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Abstract

In order to gauge ongoing and future changes to disturbance regimes, it is necessary to establish a solid baseline of historic disturbance patterns against which to evaluate these changes. Further, understanding how forest structure and composition respond to variation in past disturbances may provide insight into future resilience to climate-driven alterations of disturbance regimes.

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... A network of permanent plots was established within 11 localities and five mountain ranges using random sampling in the core zones of primary forest areas (as evaluated by a previous national-level field census; Mikoláš et al. 2019). A 141.4 × 141.4 m grid (cell size 2 ha) was overlaid on the area; within each grid cell, a circular sample plot was established at a restricted random position (the inner 0.49 ha core in each cell) using GPS (see Svoboda et al. 2014;Janda et al. 2017 for details). All study plots are included in the extensive primary forest dataset of the REMOTE project (www.remoteforests.org, ...
... For disturbance history reconstruction (involving disturbance severity and time since the disturbance event), randomly selected 25 canopy trees with DBH ≥ 10 cm within 1,000 m 2 plot were cored using Pressler increment borers at a height of 1 m above the ground. Detailed methodology of data collection, measurement, and analysis of tree rings was published in Svoboda et al. (2014) and Janda et al. (2017). ...
... Our data reflects a 250-year history of forest stands that were subjected to mixed-severity disturbance regimes. Research plots with lowseverity disturbance regimes were characterized by more frequent events compared to medium-severity disturbances (sensu Janda et al. 2017). In evaluating these disturbance histories, any dieback of a canopy tree was considered a disturbance. ...
Article
Development of primary spruce forests is driven by a series of disturbances, which also have an important influence on the understorey vegetation and its diversity. Early post-disturbance processes have been intensively studied, however, very little is known about the long-term effects of disturbances on the understorey. We quantified disturbance history using dendrochronological methods to investigate its impact on vascular plant diversity and understorey species composition. We sampled 141 plots randomly assigned throughout primary stands located in the zone of natural montane acidophilous forests dominated by Picea abies (L.) Karst. in the Western Carpathians. Dendrochronological, dendrometric, and environmental parameters were related to understorey properties using ordination methods and a Bayesian approach using multilevel linear models (GLMM). Time since the last disturbance (23–260 years ago; mostly windstorms and bark beetle outbreaks) had a significant effect on understorey species composition of the current communities, and it also interacted with disturbance severity to influence species diversity. The effect of disturbances on the understorey was largely mediated by the alteration of stand structure (age, DBH, canopy openness), Vaccinium myrtillus L. cover, and topsoil chemical properties. A period of severe disturbances between 1860 and 1890 resulted in a legacy of our current, relatively homogeneous spruce stands with less diverse sciophilous understorey dominated by V. myrtillus, which is in contrast to heterogeneous stands (in terms of age and spatial structure) driven by small-scale, lower-severity disturbances, which led to an understorey enriched by species with higher demands on light and topsoil quality (higher K concentration and lower C/N ratio). All developmental pathways following disturbances create a unique complex of spatiotemporal understorey variability in the montane spruce forests. Therefore, to preserve their full diversity, disturbances of all severities and sizes should be accepted as natural drivers, both in the field of nature conservation and close-to-nature forestry efforts.
... Regardless of the relative presence of large-scale cyclones or small-scale convective instability, forest exposure and disturbance history can mediate windthrow severity. Variables influencing forest vulnerability to windthrow that can be estimated or reconstructed across the 20th century include topographic exposure (Quine & White, 1998;Senf & Seidl, 2018), and time series of forest disturbance severity and time since the last disturbance (Janda et al., 2017). Topographic exposure is a measure of shielding based on a virtual horizon angle at a fixed distance from a point on the map. ...
... Open canopy established trees were identified as individuals that exceeded a threshold value of mean growth from 5 to 15 years of growth (Fraver & White, 2005a). These threshold values were calculated based on logistic regressions comparing empirical data from collected plot seedlings growing in the open canopy or closed canopy conditions (Janda et al., 2017). Separate regressions were performed for common tree species present (Fagus sylvatica, Abies alba, Picea abies, Acer pseudoplatanus, and a group of all other species present pooled in an additional group) in each landscape (i.e., five species groups * 4 landscapes = 20 species: landscape critical values). ...
... Second, because disturbance changes the structure of the forest, these variables can be interpreted as a rough proxy for forest structural complexity. Forests with lower severity disturbance and disturbance that happened further in the past are more likely to display higher structural complexity (Janda et al., 2017;Meigs et al., 2017). Thus, we are examining the direct effect of past disturbance on future disturbance as well as approximating an indirect effect of structure on disturbance susceptibility. ...
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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.
... Empirical research on spatial drivers of disturbances in managed forests is often limited to individual disturbance events or short time periods (Seidl et al., 2011a). Dendrochronological research of longterm disturbance dynamics, in turn, has mostly focused on primary (unmanaged) forests (Čada et al., 2020;Janda et al., 2017;Panayotov et al., 2015). Research relating disturbance dynamics to past and present management thus mostly relies on process-based simulations Temperli et al., 2017Temperli et al., , 2013Thom et al., 2018), which have found that both the legacies of past land use and current management strategies have a strong effect on forest disturbance dynamics . ...
... A study in the Carpathian mountains found a higher disturbance rate in forests established after 1860 compared to "old" forests (Munteanu et al., 2015). These "new" forests may be more susceptible to natural disturbances due to their homogeneous species composition and uniform age structure (Munteanu et al., 2015;Seidl et al., 2011b), as a high disturbance rate in recent years has also been observed in primary and unmanaged spruce stands that developed after major disturbances 19 th century (Čada et al., 2016;Janda et al., 2017;Panayotov et al., 2015). However, a higher disturbance rate in "new" forests could also be the result of different management strategies (e.g., clear ...
... Bebi et al. (2017) analysed the difference in structure between pre-and post-1880 forests in NFI plots across Switzerland, and found that "new" forests do not only have a lower total growing stock, but are also vertically more homogeneous. In unmanaged mountain spruce forests in Central and Eastern Europe, uniform stands established after large disturbance events in the mid-19 th century are now experiencing a new pulse in disturbances (Čada et al., 2016;Janda et al., 2017;Panayotov et al., 2015). In our study, homogeneous spruce stands established only 80-100 years ago are most susceptible to disturbances. ...
... Empirical research on spatial drivers of disturbances in managed forests is often limited to individual disturbance events or short time periods (Seidl et al., 2011a). Dendrochronological research of long-term disturbance dynamics, in turn, has mostly focused on primary (unmanaged) forests (Čada et al., 2020;Janda et al., 2017;Panayotov et al., 2015). Research relating disturbance dynamics to past and present management thus mostly relies on process-based simulations Temperli et al., 2017;Thom et al., 2018), which have found that both the legacies of past land use and current management strategies have a strong effect on forest disturbance dynamics . ...
... A study in the Carpathian mountains found a higher disturbance rate in forests established after 1860 compared to "old" forests (Munteanu et al., 2015). These "new" forests may be more susceptible to natural disturbances due to their homogeneous species composition and uniform age structure (Munteanu et al., 2015;Seidl et al., 2011b), as a high disturbance rate in recent years has also been observed in primary and unmanaged spruce stands that developed after major disturbances 19th century (Čada et al., 2016;Janda et al., 2017;Panayotov et al., 2015). However, a higher disturbance rate in "new" forests could also be the result of different management strategies (e.g., clear cuts of plantations after a 70-120-year rotation). ...
... Bebi et al. (2017) analysed the difference in structure between pre-and post-1880 forests in NFI plots across Switzerland, and found that "new" forests do not only have a lower total growing stock, but are also vertically more homogeneous. In unmanaged mountain spruce forests in Central and Eastern Europe, uniform stands established after large disturbance events in the mid-19th century are now experiencing a new pulse in disturbances (Čada et al., 2016;Janda et al., 2017;Panayotov et al., 2015). In our study, homogeneous spruce stands established only 80-100 years ago are most susceptible to disturbances. ...
Article
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Mountain forests provide a wide range of ecosystem services, including carbon sequestration and protection from natural hazards. Forest cover in the European Alps has increased over the last century, but in recent years, these forests have experienced an increasing rate of natural disturbances by agents such as windthrow, bark beetle outbreaks, and forest fires. These disturbances pose a challenge for forest management, making it important to understand how site and stand characteristics, land use legacies and recent management influence disturbance probability. We combined a dataset of forest disturbances detected from space with in-situ forest management records, allowing us to differentiate between different types of disturbances for the Canton of Graubünden, Switzerland, in the years 2005–2018. The resulting dataset of over 28′000 attributed disturbance patches (corresponding to a disturbed forest area of ca. 23′600 ha) was combined with information on topography, forest structure, and historical forest cover. A machine-learning approach was used to investigate the non-linear and interacting relationships between potential drivers and disturbance occurrence. Natural disturbances (especially windthrow and bark beetle outbreaks) were most common at lower elevations, on shallow and south-facing slopes, and in even-aged, spruce-dominated stands with a closed canopy. Forests established in the 20th century were significantly more susceptible to natural disturbances than forests that were already present before 1880, which may be due to the uniform age and vertical structure of secondary forests, as well as legacy effects of former agricultural use. On the other hand, forest management more often took place in forests present before 1880. Management interventions (such as thinning) in turn increased the susceptibility to natural disturbances in the short term. This finding emphasizes the need to balance short-term increases in disturbance susceptibility with long-term benefits in forest resilience when planning management interventions in mountain forests. Our findings highlight the importance of considering multiple interactive drivers, including management and land-use history, for understanding forest disturbance regimes.
... 2020; Schurman et al. 2018). Data were compiled from published regional studies across a large geographical gradient covering the Carpathian Mountains of southern and northern Romania , Ukraine (Trotsiuk et al. 2014), southern and northern Slovakia (Janda et al. 2017), the Bohemian Forest in the Czech Republic ( Cada et al. 2016), and the Harz Mountains in Germany (Meyer et al. 2017;Fig. 1). ...
