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Wind is the leading disturbance agent in European forests, and the magnitude of wind impacts on forest mortality has increased over recent decades. However, the atmospheric triggers behind severe winds in Western Europe (large‐scale cyclones) differ from those in Southeastern Europe (small‐scale convective instability). This geographic difference in wind drivers alters the spatial scale of resulting disturbances and potentially the sensitivity to climate change. Over the 20th century, the severity and prevalence of cyclone‐induced windstorms have increased while the prevalence of atmospheric instability has decreased and thus, the trajectory of Europe‐wide windthrow remains uncertain. To better predict forest sensitivity and trends of windthrow disturbance we used dendrochronological methods to reconstruct 140 years of disturbance history in beech‐dominated primary forests of Central and Eastern Europe. We compared generalized linear mixed models of these disturbance time series to determine whether large‐scale cyclones or small‐scale convective storms were more responsible for disturbance severity while also accounting for topography and stand character variables likely to influence windthrow susceptibility. More exposed forests, forests with a longer absence of disturbance, and forests lacking recent high severity disturbance showed increased sensitivity to both wind drivers. Large‐scale cyclone‐induced windstorms were the main driver of disturbance severity at both the plot and stand scale (0.1–∼100 ha) whereas convective instability effects were more localized (0.1 ha). Though the prevalence and severity of cyclone‐induced windstorms have increased over the 20 century, primary beech forests did not display an increase in the severity of windthrow observed over the same period. Plain Language Summary: Two main atmospheric patterns are driving European windthrow with large‐scale winter storms being more prevalent in Western Europe and summer thunderstorm‐generated winds being more prevalent in Eastern Europe. In central Europe, most forests display a mixed‐severity disturbance regime indicating that both large‐ and small‐scale disturbances are occurring. However, few studies have been conducted looking at the prevalence of large‐scale winter windstorms and small‐scale summer thunderstorms. Here we found evidence for both, but recently large‐scale winter windstorms have had a greater impact. Key Points: Windstorms and convective instability drive primary forest windthrow damageTopographic exposure and time and severity of last disturbance moderate windthrowWindstorms create higher severity windthrow than convective instability [ABSTRACT FROM AUTHOR]

Remote sensing-based models are the most viable means of collecting the high-resolution spatially distributed estimates of evaporative water loss needed to manage irrigation and ensure the effective use of limited water resources. However, due to the unique canopy structure and configuration of vineyards, these models may not be able to adequately describe the physical processes driving evapotranspiration from vineyards. Using data collected from 2014 to 2016 as a part of the Grape Remote sensing Atmospheric Profile and Evapotranspiration Experiment (GRAPEX), the twofold objective of this study was to (1) identify the relationship between the roughness parameters, zero-plane displacement height (do) and roughness length for momentum (zo), and local environmental conditions, specifically wind direction and vegetation density and (2) determine the effect of using these relationships on the ability of the remote sensing-based Two-Source Energy Balance (TSEB) model to estimate the sensible (H) and latent (λE) heat fluxes. Although little variation in do was identified during the growing season, a well-defined sigmoidal relationship was observed between zo and wind direction. When the output from a version of the TSEB model incorporating these relationships (TSEBVIN) was compared to output from the standard model (TSEBSTD), there were large changes to the roughness parameters, particularly zo, but only modest changes in the turbulent fluxes. When the output from TSEBVIN was compared to that of a version using a parameterization scheme representing open canopies (TSEBOPN), the mean absolute difference between the estimates of do and zo were 0.44 m and 0.25 m, respectively. While these values represent differences in excess of 45%, the turbulent fluxes differed by just 13 W m−2 or 10%, on average. The results suggest that the TSEB model is largely insensitive to changes in the roughness parameters for the range in roughness values evaluated in this study. This also suggests that the requirement for highly accurate roughness values has limited utility in the application of the TSEB model in vineyard systems. Since there is no significant advantage to using the more complex TSEBOPN and TSEBVIN models, it is recommended that the standard model be used. [ABSTRACT FROM AUTHOR]

The unique vertical canopy structure and clumped plant distribution/row structure of vineyards and orchards creates an environment that is likely to cause the wind profile inside the canopy air space to deviate from how it is typically modelled for most crops. This in turn affects the efficiency of turbulent flux exchange and energy transport as well as their partitioning between the plant canopy and soil/substrate layers. The objective of this study was to evaluate a new wind profile formulation in the canopy air space that explicitly considers the unique vertical variation in plant biomass of vineyards. The validity of the new wind profile formulation was compared to a simpler wind attenuation profile that assumes attenuation through a homogeneous canopy. We evaluated both attenuation models using measurements of wind speed in a vineyard interrow, as well as turbulent flux estimates retrieved from a two-source energy balance model, which uses land surface temperature as the key boundary condition for flux estimation. This is relevant in developing a robust remote sensing-based energy balance modelling system for accurately monitoring vineyard water use or evapotranspiration that can be applied using satellite and airborne imagery for field-to-regional scale applications. These tools are needed in intensive agricultural production regions with arid climates such as the Central Valley of California, which experiences water shortages during extended drought periods requiring an effective water management policy based on robust water use estimates for allocating water resources. Results showed that the new wind profile model improved sensible heat flux estimates (RMSE reduction from 42 to 35 W m - 2 ) when the vine canopy is in early growth stage resulting in a strongly clumped canopy. [ABSTRACT FROM AUTHOR]

To explore the interactive effects of wind and light on growth and morphogenesis, poplar saplings were subjected to two different levels of wind and light. Morphogenesis, growth, water relations and gas exchange were examined in a factorial experiment. The results showed that wind reduced both shoot height and root growth but did not affect shoot diameter or root/shoot ratio, while light promoted both shoot and root growth, and the root/shoot ratio. However, light and wind consistently increased stem taper. Wind and light reduced leaf water potential and increased stem xylem cavitation at midday. Lateral shade decreased root and stem hydraulic conductance, while wind reduced stem hydraulic conductance without influencing root hydraulic conductance. Wind and light reduced the vulnerability of poplar saplings to xylem cavitation. Lateral shade strongly reduced the CO2 assimilation rate and stomatal conductance. Wind reduced the assimilation rate at midday under full sunlight. In summary, both light and wind increased stem taper, although the two environmental factors had opposite effects on the growth of poplar saplings. Lateral shading reduced the growth of shoots and roots of poplar saplings by restricting assimilation, and light promoted greater allocation of carbon to roots than to shoots, and to a lower rather than upper portion of the stem, leading to increased root/shoot ratio and stem taper. At the sapling stage, wind reduced shoot height and root growth primarily by interrupting water balance, and also induced thigmomorphogenic responses, such as increased taper. Finally, lateral shading did not suppress the thigmomorphological responses to wind. [ABSTRACT FROM AUTHOR]

