Windthrow Events Research Articles

Deadwood Reduces the Variation in Soil Microbial Communities Caused by Experimental Forest Gaps

Downed woody debris (DWD) creates heterogeneous microsites that are beneficial to enhancing biodiversity and that represent persistent nutrient and carbon pools. Windthrow events characteristic of northern deciduous forests naturally produce abundant DWD and canopy openings that enhance structural complexity, but group selection harvesting reduces DWD biomass despite promoting vertical structural complexity. We implemented a field experiment to test the response of the soil microbial community (SMC) to DWD addition in created gap openings to compare experimental windfall to group selection harvest. Our objective was to assess the variability among microbial functional groups within canopy openings versus at the stand scale with DWD addition four- and five-year posttreatment. This study builds on previous studies at the Flambeau Experimental Research Site (Wisconsin, USA) that tested the effects of canopy openings alone on the SMC abundance and soil respiration along the gap gradient. Soils were sampled in four treatments (gaps, gaps + DWD addition, control + DWD addition and a control), and SMC abundance and composition were quantified using a modified phospholipid fatty acid (PLFA) and fatty acid methyl ester (FAME) method. Our analyses indicated a stronger response of the SMC to within-gap microenvironments than to the stand-level interaction of DWD addition and canopy openings. We found significant variation in the SMC along the north–south transect within the gaps, with higher abundance of arbuscular mycorrhizal fungi, soil temperature, unsaturation bacterial stress ratio and lower bacterial abundance in the northern portion of the canopy openings. DWD addition within gaps buffered the soil from extreme temperature changes while increasing gram-positive bacteria abundance that tend to rely on recalcitrant carbon sources and are more resistant to environmental stress. These patterns indicate that gap openings and DWD addition increased soil microenvironmental spatial heterogeneity and suggest that structural complexity may contribute to carbon storage by promoting sequestration in regenerating vegetation and by shaping the SMC to favor greater C use efficiency.

The role of tree uprooting in the transporting of sediment and mixing of soil in the Tatra Mountains

Tree uprooting is an important process which leads to many geomorphic consequences. Some of the most important are the transport of sediment and mixing of soil. The aim of this article is to make a detailed examination of the magnitude of sediment transport caused by an extreme windthrow event in three severely affected catchments. Also, a comparison is made of the windthrow event with a mass movement event in the aspect of the magnitude of sediment transport and soil mixing. The study was conducted in three second- to third-order catchments in the Tatra Mountains, where a strong foehn wind event caused extensive windthrow in 2013, and a high-magnitude rainfall event triggered mass movements in 2007. The volume of sediment uplifted by the uprooting event was calculated based on the mapping of root plates using high-resolution (0.04 m) aerial images and measurements of root plate volumes conducted in the field. The volume of sediment transported by shallow landslides was determined based on a Digital Elevation Model (DEM, 1-m resolution). Windthrows affected 34%, 76%, and 94% of the area of the investigated catchments. Most of the trees had fallen downslope. The direction of treefall was influenced by the slope aspect and steepness. Root plates and pits covered 1.3%, 4.8%, and 5.4% of the area of the catchments. Sediment flux generated by the uprooting event, calculated for the entire area of each investigated catchment ranged from 8.1 × 10−4 to 9.9 × 10−3 m3 m−1 event−1. This was notably lower than the sediment flux generated by the mass movement event (also calculated for the entire area of each catchment), which was 1.8−6.1 × 10−2 m3 m−1 event−1. By contrast, uprooting affected a much larger area than the mass movement event, which underlines its significant role in the mixing of soil.

Создание картографической базы данных и веб-сервиса «Конвективные опасные метеорологические явления на территории Центрального федерального округа»

Hazardous convective weather events (HCWE), such as heavy rainfall, large hail, squalls and tornadoes, are one of the substantial sources of natural emergencies in Russia. The territory of the Central Federal District (CFD) is characterized by the highest population density in Russia. On the one hand, this leads to increased risks associated with HCWE, but on the other hand, it provides the possibilities for collecting the most detailed information on them (including the events missed by the observation network and reported based on damage assessment). In this study, we consider the structure and information content of the GIS database of HCWE for the territory of the CFD. The main advantage of the developed database comparing with existing analogues is its structure, which includes information on both the events themselves and their consequences, and the conditions of their occurrence. This includes, in particular, the characteristics of meso-scale convective systems (convective storms) based on the images from meteorological satellites and diagnostic variables characterizing the atmospheric environments according to the data from ERA-5 and CFS reanalysis systems. Also, the developed database is associated with previously published databases on tornadoes in Northern Eurasia and large-scale windthrow events in European Russia. At present, we compiled the data on more than 2,000 cases of HCWE in the CFD for the period 2001–2020, most of which were reported based on damage assessment. The open-source PostgreSQL DBMS is used to manage and edit the database. Open access to the database on the Internet is implemented through an online web map service available at http://convective-storms.psu.ru/.