... Two types of radial growth patterns were assumed to indicate past disturbance: (1) release from suppression, characterized by an abrupt, large, and sustained growth increase, suggests a response to the mortality of surrounding trees, and (2) gap origin, characterized by rapid early growth rates, suggests the recruitment of a tree in open conditions after disturbance (Lorimer and Frelich 1989). A tree was determined to be a gap origin tree if the mean ring width of the fifth to fifteenth ring from the pith exceeded the early growth rate threshold, as previously defined by comparing early growth rates in young trees sampled in gaps vs. those growing under a forest canopy (Appendix S1: Table S2; Svoboda et al. 2014, Trotsiuk et al. 2014, Janda et al. 2017. The year FIG. 1. Location of the study area of the remaining primary mountain Norway spruce forests spanning a large geographical gradient in Central and Eastern Europe. ...
... and for the stand proportions disturbed 25.0% (6.1-77.3). The reconstructed disturbance events generally aligned with documented historic windstorms and bark-beetle outbreaks (see the regional studies for more details; Svoboda et al. 2014, Cada et al. 2016, Janda et al. 2017, Meyer et al. 2017. ...
Article
Estimates of historical disturbance patterns are essential to guide forest management aimed at ensuring the sustainability of ecosystem functions and biodiversity. However, quantitative estimates of various disturbance characteristics required in management applications are rare in longer‐term historical studies. Thus, our objectives were to: (1) quantify past disturbance severity, patch size, and stand proportion disturbed, and (2) test for temporal and sub‐regional differences in these characteristics. We developed a comprehensive dendrochronological method to evaluate an approximately two‐century‐long disturbance record in the remaining Central and Eastern European primary mountain spruce forests, where wind and bark beetles are the predominant disturbance agents. We used an unprecedented large‐scale nested design dataset of 541 plots located within 44 stands and 6 sub‐regions. To quantify individual disturbance events, we used tree‐ring proxies, which were aggregated at plot and stand levels by smoothing and detecting peaks in their distributions. The spatial aggregation of disturbance events was used to estimate patch sizes. Data exhibited continuous gradients from low‐ to high‐severity and small‐ to large‐size disturbance events. In addition to the importance of small disturbance events, moderate‐scale (25‐75% of the stand disturbed, >10 ha patch size) and moderate‐severity (25‐75% of canopy disturbed) events were also common. Moderate disturbances represented more than 50% of the total disturbed area and their rotation periods ranged from one to several hundred years, which is within the lifespan of local tree species. Disturbance severities differed among sub‐regions, whereas the stand proportion disturbed varied significantly over time. This indicates partially independent variations among disturbance characteristics. Our quantitative estimates of disturbance severity, patch size, stand proportion disturbed, and associated rotation periods provide rigorous baseline data for future ecological research, decisions within biodiversity conservation, and silviculture intended to maintain native biodiversity and ecosystem functions. These results highlight a need for sufficiently large and adequately connected networks of strict reserves, more complex silvicultural treatments that emulate the natural disturbance spectrum in harvest rotation times, sizes, and intensities, and higher levels of tree and structural legacy retention.
... Whereas fine-scale disturbances dominate the natural forest dynamics of deciduous upland forests of Central Europe [7][8][9][10], several studies have highlighted the importance of large-scale, stand-replacing events for conifer mountain forest ecosystems [11][12][13][14][15]. More recently, a mixed-severity disturbance regime, predominantly driven by gap dynamics with infrequent severe stand-replacing events, has been documented for some mixed mountain forest ecosystems [8,13,[16][17][18][19][20]. Though fine-scale processes have been abundantly studied in Central European forests, the long-term dynamics of mountain sites following high-severity disturbances needs further investigation, particularly in respect to tree-species coexistence, spatial patterns, tree-soil interactions and factors controlling mortality. ...
... These results suggest the existence of two, edaphically-dependent, spatially-explicit disturbance regimes ( Figure 4C). In contrast to mixed-severity disturbance regimes (e.g., [16,18,19]) highlighting the occurrence of several regimes mixed in time and space within a whole stand, our spatially-explicit mixed disturbance regime emphasizes the existence of spatially isolated, edaphically-determined regimes. Indeed, Figures 4C and S1 indicate that large-scale processes occupying hydromorphic areas are concentrated in relatively small, irregularly-shaped polygons as the difference in range of indicator variograms was not as dramatic as expected. ...
... Boubin forest is a typical representative of mixed mountain old-growth forest, serving as an "etalon" in the formation of traditional concepts of close-to-nature forest management [104,105]. Thus, our results might be extrapolated to analogical natural forests across the Europe, e.g., Novohradske Mts. in Central Europe [16], the Carphatians [18,19,106], the Alps [11,107], the Balkan peninsula [22,108] and Apennines [109]. This study determined several mutually overlapping factors that might contribute to wholestand resistance to severe storms. ...
Article
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The driving forces of tree mortality following wind disturbances of mountain mixed European temperate forests belongs among issues not comprehensively resolved. Hence, we aimed to elucidate the key factors of tree resistance to historical severe disturbance events in the Boubínský Primeval Forest, one of the oldest forest reserves in the Czech Republic. By using spatially explicit tree census, dendrochronological and soil data, we study spatial and temporal patterns of past disturbances and mathematically compared selected characteristics of neighboring trees that were killed by a severe storm in 2017 and those that remained undisturbed. The tendency of trees toward falling was primarily driven edaphically, limiting severe events non-randomly to previously disturbed sites occupied by hydromorphic soils and promoting the existence of two spatially-separated disturbance regimes. While disturbed trees usually recruited in gaps and experienced only one severe release event, surviving trees characteristically regenerated under the canopy and were repeatedly released. Despite the fact that disturbed trees tended to reach both lower ages and dimensions than survivors, they experienced significantly higher growth rates. Our study indicates that slow growth with several suppression periods emerged as the most effective tree strategy for withstanding severe windstorms, dying of senescence in overaged life stage. Despite the selective impact of the Herwart storm on conifer population, we did not find any difference in species sensitivity for most characteristics studied. We conclude that the presence of such ancient, high-density wood trees contributes significantly to the resistance of an entire stand to severe storms.
... Studying historical disturbances, their severity, synchronisation and consequences on present forest structure are needed to guide forest management [26]. Although several studies analysed the disturbance history of primary forests, studies that relate natural disturbance history to present forest structure in European temperate primary forests are rare [27,28]. There are few studies investigating the dynamics of primary forests in the Southern Carpathians [29,30]. ...
... The disturbance history was reconstructed following Janda et al. [41]. Chronologies of inferred canopy disturbances were based on classifying the radial growth patterns of non-suppressed trees in two patterns: (1) open canopy recruitment indicated by rapid initial growth or (2) release-trees that most likely established in a shaded environment and recruited to the canopy through gap formations in the canopy, as depicted by slow initial growth followed by an abrupt release [15,28,39] (Appendix B). The disturbance history was reconstructed from the analysis of 347 increment cores. ...
... Crown areas were predicted from a statistical relationship between crown areas estimated on cored trees and DBH ((0.0069260 × DBH + 1.8698166) 2 ). Timing and severity of the disturbances at patch level were calculated by combining crown area estimates with growth release dates for initially suppressed seedlings and the timing of open-canopy recruitment [28]. We used predefined severity classes for disturbance events, following Frelich and Lorimer [39]: low (0-10% of the canopy area disturbed), moderate (20.1-40%), high (40.1-60%), ...
Article
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Research Highlights: Past disturbances occurred naturally in primary forests in the Southern Carpathians. High-and moderate-severity disturbances shaped the present structure of these ecosystems, which regenerated successfully without forestry interventions. Background and Objectives: Windstorms and bark beetle outbreaks have recently affected large forest areas across the globe, causing concerns that these disturbances lie outside the range of natural variability of forest ecosystems. This often led to salvage logging inside protected areas, one of the main reasons for primary forest loss in Eastern Europe. Although more than two-thirds of temperate primary forests in Europe are located in the Carpathian region of Eastern Europe, knowledge about how natural disturbances shape the forest dynamics in this region is highly essential for future management decisions. Material and Methods: We established our study in a primary forest valley situated in the centre of the largest temperate primary forest landscape in Europe (Făgăras , Mountains). A dendrochronological investigation was carried out to reconstruct the natural disturbance history and relate it to the present forest structure. Results: The dendrochronological analysis revealed high temporal variability in the disturbance patterns both at the patch and stand level. Moderate severity disturbance events were most common (20-40% of canopy disturbed in 60% of the plots) but high severity events did also occur (33% of the plots). Regeneration was spruce-dominated and 71% of the seedlings were found on deadwood microsites. Conclusions: We conclude that the current structure of the studied area is a consequence of the past moderate-severity disturbances and sporadic high-severity events. The peak in disturbances (1880-1910) followed by reduced disturbance rates may contribute to a recent and future increase in disturbances in the Făgăras , Mts. Our findings show that these disturbance types are within the range of natural variability of mountain spruce forests in the Southern Carpathians and should not be a reason for salvage logging in primary forests from this area.
... These disturbances create patches, which can reach from a few hundred up to tens or hundreds of ha depending on local environmental and climatic drivers (Perry et al., 2011, Halofsky et al., 2011. In temperate coniferous forests, complex spatiotemporal patterns of different disturbance severities have been observed, which creates high heterogeneity and complexity in forest structure (Janda et al., 2017). This can result from a single disturbance event which affects a large area with variable damage severity within a landscape, or alternatively, as numerous disturbance events driven by different disturbance agents occurring in different parts of a given landscape (Trotsiuk et al., 2014). ...
... Observational studies of gap formation provide spatially explicit quantitative data that is nevertheless contemporaneous with the time period of observation, and may thus fail to adequately describe the full spectrum of disturbance processes operating within a given system, since larger more severe events occur only episodically (Orman and Dobrowolska, 2017). This potential bias may be addressed by conducting dendrochronological analyses of tree core samples, as these techniques may be used to reconstruct both the spatial and temporal aspects of historical events (Janda et al., 2017). Quantitative reconstructions of historical processes will further our understanding regarding the potential breadth of disturbance severities and frequencies that characterize particular forest systems. ...
