast to some studies, wood density did not correlate negatively with growth increment. Among angiosperms, wood density and MOE correlated positively with diameter-adjusted tree height, and MOE correlated positively with stem-diameter growth increment. Tall slender trees achieved high stiffness with high efficiency with respect to wood density, in part by low MFA, and with a higher diameter growth increment but a lower buckling safety factor. However, some tree species of a similar niche differed in whole-tree resistance to wind damage and achieved wood stiffness in different ways. * Conclusions: There was no evidence of a growth-safety trade-off in these trees. In forests that regularly experience cyclones, there may be stronger selection for high wood density and/or stiffness in fast-growing trees of the upper canopy, with the potential growth trade-off amortized by access to the upper canopy and by other plant traits. Furthermore, decreasing wood density does not necessarily decrease resistance to wind damage, resistance being influenced by other characteristics including cell-level traits (e.g., MFA) and whole-plant architecture. [ABSTRACT FROM AUTHOR]

The article presents a study, which compares forests and wind speed data from 107 winters of 1897-2007 with forest damage in Zurich, Switzerland. It explores the relationships between forest attributes, wind speed and forest damage by evaluating records on forests and wind speed of the said period. It reveals that wind speed increased from the beginning of the 1933 recordings and peaked in the early 1990s.

Disturbance of ecosystems is a major factor in regional carbon budgets, and it is believed to be partly responsible for the large inter-annual variability of the terrestrial part of the carbon balance. Forest fires have so far been considered as the most important disturbance but also other forms of disturbance such as insect outbreaks or wind-throw might contribute significantly to the largely unexplained inter-annual variability, at least in specific regions. The effect of wind-throw has not yet been estimated because of lack of data on how carbon fluxes are affected. The Gudrun storm, which hit Sweden in January 2005, resulted in ca. 66 million m3 of wind-thrown stem wood on an area of ca. 272 000 ha. Using a model (BIOME-BGC) calibrated to CO2 flux measurements at two sites, the annual net ecosystem productivity during the first year after the storm was estimated to be in the range −897 to −1259 g C m−2 yr−1. This is a much higher loss compared with harvested (clear-cut) forests in Europe, which ranged between ca. −420 and −100 g m−2 yr−1. The reduction in the carbon sink scaled to the whole wind-thrown area was estimated at ca. 3 million tons C during the first year. By historical data on wind-throw in Europe combined with modelling, we estimated that the large Lothar storm in 1999 reduced the European carbon balance by ca. 16 million tons C, this is ca. 30% of the net biome production in Europe. We conclude that the impact of increased forest damage by more frequent storms in future climate change scenarios must be considered and that intermittent large wind-throw events may explain a part of the large inter-annual variability in the terrestrial carbon sink. [ABSTRACT FROM AUTHOR]

Many studies have been conducted to quantify the possible ecosystem/landscape response to the anticipated global warming. However, there is a large amount of uncertainty in the future climate predictions used for these studies. Specifically, the climate predictions can be very different based on a variety of global climate models and alternative greenhouse emission scenarios. In this study, we coupled a forest landscape model, LANDIS-II, and a forest process model, PnET-II, to examine the uncertainty (that results from the uncertainty in the future climate predictions) in the forest-type composition prediction for a transitional forest landscape [the Boundary Water Canoe Area]. Using an improved global-sensitivity analysis technique [Fourier amplitude sensitivity test], we also quantified the amount of uncertainty in the forest-type composition prediction contributed by different climate variables including temperature, CO2, precipitation and photosynthetic active radiation (PAR). The forest landscape response was simulated for the period 2000–2400ad based on the differential responses of 13 tree species under an ensemble of 27 possible climate prediction profiles (monthly time series of climate variables). Our simulations indicate that the uncertainty in the forest-type composition becomes very high after 2200ad, which is close to the time when the current forests are largely removed by windthrow disturbances and natural mortality. The most important source of uncertainty in the forest-type composition prediction is from the uncertainty in temperature predictions. The second most important source is PAR, the third is CO2 and the least important is precipitation. Our results also show that if the optimum photosynthetic temperature rises due to CO2 enrichment, the forest landscape response to climatic change measured by forest-type composition may be substantially reduced. [ABSTRACT FROM AUTHOR]