1. Wind is an important abiotic factor that influences an array of biological processes, but it is rarely considered in studies on plant--herbivore interactions. 2. Here, we tested whether wind exposure could directly or indirectly affect the performance of two insect herbivores, Plutella xylostella and Pieris brassicae, feeding on Brassica nigra plants. 3. In a greenhouse study using a factorial design, B. nigra plants were exposed to different wind regimes generated by fans before and after caterpillars were introduced on plants in an attempt to separate the effects of direct and indirect wind exposure on herbivores. 4. Wind exposure delayed flowering, decreased plant height and increased leaf concentrations of amino acids and glucosinolates. 5. Plant-mediated effects of wind on herbivores, that is effects of exposure of plants to wind prior to herbivore feeding, were generally small. However, development time of both herbivores was extended and adult body mass of P. xylostella was reduced when they were directly exposed to wind. By contrast, wind-exposed adult P. brassicae butterflies were significantly larger, revealing a trade-off between development time and adult size. 6. Based on these results, we conducted a behavioural experiment to study preference by an avian predator, the great tit (Parus major) for last instar P. brassicae caterpillars on plants that were exposed to either control (no wind) or wind (fan-exposed) treatments. Tits captured significantly more caterpillars on still than on wind-exposed plants. 7. Our results suggest that P. brassicae caterpillars are able to perceive the abiotic environment and to trade off the costs of extended development time against the benefits of increased size depending on the perceived risk of predation mediated by wind exposure. Such adaptive phenotypic plasticity in insects has not yet been described in response to wind exposure. [ABSTRACT FROM AUTHOR]

The response of four trees in a Scots pine ( Pinus sylvestris L.) plantation to wind loading was studied using time series decomposition methods. For this purpose, wind speed and stem displacement time series recorded on a windy day were divided into intervals adjusted according to stem displacement. The real wind load acting on the sample trees during the intervals was estimated by the momentum flux at canopy top. To identify components in wind-induced stem displacement that are correlated with the wind, wavelet coherence was calculated. Results from these calculations indicate that the trees mainly responded to wind components with periods longer than their damped fundamental sway periods. Therefore, stem displacement data were decomposed into non-oscillatory and oscillatory components as well as noise using singular spectrum analysis. Results from singular spectrum analysis demonstrate that with increasing momentum flux, the importance of oscillatory components in the stem displacement time series decreases whereas the importance of non-oscillatory displacement components increases. The decreasing importance of the oscillatory components suggests that wind loading in the range of the damped fundamental sway period of the trees is inefficient and insignificant for total tree movement under non-destructive wind conditions. Consequently, there was no evidence of the occurrence of resonance effects between wind and tree response. [ABSTRACT FROM AUTHOR]

Large-eddy simulation of atmospheric flow is combined with golf ball trajectory modeling that incorporates local plant canopy information to predict the trajectory of a golf shot at any hole on a golf course in a variety of wind conditions. The model is applied to examine golf shots on hole 12 of the Augusta National Golf Club, which is particularly well known for its wind-induced difficulty. The results indicate that the tree canopies around this hole play a significant role in golf ball trajectories and also induce a strong directional sensitivity on the landing spot of the ball for this hole. [ABSTRACT FROM AUTHOR]

In nature, plants regularly interact with herbivores and with wind. Herbivores can wound and alter the structure of plants, whereas wind can exert aerodynamic forces that cause the plants to flutter or sway. While herbivory has many negative consequences for plants, fluttering in wind can be beneficial for plants by facilitating gas exchange and loss of excess heat. Little is known about how herbivores affect plant motion in wind. We tested how the mass of an herbivore resting on a broad leaf of the tulip tree Liriodendron tulipifera, and the damage caused by herbivores, affected the motion of the leaf in wind. For this, we placed mimics of herbivores on the leaves, varying each herbivore's mass or position, and used high-speed video to measure how the herbivore mimics affected leaf movement and reconfiguration at two wind speeds inside a laboratory wind tunnel. In a similar setup, we tested how naturally occurring herbivore damage on the leaves affected leaf movement and reconfiguration. We found that the mass of an herbivore resting on a leaf can change that leaf's orientation relative to the wind and interfere with the ability of the leaf to reconfigure into a smaller, more streamlined shape. A large herbivore load slowed the leaf's fluttering frequency, while naturally occurring damage from herbivores increased the leaf's fluttering frequency. We conclude that herbivores can alter the physical interactions between wind and plants by two methods: (1) acting as a point mass on the plant while it is feeding and (2) removing tissue from the plant. Altering a plant's interaction with wind can have physical and physiological consequences for the plant. Thus, future studies of plants in nature should consider the effect of herbivory on plant-wind interactions, and vice versa. [ABSTRACT FROM AUTHOR]

In Boreal North America, management approaches inspired by the variability in natural disturbances are expected to produce more resilient forests. Wind storms are recurrent within Boreal Ontario. The objective of this study was to simulate wind damage for common Boreal forest types for regular as well as extreme wind speeds. The ForestGALES_BC windthrow prediction model was used for these simulations. Input tree-level data were derived from permanent sample plot (PSP) data provided by the Ontario Ministry of Natural Resources. PSPs were assigned to one of nine stand types: Balsam fir-, Jack pine-, Black spruce-, and hardwood-dominated stands, and, Jack pine-, spruce-, conifer-, hardwood-, and Red and White pine-mixed species stands. Morphological and biomechanical parameters for the major tree species were obtained from the literature. At 5 m/s, predicted windthrow ranged from 0 to 20%, with damage increasing to 2 to 90% for winds of 20 m/s and to 10 to 100% for winds of 40 m/s. Windthrow varied by forest stand type, with lower vulnerability within hardwoods. This is the first study to provide such broad simulations of windthrow vulnerability data for Boreal North America, and we believe this will benefit policy decisions regarding risk management and forest planning. [ABSTRACT FROM AUTHOR]