... A specific threshold DBH limit was used to discriminate adult from juvenile trees at the time of the event (Appendix 2). This threshold size value was estimated from a regression model fitted with data from the measured known canopy and suppressed trees (Janda et al., 2017). ...
Article
Natural disturbances are key factors in the formation of forest ecosystem structure. Evaluation of the spatial and temporal extent of disturbance regimes is critical for understanding forest dynamics, forest structural hetero-geneity, and biodiversity habitats. Quantifying disturbance regimes is therefore imperative for appropriate management of forests and protected areas. However, natural disturbance regimes have rarely been assessed using dendrochronological methods on a regional scale across primary mixed beech-fir forest stands-one of the dominant forest vegetation types in Europe. To study the natural disturbance regimes of beech-dominated mixed-forest stands, we established 42 permanent study plots with an area of 0.1 ha across three primary forest stands in the Western Carpathians, a region that still contains large areas of primary forest. We reconstructed each stand-level disturbance history using a tree-ring based approach. The temporal synchronicity of disturbance events was then evaluated by delineating stand-level disturbance events using a kernel density function, and through the detection of plot-level disturbances with severities greater than 10 percent. The results obtained from the chronologies showed substantial variability in time and space, especially in the mid-19th century. Low-and moderate-severity plot-level disturbance events were most common, but high-and extremely high-severity plot-level disturbance events also occurred. The observed spatial and temporal variability suggests that the beech-dominated forests were primarily driven by mixed-severity disturbance regimes, with windstorms as the main disturbance agent. This reconstruction of the disturbance regime provided unique insight into the scale of mortality processes in these beech-dominated mixed forests. This information can help guide ecological forestry in areas where both wood production and biodiversity preservation are simultaneous goals, such as by employing more spatio-temporally-complex silvicultural systems that resemble natural disturbance patterns and facilitate heterogeneous forest structures.
... Wind disturbances are also a dominant structuring process across all European forests, though varying greatly in intensity and frequency, for example exhibiting periods when high intensity wind storms are of greater prevalence (Zielonka et al. 2009;Svoboda et al. 2012Svoboda et al. , Čada et al. 2016. Recent research on the role of intermediate severity disturbances suggests a much broader range of variability in the resulting stand age class structure and tree demography than previously recognized for European forests (Nagel et al. 2014, Trotsiuk et al. 2014, Janda et al. 2017. ...
... Forests dominated by Scots pine, of which more than half are in Poland, are predominantly managed by clearcutting systems. Regional studies from the Carpathians, Rila Mountains (Bulgaria), and Bohemia (Czech Republic) suggest that mixed-severity disturbance regimes with wide variation of low to high disturbance severities historically operated in temperate mountain spruce forests (Panayotov et al. 2011, Szewczyk et al. 2011, Trotsiuk et al. 2014, Čada et al. 2016, Janda et al. 2017, Frankovič et al. 2021. We showed that this variability is not emulated by contemporary forest management. ...
Article
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In Europe, forest management has controlled forest dynamics to sustain commodity production over multiple centuries. Yet over‐regulation for growth and yield diminishes resilience to environmental stress as well as threatens biodiversity, leading to increasing forest susceptibility to an array of disturbances. These trends have stimulated interest in alternative management systems, including natural dynamics silviculture (NDS). NDS aims to emulate natural disturbance dynamics at stand and landscape scales through silvicultural manipulations of forest structure and landscape patterns. We adapted a “Comparability Index” (CI) to assess convergence/divergence between natural disturbances and forest management effects. We extended the original CI concept based on disturbance size and frequency by adding the residual structure of canopy trees after a disturbance as a third dimension. We populated the model by compiling data on natural disturbance dynamics and management from 13 countries in Europe, covering four major forest types (i.e., spruce, beech, oak, and pine‐dominated forests). We found that natural disturbances are highly variable in size, frequency, and residual structure, but European forest management fails to encompass this complexity. Silviculture in Europe is skewed towards even‐aged systems, used predominately (72.9% of management) across the countries assessed. The residual structure proved crucial in the comparison of natural disturbances and silvicultural systems. CI indicated the highest congruence between uneven‐aged silvicultural systems and key natural disturbance attributes. Even so, uneven‐aged practices emulated only a portion of the complexity associated with natural disturbance effects. The remaining silvicultural systems perform poorly in terms of retention as compared to tree survivorship after natural disturbances. We suggest that NDS can enrich Europe's portfolio of management systems, for example where wood production is not the primary objective. NDS is especially relevant to forests managed for habitat quality, risk reduction, and a variety of ecosystem services. We suggest a holistic approach integrating natural dynamics silviculture with more conventional practices.
... High-severity wind storms with heavy rains caused significant blowdown in spruce forests in the Tien Shan Mountains of southeastern Kazakhstan in May and June 2011. Large-scale blowdown events provide extensive breeding material for bark beetles, and bark beetle outbreaks in spruce forests are often triggered by such events [1][2][3][4][5][6][7][8]. Bark beetle populations, especially Ips hauseri Reitter (Coleoptera: Curculionidae), began to increase in blown down Picea schrenkiana Fish. ...
... Bark beetle outbreaks are inferred and dated in tree-ring chronologies by growth releases in surviving trees and death dates of attacked trees [7,8,[40][41][42][43][44][45][46][47][48]. Release of trees subjected to inter-tree competition indicate within-stand mortality or removals. ...
Article
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Ips hauseri Reitter is the most important bark beetle on Picea schrenkiana in southeast Kazakhstan, but its biology, ecology, and outbreak dynamics are poorly known. We dendrochronologically reconstructed a 200-year history of disturbances in the Kazakh Tien Shan P. schrenkiana forests. Only localized, low-severity bark beetle events occurred during the reconstructed period, indicating that extensive high-severity bark beetle outbreaks have not occurred historically in the Tien Shan spruce forest, unlike bark beetle outbreaks in spruce forests in North America, Europe, and Russia. Disturbance frequency doubled after about 1965, probably due to warming climate. Results, combined with the failure of an outbreak to fully develop after blowdown events associated with hurricane-force windstorms in 2011, indicate that prolonged drought may be necessary to sustain I. hauseri outbreaks, or that year-to-year variation in the Tien Shan weather prevents outbreak development. I. hauseri is probably less aggressive than I. typographus, at least on their natural hosts within their natural ranges.
... Radial growth patterns of increment cores were analyzed for evidence of past disturbance events within each plot. Quantitative reconstructions of disturbance histories for different regions of the larger data set used here have been published previously (Standovár & Kenderes, 2003;Svoboda et al., 2014;Trotsiuk et al., 2014;Janda et al., 2017;Meigs et al., 2017;Nagel et al., 2017;Schurman et al., 2018;Janda et al., 2019;Schurman, Babst, Björklund, et al., 2019;Čada et al., 2020;Frankovič et al., 2020), and provide detailed descriptions of dendroecological methods. We therefore only briefly summarize the methods used to reconstruct disturbance below. ...
... out of the 68 stands had more than 10 trees ha −1 that reached the species-specific 90th percentile age. Moreover, the remarkable variation in the density of these trees across the stands likely highlights how tree longevity is strongly influenced by local disturbance histories, which cover a gradient from low-intensity gap dynamics, to partial canopy disturbance, to severe stand replacement in the study region Trotsiuk et al., 2014;Janda et al., 2017;Schurman et al., 2018;Čada et al., 2020;Frankovič et al., 2020). ...
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Aims We examined differences in lifespan among the dominant tree species (spruce (Picea abies (L.) H. Karst.), fir (Abies alba Mill.), beech (Fagus sylvatica L.), and maple (Acer pseudoplatanus L.)) across primary mountain forests of Europe. We ask how disturbance history, lifetime growth patterns, and environmental factors influence lifespan. Locations Balkan mountains, Carpathian mountains, Dinaric mountains. Methods Annual ring widths from 20,600 cores from primary forests were used to estimate tree life spans, growth trends, and disturbance history metrics. Mixed models were used to examine species-specific differences in lifespan (i.e. defined as species-specific 90th percentiles of age distributions), and how metrics of radial growth, disturbance parameters, and selected environmental factors influence lifespan. Results While only a few beech trees surpassed 500 years, individuals of all four species were older than 400 years. There were significant differences in lifespan among the four species (beech > fir > spruce > maple), indicating life history differentiation in lifespan. Trees were less likely to reach old age in areas affected by more severe disturbance events, whereas individuals that experienced periods of slow growth and multiple episodes of suppression and release were more likely to reach old age. Aside from a weak but significant negative effect of vegetation season temperature on fir and maple lifespan, no other environmental factors included in the analysis influenced lifespan. Conclusions Our results indicate species-specific biological differences in lifespan, which may play a role in facilitating tree species coexistence in mixed temperate forests. Finally, natural disturbances regimes were a key driver of lifespan, which could have implications for forest dynamics if regimes shift under global change.
... In each stand, study plots were selected to cover the whole gradient of disturbance severities and timing over the past 250 years. For this purpose, we split plots from Janda et al. (2017) according to disturbance event timing into three equally large classes. We then selected two plots within each class on every stand, with differing severity if available. ...
... The corresponding event severity was defined in terms of the proportional area of tree canopy removed by the disturbance, which was estimated using regression methods and allometric equations relating the aggregate present-day size of tree responders (individuals with a disturbance signal) to the original extent of the disturbance-induced canopy gap (Lorimer & Frelich, 1989). For more details see Janda et al. (2017Janda et al. ( , 2019. ...