A satellite-derived database for stand-replacing windthrow events in boreal forests of European Russia in 1986–2017

Abstract. Severe winds are among the main causes of disturbances in boreal and temperate forests. Here, we present a new geographic information system (GIS) database of stand-replacing windthrow events in the forest zone of European Russia (ER) for the 1986–2017 period. The delineation of windthrow areas was based on the full Landsat archive and two Landsat-derived products on forest cover change, namely the Global Forest Change and the Eastern Europe's forest cover change datasets. Subsequent verification and analysis of each windthrow was carried out manually to determine the type of related storm event, its date or date range, and geometrical characteristics. The database contains 102 747 elementary areas of damaged forest that were combined into 700 windthrow events caused by 486 convective or non-convective storms. The database includes stand-replacing windthrows only with an area > 0.05 and > 0.25 km2 for the events caused by tornadoes and other storms, respectively. Additional information such as weather station reports and event descriptions from media sources is also provided. The total area of stand-replacing windthrows amounts to 2966 km2, which is 0.19 % of the forested area of the study region. Convective windstorms contribute 82.5 % to the total wind-damaged area, while tornadoes and non-convective windstorms are responsible for 12.9 % and 4.6 % of this area, respectively. Most of the windthrow events in ER happened in summer, which is in contrast to Western and Central Europe, where they mainly occur in autumn and winter. Due to several data and method limitations, the compiled database is spatially and temporally inhomogeneous and hence incomplete. Despite this incompleteness, the presented database provides a valuable source of spatial and temporal information on windthrow in ER and can be used by both science and management. The database is available at https://doi.org/10.6084/m9.figshare.12073278.v6 (Shikhov et al., 2020).

The Economy-Wide Value-at-Risk from the Exposure of Natural Capital to Climate Change and Extreme Natural Events: The Case of Wind Damage and Forest Recreational Services in New Zealand

The long-term management of natural capital is essential for the stable and resilient flow of ecosystem services for future generations facing climatic uncertainty. Understanding its resilience to extreme natural events, using biological principles, and integrating them into more holistic systems-wide modelling techniques is crucial to evaluate and design the wider economic impacts from alternative management interventions. Here we developed a probabilistic and system-wide bio-economic model to measure extreme economic impacts from natural events using the financial concept of Value at Risk. We have applied the new extreme economic impact metric to measure the economy-wide impact from the disruption of mountain-biking recreational services in the Whakarewarewa peri-urban forest in Rotorua, New Zealand from a potential windthrow event. We identified that extreme natural events, such as windthrows, could exert a substantial impact on the urban forest-dependent regional economy. This impact could potentially be intensified by the CO2 forest fertilization effects predicted under future climate scenarios and by adopting low-intensity silvicultural regimes currently rewarded by national climate change mitigation policies. Some of the insights from this study could be the precursors to develop robust adaptation strategies using robust decision-making techniques considering inclusive environmental-economic accounting frameworks.

Projected Wind Impact on Abies balsamea (Balsam fir)-Dominated Stands in New Brunswick (Canada) Based on Remote Sensing and Regional Modelling of Climate and Tree Species Distribution

The paper describes the development of predictive equations of windthrow for five tree species based on remote sensing of wind-affected stands in southwestern New Brunswick (NB). The data characterises forest conditions before, during and after the passing of extratropical cyclone Arthur, July 4–5, 2014. The five-variable logistic function developed for balsam fir (bF) was validated against remote-sensing-acquired windthrow data for bF-stands affected by the Christmas Mountains windthrow event of November 7, 1994. In general, the prediction of windthrow in the area agreed fairly well with the windthrow sites identified by photogrammetry. The occurrence of windthrow in the Christmas Mountains was prominent in areas with shallow soils and prone to localised accelerations in mean and turbulent airflow. The windthrow function for bF was subsequently used to examine the future impact of windthrow under two climate scenarios (RCP’s 4.5 and 8.5) and species response to local changes anticipated with global climate change, particularly with respect to growing degree-days and soil moisture. Under climate change, future windthrow in bF stands (2006–2100) is projected to be modified as the species withdraws from the high-elevation areas and NB as a whole, as the climate progressively warms and precipitation increases, causing the growing environment of bF to deteriorate.