A transient state canopy-chamber was developed to monitor CO2 exchange of shrubland ecosystems. The chamber covered 0.64 m² and it was modular with a variable height. Several tests were carried out to check the potential errors in the flux estimates due to leakages and the environment modifications during the measurements inside the chamber. The laboratory leakages test showed an error below 1% of the flux; the temperature increases inside the chamber were below 1.3 °C at different light intensity and small pressure changes. The radial blowers inside the chamber created different wind speed at different chamber height, with faster speed at the top of the chamber and the minimum wind speed that was recorded at soil level, preventing detectable effects on soil CO2 emission rates. Moreover, the chamber was tested for two years in a semi-arid Mediterranean garrigue, identifying a strong seasonality of CO2 fluxes with the highest rates during spring and lowest rates recorded during the hot dry non-vegetative summer. [ABSTRACT FROM AUTHOR]

While uneven-aged silviculture may appear preferable to even-aged silviculture in terms of stand susceptibility to windthrow (major wind damage), the scientific evidence is equivocal on this issue, because the two systems do not operate over the same time frame. The goal of this study was to evaluate the windthrow susceptibility of even- and uneven-aged stands over a 100-year period. Susceptibility to windthrow of North American hardwood stands was evaluated by coupling a stand growth model (Forest Vegetation Simulator, or FVS) to stem windthrow probability equations from the literature. This coupling was straightforward given that FVS provides the diameter at breast height (DBH) of each tree within a stand over the simulation period. Windthrow susceptibility equations also use DBH to calculate stem windthrow probability. Our results show that average loss due to windthrow under uneven-aged management can be twice that observed under even-aged management at moderate wind severity for sugar maple-dominated stands. This result should be interpreted with caution because of the impossibility in our simulations of considering differences in tree form development between the two approaches. Nevertheless, this study clearly shows that even-/uneven-aged silviculture comparisons should be made on a long-term basis since uneven-aged stands are continuously susceptible to windthrow, while even-aged stands tend to be little affected by windthrow in their early developmental stages. [ABSTRACT FROM AUTHOR]

Since the 1950s, wind has represented one of the main disturbances to forest ecosystems in Europe, causing an increase in the frequency and amount of trees uprooted or broken by wind. Such phenomenon has also increased the incidence of compression wood in the xylem of remnant trees, thus leading to a general decrease in timber quality. In this study, we aimed to determine how wind regime affects the incidence of compression wood by reconstructing its chronology at both inter- and intra-annual scale using dendroclimatic methods. Six silver fir stands at different elevations were selected in central Romania, and compression wood time series were obtained from both increment cores from standing trees and radial discs from felled trees. Wood-structure variables were statistically analyzed as time series, while fluctuations of wind frequency and speed over the period 1921-present were reconstructed based on meteorological data. The structural response of sampled trees to wind was assessed based on the annual fluctuation in the frequency and intensity of compression wood. Results showed that the incidence of compression wood in the time series was synchronized with the intensity of the wind, rather than its duration. Wind regime in December of the preceding calendar year was significantly correlated with the frequency of compression wood, whereas its intensity was significantly correlated with wind load of previous September. The response of cambium to the wind stimulus increased with distance from the tree collar, peaking in the section at the base of the crown. At a decennial scale, only high-intensity wind stress triggered structural responses in the studied trees. Wind effects on xylogenesis in the analyzed stands increased over the last decades as a consequence of the local forest management. A bet - ter understanding of the structural response of forest trees to wind regime may explain how individual and groups of trees compete for stability and can help to improve forest management strategies in windy regions. [ABSTRACT FROM AUTHOR]

* Background and Aims Storms can cause huge damage to European forests. Even pole-stage trees with 80-cm rooting depth can topple. Therefore, good anchorage is needed for trees to survive and grow up from an early age. We hypothesized that root architecture is a predominant factor determining anchorage failure caused by strong winds. * Methods We sampled 48 seeded or planted Pinus pinaster trees of similar aerial size from four stands damaged by a major storm 3 years before. The trees were gathered into three classes: undamaged, leaning and heavily toppled. After uprooting and 3D digitizing of their full root architectures, we computed the mechanical characteristics of the main components of the root system from our morphological measurements. * Key Results Variability in root architecture was quite large. A large main taproot, either short and thick or long and thin, and guyed by a large volume of deep roots, was the major component that prevented stem leaning. Greater shallow root flexural stiffness mainly at the end of the zone of rapid taper on the windward side also prevented leaning. Toppling in less than 90-cm-deep soil was avoided in trees with a stocky taproots or with a very big leeward shallow root. Toppled trees also had a lower relative root biomass - stump excluded - than straight trees. * Conclusions It was mainly the flexural stiffness of the central part of the root system that secured anchorage, preventing a weak displacement of the stump. The distal part of the longest taproot and attached deep roots may be the only parts of the root system contributing to anchorage through their maximum tensile load. Several designs provided good anchorage, depending partly on available soil depth. Pole-stage trees are in-between the juvenile phase when they fail by toppling and the mature phase when they fail by uprooting. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Forest wind damage occurs under the passage of strong intermittent wind gusts at tree level. In order to predict the probability of tree damage of a forest, a simple statistical wind speed model was developed and coupled to a tree swaying model. The wind model is based on a stochastic approach and on some universal characters of normalized wind statistics at canopy top. This model aims at generating high frequency (10 Hz) time series of the three wind velocity components at canopy top knowing only the wind intensity from a nearby meteorological station and the height and cumulative plant area index of the forest. Compared to field measurements and large-eddy simulations over different canopy structures and densities, the wind model was able to reproduce accurately the main features of canopy-top wind dynamics, in particular the signature of the mixing-layer type coherent eddy structures developing at canopy top. Coupled with a tree swaying model, the model has allowed to predict the probability of wind damage of forest following the windstorm intensity and duration, and following the main tree characteristics resulting from silvicultural scenarios. By responding to some weaknesses of existing mechanistic wind risk models, this simple wind–tree interaction model may represent the first step toward a new generation of mechanistic wind risk models based on a probabilistic approach. [ABSTRACT FROM AUTHOR]