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Aim Natural disturbances influence forest structure, successional dynamics, and, consequently, the distribution of species through time and space. We quantified the long-term impacts of natural disturbances on lichen species richness and composition in primary mountain forests, with a particular focus on the occurrence of endangered species. Location Ten primary mountain spruce forest stands across five mountain chains of the Western Carpathians, a European hotspot of biodiversity. Methods Living trees, snags, and downed logs were surveyed for epiphytic and epixylic lichens in 57 plots. Using reconstructed disturbance history, we tested how lichen species richness and composition was affected by the current forest structure and disturbance regimes in the past 250 years. We also examined differences in community composition among discrete microhabitats. Results Dead standing trees as biological legacies of natural disturbances promoted lichen species richness and occurrence of threatened species at the plot scale, suggesting improved growing conditions for rare and common lichens during the early stages of recovery post-disturbance. However, high-severity disturbances compromised plot scale species richness. Both species richness and the number of old-growth specialists increased with time since disturbance (i.e. long-term uninterrupted succession). No lichen species was strictly dependent on live trees as a habitat, but numerous species showed specificity to logs, standing objects, or admixture of tree species. Main conclusions Lichen species richness was lower in regenerating, young, and uniform plots compared to overmature and recently disturbed areas. Natural forest dynamics and its legacies are critical to the diversity and species composition of lichens. Spatiotemporal consequences of natural dynamics require a sufficient area of protected forests for provisioning continual habitat variability at the landscape scale. Ongoing climatic changes may further accentuate this necessity. Hence, we highlighted the need to protect the last remaining primary forests to ensure the survival of regionally unique species pools of lichens.
... Knowledge of canopy accession strategies, and thus the ability of trees to persist in the understorey, and their changes along the wider latitudinal gradient, is very limited (but see Janda et al., 2017;Niukkanen & Kuuluvainen, 2011;Svoboda et al., 2014;Trotsiuk et al., 2014). Hence, it is important to gain information about life-history trait variability for more species, as a useful tool for promoting regeneration and silvicultural strategies (Franklin et al., 2002;Lindenmayer et al., 2012). ...
... The life-history traits of Q. mongolica have been described differently by many authors, from light demanding to shade tolerant (Abrams et al., 1999;Ishikawa & Ito, 1989;Wang et al., 2010;Yamamoto, 1996). Our results suggest that Q. mongolica is a shade mid-tolerant species because it has a similar proportion of RTs (17-49%) to the previously described shade mid-tolerant Pinus abies (14-48% RTs; Janda et al., 2017;Niukkanen & Kuuluvainen, 2011;Svoboda et al., 2014;Trotsiuk et al., 2014). ...
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Aim Understanding how natural forest disturbances control tree regeneration is key to predicting the consequences of globally accelerating forest diebacks on carbon stocks and forest biodiversity. Tropical cyclones (TCs) are important drivers of forest dynamics in Eastern Asia, and it is predicted that their importance will increase. However, little is known about the impact of TCs on forest regeneration. Location Latitudinal gradient from south Korea (33° N) to the Russian Far East (45° N). Time period Last 300 years. Major taxa studied Quercus mongolica, Abies nephrolepis and Pinus koraiensis. Methods We explored the effects of TC activity on canopy accession strategies derived from long‐term tree radial growth patterns along a 1,500‐km latitudinal gradient of decreasing TC activity. We analysed canopy accession strategies for > 800 trees of three widely distributed tree species by dividing them into gap trees (GTs), which established immediately after gap formation, and released trees (RTs), which accessed the upper canopy after a period of competitive suppression. Results We found a substantial decrease in GTs and increase in RTs proportionally along the gradient of decreasing TC activity. Pinus koraiensis and A. nephrolepis exhibited high variability in the proportions of the individual canopy accession strategies along the latitudinal gradient, whereas it was more stable for Q. mongolica. We identified the gradient of TC activity as the main driver influencing canopy dynamics and thus changes in life‐history traits for P. koraiensis and Q. mongolica, whereas maximal growth rate was the main driver for A. nephrolepis. Main conclusions Flexibility in growth strategies enabled the studied species to cover extensive areas and indicates that they will be able to cope with shifts in disturbance regimes induced by the poleward migration of TCs and increasing TC intensity. Our results highlight the canopy accession strategy as an ecological indicator of past disturbance activity.
... The elevation ranges from 1286 to 1596 m above sea level (m asl) with a mean of 1431 m asl and slope ranges from 12 • to 43 • with a mean of 30 (Appendix Table S1). Annual mean temperature ranges between 1.4 • and 5.0 • C Janda et al., 2017). Windstorms, which are often followed by outbreaks of the native European spruce bark beetle (Ips typographus), are the most prevalent natural disturbance agents in the region, causing tree mortality and regeneration responses at different temporal and spatial scales Janda et al., 2017). ...
... Annual mean temperature ranges between 1.4 • and 5.0 • C Janda et al., 2017). Windstorms, which are often followed by outbreaks of the native European spruce bark beetle (Ips typographus), are the most prevalent natural disturbance agents in the region, causing tree mortality and regeneration responses at different temporal and spatial scales Janda et al., 2017). ...
Article
Natural disturbances strongly influence forest structural dynamics, and subsequently stand structural heterogeneity, biomass, and forest functioning. The impact of disturbance legacies on current forest structure can greatly influence how we interpret drivers of forest dynamics. However, without clear insight into forest history, many studies default to coarse assumptions about forest structure, for example, whether forests are even or unevenly aged. The aim of this study was to analyze the effects of past disturbances on the current diameter distributions of Norway spruce (Picea abies (L.) Karst.)-dominated landscapes throughout the Carpathian Mountains. Our dendroecological dataset comprises tree cores from 339 plots (7,845 total tree cores), nested within 28 primary forest stands, known to vary greatly in the severity of historical disturbances. Our analyses revealed that historical disturbances had a strong and significant effect on the current diameter distribution shapes at the plot level. We demonstrated that mixed-severity disturbance regimes were more frequent and create a complex pattern of diameter distributions at the plot and stand scale. Here, we show that high severity disturbance was associated with unimodal diameter distributions, while low and moderate severity was associated with the reverse J-shaped distribution. This is a result of complex disturbance patterns, with structural biological legacies. Our results will have important management implication in the context of tree size heterogeneity, biomass storage, and productivity as influenced by natural disturbances. Lastly, these results demonstrate that structural changes may arise as consequences of changing disturbance regime associated with global change.
... Natural disturbances represent key drivers in forest ecosystems dynamics Stephens et al., 2013;Seidl et al., 2014). For the Carpathian Norway spruce (Picea abies) forests, mixed-severity disturbance regimes have been identified as the dominant driver (Svoboda et al., 2014;Janda et al., 2017;Meigs et al., 2017;Schurman et al., 2018). The European bark beetle (Ips typographus) can be considered one of key factors determining the dynamics of European spruce-dominated forests (Temperli et al., 2013) and together with wind, are the major disturbance factors in the Carpathians . ...
... The stands are situated within four mountain ranges with the largest portion of spruce primary forests in Slovakiathe High Tatras (four stands), the Low Tatras (two stands), the Great Fatra mountains (two stands) and the Orava Beskids (one stand). For the fungal surveys, we used plots previously established by Janda et al. (2017) and from the total 134 plots within the nine stands, 51 study plots were surveyed. Each plot measured 1000 m 2 (17.84 m radius from the plot centre). ...
Article
Understanding the processes shaping the composition of assemblages at multiple spatial scales in response to disturbance events is crucial for preventing ongoing biodiversity loss and for improving current forest management policies aimed at mitigating climate change and enhancing forest resilience. Deadwood-inhabiting fungi represent an essential component of forest ecosystems through their association with deadwood decomposition and the cycling of nutrients and carbon. Although we have sufficient evidence for the fundamental role of deadwood availability and variability of decay stages for fungal species diversity, the influence of long-term natural disturbance regimes as the main driver of deadwood quantity and quality has not been sufficiently documented. We used a dendroecological approach to analyse the effect of 250-years of historical natural disturbance and structural habitat elements on local (plot-level) and regional (stand-level) species richness of deadwood-inhabiting fungi. We used data collected from 51 study plots within nine best-preserved primary spruce forest stands distributed across the Western Carpathian Mountains. Historical disturbances shaped the contemporary local and regional species richness of fungi, with contrasting impacts of disturbance regime components at different spatial scales. While local diversity of red-listed species has increased due to higher disturbance frequency, regional diversity of all species has decreased due to higher severity historical disturbances. The volume of deadwood positively influenced the species richness of deadwood-inhabiting fungi while canopy openness had a negative impact. The high number of observed rare species highlights the important role of primary forests for biodiversity conservation. From a landscape perspective, we can conclude that the distribution of species from the regional species pool is-at least to some extent-driven by past spatiotemporal patterns of disturbance events. Natural disturbances occurring at higher frequencies that create a mosaic forest structure are necessary for fungal species-especially for rare and endangered taxa. Thus, both the protection of intact forest landscapes and forest management practises that emulate natural disturbance processes are recommended to support habitats of diverse fungal communities and their associated ecosystem functions.
... Episodic windstorms and the frequently following waves of cambiofagous spruce bark beetle (Ips typographus L.) outbreaks are the primary forces inducing dynamic processes in the mountain forests of Europe, where Norway spruce is one of the most important forestforming species (Marini et al., 2017;Mezei et al., 2017;Dobor et al., 2019). Both phenomena strongly affect forest associations developed by spruce, i.e., single-species upper mountain spruce forests and mixed forests located lower down the mountains (Janda et al., 2017;Dobor et al., 2019). The phenomenon of spruce tree stands dying under the pressure of natural disturbances, currently observed around the globe (Rehfuess, 1985;Roberts et al., 1989;Kharuk et al., 2015), intensified in the West Carpathians in the first decade of this century as a result of a hurricane that led to extensive breaking of trees in 2004. ...
... The research conducted three times over a period of 25 years at permanent plots in Gorce National Park permitted a more thorough investigation and understanding of the directions and scale of lichen communities changes on Norway spruce, resulting mainly from spruce bark beetle outbreaks and windstorms affecting West Carpathian forests over the last quarter century (Holeksa et al., 2017;Janda et al., 2017;Wężyk et al., 2017). A shift of lichen communities in accordance with the time vector shows a progressing character of the transformation process. ...
