Catastrophic Windthrow Research Articles

Quantitative analysis of factors influencing damage to old-growth hemiboreal stands as a result of a catastrophic windthrow, based on remote sensing and merged data

The consequences of a catastrophic windthrow in a old-growth hemiboreal stands of the Kologrivsky Forest Reserve were investigated. The degree of damage to tree stands was assessed by interpretation of the Sentinel-2 satellite images. Data from the GBIF portal, SRTM global terrain height models, and tree stand heights were used for the quantitative analysis of factors affecting the presence of wind damage. It was found that tree stands on an area of 277.9 hectares (40.5% of the entire massif) were damaged by windthrow. The results of the analysis of height models and regression models showed that spruce stands are more vulnerable to wind damage, as well as stands of greater height or those growing at higher elevation on the ground.

Quantitative Analysis of Factors Influencing Damage to Old-Growth Hemiboreal Stands as a Result of a Catastrophic Windthrow, Based on Remote Sensing and Merged Data

Quantitative Analysis of Factors Influencing Damage to Old-Growth Hemiboreal Stands as a Result of a Catastrophic Windthrow, Based on Remote Sensing and Merged Data

Streamflow response to catastrophic windthrow and forest recovery in subalpine spruce forest

Windstorms account for about half of forest disturbances in Europe and are considered as drivers of natural regeneration of plant species, accompanied by significant changes in hydrological and soil moisture conditions. Our study aims to identify the effects of deforestation caused by catastrophic windthrow on streamflow characteristics in conjunction with meteorological and soil moisture data. The research was conducted in the headwater catchment (34.4 km2), in the Western Tatra Mountains, Poland. Streamflow characteristics such as average, high, and low flows, coefficient of variability, as well as flashiness of the streamflow (Richard-Baker Flashiness Index) and drought frequency (Standardised Streamflow Index) were calculated in the pre-event (2007–2013) and post-event (2013–2020) periods. The analysis was carried out for calendar months, seasons of the year, as well as for the growing and non-growing seasons. Wavelet Analysis was applied to track the changes in streamflow time series in relation to meteorological conditions (precipitation, air temperature) and remotely sensed soil wetness in the root zone. Principal Components Analysis was applied in order to identify the major drivers of the observed variability. The results revealed increasing low (+14%), average (+8%), and maximum monthly flows (16%) in the post-event period. The most significant increase in low flows (+47%, p<0.1) occurred during snowmelt. The increase in average (+31%, p<0.1) and high flows (+90%, p<0.05) occurred during mid-winter thaws. The frequency of hydrological droughts decreased by up to 36% in the post-event period, despite similar climatic conditions. The flashiness of streamflow increased during mid-winter thaws and rainfall events. The short-scale periodicity in streamflow increased in the post-event period. The results revealed the presence of 3-month periodicity in the root zone soil wetness associated with long-term soil water storage, which decreased after the catastrophic windthrow. Streamflow in the post-event period became strongly coupled with precipitation and root zone soil wetness at short period bands (∼3–16 days) in hydrologically active season. Short-scale correlation between precipitation and streamflow was decreasing with the gradual succession of vegetation.

Wood decomposition, carbon, nitrogen, and pH values in logs of 8 tree species 14 and 15 years after a catastrophic windthrow in a mesic broad-leaved forest in the East European plain