Severe tropical Cyclone Monica impacted the coast of northern Australia in April 2006 with estimated maximum wind gusts of 360 km h−1. It rapidly moved inland losing intensity and passed over the town of Jabiru as a category 2 system, with maximum wind gusts recorded at 135 km h−1. The cyclone had a significant impact on the landscapes within the Alligator Rivers Region and significant windthrow of trees occurred. This paper describes the level of impact that category 2 level winds had on tree canopy loss 10 days after cyclone and then again 1 year later. Recovery was assessed using multispectral satellite imagery in sub-catchments of the Magela Creek catchments. A non-linear relationship was fitted between a modified vegetation index (derived from Landsat TM5 satellite data) and percentage tree canopy cover (measured from very high resolution QuickBird satellite data). The results of the non-linear relationship, used to estimate percentage canopy cover, indicate that 10 days after cyclone, there was significant disturbance to tree canopy. However, data 1 year after cyclone show that recovery of canopy across the studied catchments varied between 8% and 19% of the percentage canopy cover that remained after the initial impact of the cyclone. Further analysis in the three sub-catchments using Geographical Information System showed that proportionally, riparian zones and inundated areas in each of the sub-catchments suffered greater loss of tree canopy cover compared with upland areas. [ABSTRACT FROM AUTHOR]

Wind disturbance is an important ecological force in the tropics, especially in the cyclonic and hurricane zones from about 7–20° latitude. Damage from intense winds may be especially severe in fragmented forests because of their abrupt artificial margins and denuded surrounding landscapes. We review available information on the effects of windstorms on fragmented forests, synthesizing studies from Australasia, Amazonia and elsewhere in the tropics. Wind damage in fragmented landscapes can be influenced by a range of factors, such as forest-edge orientation, edge structure, the size of nearby clearings and local topography. We argue that wind disturbances are likely to interact with, and exacerbate, a range of deleterious environmental changes in fragmented forests. Among the most important of these are altered forest structure, shifts in plant species composition, exotic-plant invasions, reduced carbon storage and elevated vulnerability to fire. The damaging impacts of winds on fragmented forests could potentially increase in the future, particularly if global warming leads to increasingly severe or frequent windstorms. [ABSTRACT FROM AUTHOR]

Ecological degradation within areas of remnant forest may be amplified if the effects of fragmentation interact with the effects of other environmental disturbances such as wind storms. We used before–after comparisons to assess the effects of Tropical Cyclone Larry on remnant and continuous rainforest in the Wet Tropics uplands of north-eastern Australia. Vegetation structure was measured 3 years before the cyclone and 6 months afterwards, at eight continuous forest sites and eight remnants (6–37 ha), within 20 km of the cyclone's track. The cyclone caused extensive defoliation, felling and breakage of stems and branches (greatest among the trees >100 cm diameter which had around 50% stem loss), and increased litter and woody debris. Cyclone effects were strongly influenced by a site's spatial position ( P = 0.005, 0.001 in multivariate analyses of overall damage). Maximum damage occurred 10–15 km south of the cyclone track, perhaps because of the additive effects of the west-moving air at the southern eyewall combined with the cyclone's own rapid westward movement. Most fragments were south of the cyclone track, as a consequence of spatially selective deforestation practices, and therefore, showed greatest damage. However, once the effects of spatial position were considered, the independent differences in cyclone effects between fragments and continuous forest were lost ( P = 0.23, 0.41 when north-south distance was included as a covariate in analyses). The expected protection afforded by a continuous forest canopy seems to have disappeared in the face of extremely strong cyclonic winds and down-draughts. Nevertheless, an interaction between fragmentation and disturbance may yet occur, during the period of post-cyclone recovery, owing to the effects of landscape context on plant recruitment. For example, there was a higher diversity of exotic seedling germination in fragments, independent of the extent of cyclone damage. [ABSTRACT FROM AUTHOR]

The role of tropical cyclones in structuring tropical rainforests has long been recognized in the Americas and northern Australia. However, their role in the dynamics of Australian savannas has received little attention compared with the effects of fire and drought. In April 2006, Tropical Cyclone Monica caused trees to be snapped or uprooted across a swath about 50 km wide and 130 km inland in northern Australia. The proportion of trees damaged was assessed using on-ground surveys and interpretation of aerial photographs along the cyclone path and along several perpendicular transects. From these data, a relationship between the damage to trees and estimated maximum gust speed was developed. From knowledge of gust recurrence, curves were then derived describing the changes with distance inland in the average recurrence interval for tree windthrow events. These relationships were consistent with the historical record of tree damage in the northwest of the Northern Territory. It was concluded that windthrow has profound, but hitherto unrecognized implications for ecological processes such as tree dynamics and fluxes of carbon and water in Australian tropical savannas. [ABSTRACT FROM AUTHOR]