Article
Over the last decades the West Carpathian spruce and mixed forests with a share of Picea abies, have been undergoing intensified dynamic changes, determined by windstorms and European spruce bark beetle outbreaks. Those changes should have a decisive effect on the survivability of species and shifts in epiphytic lichen communities on this phorophyte. Research conducted in the Gorce Mts (West Carpathians, Poland) in 1993, 2013 and 2018, on the same 186 spruce trees at 33 sites, revealed an increase in the species diversity of lichen communities in a long-term perspective (25 years). At the same time, there was a decrease in the coverage of the dominant species. Such changes are a result of long-term tree composition processes: the natural thinning of upper mountain spruce forests and the increase of lower mountain forests density after a decrease in the share of Norway spruce. The former prefers photophilous epiphytes, and the latter leads to an increase in the share of shade-tolerant species. The analysis of lichen communities by means of the principal components analysis (PCA) method for all three study periods combined showed that long-term changes were the most significant for this lichen biota, and short-term changes had no considerable effect. The conducted Redundancy Analysis (RDA) revealed, that the forest plant association was a stronger factor affecting the lichen community composition and coverage than tree stand density and saplings density in each observation term. The changes taking place in stands under bark beetle and wind disturbances should be treated differently in different types of forest associations, but in both, they cause differentiation of niches used by more specialized species of epiphytic lichens. Full article available to download by URL Share Link https://authors.elsevier.com/c/1ey36,Q4YJXeD8
... [8]. Spruce forests in the latter are shaped by infrequent disturbances ranging from low severity events to stand replacing ones, with wind and bark beetle outbreaks being the key drivers [9,10]. Wind disturbances in the Carpathian spruce forests act as resource pulses [11] recorded at the frequency of at least 14 events in the last 200 years [9,10]. ...
... Spruce forests in the latter are shaped by infrequent disturbances ranging from low severity events to stand replacing ones, with wind and bark beetle outbreaks being the key drivers [9,10]. Wind disturbances in the Carpathian spruce forests act as resource pulses [11] recorded at the frequency of at least 14 events in the last 200 years [9,10]. Windthrow, a primary disturbance, often leads to bark beetle epidemic population levels. ...
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Research Highlights: Bark beetles are important agents of disturbance regimes in temperate forests, and specifically in a connected wind-bark beetle disturbance system. Large-scale windthrows trigger population growth of the European spruce bark beetle (Ips typographus L.) from endemic to epidemic levels, thereby allowing the killing of Norway spruce trees over several consecutive years. Background and Objectives: There is a lack of evidence to differentiate how outbreaks are promoted by the effects of environmental variables versus beetle preferences of trees from endemic to outbreak. However, little is known about how individual downed-tree characteristics and local conditions such as tree orientation and solar radiation affect beetle colonization of downed trees. Materials and Methods: To answer this question, we investigated the infestation rates and determined tree death categories (uprooted, broken, and stump) in wind-damaged areas in Western Tatra Mts. in Carpathians (Slovakia) from 2014-2016, following a windthrow in May 2014. In total, we investigated 225 trees over eight transects. For every tree, we measured its morphological (tree height, crown characteristics), environmental (solar radiation, terrain conditions, trunk zenith), temporal (time since wind damage), and beetle infestation (presence, location of attack, bark desiccation) parameters. We applied Generalized Additive Mixed Models (GAMM) to unravel the main drivers of I. typographus infestations. Results: Over the first year, beetles preferred to attack broken trees and sun-exposed trunk sides over uprooted trees; the infestation on shaded sides started in the second year along with the infestation of uprooted trees with lower desiccation rates. We found that time since wind damage, stem length, and incident solar radiation increased the probability of beetle infestation, although both solar radiation and trunk zenith exhibited nonlinear variability. Our novel variable trunk zenith appeared to be an important predictor of bark beetle infestation probability. We conclude that trunk zenith as a simple measure defining the position of downed trees over the terrain can anticipate beetle infestation. Conclusions: Our findings contribute to understanding of the bark beetle's preferences to colonize windthrown trees in the initial years after the primary wind damage. Further, our findings can help to identify trees that are most susceptible to beetle infestation and to prioritize management actions to control beetle population while maintaining biodiversity.
... Mean annual precipitation ranges from 1000 mm at lower elevations to more than 2000 mm at higher elevations (UNEP, 2007). The bedrock varies from acidic to basic minerals in Slovakia (Janda et al., 2017), is mainly sandstone in Ukraine (Valtera et al., 2013) and volcanic and crystalinic in Romania (Table 1). ...
... To detect past disturbances and their severity, growth patterns of trees were screened for evidence based on their canopy accession type; gap-recruited (rapid early growth) or released, i.e. rapid change in growth rate indicating improvement in growth conditions associated with mortality of neighbouring canopy trees due to disturbance (Frelich and Lorimer, 1991;Svoboda et al., 2012). Trees were considered gaprecruited when they exhibited high (> 1.7 mm, 1.6 mm, 1.7 mm, and 1.3 mm in northern Romania, southern Romania, Slovakia, and Ukraine, respectively) average annual growth rate during first 15 years (Janda et al., 2017;Svoboda et al., 2014;Trotsiuk et al., 2014). The growth rate cut off is location specific because tree growth is climate sensitive and this has to be considered . ...
Article
Accurate estimations of changes in the forest carbon (C) pools over time are essential for predicting the future forest C balance and its part in the global C cycle. While the overall understanding of global forest C dynamics has improved, some significant forest ecosystem processes have been largely overlooked, resulting in possible biases. As an example, the effects of low and moderate severity disturbances have received disproportionately little attention. In this study, we use an extensive database of 9610 tree increment cores from 400 plots in primary uneven-aged Norway spruce (Picea abies) forests in the Carpathian Mountains, to explore the dynamics of live and dead wood C after disturbance. The data represents a chronosequence of more than 250 years since disturbance, varying highly in severity. We found that disturbance severity had a substantial impact on the post-disturbance long-term accumulation of C. Initially, live tree C accumulated at a similar rate independent of disturbance severity. However, the increase in C leveled off earlier after low disturbance severity while the most heavily disturbed forests continued to accumulate C to the latest stages of stand development. These results stress the importance of taking disturbance severity into account when predicting the long-term dynamics of C storage in forests under climate change. The results also highlight the importance of these forests as significant C pools. If harvested and turned into managed forest they would not reach their maximum C storing capacity.
... In Europe, forests are not only under indirect human influence through climate change, but many are considered to be the most intensively managed forest ecosystems, some forest types have been recognized as the most endangered ecosystems in the world (Bengtsson et al. 2000). On the one hand, the frequency and intensity of perturbations caused by climate change are likely to increase species biodiversity; on the other hand, the provisioning of some forest ecosystem services (timber, protection against natural hazards) could come under increasing pressure (Schelhaas et al. 2003;Janda et al. 2016). ...
... Various research activities studying different parts of the ecosystems were carried out at the windthrow areas in the Tatra Mts. They included studies of changes in landscape structure (Falťan et al. 2011), the geomorphic effects of the windthrow (Dąbrowska 2009), the evolution of post-windthrow forest ecosystems (Michalová et al. 2017;Havašová et al. 2017), dendrochronological analyses of the long-term disturbance regime (Zielonka et al. 2010;Janda et al. 2016), soil physical properties (Mičuda 2006;Šimkovic et al. 2009), soil microbial activity (Hanajík et al. 2017), microbial community structure (Gömöryová et al. 2014(Gömöryová et al. , 2017Hanajík et al. 2016), plant-soil interactions (Gáfriková et al 2019) and organic matter fractions (Hanajík et al. 2015;Gáfriková et al. 2018). ...
Article
Perturbations caused by windstorms usually lead to the harvesting and clearcutting of fallen trees and wood debris, especially in the areas of managed forest ecosystems. Induced shifts in soils due to management practices play a crucial role in the restoration and maintaining of key ecosystem services. This paper focuses on topsoil chemical properties in relation to vegetation type (trees, shrubs and herbs) evolving at windstorm damaged (in 2004) areas with former Norway spruce (Picea abies) forests in the Tatra Mts. region (Slovakia). We assessed the content of topsoil organic matter fractions (extractives, holocellulose (HC) and lignin (Lig)), carbon in microbial biomass (Cmic), soil organic matter (SOM) and the content of elements N, C, H and S. The study plots represent different types of post-windthrow disturbance history/regime: wooden debris extraction (EXT), wooden debris not extracted (NEX), wooden debris extraction followed by wildfire (FIR), affected by the windstorm in 2014 with the subsequent wooden debris extraction (REX) and unaffected (REF). Our results revealed significant differences among sites in the content of dichloromethane extractives (EXT vs. REX and FIR), acetone extractives (NEX vs. EXT, FIR and REF), ethanol extractives (FIR vs. EXT, NEX and REF), water extractives (FIR vs. REX, NEX) and Cmic (EXT vs. NEX, FIR and REF). The topsoil of Vaccinium myrtillus and Picea abies showed a higher ratio of C/N, N/Lig, and Lig/HC compared to Rubus idaeus, Avenella flexuosa, Calamagrostis villosa, and Larix decidua. The content of N, C, H and S varied between topsoil with shrubs (Vaccinium myrtillus, Rubus idaeus) and grasses (Avenella flexuosa, Calamagrostis villosa). A positive correlation between soil organic matter (SOM) and polar extractives (r=0.81) and a negative correlation between SOM and HC (r=−0.83) was revealed. The carbon content in microbial biomass (Cmic) is positively correlated with acid soluble lignin (ASL) (r=0.85). We also identified a strong correlation between Klason lignin (KL) and the Lig/HC ratio (r=0.97).
... The view emerging from these studies is that the dynamics of natural montane mixed-species forests is driven by disturbances of minor intensity that kill single trees or lead to the death of small groups of trees (Standovár and Kenderes 2003;Splechtna et al. 2005;Zeibig et al. 2005;Firm et al. 2009;Trotsiuk et al. 2012;Motta et al. 2015;Petritan et al. 2015;Orman and Dobrowolska 2017). Severe disturbances occurring in the form of insect outbreaks, wind and/or ice storms are infrequent Jaloviar et al. 2017;Janda et al. 2017), and the pattern of live canopy tree distribution and their mortality is close-to-random (Szwagrzyk and Czerwczak 1993;von Oheimb et al. 2005;Paluch 2007;Šebková et al. 2011;Paluch et al. 2015). As a result, canopy heterogeneity is usually characterized by a reverse J-shaped gap size frequency distribution, with larger gaps usually containing retained trees and gap expansion playing only a minor role (Kenderes et al. 2009;Kucbel et al. 2010;Nagel and Svoboda 2008;Standovár and Kenderes 2003;Zeibig et al. 2005;Parobeková et al. 2018). ...