There are limited studies of decomposition of coarse woody debris (CWD) in natural conditions of multi-species mesic broad-leaved forests. We investigated 49 lying logs of 7 angiosperm and 1 gymnosperm species 14 and 15 years after a mass windthrow in an old-growth broad-leaved forest. We observed high heterogeneity of logs in terms of decomposition stages: up to 4 stages in one transverse disk and up to 5 stages in longitudinal fragments of one log. Due to the high heterogeneity of logs, we investigated traits of wood samples rather than individual logs. Bulk density, carbon and nitrogen concentrations, and pH values were examined for 188 CWD samples of 8 species at 5 decomposition stages (from stage 1 least to stage 5 most decayed wood) and 24 control samples of live trees (3 replicates for each species; zero stage of decay). Changes of deadwood volume, carbon and nitrogen stocks over 14 and 15 years after the windthrow were estimated by re-surveying transects established in 2010. From the first to the fifth decay stage, the mean CWD density decreased for all species and averaged 54 ± 16 kg m−3 (SD) at the 5th stage of decay. Regarding decomposition rates, the tree species were arranged in descending rate from diffuse-porous (Populus tremula, Betula pendula, Tilia cordata, and Acer platanoides) to ring-porous (Ulmus glabra, Fraxinus excelsior, and Quercus robur) angiosperms and the coniferous Picea abies was after the diffuse-porous species series and before the ring-porous species. Carbon concentration ranged from 39 to 54 %, but did not change significantly during decomposition (mean value for all species in all decay stages was 45.8 ± 2.5 %). Nitrogen concentration (percentage of dry mass) increased with increasing decay stage and the mean value was 0.2 ± 0.1 % at the zero stage and 0.9 ± 0.5 % at the last decay stage. Despite the increase in N concentration, the mass N per volume decreased during decomposition for all samples considered together due to a significant decrease in wood density. The change in C/N values during deadwood decay reflected the transition of organic matter from the CWD to the SOM (soil organic matter) in forest ecosystems: the ratio C/N varied from 829 (Picea, zero stage) to 16 (Ulmus, last stage) with the mean values 286 ± 149 and 75 ± 45 at the zero and the last stages, respectively. We observed a quadratic trend in the variation of wood pH values by stages: pH mainly decreased from the initial values to the minimum in the middle stages of decay, and then increased in the advanced stages. The mean deadwood volume in the surveyed plots decreased 1.4-fold in the 14–15 years after the windthrow, but the mean stocks of carbon and nitrogen decreased 3 and 2-fold, respectively. Over time, the different decomposition rate of fallen logs leads to a decrease in the proportion of C and N stored in diffuse-porous species at the expense of an increase in this proportion in ring-porous species. This result is worth considering in a carbon management strategy: planting, maintaining stands, and retaining deadwood of ring-porous species, such as Quercus, Ulmus and Fraxinus, promote relatively long-term carbon storage.

The 30-year impact of post-windthrow management on the forest regeneration process in northern Japan

The frequency and intensity of typhoons are expected to increase over time due to climate change. These changes may expose forests to more windthrow in the future, and increasing the resilience of hemiboreal forests through forest management after windthrow is important. Here, we quantified forest structure recovery using aerial photos and light detection and ranging (LiDAR) data after catastrophic windthrow events. Our aims are to test the following three hypotheses: (1) forest structure will not recover within 30 years after windthrow, (2) forest recovery will be affected not only by salvaging but also pre-windthrow attributes and geographical features, and (3) various post-windthrow management including salvaging will drastically alter tree species composition and delay forest recovery. Our results revealed that hypothesis (1) and (2) were supported and (3) was partially supported. The ordination results suggested that more than 30 years were needed to recover canopy tree height after windthrow in hemiboreal forests in Hokkaido, Japan. Salvage logging did not delay natural succession, but it significantly decreased the cover ratio of conifer species sites (0.107 ± 0.023) compared with natural succession sites (0.310 ± 0.091). The higher the elevation, the steeper the site, and the higher the average canopy height before windthrow, the slower the recovery of forest stands after windthrow and salvaging. Scarification and planting after salvage logging significantly increased the number of canopy trees, but those sites differed completely in species composition from the old growth forests. Our study thus determined that the choice and intensity of post-disturbance management in hemiboreal forests should be carefully considered based on the management purpose and local characteristics.

Tree stand assessment before and after windthrow based on open-access biodiversity data and aerial photography