How multiple and interacting disturbances shape tree diversity in European mountain landscapes

The relationship between disturbances and diversity remains uncertain, especially in forest landscapes where large spatial extents need to be considered, dynamics are slow, and disturbance interactions are common. To analyse the individual and combined effects of ungulate browsing and wind disturbance on tree species diversity at the landscape scale. We used a dynamic forest landscape model to simulate the effects of browsing and wind disturbances (i.e., frequency and windthrow size) on tree species diversity in four mountain landscapes in Central Europe. Using boosted regression trees, we analysed the relative importance of each disturbance type for diversity at different layers (i.e., regeneration versus overstorey, and all tree sizes), the shapes of the diversity–disturbance relationships and the combined effect of wind and browsing disturbances on diversity. Across all landscapes, browsing and windthrow were equally important for tree species diversity when considering all forest layers, but no consistent patterns could be observed for the regeneration and overstorey layer. The shape of the disturbance–diversity relationships differed between disturbance types. More frequent and severe windthrow events typically increased diversity almost linearly, while browsing showed a non-linear response with the highest diversity at intermediate browsing pressure. However, these relationships were not consistent across the four landscapes. Tree species diversity can be influenced by both browsing and windthrow disturbances. Forested landscapes are likely to experience multiple disturbances, and their relative influence on diversity needs to consider their different spatial and temporal scales.

Stand-level windthrow patterns and long-term dynamics of surviving trees in natural secondary stands after a stand-replacing windthrow event

Abstract We examined typhoon windthrow patterns in stand-scale permanent plots within three natural forests and the long-term dynamics of surviving trees in two of these plots. The aim was to verify whether pre-disturbance composition and structure affected windthrow damage and stand recovery. The stands, which were in Hokkaido, the northernmost main island of Japan, differed in pre-disturbance composition (coniferous, mixed and broadleaved stands) and structure, and the basal area losses by the windthrow event were 81–93 per cent. Tree mortality was significantly related to tree size (diameter at breast height) and species. The windthrow patterns differed among the three stands; and, windthrow severity was affected by the pre-disturbance composition and structure. The mortality of trees that survived the windthrow event was ~60 per cent in the two plots. The surviving trees comprised a majority of the canopy layer in the secondary stands. The relative basal area of surviving trees decreased rapidly with increasing tree density in the stand initiation stage but differed between plots. Consequently, the pre-disturbance composition and structure influenced windthrow severity, stand recovery and secondary succession in the recovered stands.

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.

Comparison of vulnerability to catastrophic wind between Abies plantation forests and natural mixed forests in northern Japan

AbstractThe risk of extreme events due to weather and climate change, such as winds of unprecedented magnitude, is predicted to increase throughout this century. Artificial ecosystems, such as coniferous plantation forests, can suffer irreversible deterioration due to even a slight change in environmental conditions. However, few studies have examined the effects of converting natural forests to plantations on their vulnerability to catastrophic winds. By modelling the 2004 windthrow event of Typhoon Songda in northern Japan using the random forest machine learning method, we answered two questions: do Abies plantation forests and natural mixed forests differ in their vulnerability to strong winds and how do winds, topography and forest structure affect their vulnerability. Our results show that Abies plantation forests are more vulnerable to catastrophic wind than natural mixed forests under most conditions. However, the windthrow process was common to both types of forests, and the behaviour of wind inside the forests may determine the windthrow probability. Future management options for adapting to climate change were proposed based on these findings, including modifications of plantation forest structure to reduce windthrow risk and reconversion of plantations to natural forests.

The Effects of a Tornado Disturbance and a Salvaged Timber Extraction on the Seed-Rain and Recruitment Community of an Eastern Temperate Deciduous Forest

Understanding forest-regeneration pathways following salvage-logging operations and windthrow disturbances is a step towards the sustainable management of forests. To accomplish this, assessment of the relative contribution of seed dispersal and post-dispersal abiotic and biotic factors in shaping post-disturbance seedling recruitment is necessary. In a temperate deciduous forest located in western Pennsylvania, we measured the seed rain over 2 years and the resulting woody-plant recruitment in 2 tornado-disturbed stands. Our data shows that the salvage logging operation and the dispersal mode of plants (wind, animal) affected the composition of the seed rain. Communities of plant recruits, in contrast, were more strongly determined by soil-cover variables than by the net inputs of seed rain. Our results indicate that salvage logging following natural windthrow events has minimal negative impacts on forest regeneration capacity.