Article
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In this study, we analysed patterns of spatial variation in the basal area of live and dead trees and structural complexity in close-to-primeval forests in the Dinaric Mts. The results were compared with an analogous study conducted in the Western Carpathians. The research was carried out in the Janj, Lom and Perucića forest reserves (Bosnia and Herzegovina) in mixed-species stands of silver fir Abies alba Mill., European beech Fagus sylvatica L. and Norway spruce Picea abies (L.) H. Karst. In the core zones of the reserves, concentric sample plots (154 and 708 m2) were set in a regular 20 × 20 m grid covering approximately 10 ha. The analyses revealed varying distribution patterns of live canopy trees, suggesting that these characteristics may fluctuate to some extent at the regional level. At the spatial scale of 708 m2, attractive associations between dead canopy trees were found, but this tendency disappeared with increasing area. Although stands in the Dinaric Mts. are characterized by an almost twofold greater biomass accumulation compared to those from the Western Carpathians, the study revealed analogous bell-shaped distributions of stand basal areas of live trees and a very similar trend of decreasing variation in stand basal area and structural heterogeneity with increasing spatial scale. Nonetheless, the higher growing stocks, lower ratios of dead to live tree basal area and lower proportion of homogeneous structure types found in the Dinaric Mts. may suggest a less severe disturbance history over recent decades in this region compared to the Western Carpathians.
... Spruce stands have been dying out since the end of the 1950s. The dying-off process in mountain spruce forests was caused by several biotic (bark beetles) and non-biotic factors (air pollution), forming a cause-and-effect chain that reinforced the disease process, resulting in a total annihilation of the stand over an extended period of time [81][82][83]. Air pollution, prolonged summer droughts in the years 2003-04 and 2006-07, and the catastrophic hurricane of 2004 resulted in the weakening of spruce stands in the montane zone [84,85]. ...
Article
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Changes in forest range are caused by human activity in many regions of the world. The aim of this paper is an attempt to determine the impact of pastoral and forest management on changes in forest cover and their fragmentation in the Silesian Beskids (southern Poland) in 1848–2015. Historical maps and landscape metrics were used to study changes in forest cover. Using a digital map of forests, analyses of the distribution of forest communities, site types and their condition were conducted. Since 1848 the forest area has increased by 11.8%, while the area of forest core zones has increased by 16.2%, accompanied by a 4.5% reduction in the forest’s internal bu�er zone. From the mid-nineteenth century, the forest range has been systematically growing from 82.1 to 93.9% because of the pastureland abandonment and forest regeneration, despite temporary logging resulting in forest fragmentation. Minor changes in core area index (CAI) from 80.41 to 87.55 indicate that pastoral economy did not result in considerable fragmentation of forests. The impact of forest management was greater as the sites characterised by natural condition occupy only 28% of the forest land and anthropogenically transformed ones dominate occupying over 50%. An artificial spruce monoculture was died-o� and large felling areas were created at the beginning of the twenty-first century covering almost 40% of the study area.
... Zmenená ekologická situácia sa prejavuje rastom teploty, nerovnomerným rozložením a deficitom zrážok vo vegetačnom období (Vencurik et al. 2017), ale aj zvýšenou frekvenciou víchric a následnou abundanciou lykožrúta smrekového (Škvarenina et al. 2018). Tieto faktory spôsobili za posledných 30 rokov veľkoplošný rozpad smrekových prírodných lesov na území Slovenska, hlavne v orografických celkoch Pilsko, Babia hora a Vysoké Tatry (Saniga 2002;Vorčák et al. 2006;Grodzki et al. 2010), ako aj v celej strednej Európe (Bauer et al. 2008;Svoboda et al. 2012;Janda et al. 2017). ...
Article
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The research deals with the description of basic characteristics of stand structure and regeneration processes according to affecting factors. Characteristics are described before and after large-scale bark beetle outbreak in the high mountain spruce forest of the National Nature Reserve (NNR) Kotlov žľab. In 1968, a series of three permanent research plots (PRP) with the size of 0.50 ha was established at an altitude of 1400– 1500 m. Measurements of the stand structure and regeneration processes were carried out in 1968, 1978, 1988, 1998 and 2019. Before the largescale disturbance, the high mountain spruce forest was little differentiated and was dominated by single tree layer with stagnant regeneration. The development in PRP 3, which had initially the lowest number of trees, the highest variability of tree diameters and was located at the lowest altitude, responded best to the effect of disturbance. However, taking into account the forest development after disturbance, we can state that in 2019 there was a sufficient amount of advanced spruce regeneration in all PRPs, which will ensure that development does not take place through early successional stages. In the initial stage of the forest development, rowan could be expected to fill openings among remaining spruce trees
... In regard to Europe there is currently little quantitative information available on disturbance regimes and their changes over time, especially when considering both natural and human disturbances. While previous studies have characterized the disturbance regimes of some of Europe's forest ecosystems 4,18,[25][26][27] , those studies have either focused on purely natural processes, lack a spatially and temporally consistent data source or focus only on the regional scale. Due to this lack of quantitative information at a continental scale, we do not know, for instance, how disturbance size, frequency and severity vary across Europe. ...
Article
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Changes in forest disturbances can have strong impacts on forests, yet we lack consistent data on Europe’s forest disturbance regimes and their changes over time. Here we used satellite data to map three decades of forest disturbances across continental Europe, and analysed the patterns and trends in disturbance size, frequency and severity. Between 1986 and 2016, 17% of Europe’s forest area was disturbed by anthropogenic and/or natural causes. We identified 36 million individual disturbance patches with a mean patch size of 1.09 ha, which equals an annual average of 0.52 disturbance patches per km2 of forest area. The majority of disturbances were stand replacing. While trends in disturbance size were highly variable, disturbance frequency consistently increased and disturbance severity decreased. Here we present a continental-scale characterization of Europe’s forest disturbance regimes and their changes over time, providing spatial information that is critical for understanding the ongoing changes in Europe’s forests. Changes in forest disturbance affect their sustainability. This study finds that between 1986 and 2016, 36 million disturbances by humans or other causes affected 17% of Europe’s forest area.
... Zmenená ekologická situácia sa prejavuje rastom teploty, nerovnomerným rozložením a deficitom zrážok vo vegetačnom období (Vencurik et al. 2017), ale aj zvýšenou frekvenciou víchric a následnou abundanciou lykožrúta smrekového (Škvarenina et al. 2018). Tieto faktory spôsobili za posledných 30 rokov veľkoplošný rozpad smrekových prírodných lesov na území Slovenska, hlavne v orografických celkoch Pilsko, Babia hora a Vysoké Tatry (Saniga 2002;Vorčák et al. 2006;Grodzki et al. 2010), ako aj v celej strednej Európe (Bauer et al. 2008;Svoboda et al. 2012;Janda et al. 2017). ...
Article
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PRED A POSTDISTURBANČNÝ VÝVOJ SMREKOVÉHO PRÍRODNÉHO LESA V ZÁPADNÝCH TATRÁCH ZLV, 65, 2020 (4): 223-231 223 p r o o f c o p y ÚVOD Disturbančné procesy sú kľúčovým faktorom, ktorý ovplyvňuje štruktúru a vývoj lesných ekosystémov (Oliver, Larson 1996). Skú-manie a pochopenie rastových a vývojových procesov prebiehajúcich pri disturbančnom pôsobení má podstatný vplyv pre odvodenie zásad a princípov trvalo udržateľného obhospodarovania lesných ekosysté-mov (Attiwill 1994). Najčastejšie sa vyskytujúcimi disturbanciami vo vysokororských smrekových ekosystémoch sú vetrové a podkôr-nikové kalamity (Seidl et al. 2011; Zeppenfeld et al. 2015; Holeksa et al. 2017). Ako potvrdili dendrochronologické analýzy, rizikom rozpadu smrekových prírodných lesov na Slovensku je skutočnosť, že v minulosti boli tieto lesné ekosystémy veľkoplošne atakované vetrom s následným vytvorením realtívne rovnovekých štruktúr. V súčasnom období sa prevažná časť smrekových prírodných lesov Slovenska na-chádza v štádiu optima (Janda et al. 2017). Takáto textúra vysoko-ZPRÁVY LESNICKÉHO VÝZKUMU, 65, 2020 (4): 223-231 ABSTRACT The research deals with the description of basic characteristics of stand structure and regeneration processes according to affecting factors. Characteristics are described before and after large-scale bark beetle outbreak in the high mountain spruce forest of the National Nature Reserve (NNR) Kotlov žľab. In 1968, a series of three permanent research plots (PRP) with the size of 0.50 ha was established at an altitude of 1400-1500 m. Measurements of the stand structure and regeneration processes were carried out in 1968, 1978, 1988, 1998 and 2019. Before the large-scale disturbance, the high mountain spruce forest was little differentiated and was dominated by single tree layer with stagnant regeneration. The development in PRP 3, which had initially the lowest number of trees, the highest variability of tree diameters and was located at the lowest altitude, responded best to the effect of disturbance. However, taking into account the forest development after disturbance, we can state that in 2019 there was a sufficient amount of advanced spruce regeneration in all PRPs, which will ensure that development does not take place through early successional stages. In the initial stage of the forest development, rowan could be expected to fill openings among remaining spruce trees. For more information see Summary at the end of the article.
... This plot network comprises the Research of Mountain Temperate (REMOTE) forest network (see www.remot efore sts.org for more details). Forest stands are distributed both among protected and isolated unprotected areas, and were located with assistance from park managers and other local experts (Janda et al., 2017;Svoboda et al., 2014;Trotsiuk et al., 2014). Stand boundaries were delineated and inventory plot locations were determined using a stratified random design, where a 1 ha resolution grid was superimposed over the stand and plot locations were randomly selected at grid cell intersections (mean plot density per stand = 13.2, mean stand area = 30.5 ha). ...