The ground-based surveys of areas affected by storms might be difficult or even impossible because of the limited ability to move within the damaged area. Therefore, this work was aimed to estimate storm damage based on aerial photography and open biodiversity data available via the Internet. The study was carried out in the old-growth hemiboreal forests of the Kologrivsky Forest State Nature Reserve (Kostroma Region, Russia), which was affected by a catastrophic windthrow caused by a storm on 15.05.2021. The sampling area was 100 000 m2. We used our previous ground-survey studies and open-access biodiversity data available through the Global Biodiversity Information Facility for describing the forest stands composition before the catastrophic event. The aerial photography data were used for estimating tree stands damages after the windthrow. For remote data collecting, we used an unmanned aerial vehicle – quadrocopter DJI Phantom 4. Agisoft Metashape software was used for aerial photographs processing. The obtained photogrammetric digital elevation model (DEM) and orthophoto-mosaic were processed with QGIS software. Damaged areas were detected automatically based on the DEM. Individual fallen trees were visually detected using the orthophoto-mosaic. We found before the windthrow the study area was covered by old-growth stands developed naturally over a long time. The stand structure was multi-layered and uneven-aged. The ontogenetic spectra of late-successional tree species Picea abies (hereinafter – spruce) and Tilia cordata (hereinafter – linden) were normal. The old-growth stands were heterogeneous before the windthrow: the canopy closed multi-layered and uneven-aged stands, decaying spruce stands and areas where spruce completely fell out and the tree stand was absent. In addition, old-growth linden stands were present. According to the obtained results, the stand structure was critically changed caused by the windthrow. The DEM-processing results showed the windthrow strongly damaged 33.1% stands in the study area. Using the orthophoto-mosaic, we visually detected 759 fallen trees. Among them, 82.9% were associated with strongly-damaged areas. According to the DEM classification, the rest of the visually detected fallen trees were in non-damaged areas and canopy gaps established before the windthrow. The analysis showed that these were less damaged areas with survived stands or groups of trees after the storm. Thus, our results showed that it is necessary to use both the DEM and the orthophoto-mosaic for more accurate estimates. Our exploratory analysis of different tree stand damages found that apparently, spruce stands were more affected by the storm than linden stands. It is explained by the different wind resistance of spruce and linden and differences in regrowth density and species composition in these stands.

Delay of growth release after a windthrow event and climate response in a light-demanding species (European larch Larix decidua Mill.)

Key messageLarch trees respond to stand opening with an approximately 4-year delay of growth, and low precipitation in July limits radial growth after a windthrow event.Precise cross-dating of disturbance events is crucial to understanding the functioning of forest stands, and may help explain ongoing ecological processes in a forest. Tree rings are very often used to reconstruct the history of disturbances and to study the response of trees to climatic factors. This study analyzed how quickly European larch can benefit from an abrupt change after catastrophic windthrow events and the extent of trees’ sensitivity to climate. The study is based on cores from 83 larch trees collected in a post-disturbance 100 ha plot established after a catastrophic windstorm in 2004 in the Slovakian High Tatras. Growth release was calculated from the percentage of growth change (PGC) measured in tree rings. The time lag between the disturbance event and release was related to tree diameter at breast height, tree age, and tree’s previous growth. The time lag between the year of the event and the year of growth reaction was 4.6 years on average (median 4 years) in a multi-aged group of trees. The climate analyses employed residual chronology. The new environmental conditions in the post-disturbance area have altered the trees’ growth reaction to climate; in particular, they show sensitivity to water deficit in July.

The intensity of slope and fluvial processes after a catastrophic windthrow event in small catchments in the Tatra Mountains

Strong wind events frequently result in creating large areas of windthrow, which causes abrupt environmental changes. Bare soil surfaces within pits and root plates potentially expose soil to erosion. Absence of forest may alter the dynamics of water circulation. In this study we attempt to answer the question of whether extensive windthrows influence the magnitude of geomorphic processes in 6 small second- to third-order catchments with area ranging from 0.09 km2 to 0.8 km2. Three of the catchments were significantly affected by a windthrow which occurred in December 2013 in the Polish part of the Tatra Mountains, and the other three catchments were mostly forested and served as control catchments. We mapped the pits created by the windthrow and the linear scars created by salvage logging operations in search of any signs of erosion within them. We also mapped all post-windthrow landslides created in the windthrow-affected catchments. The impact of the windthrow on the fluvial system was investigated by measuring a set of channel characteristics and determining bedload transport intensity using painted tracers in all the windthrow-affected and control catchments. Both pits and linear scars created by harvesting tend to become overgrown by vegetation in the first several years after the windthrow. The only signs of erosion were observed in 10% of the pits located on convergent slopes. During the period from the windthrow event in 2013 until 2019, 5 very small (total area <100 m2) shallow landslides were created. The mean distance of bedload transport was similar (t-test, p=0.05) in most of the windthrow-affected and control catchments. The mapping of channels revealed many cases of root plates fallen into a channel and pits created near a channel. A significant amount of woody debris delivered into the channels influenced the activity of fluvial processes by creating alternating zones of erosion and accumulation.