The 3D measurement technique of terrestrial laser scanning (TLS) in forest inventories has shown great potential for improving the accuracy and efficiency of both individual tree and plot level data collection. However, the effect of wind has been poorly estimated in the error analysis of TLS tree measurements although it causes varying deformations to the trees. In this paper, we evaluated the effect of wind on tree stem parameter estimation at different heights using TLS. The data consists of one measured Scots pine captured from three different scanning directions with two different scanning resolutions, 6.3 mm and 3.1 mm at 10 m. The measurements were conducted under two different wind speeds, approximately 3 m/s and 9 m/s, as recorded by a nearby weather station of the Finnish Meteorological Institute. Our results show that the wind may cause both the underestimation and overestimation of tree diameter when using TLS. The duration of the scanning is found to have an impact for the measured shape of the tree stem under 9 m/s wind conditions. The results also indicate that a 9 m/s wind does not have a significant effect on the stem parameters of the lower part of a tree (<28% of the tree height). However, as the results imply, the wind conditions should be taken into account more comprehensively in analysis of TLS tree measurements, especially if multiple scans from different positions are registered together. In addition, TLS could potentially be applied to indirectly measure wind speed by observing the tree stem movement. [ABSTRACT FROM AUTHOR]

Premise of research. Propagule dispersal allows for the movement of plants across landscapes, establishing spatial structure and driving geographic range expansions and shifts. Because this movement is critical to the survival of plant populations and species, particularly during times of rapid and large-scale climate change, dispersal patterns and potential are important to consider when both exploring the past and predicting the future. Methodology. This study analyzes wind dispersal patterns in the genus Carpinus using field collections of dispersed fruits, sampled with high spatial resolution over two complete dispersal seasons and in multiple directions away from parent plants. These detailed collections, with direction-specific information, were then used in an observation-based migration simulation developed to identify the impact of dispersal patterns on population movement. Pivotal results. Field observations indicate short dispersal distances for the vast majority of fruits as well as a high level of directional asymmetry for both species of Carpinus. This asymmetry was intensified in the environment with an open vegetative structure, consistent with wind variability being the primary driver of dispersal distances. Migration simulations that incorporate local dispersal processes suggest low migration potential with a high level of directional asymmetry. Conclusions. Results stress the importance of rare long-distance-dispersal events in circumventing dispersal limitation in Carpinus and identify an important directional aspect to the process of wind dispersal. Because of the significant relationship found between dispersal patterns and wind directionality, the addition of a direction parameter to dispersal analyses and models could enhance the understanding of historic tree population dynamics, more accurately predict future movements, and inform conservation strategies of abiotically dispersed organisms. The enhanced asymmetry found in open forest structures makes it even more important to consider wind direction for predictive methods and conservation approaches as environments become more open due to forest clearing and other human disturbances. [ABSTRACT FROM AUTHOR]

This paper reports the processes by which a single-phase 3-D CFD model of hydrodynamics in a 17-km-long dam reservoir was developed, verified and tested. A simplified VOF model of flow was elaborated to determine the effect of wind on hydrodynamics in the lake. A hexahedral mesh with over 17 million elements and a k-ω SST turbulence model were defined for single-phase simulations in steady-state conditions. The model was verified on the basis of the extensive flow measurements (StreamPro ADCP, USA). Excellent agreement (average error of less than 10%) between computed and measured velocity profiles was found. The simulation results proved a strong effect of wind on hydrodynamics in the lake, especially on the development of the water circulation pattern in the lacustrine zone. [ABSTRACT FROM AUTHOR]

The aims of the investigation were to (i) quantify the changes in natural regeneration and stand structure, (ii) determine the role of deadwood in the process of regeneration following the disturbance, and (iii) determine the effect of disturbance severity on tree recruitment. The study was conducted in the Szast Protected Forest, which was established after a blowdown in 2002. The results showed that the trees were mainly wind-snapped. The basal area of the slightly disturbed stands increased over time. Herb cover increased, whereas moss cover decreased in 2011. The disturbance severity influenced the density of tree species regeneration, moss and herb ground cover, species diversity, average tree height, tree vitality, and damage caused by herbivores. The density of natural regeneration increased and new species became established after the disturbance. Scots pine (Pinus sylvestris L.) was the dominant tree species during the regeneration process except in the severely disturbed stand from which wood had been removed; in this case, birch was the dominant species. Wind disturbance increased species diversity and created a new forest with a particular species structure and trees that varied in age and height. The results of this study will be useful for foresters and policymakers to change the existing approaches to large-scale disturbances in the Polish forests. [ABSTRACT FROM AUTHOR]

Natural disturbances are among the most important factors that shape forest dynamics and forest landscapes. However, the natural disturbance regime of Norway spruce (Picea abies (L.) Karst.) forests in Europe is not well understood. We studied the disturbance regimes in three forest reserves in Bulgaria (Parangalitsa, Bistrishko branishte, and Beglika), which are representative of the range of conditions typical for P. abies ecosystems in central and southern Europe. Our data indicated that large-scale disturbances were most numerous in forests that were between 120 and 160 years old, those with unimodal diameter at breast height (DBH) distributions, and especially those located in vulnerable topographic settings. Wind disturbances ranged up to 60 ha, followed in one case by a 200 ha Ips typographus (Linnaeus, 1758) outbreak. Older forests and those with more complex structures (i.e., reverse-J DBH) were characterized by numerous small gaps but were also affected by a few larger disturbances. In some old-growth forests at highly productive sites, gaps could be so numerous that the long-term existence of old trees may become an exception. Over the past centuries, the natural range of variability of these Norway spruce forests in Bulgaria appears to have been shaped mostly by wind and bark beetle disturbances of various sizes. [ABSTRACT FROM AUTHOR]