Forest conversion from Norway spruce to European beech increases species richness and functional structure of aboveground macrofungal communities

This study investigated the response patterns of aboveground macrofungal communities to different management stages representing a forest conversion from Norway spruce (Picea abies) to European beech (Fagus sylvatica) in the Eifel National Park, Germany. We used a space-for-time substitution approach with three replicate study sites for each forest conversion stage: (I) even-aged single species Norway spruce, (II) unmanaged Norway spruce windthrow, (III) salvage-logged Norway spruce windthrow, (IV) single Norway spruce tree selection cutting (close-to-nature managed) with European beech underplanting and (V) old-growth, uneven-aged European beech (as reference). We assessed environmental variables and macrofungal sporocarps, while the latter were categorized into functional groups to link taxonomic information to potential ecosystem functions.Overall, we observed 235 macrofungal species. The highest species richness was found in the European beech reference stage, followed by the close-to-nature managed spruce/beech stage, while the Norway spruce stage showed approximately half the species richness, similar to the species level of both windthrow stages. Non-metric multidimensional scaling (NMDS) ordination separated each forest conversion stage into distinct fungal communities, while both windthrow stages could not be distinguished from each other. Beside tree species composition change and forest management, nutrient availability and microclimate were the main drivers of fungal community changes among the five differently-managed stages. Further, different functional groups responded in different patterns to forest management and to explanatory environmental variables.We reinforced the assumption, that old-growth, uneven-aged European beech forests (>120 years) can act as a refugium for unique forest type specific fungal communities with a higher functional structure, especially contrary to non-native, even-aged Norway spruce forests (∼70 years). Single Norway spruce tree selection cutting with further introduction of European beech trees can be an adequate strategy to allow a spruce forest conversion without necessarily reducing the macrofungal species richness and its functional structure. We displayed that ecological consequences of windthrow events can be a depression of fungal species richness and a collapse for the functional structure of fungi, especially after salvage logging. Our study underlines the need of including fungal conservation in forest conversion plans to optimize forest ecosystem integrity and resilience against biotic and abiotic agents, such as windstorm events.

Drivers of regeneration dynamics following salvage logging and different silvicultural treatments in windthrow areas in Slovenia

Abstract We studied regeneration dynamics in forests disturbed by three different windthrow events in 2008 in Slovenia to assess the success of natural regeneration vs planting and subsequent silvicultural treatments. Fifty-three plots with planted saplings of Norway spruce and sycamore maple and 50 plots with dominant naturally regenerated saplings were selected in a randomly stratified manner. Sapling characteristics (height, height increment, root collar diameter, free-to-grow score, browsing and micro-site) were assessed in 2012 and 2014. Herbs and seedling establishment were studied in two subplots within each plot. Average seedling density was 13,074 and 14,674 ha−1 four and six years after the windthrows, respectively. Seedlings were irregularly distributed, which suggests micro-site differences in regeneration dynamics. The results indicated lower seedling success on sites that were southerly exposed, farther from the forest edge and seed trees, on undisturbed micro-sites and at higher altitudes. On such sites planting was justified. While seedling density indicated a positive relation to herb coverage, sapling survival was negatively associated with it as well as with browsing. Initial sapling height was the strongest predictor of survival. Spruce saplings had the lowest mortality, while shade-tolerant silver fir and beech experienced high mortality. The study indicated a high density and species diversity of naturally regenerated seedlings within windthrow areas, which was reduced by planting, mowing of competing vegetation and protection measures favouring planted saplings. Recommendations for the improvement of silvicultural operations for post windthrow restoration are given.

Sediment transport by uprooting in the forested part of the Tatra Mountains, southern Poland