Recovery and allocation of carbon stocks in boreal forests 64 years after catastrophic windthrow and salvage logging in northern Japan

To mitigate the negative effects of climate change, it is necessary to conserve carbon stocks in forests. Typhoons fell many standing trees and generate a substantial amount of coarse woody debris (CWD). In boreal forests, CWD contributes to maintaining carbon stocks for a long time after a disturbance because the decomposition rate of CWD is relatively low. We know that salvage logging after a disturbance tremendously decreases the forest carbon stock over the short term after logging but know little about its long-term effects. We targeted a catastrophic windthrow caused by a super typhoon in 1954 in boreal forests in northern Japan and estimated the long-term effects of salvage logging after the windthrow on the above- and belowground carbon stocks by comparing old-growth forests with low damage from the super typhoon in 1954 or any subsequent typhoons (OG), forests damaged by the typhoon with remaining CWD (i.e., windthrow, WT), and forests damaged by the typhoon followed by salvage logging (WT + SL). The CWD carbon stock of decay class 5 (i.e., the most decayed CWD) in WT was significantly larger than that in OG and WT + SL, suggesting that the CWD in decay class 5 in WT had been generated by the typhoon 64 years ago, and the negative effect of salvage logging on the carbon stock still remains apparent in the CWD carbon stock of decay class 5. The carbon stock of the organic (O) layer in WT was larger than that in WT + SL, probably because of three factors: (1) the slower decomposition rate of fallen leaves and twigs of conifers than broadleaves, as conifer litter is abundant in WT; (2) greater carbon transition from the CWD to the O layer in WT; and (3) the occurrence of a lower decomposition rate in the O layer in WT. However, the total carbon stock in WT + SL has almost recovered to the level of that in WT within the last 64 years. The carbon stocks of broadleaves that grew rapidly after the disturbance and the newly accumulated dead trees generated throughout the stand developmental process might contribute to the recovery of carbon stock in WT + SL. These results indicate that salvage logging affects the allocation of carbon in the forest even after 64 years after a catastrophic windthrow, although there was no large difference in total carbon stock.

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

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

The first record of catastrophic windthrow in boreal forests of South Sakhalin and the South Kurils (Russia) during October 2015 tropical cyclones

The first record of catastrophic windthrow in boreal forests of South Sakhalin and the South Kurils (Russia) during October 2015 tropical cyclones

Long‐term data on forest regeneration after catastrophic windthrow in Tomakomai, Hokkaido, northern Japan

AbstractTyphoon No. 15 in 1954 (Marie) caused catastrophic windthrow in Hokkaido, northern Japan. The Tomakomai District of the National Forest was one of the forests severely damaged. A study site was established in a stand of the National Forest within the jurisdiction of the Iburi East District Forest Office. The stand was located on the eastern slope of Mt. Tarumae at an elevation of approximately 300–310 m a.s.l. at an angle of approximately 5°. Two belts sized 4 m × 40 m, crossing at right angles at the center, were established within the site in 1957, and censuses on regeneration were conducted in 1957, 1970, 1973, 1978, 1983, 1990, 1996, 2001, 2006, 2011, and 2016. All stems of coniferous tree species (height ≥ 10 cm) that regenerated in the belts were marked. For broadleaved tree species, all stems with height ≥ 1.3 m were marked in 1957–1990, but stems with height ≥ 10 cm were marked after 1996. Height was measured for all marked stems, and the diameter at breast height was measured for stems with height ≥ 1.3 m. During the censuses, 27 coniferous and broadleaved tree species were identified and three more species were identified to the genus level. There are 2152 records for the occurrence data and 10,660 records for the measurement data, including missing values. The stem occurrence data were compiled following the Darwin Core format, and the measurement data were compiled following the Darwin Core Measurement or Fact Extension format. Finally all data were compiled for the Darwin Core Archive, an international standard format for biodiversity data. These data can help in understanding the succession of forests following large‐scale disturbance and in managing this type of forest properly.

Typhoon diverged forest succession from natural trajectory in the treeline ecotone of the Changbai Mountains, Northeast China

Abstract Windthrow is a typical gap phrase disturbance that changes forest composition but rarely alter succession trajectories of a forest stand. Catastrophic windthrow such as typhoons is a large but infrequent disturbance that can have long-lasting effects on forest ecosystems. Whether catastrophic windthrow resets successional pathways of forest ecosystems remains inconclusive. We compared forest structure and regeneration patterns between undisturbed and disturbed stands 30 years after a typhoon event in the treeline ecotone of the Changbai Mountains, Northeastern China. Measurements were made using WorldView-1 satellite imaging and fieldwork in two types of large plots, one located in areas affected by the typhoon event and the other in adjacent undisturbed areas. Results showed that community divergence at landscape scale occurred following the typhoon. In non-wind–disturbed stands, forest development followed the successional pathway of both broadleaved and coniferous trees. By contrast, the late-successional coniferous rather than the early successional broadleaved trees occupied the wind–disturbed stands. The alteration mechanism on the forest succession pathway was that herbs formed tall, dense, and persistent mono-dominant thickets after the typhoon, which inhibited the regeneration of broadleaved trees. In contrast to the common knowledge that forest would return to initial successional stage after catastrophic disturbance, we concluded that catastrophic windthrow, different from gap phase windthrow, altered forest successional trajectory.