Article
Climatic constraints on tree growth mediate an important link between terrestrial and atmospheric carbon pools. Tree rings provide valuable information on climate‐driven growth patterns, but existing data tend to be biased towards older trees on climatically extreme sites. Understanding climate change responses of biogeographic regions requires data that integrate spatial variability in growing conditions and forest structure. We analyzed both temporal (c. 1901‐2010) and spatial variation in radial growth patterns in 9 876 trees from fragments of primary Picea abies forests spanning the latitudinal and altitudinal extent of the Carpathian arc. Growth was positively correlated with summer temperatures and spring moisture availability throughout the entire region. However, important seasonal variation in climate responses occurred along geospatial gradients. At northern sites, winter precipitation and October temperatures of the year preceding ring formation were positively correlated with ring width. In contrast, trees at the southern extent of the Carpathians responded negatively to warm and dry conditions in autumn of the year preceding ring formation. An assessment of regional synchronization in radial growth variability showed temporal fluctuations throughout the 20th century linked to the onset of moisture limitation in southern landscapes. Since the beginning of the study period, differences between high and low elevations in the temperature sensitivity of tree growth generally declined, while moisture sensitivity increased at lower elevations. Growth trend analyses demonstrated changes in absolute tree growth rates linked to climatic change, with basal area increments in northern landscapes and lower altitudes responding positively to recent warming. Tree growth has predominantly increased with rising temperatures in the Carpathians, accompanied by early indicators that portions of the mountain range are transitioning from temperature to moisture limitation. Continued warming will alleviate large‐scale temperature constraints on tree growth, giving increasing weight to local drivers that are more challenging to predict. This article is protected by copyright. All rights reserved.
... Although fire events cannot be excluded in general, these were common, particularly in early and middle Holocene [4,5]. Occasional uprooting and breaking of single to several trees or the whole-stand disturbance during storms usually followed by an outbreak of bark beetles can result in canopy openings on scales from small gaps in the size of fractions of a hectare to large areas spanning over thousands of hectares [6][7][8][9]. The disturbance regime of mountain spruce forests shapes their physiognomy, spatial structure, pedocomplexity and even the landform form [10] by enabling re-occurrence of early phases of forest succession and their further development towards the re-establishment of the old-growth forest [3]. ...
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Stand-replacing disturbances are a key element of the Norway spruce (Picea abies) forest life cycle. While the effect of a natural disturbance regime on forest physiognomy, spatial structure and pedocomplexity was well described in the literature, its impact on the microbiome, a crucial soil component that mediates nutrient cycling and stand productivity, remains largely unknown. For this purpose, we conducted research on a chronosequence of sites representing the post-disturbance development of a primeval Norway spruce forest in the Calimani Mts., Romania. The sites were selected along a gradient of duration from 16 to 160 years that ranges from ecosystem regeneration phases of recently disturbed open gaps to old-growth forest stands. Based on DNA amplicon sequencing, we followed bacterial and fungal community composition separately in organic, upper mineral and spodic horizons of present Podzol soils. We observed that the canopy opening and subsequent expansion of the grass-dominated understorey increased soil N availability and soil pH, which was reflected in enlarged bacterial abundance and diversity, namely due to the contribution of copiotrophic bacteria that prefer nutrient-richer conditions. The fungal community composition was affected by the disturbance as well but, contrary to our expectations, with no obvious effect on the relative abundance of ectomycorrhizal fungi. Once the mature stand was re-established, the N availability was reduced, the pH gradually decreased and the original old-growth forest microbial community dominated by acidotolerant oligotrophs recovered. The effect of the disturbance and forest regeneration was most evident in organic horizons, while the manifestation of these events was weaker and delayed in deeper soil horizons.
... We here assessed economic resilience to a severe natural disturbance event, yet the probability for such an event to occur can vary widely. In Central Europe, for instance, the historical return interval of such events lies between approximately 150 and 700 years, depending on site conditions, management regimes, and other parameters (e.g., Thom et al., 2013;Janda et al., 2017). ...
... Generally, results of disturbance detection are merged to multi-year intervals, mostly of 5-or 10-years (e.g. Altman et al., 2016;Janda et al., 2017;Lorimer, 1985;Petritan et al., 2017;Svoboda et al., 2014), with only a few studies presenting results with annual resolution (Pederson et al., 2014;Rozas, 2001). Merging the results to longer intervals may be surprising since the information about detected GRs in individual years will be lost. ...
Article
Disturbances play an important role in forest dynamics. The determination of long-term spatiotemporal characteristics of disturbance regimes is essential for understanding forest dynamics and its shifts under global changes. Tree rings are known to provide detailed insight into both temporal and spatial patterns of forest disturbance history. One of the most commonly used indirect tree-ring techniques for investigating past disturbances is growth release detection (GRD), i.e. the abrupt radial growth increase of trees as a reaction to improved light conditions after the death of a disturbed neighbouring canopy tree or trees. However, there are several issues which have not been addressed so far. Here, an overview of GRD and guide for researchers aiming to incorporate GRD into their research is provided, with focus on conventional running mean methods. The aim is to cover various issues of the GRD procedure such as sampling strategy and data quality, selection of appropriate methods and parameter settings, suggested analysis procedures as well as result presentation. Overall, the importance of GRD incorporation in multidisciplinary studies of forest dynamics is highlighted, as it offers a precise tool for gathering long-term information about past disturbances. Lastly, this paper also suggests several future challenges focused on possible utilization of GRD in mainstream ecology to answer long-standing global ecological questions and improve understanding of past processes in forest ecosystems.
... We excluded stand-replacing disturbances because many of the historical disturbances were large-scale clear-cuts and because natural disturbances are commonly followed by salvage logging, which affects natural regenerative processes . However, many of the HCVFs in our analyses likely experienced small-scale, natural disturbances or management that may have contributed to the diverse structures of these forests (Janda et al., 2017;Jõgiste et al., 2017;Senf et al., 2020). We further caution that certain characteristics of primary and old-growth forests (e.g., amount of standing and downed deadwood) cannot be estimated with the remotely sensed data we used. ...
Article
High conservation value forests (HCVF) are critically important for biodiversity and ecosystem service provisioning, but face manifold threats. Where systematic HCVF inventories are missing, such as in parts of Eastern Europe, these forests remain largely unacknowledged and therefore often unprotected. Here, we propose a novel, transferable approach for detecting HCVF, based on integrating historical spy satellite images, contemporary remote sensing data and information on current anthropogenic pressures. Using Romania as a pilot‐study, we mapped forest continuity (1955‐2019), canopy structural complexity, and anthropogenic pressures, and identified a large area (738,000 ha) of HCVF. More than half of this area is susceptible to current anthropogenic pressures and lacks formal protection. By providing a framework for broad‐scale HCVF monitoring, our approach facilitates integration of HCVF into forest conservation and management. This is urgently needed to achieve the goals of the European Union's Biodiversity Strategy to maintain valuable forest ecosystems. This article is protected by copyright. All rights reserved
... In the last 5 years, landscape ecologists have continued their seminal focus on the relationships of pattern and process [1], addressing questions of landscape structure, landscape function, and landscape change [2]. For example, recent studies have analyzed landscape structure by examining urban green cover, rangeland distribution, wetland extent [3][4][5][6], fragmentation of forests [7], land cover and land use [8][9][10], and heterogeneity of urban and agricultural landscapes [11][12][13][14]. For relating landscape structure to ecological processes, studies have focused on habitat and resource selection by plants and animals [15][16][17][18], forest dynamics and structure [19], and pollination on agricultural lands [20,21]. ...
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Purpose of Review The purpose of this article is to review landscape ecology research from the past 5 years to identify past and future contributions from remote sensing to landscape ecology. Recent Findings Recent studies in landscape ecology have employed advances made in remote sensing. These include the use of reliable and open datasets derived from remote sensing, the availability of new sources for freely available satellite imagery, and machine-learning image classification techniques for classifying land cover types. Remote sensing data sources and methods have been used in landscape ecology to examine landscape structure. Additionally, these data sources and methods have been used to analyze landscape function including the effects of landscape structure and landscape change on biodiversity and population dynamics. Lastly, remote sensing data sources and methods have been used to analyze historical landscape changes and to simulate future landscape changes. Summary The ongoing integration of remote sensing analyses in landscape ecology will depend on continued accessibility of free imagery from satellite sources and open-access data-analysis software, analyses spanning multiple spatial and temporal scales, and novel land cover classification techniques that produce accurate and reliable land cover data. Continuing advances in remote sensing can help to address new landscape ecology research questions, enabling analyses that incorporate information that ranges from ground-based field samples of organisms to satellite-collected remote sensing data.
... expected potential natural vegetation (PNV; Appendix S1: Table S5). For the old-growth simulations, mortality due to major landscape-level (stand-replacing) disturbances was excluded, while we applied an average disturbance period of 300 yr (Schumacher 2004, Janda et al. 2017 for the shifting-mosaic simulations. For all long-term applications, we started the simulations from bare ground and ran them for 1500 yr (i.e., to a dynamic equilibrium state). ...
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Citation: Huber, N., H. Bugmannand V., Lafond. 2020. Capturing ecological processes in dynamic forest models: why there is no silver bullet to cope with complexity. Ecosphere 11(5):e03109. Abstract. Dynamic forest models are a key tool to better understand, assess, and project decadal-to centennial scale forest dynamics. Despite their success, many questions regarding appropriate model formulations remain unresolved, and few models have found widespread application, for example, across a whole continent. We aimed to scrutinize the representation of ecological processes in dynamic forest models so as to rigorously test core assumptions underlying forest dynamics and the consistency of their interplay, taking the ForClim model as a case study. We developed a set of alternative representations for the main ecological processes, that is, tree establishment, growth, and mortality, and light extinction through the canopy, based on diverse sources of empirical data. We applied a pattern-oriented modeling (POM) approach to test all combinations of the standard and alternative formulations (>500 model versions) against a comprehensive set of patterns for diverse model applications across a wide range of site conditions. We found that adapting one process in isolation can improve model performance for one specific application. However, the best model versions typically included more than one alternative formulation. Importantly, the best version for an individual application was generally not the best across multiple applications , emphasizing the varying influences of ecological processes. We conclude that the behavior and performance of complex models should not be analyzed for a few specific applications only. Rather, multiple applications, system states, and dynamics of interest should be scrutinized across a wide range of site conditions. This allows for avoiding overfitting and detecting and eliminating structural shortcomings and parameterization problems. We thus propose to make use of the ever-increasing data availability and the POM framework to challenge the core processes of dynamic models in a holistic manner. For model applications , we propose that a set of alternative formulations (ensemble simulations) should be used to quantify the impacts of structural uncertainty, rather than to rely on the projections from one single model version.