We examined the impact of severe cyclone ‘Larry’ on the vegetation structure of monoculture and mixed species timber plantations, restoration plantings and reference sites in upland rainforests on the Atherton Tableland, north Queensland, Australia. Sites were initially assessed in 2000 and resurveyed in 2006, 6–8 months after the cyclone traversed the region. In both surveys, timber plantations had a relatively open canopy, grassy understorey and few shrubs or small-sized trees; whereas restoration plantings had a relatively closed canopy, an understorey of bare ground, leaf litter and rainforest seedlings, a high density of small-diameter trees and a moderate representation of special life forms characteristic of rainforest. Cyclone damage varied with tree size, site type, proximity to the cyclone and stem density. First, the proportion of trees that were severely damaged by the cyclone (major branches broken, stem snapped or pushed over) increased with the diameter of trees across all site types. Second, damage to larger-sized trees (>10 cm d.b.h., >20 cm d.b.h.) was proportionally highest in monoculture plantations, intermediate in mixed species plantations and rainforest, and lowest in restoration plantings. Third, within site types, damage levels decreased with distance from the cyclone track and with stem density. There was no evidence that topographical position influenced damage levels, at least for timber plantations. We tentatively attribute the high levels of damage experienced by timber plantations to their relatively open structure and the large size of stems in plantations. Restoration plantings generally escaped severe damage by the cyclone, but their continued development towards rainforest conditions may require a coordinated monitoring and maintenance programme to address the potential threat of weed invasion. [ABSTRACT FROM AUTHOR]

Severe Tropical Cyclone Larry damaged a large swathe of rainforest to the west of Innisfail in north-eastern Queensland on 20 March 2006. Within the path of the most destructive core of the cyclone were sites previously established along human-made (powerlines and highways) and natural (streams) linear canopy openings for a study of edge effects on adjacent rainforest plant communities and associated microclimates. Vegetation damage and understorey microclimate parameters were measured 6 months after the passage of Cyclone Larry and compared with results before the cyclone. We examined the spatial patterns of vegetation damage in relation to natural and artificial linear clearing edges and the vegetation structural factors influencing these patterns as well as resulting alterations to microclimate regimes experienced in the rainforest understorey. Vegetation damage was spatially patchy and not elevated near linear clearing edges relative to the forest interior and did not differ between edge types. Vegetation damage was influenced, albeit relatively weakly, by structural traits of individual trees and saplings, especially size (diameter at breast height, d.b.h.) and successional status: tree damage was greater in pioneer species and in larger trees, while sapling damage was greater in canopy tree species than in understorey tree or shrub species. Changes in the understorey microclimate mirrored the degree of damage to vegetation. Where vegetation damage appeared greater, the understorey microclimate was brighter, warmer, drier and windier than below less-damaged areas of the forest canopy. Overall, understorey light availability, wind speed and the diurnal ranges of air temperature and vapour pressure deficit increased dramatically after Cyclone Larry, while pre-cyclone edge gradients in light availability were lost and temperature and vapour pressure deficit gradients were reversed. [ABSTRACT FROM AUTHOR]

Cyclones have been instrumental in shaping the structural and floristic composition of tropical forests, including tropical rainforests of north Queensland, Australia. The response of tropical riparian rehabilitation sites to cyclonic wind damage, however, is currently unknown. This lack of knowledge may severely hamper long-term success of riparian restoration efforts, particularly in light of predictions that cyclones in north Queensland may become less frequent but more severe. In this study, we examined the extent, type and magnitude of damage inflicted on revegetation works in the Tully-Murray floodplain of north Queensland by Severe Tropical Cyclone Larry. We compared wind damaged in 20 paired revegetated and associated rainforest remnant sites, using (i) gross community damage scores, (ii) mean weighted damage scores, and (iii) type of damage sustained by individual plants. Overall, wind damage due to Severe Tropical Cyclone Larry was surprisingly similar in revegetated and remnant sites. Both gross community damage scores and mean weighted damage scores did not differ between paired revegetated and remnant sites. In contrast, the type of damage sustained by individual plants was not independent of site, with a larger proportion in revegetated sites sustaining severe damage compared with remnant sites. This larger proportion of severely damaged individuals in revegetated sites was at least in part due to the significantly higher proportion of pioneers at these sites. The pioneer species Homalanthus novoguineensis was particularly susceptible to wind damage. The potential effects of spatial differences, such as consistent bias due to size, shape or exposure between the remnants and revegetated sites, on our results are discussed. In light of our results, we recommend that future revegetation sites include fewer pioneer species that are highly susceptible to wind damage, more pioneer species that are resistant to wind damage. [ABSTRACT FROM AUTHOR]