The process of tree uprooting plays an important role in sediment transport within forested slopes. In this study we determine the intensity of sediment transport by uprooting and its dependencies. We use the Principal Component Analysis (PCA) to determine the most important factors influencing root plate sizes, and we calculate sediment flux by windthrow for the area of the Tatra National Park (211.6km2), for the year 2013, when an extreme windthrow event occurred. For this purpose we combine field data with the results of windthrow areas mapping based on satellite imagery. We also use data recorded by the Tatra National Park concerning the amount of destroyed wood in the forests of the Tatra National Park to calculate sediment flux by windthrow for the period between 1968 and 2015 (48years). To calculate the transport distance by the uprooting needed to compute sediment flux, we modified the Gabet et al.'s (2003) Eq. (11), which in our opinion gives results which are twice the actual size. The PCA identified two the most important factors influencing root plate sizes. The first factor shows that all root plate dimensions increase with increasing tree DBH (diameter at breast height), and, to a lesser degree, with an increase in the content of coarse material. The second factor shows that the depth of a root plate increases with the downslope angle of tree fall, decreasing slope inclination, and decreasing the content of coarse material. The sediment flux by windthrow in 2013 in the area of the Tatra National Park was 3.55×10−4m3m−1yr−1. Mean annual sediment flux for the period of the last 48years was 2.76×10−5m3m−1yr−1.

Succession of ground beetle (Coleoptera: Carabidae) communities after windthrow disturbance in a montane Norway spruce forest in the Hrubý Jeseník Mts. (Czech Republic)

Abstract Wind disturbances are a key factor that is significantly involved in the life cycle of natural boreomontane coniferous forests. As most of these forests are currently intensively managed, we have limited knowledge on succession following natural disturbance. Succession in a Norway spruce stand after a windthrow event was studied using ground beetles as model bioindication taxa in the Hrubý Jeseník Mts. (Czech Republic). The study documented that the composition of ground beetle communities was significantly associated with stand age and its microclimatic parameters (particularly the minimal temperature and average and minimal humidity). Forest species including prey specialists, hygrophilous species, as well as habitat generalists were the most abundant in the mature stand, where the forest had the highest humidity and the least profound minimal temperatures. In contrast, open-habitat species, including euryoecious species and relict species of higher elevations, reached their highest abundances in clearing shortly after the windthrow. In clearing the humidity was lower and the temperature fluctuated significantly (the lowest minimal temperatures). Ground beetles, including forest species, were the least abundant in young stands (10 and 20 years after windthrow). We conclude that old stands are of particular importance because they harbour the highest abundance and diversity of ground beetles with various ecological requirements. Natural wind disturbances are important as well since they increase diversity by enabling the occurrence of many non-forest species. Hence, a mosaic of stands of different ages with a sufficient proportion of old stands should be maintained when managing montane coniferous forests.

Simulating bark beetle population dynamics in response to windthrow events

The relationship between windthrow disturbance and outbreaks of European spruce bark beetle Ips typographus L. in European Norway spruce forests has been the focus of recent studies. However, the nature in which the spatial characteristics of windthrow events influence bark beetle population dynamics is rarely examined. This represents a significant gap in the literature, as our understanding of how spatial windthrow patterns influence bark beetles can be useful for management efforts to help mitigate large-scale bark beetle disturbance. The objective of this study is to simulate how windthrow events facilitate bark beetle population state transitions from endemic and epidemic levels using a spatially explicit agent-based model. We examined how the spatial extent of windthrow events and the size of tree clusters impacted by windthrow influence this state transition. The results show that the beetle population transition slows with increasing spatial extent of a windthrow event and with larger clusters of windthrown trees, while scattered patterns of windthrown trees accelerate the timing of this transition. This study contributes to our understanding of the role of large-scale wind disturbance in European bark beetle outbreaks. Moreover, it provides a basis for further research to discover the impact of potential forest management applications aiming to mitigate the risk of bark beetle outbreaks.

Monitoring succession after a non-cleared windthrow in a Norway spruce mountain forest using webcam, satellite vegetation indices and turbulent CO2 exchange

Forests cover approximately 30% of the world’s land area and are responsible for 75% of terrestrial gross primary production. Disturbances, such as fire, storm or insect outbreaks alter the dynamics and functioning of forest ecosystems with consequences, in terms of species distribution and/or gross primary production, not fully understood. Large forest areas are intensively managed and natural disturbances are yet rare events but expected to increase with climate change. Here, we used digital repeat photography to observe the ecological succession in a windthrow disturbed forest in the Bavarian Forest National Park (Germany) and compared it to satellite-derived vegetation indices (NDVI, EVI, and PPI) as well as turbulent CO2 exchange. A data-driven clustering of the webcam images identified three regions of interest: spruce, grass and a transition region that showed grass in the beginning and became successively overgrown by spruce. The succession was mirrored in trends of annual maxima of gross primary production (GPP), satellite vegetation indices and derived image greenness (green chromatic coordinate, GCC) in the transition region. These trends were also responsible for a positive link between seasonal GPP and proxies. Start and end of growing season were estimated from GCC, NDVI, EVI, PPI, and GPP, compared to each other, and were linked partly to climatological growing season indices and phenological observations. This study demonstrates the suitability and benefits of a webcam in monitoring forest recovery after a severe windthrow event, thus offering a versatile tool that helps to understand successional and phenological processes after a disturbance.