Spatial diversity of forest regeneration after catastrophic wind in northeastern Poland

Abstract: We examined the spatial diversity of young growth established after the catastrophic windthrow occurred in 2002 in the northeastern part of Poland. Our observations and measurements were conducted on permanent circular measurement plots located in the Szast Protected Forest (continental lowland temperate forests) that were established 3 years after the windstorm and left to natural succession. We evaluated the spatial indices characterizing the four main aspects of stand structure: the spatial arrangement of seedlings and saplings, species mingling, tree size diversity at the local spatial scale and the overall structural complexity index. The calculations were conducted in parts of the forest with differing severity of disturbance. The obtained results indicated the prevalence of a random arrangement of young growth. Clumps of regeneration were observed to a lesser degree in all parts of the forest. The species diversity was moderate and was the highest in the slightly or severely disturbed stands. Scots pine formed homogenous groups of regeneration and oaks were intermingled among other tree species. The height of the natural regeneration was moderately or highly differentiated in all stands. The overall structural diversity index showed that stand regeneration in the slightly or moderately disturbed stands was more differentiated than the young growth in the severely disturbed stands. The size differentiation of young growth is a long-lasting process and thus should be considered in practices aimed at the re-growing of areas after a natural disturbance. This process might be used to the replace monocultures with more diversified forests even in poor forest site types.

Soil CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; efflux from mountainous windthrow areas: dynamics over 12 years post-disturbance

Abstract. Windthrow-driven changes in carbon (C) allocation and soil microclimate can affect soil carbon dioxide (CO2) efflux (Fsoil) from forest ecosystems. Although Fsoil is the dominant C flux following stand-replacing disturbance, the effects of catastrophic windthrow on Fsoil are still poorly understood. We measured Fsoil at a montane mixed-forest site and at a subalpine spruce forest site from 2009 until 2012. Each site consisted of an undisturbed forest stand and two adjacent partially cleared (stem-fraction-harvested) windthrow areas, which differed with regard to the time since disturbance. The combination of chronosequence and direct time-series approaches enabled us to investigate Fsoil dynamics over 12 years post-disturbance. At both sites Fsoil rates did not differ significantly from those of the undisturbed stands in the initial phase after disturbance (1–6 years). In the later phase after disturbance (9–12 years), Fsoil rates were significantly higher than in the corresponding undisturbed stand. Soil temperature increased significantly following windthrow (by 2.9–4.8 °C), especially in the initial phase post-disturbance when vegetation cover was sparse. A significant part (15–31%) of Fsoil from the windthrow areas was attributed to the increase in soil temperature. According to our estimates, ~500–700 g C m−2 year−1 are released via Fsoil from south-facing forest sites in the Austrian Calcareous Alps in the initial 6 years after windthrow. With a high browsing pressure suppressing tree regeneration, post-disturbance net loss of ecosystem C to the atmosphere is likely to be substantial unless forest management is proactive in regenerating such sites. An increase in the frequency of forest disturbance by windthrow could therefore decrease soil C stocks and feed back positively on rising atmospheric CO2 concentrations.

Robust Prediction of Treefall Pit and Mound Sizes from Tree Size Across 10 Forest Blowdowns in Eastern North America