If changes in the structural characteristics of rainforest at edges are caused by wind, then physical damage from a tropical cyclone might be greatest at edges or in small fragments that have a high proportion of edge. We tested whether this was true of a fragmented rainforest landscape impacted by a category 4 severe tropical cyclone in March 2006. Six structural variables (canopy cover, canopy height, cover of ground vegetation, leaf litter, stem density and counts of woody debris) were surveyed at 18 rainforest sites (six small linear remnants, and both edges and interiors of six large remnants) on the Atherton Tableland in north-eastern Queensland, Australia. Data collected 7 and 12 months after the passage of Cyclone Larry were compared with an identical survey conducted 4 years prior to the cyclone. The cyclone had large effects across many components of forest structure. However, sites within 30 m of forest edges in small and large remnants were not impacted more than the interiors of large remnants. It is likely that the high wind intensity from severe tropical cyclones overrides the modest wind protection provided by surrounding forest. The cyclone's effects were highly patchy at local scales (0.5–1.0 km), leading to an increase in among-site variation in forest structure and the disappearance of significant spatial autocorrelation among large remnant edge-interior site pairs which had existed prior to the cyclone. The main effect of Cyclone Larry at these study sites was to increase the spatial heterogeneity of forest structure at local scales. [ABSTRACT FROM AUTHOR]

Bird surveys were conducted to assess the impact of a severe cyclone on bird communities in three fragments of the endangered rainforest Type 5b on the Atherton Tablelands of far north Queensland. Bird communities were surveyed using timed area searches in three sites in each of the three fragments and were undertaken prior to and following Tropical Cyclone Larry. Cyclone Larry caused short-term changes in the abundance of some species of birds in Type 5b rainforest fragments. Two weeks after the storm, in two of three fragments surveyed, abundance of the frugivorous wompoo fruit-dove ( Ptilinopus magnificus) and figbird ( Sphecotheres viridis) had decreased while the omnivorous Macleay's honeyeater ( Xanthotis macleayana) and Lewin's honeyeater ( Meliphaga lewinii) decreased in abundance in all three locations. Most insectivorous species increased in some sites and decreased in others following Cyclone Larry. Rapid recovery of bird communities to approximately their pre-cyclone state after only 7 months appeared to reflect the capacity of species to either modify their foraging behaviour, switch foods, or to move within or between fragments or to other food sources in the landscape. [ABSTRACT FROM AUTHOR]

This article presents an overview of the effects of cyclones on the rain forests of Australia. Since the 1990s, several studies have been done to determine the effects of cyclones on forests. Other studies have looked at how the forest ecosystems respond to the storms. The author cites early studies done on the effects of multiple cyclones on the same rain forests. The effects of cyclones on fragmented forests is also discussed.

Question: The prominent role of wind dispersal in alpine habitats has been recognized early but has rarely been quantified. The aim of this study is to compare wind dispersal under alpine and lowland conditions and to analyse whether differences are caused by species traits, e.g. terminal velocity of seeds (Vterm) or weather conditions. Location and Methods: We characterized wind dispersal potential of >1100 Central European species using measured Vterm. To quantify the habitat effect on wind dispersal, we measured meteorological key-parameters and simulated dispersal distance spectra of nine selected species under typical alpine conditions (foreland of the Scaletta-glacier, Switzerland) and typical lowland conditions (grassland in Bad Lippspringe, Germany). Results: Lowland species had higher Vterm compared to alpine species. However, this difference is absent when only species of species of open habitats are concerned. The meteorological measurements showed that the alpine habitat was mainly characterized by higher frequency and strength of updrafts. The simulations showed that under alpine conditions long distance dispersal occurred much more frequent. Conclusions: More than 50% of the alpine species have a fair chance to be dispersed by wind over long distances, while this proportion is less than 25% for species from open habitats in the lowland. The more prominent role of wind dispersal in alpine habitats is mainly a result of differences in environmental conditions, namely more intense vertical turbulence in the alpine habitat, and does not result from prominent differences in plant traits, namely Vterm, between alpine and lowland species. [ABSTRACT FROM AUTHOR]