Climate models predict increases in frequency and intensity of extreme environmental conditions, such as changes to minimum and maximum temperatures, duration of drought periods, intensity of rainfall/snowfall events and wind strength. These local extremes, rather than average climatic conditions, are closely linked to woody plant survival, as trees cope with such events over long lifespans. While the xylem provides trees with structural strength and is considered the most robust part of a tree's structure, it is also the most physiologically vulnerable as tree survival depends on its ability to sustain water supply to the tree crown under variable environmental conditions. Many structural, functional and biological tree properties evolved to protect xylem from loss of transport function because of embolism or to restore xylem transport capacity following embolism formation. How 'the new climate normal' conditions will affect these evolved strategies is yet to be seen. Our understanding of xylem physiology and current conceptual models describing embolism formation and plant recovery from water stress, however, can provide insight into near-future challenges that woody plants will face. In addition, knowledge of species-specific properties of xylem function may help guide mitigation of climate change impacts on woody plants in natural and agricultural tree communities. [ABSTRACT FROM AUTHOR]

Forest fragmentation creates forest edges, and the effect of those edges increases as the size of forest fragments decreases. Edge effects include changes to microclimatic conditions at the forest edge, which affect vegetation structure. No previous studies have directly tested the relationship between microclimate and vegetation structure (for instance, basal area, trees mean height, dead trees and damage trees) at the edge of forest fragments in the Atlantic Forest domain. We tested the following three hypotheses: (i) the microclimatic conditions differ between the edge and the interior of the forest, (ii) the forest structure differs between the edge and the interior of the forest and (iii) changes to microclimatic conditions at the forest edge negatively affect vegetation structure at the edges. Our results demonstrate that edge habitats are significantly more susceptible to strong winds, lower humidity and higher air temperatures than forest interiors. The microclimate may be considered the principal factor that explains the difference between the vegetation structure of the forest edge and the forest interior. Our results suggest that even large forest fragments in the Brazilian Atlantic Forest may be impacted by negative edge effects. [ABSTRACT FROM AUTHOR]

This paper describes the "Variation Guggenheim 3: Mirador de la Palmera" project in Daya Vieja (Alicante, Spain). This structure was inspired by the Guggenheim Museum in New York and was designed to protect a landmark palm tree from wind loads. This six-trunk palm tree was declared a monument by the Valencian government in 2012. The structure that now protects it appears to fly around the palm tree creating a helicoidal skywalk made of steel, while retrofitting the lateral trunks of the tree to protect them from collapse. An 18 m long straight beam starts on the top of this helix, and stretches towards a lookout point that offers a view of the whole village and its surroundings. The reduction of the visual impact of the structure on the tree was a major aim for the project design. The structural elements are as slender as possible to avoid visual obstruction of the tree. They are painted white, while the walkway steel corrugated plate is painted green in order to highlight its neat shape among the blur created by the apparent mess of bars of the supporting structure. The two main pillars of this pedestrian bridge were designed in steel and geometrically resemble trees. A ground penetrating radar analysis was performed to detect the palm root location and to decide the best foundation system. Slender cast-in situ steel-concrete micropiles along with a concrete pile-cap, raised some centimetres above the ground level, were used to reduce the damage to the roots. The projected pile-cap is a slender, continuous, circular ring whose geometry resembles that of a concrete bench. This structure was a finalist for the Architecture Awards for the best construction projects in 2010-2014, presented by the Diputacion de Alicante. [ABSTRACT FROM AUTHOR]

Effective sprinkler irrigation for cold protection requires an adequate and uniform water application rate (AR) in order to provide enough heat by freezing to compensate for heat loss by other means (i.e., evaporation). Several models have estimated the sufficient AR for cold protection as 6.35 mm/h; however, this value has little field verification. The objective of this study was to evaluate the effect of sprinkler type, sprinkler spacing, and water supply pressure under varied wind conditions on low quarter irrigation distribution uniformity (DUlq) and AR. Distribution uniformity was tested using four sprinkler types (Wade Rain WR-32 and Nelson: R33, R33LP, and R2000WF) assessed at three pressure levels (345, 276, and 207 kPa), two sprinkler spacings (14.6 and 12.2 m), and varied wind conditions ranging from low (0.2 m/s) to high (7.2 m/s). The interactions (1) sprinkler type--pressure, (2) sprinkler type--spacing, and (3) pressure-spacing resulted in a significant effect on DUlq and AR, as well as, the effect of wind speed, which was included as a covariate in the analysis. The R2000WF and WR-32 sprinklers at 345 kPa and 12.2 m spacing resulted in the highest uniformity, and by contrast, obtained the lowest AR when evaluated at 207 kPa and 14.6 m spacing. Overall DUlq did not differ drastically across the factors tested, whereas AR was substantially impacted by these factors. Current strawberry growers systems are set up at 14.6 m sprinkler spacing with 2-3 mm/h AR, which is substantially lower than the recommended AR of 6 mm/h and may result in inadequate cold protection. Using manufacturer recommended spacing with commonly used sprinklers (WR-32) would result in 4-5 mm/h AR depending on supply pressure available; hence, a greater level of cold protection. [ABSTRACT FROM AUTHOR]

Tropical tree species adapted to high wind environments might be expected to differ systematically in terms of stem allometry and life-history patterns, as compared with species found in less windy forests. We quantified height-diameter (H-D) allometries and relative size at onset of maturity ( RSOM) for rain forest tree and tree fern species native to Dominica, West Indies, an island that experiences some of the highest average wind speeds pantropically., H-D allometries for 17 Dominican angiosperm tree species were strongly concave on a log-log scale with asymptotic heights ranging from 9 to 32 m among species, averaging 25 m for canopy trees. H-D allometries for species-pooled data deviated strongly from recorded patterns for other tropical forest trees: asymptotic heights for trees in Dominica were 30-116% lower than those recorded for continental rain forest trees in Australia, South America, Africa and South-East Asia. In a subset of canopy trees sampled in steep, sheltered valleys, heights were 12-26% larger at a given diameter and approached those observed in other tropical regions, suggesting large phenotypic responses of H-D allometries to wind conditions., RSOM (quantified as the ratio of height at onset of reproduction to asymptotic maximum height) for Dominican angiosperm species was highly variable, ranging from 0.23 to 0.89 (mean 0.54), similar to patterns observed in Malaysia and Panama; very low RSOM values were estimated for two tree fern species. Pooling data from Dominica with published values from other tropical forests, we observed a significant negative correlation between RSOM and wood density., Synthesis. Our data suggest that wind regimes are a critical determinant of height-diameter (H-D) allometries of tropical trees at both the local and global scale. Although we found no evidence for a systematic differences in reproductive onset related to wind regime, RSOM was negatively correlated with species' wood density, suggesting that more shade-tolerant tree species show a longer period of gradually increasing reproductive allocation through ontogeny. [ABSTRACT FROM AUTHOR]