Treefall pits and mounds, formed when trees are uprooted by wind, influence an exceptionally broad range of phenomena in forests, having impacts on vegetation composition, soil formation, erosion, and soil respiration, among other processes. For example, treefall pits and mounds are known to have plant species composition with more pioneer species than nearby undisturbed soil; these microsites also are wetter (pits) or drier (mounds) than undisturbed soil; and have lower rates of soil respiration. Therefore, knowledge of the extent or coverage of these microsites will improve estimates of several processes as well as vegetation composition at the stand and landscape scale. Such information would be timely, given predictions of climate-change driven increases in severe weather that is the primary agent of pit and mound formation. However, to date, there have been no attempts to define a robust relationship to predict the sizes of these microsites across multiple forest types in eastern North America. Here, we summarize field measurement of the relationship between tree size and treefall pit and mound sizes, across ten catastrophic windthrow study sites. We find that for all ten sites pooled, simple ln–ln regression explains almost 54% of the variation in sizes of treefall pits (n = 1,039) and treefall mounds (n = 962) on the basis of tree diameter. This relationship spans numerous soil types, 31 tree species, and tree sizes ranging from 5 cm to greater than 105 cm diameter. Such a relationship may be coupled with information on the severity of disturbance (for example, proportion of stems uprooted) and pre-disturbance tree size structure, to provide a basis for predicting the area covered by pit and mound microsites at the landscape scale, and thereby a basis to frame expected impacts on soil formation, carbon cycling, vegetation establishment, and other ecological, edaphic, and biogeochemical processes.

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

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

A three-year study of soil Collembola communities in spruce forest stands of the High Tatra Mts (Slovakia) after a catastrophic windthrow event

Soil Collembola communities were investigated in spruce forest stands of the High Tatra Mts that had been heavily damaged by a windstorm in November 2004. The study focused on the effect two different forest practices had on collembolan community distribution and structure in the three years after the windstorm. Three different treatments were selected for the study: intact forest stands (REF), clear-cut windthrown stands (EXT), and non-extracted windthrown stands (NEX), with each treatment having three study stands. From a total 6829 individuals, 65 species were identified. The highest Collembola abundance means were recorded in NEX stands, with the same parameter being lower in REF stands and the lowest in EXT stands. Although there was a significant increase in abundance over time observed in EXT stands, this increase in abundance over time was much higher in NEX stands. The ordination method used demonstrated a significant influence of both treatment and sampling date on the abundance of Collembola. The present study shows that clearing windthrown spruce forests following a catastrophic storm is less favourable for communities of soil collembolans and slow down the recovery process.

Wind speed measurements and forest damage in Canton Zurich (Central Europe) from 1891 to winter 2007

AbstractThe most severe damage to forests in central Europe occurs during winter storms that are caused by Northern Hemispheric mid‐latitude cyclones. These winter storms have caused several catastrophic windthrows during the past four decades. Amounts of forest storm damage are believed to be a function of both the size of the forest and the storm intensity. To test this hypothesis, the Zurich region (city and canton) was chosen because long‐term climate observation data is available for the region. The relationships between forest attributes, wind speed and forest damage were explored by comparing data on forests and wind speed from 107 winters with forest damage. Storm damage was defined as the proportion of damaged forests with respect to the growing stock. The variables: daily wind run (91 years), daily maximum hourly average wind speed (107 years) and peak gust wind speed (74 years) were homogenized with respect to high wind speed and related to levels of forest damage.High maximum wind speed at the end of the 19th century and at the beginning of the 20th century was followed by low maximum wind speed in the 1940s, 1960s and 1970s. Since then, maximum values have increased. Gusts (extremes of the maximum wind speed) increased from the beginning of the recordings in 1933 and peaked in the early 1990s.Forest damage due to winter storms is best correlated with peak wind speed. Gusts exceeding 40 m/s and resulting in catastrophic windthrow have increased in recent winters. Copyright © 2009 Royal Meteorological Society

Changes in understory composition following catastrophic windthrow and salvage logging in a subalpine forest ecosystem

Catastrophic windthrow and postdisturbance salvage logging each have the potential to profoundly influence understory vegetation communities. This study compared understory vegetation cover, composition, and diversity in Routt National Forest, a subalpine forest in northwestern Colorado that sustained a 10 000 ha blowdown in 1997 and was partially salvage logged in 1999. Understory and edaphic variables were measured in five heavily wind-disturbed Picea–Abies stands, five stands salvage logged 20 months after the blowdown, and five intact stands. Understory species cover and diversity were greater in blown down areas than in salvage-logged or control areas. Community composition of each treatment area was distinct and related to a gradient in organic soil depth, which reflected the severity of understory disturbance. Composition and diversity in blowdown areas relative to control areas stabilized in the 5 years following the blowdown, but vegetation cover continued to increase. Blowdown areas contained early and late successional species. Salvage-logged areas exhibited a shift towards graminoid dominance. This structural change could delay future conifer seedling establishment. The interaction among disturbance severity, understory vegetation composition, and regeneration dynamics should be considered in future decisions to salvage log similar areas because the long-term effects of salvage logging are unknown.