The effect of disturbance on local communities may operate within the context of the spatial landscape. We examined the scale-dependent effects of windthrow disturbance caused by a large typhoon on three arthropod communities in a temperate forest of Japan. Canopy arthropods were collected by beating foliage, forest-floor arthropods were collected by sweeping the vegetation, and flying arthropods were collected in Malaise traps. To assess the “functional spatial scale” at which arthropods responded to tree-fall disturbance, the gap rate was quantified at different spatial scales by sequentially enlarging the radius of a circular landscape sector in 10-m increments from 10 to 500 m. We then analyzed the responses of order richness and abundance to the gap rate for each arthropod community. The spatial scale of the significant best-fitting model, which was selected from the models fitted to the gap rate at stepwise spatial scales, was regarded as the arthropod-specific functional spatial scale. Arthropod order richness was not dependent on the gap rate. In contrast, arthropod order abundance depended significantly on the gap rate in many orders, but varied in the response direction and functional spatial scale. These order-specific, scale-dependent responses to tree-fall gaps could complicate interactions among organisms, leading to complex community organization. An understanding of the spatial processes that link the use of space by organisms with the spatial scale at which ecological processes are experienced is required to elucidate the responses of populations, communities, and biotic interactions to disturbances in a spatial landscape context. [ABSTRACT FROM AUTHOR]

• This study aims to link three-dimensional coarse root architecture to tree stability in mature timber trees with an average of 1-m rooting depth. • Undamaged and uprooted trees were sampled in a stand damaged by a storm. Root architecture was measured by three-dimensional (3-D) digitizing. The distribution of root volume by root type and in wind-oriented sectors was analysed. • Mature Pinus pinaster root systems were organized in a rigid ‘cage’ composed of a taproot, the zone of rapid taper of horizontal surface roots and numerous sinkers and deep roots, imprisoning a large mass of soil and guyed by long horizontal surface roots. Key compartments for stability exhibited strong selective leeward or windward reinforcement. Uprooted trees showed a lower cage volume, a larger proportion of oblique and intermediate depth horizontal roots and less wind-oriented root reinforcement. • Pinus pinaster stability on moderately deep soils is optimized through a typical rooting pattern and a considerable structural adaptation to the prevailing wind and soil profile. [ABSTRACT FROM AUTHOR]

In the coming century, forecast climate changes caused by increasing greenhouse gases may produce dramatic shifts in tree species distributions and the rates at which individual tree species sequester carbon or release carbon back to the atmosphere. The species composition and carbon storage capacity of northern Wisconsin (USA) forests are expected to change significantly as a result. Projected temperature changes are relatively large (up to a 5.8°C increase in mean annual temperature) and these forests encompass a broad ecotone that may be particularly sensitive to climate change. Our objective was to estimate the combined effects of climate change, common disturbances, and species migrations on regional forests using spatially interactive simulations. Multiple scenarios were simulated for 200 years to estimate aboveground live biomass and tree species composition. We used a spatially interactive forest landscape model (LANDIS-II) that includes individual tree species, biomass accumulation and decomposition, windthrow, harvesting, and seed dispersal. We used data from two global circulation models, the Hadley Climate Centre (version 2) and the Canadian Climate Center (version 1) to generate transient growth and decomposition parameters for 23 species. The two climate change scenarios were compared with a control scenario of continuing current climate conditions. The results demonstrate how important spatially interactive processes will affect the aboveground live biomass and species composition of northern Wisconsin forests. Forest composition, including species richness, is strongly affected by harvesting, windthrow, and climate change, although five northern species (Abies balsamea,Betula papyrifera,Picea glauca,Pinus banksiana,P. resinosa) are lost in both climate scenarios regardless of disturbance scenario. Changes in aboveground live biomass over time are nonlinear and vary among ecoregions. Aboveground live biomass will be significantly reduced because of species dispersal and migration limitations. The expected shift towards southern oaks and hickory is delayed because of seed dispersal limitations. [ABSTRACT FROM AUTHOR]