Field experiments were conducted in Central Taiwan for 2 crop seasons to examine the effect of non-coincidence flowering on the cross-pollination (CP) rate of maize at various distances. Four local maize hybrid varieties with different flowering dates and one local maize variety were sown as the pollen sources and recipient, respectively. All varieties were sown on the same day to simulate the real situation of coexistence in which adjacent fields are sown with different genetically modified (GM) and non-GM varieties of maize. The CP rate was <0.2% at a distance of 3 m for the first crop season when the flowering time for the recipient was 5 d later than that of the pollen source variety. The CP rate was <0.02% at all distances for the second season when the flowering time for the recipient was 7 d later than that of the pollen source variety. The CP rate was <1% at a distance of 0.75 m when the flowering time was 3 d later. However, varieties with closer synchrony may result in a CP rate of >1% at a distance of 1.5 m and <1% at 2.25 m. Temporal separation and isolation distances can work together in Taiwan with fragmented landscapes to minimize the adventitious presence of one crop with another. [ABSTRACT FROM AUTHOR]

* Premise of the study: The force of the wind is a significant hazard to the survival of trees and can affect tree morphology. However, the actual distribution of the stress that wind causes to a tree trunk is not well understood in spite of its expected importance to tree morphology. The uniform stress hypothesis (i.e., tree trunks take a form that equalizes the distribution of stress along the outer surface of the stem) has been tested indirectly as a model, placing high importance on the mechanical safety of a trunk, and rejected theoretically. But stress on a tree's trunk has not yet been measured directly. * Methods: Actual strains at the surface of the trunk of an isolated Larix kaempferi tree due to wind loads were measured at seven heights on the trunk for 1 yr. * Key results: During the measurement period, wind-induced stress was higher in the upper portions of the trunk than in the lower portions, regardless of wind speed, and the difference increased as wind speed increased. The deflection of the trunk recorded at each position was also larger in the upper portions than in the lower portions. * Conclusions: The results indicate that the upper portions of the trunk of an isolated Larix kaempferi tree are more susceptible to wind than are the lower portions. These results do not support the uniform stress hypothesis and suggest that another limitation (either mechanical or nonmechanical) acts on the morphology of the tree. [ABSTRACT FROM AUTHOR]

Many plants persist by resprouting after disturbance. However, the benefits of resprouting (survival) may be traded off against height growth and reproduction. Resources (total non-structural carbohydrates-TNC) that could be allocated to growth or reproduction are stored or mobilised to support resprouting. TNC may either be stored by accumulation where availability exceeds the requirements for growth, or by reserve formation when storage is at the expense of growth. Thus, the mechanism of storage and resource allocation may differ between good (R+) and poor (R−) resprouters in response to nutrient availability and disturbance regime. R+ species typically reserve resources to ensure a rapid resprouting response to disturbance. We test whether R+ and R− species in coastal forest, under chronic wind disturbance, differ in growth rates, biomass allocation, leaf traits, water relations and storage of TNC. Seedlings from three confamilial pairs of R+ and R− tree species were subjected to nitrogen addition, water stress and clipping (simulating herbivory) treatments under greenhouse conditions. R− species had greater height growth rates, larger specific leaf area, lower root mass ratio and lower root TNC than R+ species. These differences between R+ and R− species were maintained irrespective of the levels of nitrogen, water and clipping treatments. R+ species did not increase their TNC concentration under nutrient and water stress, indicating that TNC is stored by reserve formation. R+ species appeared to trade-off growth against storage, while R− species did not. In R+ species, reserve formation is likely a bet-hedging strategy against occasional strong selection events in addition to chronic wind stress. By trading off height growth for better resprouting ability, good resprouters may be able to persist at more frequently disturbed sites (e.g., dune crests and windward slopes), while poor resprouters that have faster height growth can dominate less disturbed sites. [ABSTRACT FROM AUTHOR]

Diaspore abscission determines many aspects of seed dispersal by wind. While there is yet no complete mechanistic framework for understanding abscission by wind, empirical studies to date have suggested that abscission generally (i) occurs above some threshold wind speed and (ii) depends on the drag force generated by the wind., We revisit these findings and formulate two alternative hypotheses for abscission mechanisms based on a simple model of a forced harmonic oscillator: large diaspore displacement [through a maximum deflection threshold, ( MDT)] and material fatigue [through a maximum cumulative stress threshold ( MCST)]. We use simulations of abscission events based on these hypotheses and experiments on diaspore abscission of three Patagonian grasses and a cosmopolitan herb to test the performance of two abscission functions differing in whether they have a threshold wind speed for abscission. We also quantify the effects of non-random diaspore abscission on dispersal distances using a well-tested model for seed dispersal by wind., Both the MDT and MCST hypotheses appear realistic and indicate that while the instantaneous wind speed determines abscission, the history of wind speeds experienced prior to the detachment from the plant also plays a role., An evaluation of abscission functions against simulated and experimental abscission data shows that while the presence of a threshold wind speed in theory appears unrealistic, in practice a threshold may appear to exist in high-wind-speed environments where all diaspores are blown off the plant before the abscission layer can develop sufficiently to break during lower wind speeds., Under non-random diaspore abscission, high-wind-speed events during otherwise calm periods increase long-distance dispersal ( LDD), thereby decreasing differences in dispersal distances between low- and high-wind-speed environments., Synthesis. We formulated two realistic mechanisms of diaspore abscission by applying concepts from materials science: large diaspore displacement and material fatigue. These reveal that the ambient wind speed 'history' experienced by a diaspore plays an important role in the timing of abscission and in the distance travelled, without any thresholds, and that the effect of the diaspore-wind interaction on LDD varies between environments with different wind speed regimes. [ABSTRACT FROM AUTHOR]