Storms, temperature maxima and the Eurasian spruce bark beetle Ips typographus—An infernal trio in Norway spruce forests of the Central European High Tatra Mountains

Norway spruce forests (Picea abies Karst.) of the Carpathian High Tatra Mountains have been subject to unprecedented tree mortality caused by attacks of the Eurasian spruce bark beetle (Ips typographus L.) in recent decades. The outbreaks were preceded and accompanied by wind throw events and periods of increased seasonal temperature.We obtained climatic data and data on tree mortality due to storm throw and bark beetles by using a combination of direct dead tree inventory and remote sensing techniques, and examined annual tree loss change over a 26-year period in a forest district of the Slovak High Tatra National Park. In particular, we found that the combination of the previous year’s maximum daily temperature sum, tree mortality caused by wind, and bark beetle-caused tree mortality best explained the annual tree loss change in nonlinear regression models. The number of trees infested by bark beetles clearly increased with maximum air temperature sums ranging from 2850 to 3150° days, but declined below or above this thermal optimum. Annual tree mortality clearly increased subsequent to years associated with seasonal temperature sums allowing for the development of sister broods. Given consistently favourable future climatic conditions for development of I. typographus populations in the study area, a possible shift from the now predominantly uni-voltine to multi-voltine bark beetle populations might increase attack pressure also at high elevation sites.

Tree Age Distributions Reveal Large-Scale Disturbance-Recovery Cycles in Three Tropical Forests.

Over the past few decades there has been a growing realization that a large share of apparently ‘virgin’ or ‘old-growth’ tropical forests carries a legacy of past natural or anthropogenic disturbances that have a substantial effect on present-day forest composition, structure and dynamics. Yet, direct evidence of such disturbances is scarce and comparisons of disturbance dynamics across regions even more so. Here we present a tree-ring based reconstruction of disturbance histories from three tropical forest sites in Bolivia, Cameroon, and Thailand. We studied temporal patterns in tree regeneration of shade-intolerant tree species, because establishment of these trees is indicative for canopy disturbance. In three large areas (140–300 ha), stem disks and increment cores were collected for a total of 1154 trees (>5 cm diameter) from 12 tree species to estimate the age of every tree. Using these age estimates we produced population age distributions, which were analyzed for evidence of past disturbance. Our approach allowed us to reconstruct patterns of tree establishment over a period of around 250 years. In Bolivia, we found continuous regeneration rates of three species and a peaked age distribution of a long-lived pioneer species. In both Cameroon and Thailand we found irregular age distributions, indicating strongly reduced regeneration rates over a period of 10–60 years. Past fires, windthrow events or anthropogenic disturbances all provide plausible explanations for the reported variation in tree age across the three sites. Our results support the recent idea that the long-term dynamics of tropical forests are impacted by large-scale disturbance-recovery cycles, similar to those driving temperate forest dynamics.

Individual-tree- and stand-based development following natural disturbance in a heterogeneously structured forest: A LiDAR-based approach

Large-scale severe natural disturbance events drive spatial and temporal patterns of forests by altering forest structure, composition, and functions. In the Bavarian Forest National Park in Germany, windthrow events led to large disturbances caused by the European bark beetle (Ips typographus L.). Until recently, it was assumed that at the initial stage of regeneration, trees tend to form a homogeneous stand structure, whereas structural heterogeneity is an attribute of later developmental stages. Yet recent studies provide evidence that under certain conditions structural heterogeneity can arise much earlier in stand development. Here we combined LiDAR data and forest growth modeling based on individual trees to develop a workflow for studying forest development in post-disturbed areas in the upper montane regions of the national park. The current forest structure was derived from LiDAR data of individually detected trees and a set of forest structural attributes were derived. The results served as input to simulate tree development spatio-temporally for a period of 80years. Several spatial statistics, including landscape and spatial point pattern metrics, were calculated to assess the structural heterogeneity. The results showed that naturally regenerating forests on post-disturbed sites reveal structural heterogeneity already at the early-seral stage. Moreover, a significant portion of the eventual old-growth structural heterogeneity might already be determined in the early successional stages. Our workflow highlights the use of multi-sensor aerial remote sensing to provide detailed structural information useful for the investigation of early-phase forest dynamics.