We documented the occurrence of a 1934 blowdown in a subalpine forest in northwestern Colorado, USA. Prior to the blowdown, the stand was dominated by old-growth Picea engelmannii - Abies lasiocarpa forests. Although blowdowns are believed to trigger outbreaks of Dendroctonus rufipennis (spruce beetle), we found no detectable increase in beetle caused mortality. Forest recovery was by both release of the previously suppressed regeneration and by new seedling establishment. Both recovery pathways were dominated by Abies. The blowdown thus caused a shift in species dominance from Picea to Abies; 65 yr after the blowdown, the fallen logs and tip up mounds continue to provide favourable habitat for seedling establishment of both species. The present study shows that the legacy of blowdowns can influence forest dynamics for decades following the disturbance event. [ABSTRACT FROM AUTHOR]

We investigated the influence of differing patch types on the germination, growth, and survival of two species of tree seedlings in a catastrophic, old-growth forest windthrow. We documented environmental conditions, and experimentally introduced seeds, transplanted seedlings, and manipulated litter and herbivore access to determine the effects of patch types during initial forest regrowth. Among patch types defined by substrate condition and exposure, we found significant differential influence of patch type on germination of seeds of a common colonizer, Betula alleghaniensis . Patch types that provided exposed mineral soil allowed greater germination than other patch types, regardless of light availability. Germination of Acer rubrum varied among patch types in a fashion similar to that of B . alleghaniensis , although differences among patch types were not significant. Litter can also be the basis of patch classification. Both type and amount of litter significantly influenced emergence of seedlings, with broad-leaf litter (in amounts typical of intact forest) producing greater inhibition of emergence than amounts of conifer needles typical of intact forest. Survival and performance of fenced and unfenced Acer rubrum seedlings transplanted into different patch types reflected influences of both herbivory and competition with existing vegetation. Survival was lowest where the Acer seedlings were most apparent to mammalian herbivores. Growth of Acer seedlings was greater when they were protected from herbivory and free of competition from surrounding vegetation. These findings demonstrate that patch types offer different suitability as regeneration microsites during early tree life history stages. Because these patch types are common and easy to recognize, the differences in species’ responses may be sufficiently general to apply in other disturbances of this type. If general species responses to patch types can be combined with knowledge of propagule abundance and patch abundance, it could provide a basis for improved understanding of post-disturbance regeneration, via patch influences. [ABSTRACT FROM AUTHOR]

Examines the relationship among forest landscape dynamics, environmental factors and disturbance history in the Bull Run Basin, Oregon. Analysis of environmental factors and windthrow patterns; Disturbance type and forest composition and structure; Climate and landform controls; Use of biotic controls; Climate-disturbance and forest management interactions.

Examines forest response to catastrophic wind in the United States. Relationship of tree damage patterns with mortality and regeneration, vegetation recovery and ecosystem processes; Importance of pre-disturbance forest structure in determining severity of impact; Role of tree resilience and understory vegetation in ecosystem processes.

Investigates the windfall history and landscape patterns in the Andes of Tierra del Fuego in Argentina. Description of the study region; Dynamics of forests and wind; Distance limitations for the effective dispersal of seeds; Factors involved in blowdown susceptibility; Development of landscape patterns; Interactions between the wind and landscape patterns.

Studies the patterns and mechanisms of regeneration of a 400-hectare wind-throw in an old-growth beech-hemlock forest caused by a tornado on May 31, 1995. Percent cover and density of woody stems; Seedling demography; Plant community response to the disturbance.

Describes and quantifies the widespread occurrence of large blowdowns in mature Amazonian forest in Brazil. Related studies; Confirmation of aging of individual blowdowns; Occurrence of blowdowns throughout the Amazon.

Examines the rate of changes in soil properties during the first four centuries of secondary succession in pristine forests. Examination of soil surfaces created by different windthrow events of known or estimated age; Development of windthrow mounds and soil horizons; Change in soil on an ecosystem basis; Mechanisms of change.

Assesses the soil respiration in pits and mounds after an experimental forest blowdown at the Harvard Forest Long-Term Ecological Research site in Massachusetts. Soil disturbance in temperate forests by uprooting of trees; Comparison between area-weighted soil respiration estimate and control measurements; Measurements from undisturbed plots.