Non-native invasive plant species pose a serious threat to forest ecosystems around the world. Forest edges are associated with non-native invasive plants and forest interiors are often regarded as more resistant to invasion. The objective of this study was to determine if a large-scale wind dis-turbance facilitated the invasion of forest interiors by non-native invasive plant species. The northern portion of LaRue Pine Hills - Otter Pond Research Natural Area in the Shawnee National Forest of southern Illinois, was severely damaged by high winds during a powerful storm event on 8 May 2009. In the summer of 2011, 53 permanent research plots, as well as 20 additional plots located along roads that form the boundaries of the study site, were surveyed for the presence of 20 non-native invasive plant species. Only three of 53 interior plots (5.6%) contained invasive plant species (Lonicera japónica Lonicera maackii, and Rosa multiflora). Sixteen of 20 road plots contained a non-native invasive species (80%), and six species were identified (Dioscorea oppositifolia, Lactuca serriola, Lonicera maackii, Microstegium vimineum, Rosa multiflora, and Sorghum halepense). These findings indicate that wind damage does not appear to have facilitated invasion of forest interiors in the first two years following the storm. The spatial distribution of non-native invasive plants in the study area fits the pattern of other studies conducted in southern Illinois with non-native invasive plants associated primarily with forest edges and diminishing in the forest interior despite the apparent opportunity for establishment following the wind disturbance. [ABSTRACT FROM AUTHOR]

Windthrow is all too often looked at as an exceptional, catastrophic phenomenon rather than a recurrent natural disturbance that falls within the spectrum of chronic and acute effects of wind on forests, and that drives ecosystem patterns and processes. This paper provides an integrative overview of the nature, contributing factors and impacts of wind-caused disturbance in forests, including its effects on trees, stands, landscapes and soils. Windthrow is examined through the integrating concepts of: the capacity of trees for acclimative growth, the limitation of acclimative growth under inter-tree competition, the recurrent nature of severe weather, how terrain and soil conditions affect local stand vulnerability and the effect of recurrent windthrow on stand dynamics and soils. Windthrow management should take place within a framework of general risk management, with evaluation of the likelihood, severity and potential impacts of wind damage considered – with reference to the broad and specific aims of management. There is much to be gained from interdisciplinary communication about the nature and consequences of recurrent wind damage. There are opportunities for climatologists, engineers, ecologists, geomorphologists and others to develop integrative process models at the tree, stand and landscape scales that will improve our collective understanding, and inform management decision-making. [ABSTRACT FROM PUBLISHER]

Vigor is important in rubber tree cropping because of its association with early latex exploitation, resistance to wind breakage and wood production. The objective of the present study was to assess the vigor stability of 25 rubber tree genotypes in the pre- and post-tapping phases using different methods. A randomized block design was used with three replications and six plants per plot. Seven annual trunk girth increments were used in the pre-tapping and six in the post-tapping phases. Stability was assessed by the methods by Wricke, Eberhart and Russell, Lin and Binns, and the AMMI statistical model (Model Additive Main Effects and Multiplicative Interaction). The association among the different stability parameters ωι, $$ \hat{S}_{di}^{2} $$, Pi, and IPCA 1 was verified by the Spearman correlation. Joint ANOVA showed highly significant effects for genotypes, years, and genotypes × years interaction in the two phases. In the pre-tapping phase, the IAC 311 genotype was stable in all the methods and in the post-tapping presented stability in Eberhart and Russell, Wricke, and AMMI. In the post-tapping phase, the IAC 312 genotype was stable in Eberhart and Russell, AMMI and Lin and Binns. While in the pre-tapping the correlations were positive and significant among all the parameters, in the post-tapping it only occurred between ωι with $$ \hat{S}_{di}^{2} $$ and ωι with IPCA 1. In the stability assessment of rubber tree vigor, the association among the methods depended on the assessment period. Stability methods based on different principles can show agreement in identifying stable genotypes in rubber tree vigor. The tapping procedure affected vigor stability of rubber trees. [ABSTRACT FROM AUTHOR]

Wind damage in Japan is mainly caused by typhoons (i.e., tropical cyclones), which are characterized by intensive heavy rainfall and strong winds. In this study, we conducted tree-pulling experiments on two sites to find out whether rapidly supplied water on the soil would affect stability of root anchorage of hinoki (Chamaecyparis obtuse (Sieb. Et Zucc.) Endl.), as expected. For the experiments, we first supplied several quantities of water around the target trees, and then they were pulled down using a wire winch. On study site 1 (Kamiatago experimental forest), we applied general tree-pulling experiments (no water supply) in 2008 and six different irrigation treatments around the target trees in 2009. On study site 2 (Chiyoda experimental forest), we applied one irrigation treatment in 2009. As a result, five trees were uprooted and two were broken in 2008, and all nine trees were uprooted in 2009 on study site 1, regardless of irrigation treatment. On study site 2, two trees pulled down after 4 h of water supply were ruptured at the stem base, opposite to two trees pulled down immediately after supplying water. The water content below the root plate significantly affected root anchorage and more specifically, the maximum turning moment, stem angle at the maximum force, and stiffness index. Moreover, water inside the root plate increased root anchorage at the beginning of a tree failure process. However, it also reduced the root plate area of the hinge side. Conversely, high water content below the root plate decreased root anchorage. [ABSTRACT FROM AUTHOR]

The dispersal capabilities of organisms play an important role in defining their ability to colonise new areas and to maintain populations in fragmented or dynamic environments. For invasive organisms that undergo passive, wind-assisted dispersal the speed and spatial structure of unfolding epidemics are largely determined by wind conditions in the area under invasion. For the conservation of endangered species, local wind conditions influence the ability of wind-dispersing organisms to survive habitat fragmentation. Therefore, models of wind-assisted dispersal are required that capture the dynamics of local wind conditions and the effect of prevailing winds on resulting spread. We tested the ability of a simple two-dimensional kernel to encapsulate these dynamics and to make accurate predictions of spread based only on wind data and the physical characteristics of the organism in question. The kernel uses a mixture of von Mises distributions to capture the anisotropic nature of local wind conditions and a mechanistically parameterised kernel to describe dispersal distance. Comparisons with a mechanistic model showed that this kernel was able to provide a good estimate of spread and provide a far more informative and useful prediction than an isotropic equivalent. [Copyright &y& Elsevier]

Abstract: This paper deals with the dynamic responses of three plantation-grown Scots pine trees to turbulent wind loading. Although individual tree movement was complicated and irregular in the analyzed wind speed range (hourly mean wind speeds at canopy top below 4ms−1), results from the cross-wavelet transform and wavelet coherence calculations demonstrate that wind-induced tree displacement strongly covaried with wind loads exerted on the trees by coherent structures. These wind loads caused largest tree displacements in the along wind direction as well as in the across wind direction. The absorption of energy available from wind loads in the range of the damped natural sway frequencies of the sample trees’ stems was of minor importance for tree displacement. The application of the bi-orthogonal decomposition provided insight into the resulting modal deformations of the sample trees’ stems. Based on measured stem displacement data, the mean mode shapes for the first eight stem vibration modes (four mean mode shapes in along wind direction and four mean mode shapes in across wind direction) could be identified. The shapes of these modes were quite similar to the normal mode shapes of a clamped-free beam. For the analyzed wind speed range it is shown that most of the energy absorbed by the trees from the wind is dissipated by tree sway in the first mode. Higher vibration modes localized on the sample trees’ stems were only of minor importance for the trees’ responses to wind. [Copyright &y& Elsevier]

Abstract: Wind routinely topples trees during storms, and the likelihood that a tree is toppled depends critically on its allometry. Yet none of the existing theories to explain tree allometry consider wind drag on tree canopies. Since leaf area index in crowded, self-thinning stands is independent of stand density, the drag force per unit land can also be assumed to be independent of stand density, with only canopy height influencing the total toppling moment. Tree stem dimensions and the self-thinning biomass can then be computed by further assuming that the risk of toppling over and stem maintenance per unit land area are independent of stand density, and that stem maintenance cost is a linear function of stem surface area and sapwood volume. These assumptions provide a novel way to understand tree allometry and lead to a self-thinning line relating tree biomass and stand density with a power between −3/2 and −2/3 depending on the ratio of maintenance of sapwood and stem surface. [Copyright &y& Elsevier]

Effects of a catastrophic blowdown event in northern Minnesota, USA were assessed using field inventory data, aerial sketch maps and satellite image data processed through the North American Forest Dynamics programme. Estimates were produced for forest area and net volume per unit area of live trees pre- and post-disturbance, and for changes in volume per unit area and total volume resulting from disturbance. Satellite image-based estimates of blowdown area were similar to estimates derived from inventory plots and aerial sketch maps. Overall accuracy of the image-based damage classification was over 90%. Compared to field inventory estimates, image-based estimates of post-blowdown mean volume per unit area were similar, but estimates of total volume loss were substantially larger, although inaccessibility of the most severely damaged inventory plots may have depressed the inventory-based estimate. This represents the first application of state model differencing to storm damage assessment. The image-based procedure can be applied to historical archives of satellite imagery and does not require pre-disturbance field inventory data. [ABSTRACT FROM AUTHOR]

Root distribution and characteristics were investigated on a 70-year-old Tamarix taklamakanensis individual through uprooting. Rooting depth was restricted by water table, and root morphology adapted to resist the wind movement associated with shallow rooting. Root systems had more structural root mass and length on the leeward side than the windward side of the tree relative to the prevailing wind direction. Additional resistance to wind bending can occur as a result of increased thickening of the lower stem along the axis of the prevailing wind direction, and in T. taklamakanensis, this thickening is greater on the lee side of the stem. We conclude that increased root distribution and thickening of the lower stem on the leeward are an important strategy for T. taklamakanensis in response to wind action in the hinterland of Taklimakan Desert. [ABSTRACT FROM AUTHOR]

The article describes how the authors tested three shade tree species to examine the effects of pruning on drag and bending moment of shade trees. It notes arborists' assumptions that pruning can help reduce the risk of tree failure by reducing the pressure exerted on trunks by wind. It also discusses the drag-induced bending moment as well as tree morphometric data for Freeman maple, swamp white oak and shingle oak.

This paper reviews the current status of mechanistic models for wind damage risk assessment, describing model structure, applicability, validation and current limitations. We focus particularly on the hybrid mechanistic/empirical models GALES and HWIND, which have been designed for calculating wind damage risk at the stand level within uniform forests and which are the most widely adopted models within the research community. These models have been integrated with different methods for predicting the local wind climate in order to calculate the probability of wind damage in a number of different countries. We also discuss ongoing modelling work and proposals for future development in order to deal with complex forest structures and to predict the wind damage risk of individual trees within stands through the integration of mechanistic risk models with forest growth and yield models within a geographical information system framework. This kind of model integration will enable spatial representation of tree lists and damage propagation and allow managers to evaluate the effect of different harvesting and thinning scenarios on the risk of windthrow of both stands and individual trees within a stand. [ABSTRACT FROM AUTHOR]

This study presents a predictive dynamic model developed to analyse the mechanical response of trees submitted to a turbulent airflow. This finite-element model integrates a three-dimensional description of tree architecture and is driven by fluctuating drag forces applied on all parts. For validation purposes, instantaneous wind velocities and wind-induced stem displacements of two trees were recorded in a mature Maritime pine stand (Pinus pinaster) at several heights. The tree geometrical and physical characteristics were measured to describe their architecture. No model parameter was adjusted. Tree motions appear to be driven by wind pulses reflecting turbulence intermittency. No evidence is found for resonant behaviour. In the mean wind direction, the simulated oscillations agree well with the measured time series. The underestimation of tree movement in the cross-stream direction outlines the importance of torque behaviour on the predictive accuracy of the model. The mechanical transfer functions of the modelled trees show vibration peak frequencies very similar to the measured ones. At higher frequencies, the simulated damping appears overestimated, with the set of parameters used. The model provides a sound basis to further investigate the influence of tree aerial architecture and turbulence structure on tree stability to wind. [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]