... Recent dendroecological studies on European primary Picea forests show that increasingly common high-severity disturbances are not only a result of climate change and should be reinterpreted considering legacy effects (resulting in increased susceptibility e.g., Schurman et al., 2018). In contrast with the literature on stand scale natural disturbance reconstructions (e.g., Szewczyk et al., 2011), recent landscape level studies show that large scale natural disturbances historically occurred in primary (unmanaged) forest landscapes (Svoboda et al., 2014;Janda et al., 2017). This study contributes to the conception that bark beetle outbreaks, even in their unprecedented magnitude, are acting as a natural disturbance agent in temperate conifer mountain forest (e.g., Kulakowski, 2016). ...
Article
Temperate mountain forests have experienced an increase in frequency and severity of natural disturbances (e.g., droughts, fires, windstorms and insect outbreaks) in recent decades due to climate and environmental change. Outbreaks of bark beetles have caused significant dieback of conifer forests in Central Europe and it is essential to model and predict the potential severity of future bark beetle outbreaks. However, to predict future bark beetle activity, historical baseline information is required to contextualize the magnitude of current and potential future outbreaks. A fossil beetle record from a forest hollow in the Tatra Mountains, Slovakia; one of the best-preserved national parks in Central Europe, was produced to identify insect outbreaks during the last millennia. Sub-fossil bark beetle re-mains were compared with parallel pollen and charcoal to assess whether peaks in conifer bark beetle remains correspond with indications of disturbance documented in historical or sedimentary fossil records. Three peaks in bark beetle remains were detected (1) post-2004, (2) AD 1140-1440, and (3) AD930-1030. The abundance of speciesPityogenes chalcographusandPityophthorus pityographus in the two top samples can be linked directly to large bark beetle outbreaks in the High Tatra Mountains after 2004. P. chalcographus and P. pityographus are also the abundant species in the second peak (AD 1140e1440) while the third peak (AD 930e1030) consists of the species Polygraphus poligraphus. The most prominent conifer bark beetle in Central Europe, Ips typographus, was found to be present in most of the samples but always at very low numbers. It is plausible that P. chalcographus and P. pityographus fossils might be useful proxies for past conifer bark beetle outbreaks in Central Europe, as they occur together with fossils of I. typographus but appear to be well-preserved. A significant correlation was found between primary bark beetles and macroscopic charcoal densities in the sediment, highlighting the complex interactions between disturbance agents, bark beetles and fire, in this long-term regime of natural disturbances. Our 1400-year disturbance record shows how bark beetle outbreaks have been an important component of the regional natural disturbance regime for over a millennium and have intensified with increasing anthropogenic activity. Bark beetle outbreaks are likely one of the drivers promoting the future ecological stability of the temperate conifer ecosystem over decades to centuries.
... Disturbances are recognized as a natural part of the dynamics of ecosystems (Janda et al. 2016), and some are even considered necessary for the functioning of certain biological systems (Andersen 1991;Bunnell 1995). Therefore, natural disturbances are essential since they directly or indirectly influence the world's ecosystems. ...
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Background Recruitment after disturbance events depends on many factors including the environmental conditions of the affected area and the vegetation that could potentially grow in such affected areas. To understand the regeneration characteristics that occurs in temperate forests, we evaluated differences in the number of seedlings from trees and shrubs along an altitudinal gradient in Sierra Norte of Oaxaca, Mexico in different biological, climatic, edaphic, light, topographic, and disturbance regimes. Here, we aimed to test the hypothesis that the environmental disturbances influence on recruitment (positive or adverse influence). We sampled the vegetation to obtain recruitment and adult data, and species composition. Results We identified three disturbance regimes: areas affected by forest harvesting, areas exposed to pest management, and undisturbed areas. We identified 29 species of trees and shrubs (9 species of the genus Pinus , 1 species of the genus Abies , 10 species of the genus Quercus, and 9 of other species of broadleaf). We found that both environmental conditions and disturbances influence the recruitment of vegetation in the study area. In particular, disturbances had a positive influence on the regeneration of oak and other broadleaf species by increasing the number of seedlings, and a negative influence on the regeneration of conifers by decreasing the recruitment. Because the recruitment of conifers is more likely in undisturbed areas (sites over 3050 m). Conclusions Environmental factors and anthropogenic disturbances can alter the recruitment of forests. Consequently, knowing which factors are key for the recruitment of vegetation is fundamental for decision-making processes. This is particularly relevant in areas as the one in this study because it provides knowledge to local people on vegetation recovery for a proper management of their biological resources.
... Mountain spruce forests (Picea abies L. Karst.) are shaped by disturbances, ranging in severity from low-to stand-replacing. The main drivers of such disturbances in the Carpathians are wind and bark beetle outbreaks [2,3], the latter usually initiated by extreme weather events [4,5] and affected by forest management [6][7][8]. ...
Article
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In recent decades, Norway spruce (Picea abies L. Karst.) forests of the High Tatra Mountains have suffered unprecedented tree mortality caused by European spruce bark beetle (Ips typographus L.). Analysis of the spatiotemporal pattern of bark beetle outbreaks across the landscape in consecutive years can provide new insights into the population dynamics of tree-killing insects. A bark beetle outbreak occurred in the High Tatra Mountains after a storm damaged more than 10,000 ha of forests in 2004. We combined yearly Landsat-derived bark beetle infestation spots from 2006 to 2014 and meteorological data to identify the susceptibility of forest stands to beetle infestation. We found that digital elevation model (DEM)-derived potential radiation loads predicted beetle infestation, especially in the peak phase of beetle epidemic. Moreover, spots attacked at the beginning of our study period had higher values of received solar radiation than spots at the end of the study period, indicating that bark beetles prefer sites with higher insolation during outbreak. We conclude that solar radiation, easily determined from the DEM, better identified beetle infestations than commonly used meteorological variables. We recommend including potential solar radiation in beetle infestation prediction models.
... Forest structure is shaped by highly variable mixed-severity natural disturbances (Svoboda et al., 2012), consisting of windstorms and outbreaks of bark beetles (Emborg et al., 2000). At local site scales, gap forming wind disturbances re-occur with an average frequency of ~40 years (Janda et al., 2017). High-severity landscape-scale wind or insect events that cause extensive tree mortality (>50% of canopy trees) are also prevalent. ...
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Plant traits are an expression of strategic tradeoffs in plant performance that determine variation in allocation of finite resources to alternate physiological functions. Climate factors interact with plant traits to mediate tree survival. This study investigated survival dynamics in Norway spruce (Picea abies) in relation to tree-level morphological traits during a prolonged multi-year outbreak of the bark beetle, Ips typographus, in Central Europe. We acquired datasets describing the trait attributes of individual spruce using remote sensing and field surveys. We used nonlinear regression in a hypothesis-driven framework to quantify survival probability as a function of tree size, crown morphology, intraspecific competition and a growing season water balance. Extant spruce trees that persisted through the outbreak were spatially clustered, suggesting that survival was a non-random process. Larger diameter trees were more susceptible to bark beetles, reflecting either life history tradeoffs or a dynamic interaction between defense capacity and insect aggregation behavior. Competition had a strong negative effect on survival, presumably through resource limitation. Trees with more extensive crowns were buffered against bark beetles, ostensibly by a more robust photosynthetic capability and greater carbon reserves. The outbreak spanned a warming trend and conditions of anomalous aridity. Sustained water limitation during this period amplified the consequences of other factors, rendering even smaller trees vulnerable to colonization by insects. Our results are in agreement with prior research indicating that climate change has the potential to intensify bark beetle activity. However, forest outcomes will depend on complex cross-scale interactions between global climate trends and tree-level trait factors, as well as feedback effects associated with landscape patterns of stand structural diversity.
... on, supporting our initial hypothesis (H2). These findings are in line with previous studies relating forest composition and structure to disturbances.Panayotov, Kulakowski, Laranjeiro Dos Santos, and Bebi (2011), for instance, using empirical data and remote sensing, related large variation in tree heights and diameters to prior wind disturbances.Janda et al. (2017) documented that past disturbance severity is a strong driver of current stand structure, using a combination of dendroecology and historical data sources.Kayes and Tinker (2012) andVeblen, Hadley, Reid, and Rebertus (1991) found that bark beetles increase the structural and compositional diversity by releasing advanced regeneration and ...
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Bark beetle outbreaks have intensified in many forests around the globe in recent years. Yet, the legacy of these disturbances for future forest development remains unclear. Bark beetle disturbances are expected to increase further because of climate change. Consequently, feedbacks within the disturbance regime are of growing interest, for example, whether bark beetle outbreaks are amplifying future bark beetle activity (through the initiation of an even‐aged cohort of trees) or dampening it (through increased structural and compositional diversity). We studied bark beetle–vegetation–climate interactions in the Bavarian Forest National Park (Germany), an area characterised by unprecedented bark beetle activity in the recent past. We simulated the effect of future bark beetle outbreaks on forest structure and composition and analysed how disturbance‐mediated forest dynamics influence future bark beetle activity under different scenarios of climate change. We used process‐based simulation modelling in combination with machine learning to disentangle the long‐term interactions between vegetation, climate and bark beetles at the landscape scale. Disturbances by the European spruce bark beetle were strongly amplified by climate change, increasing between 59% and 221% compared to reference climate. Bark beetle outbreaks reduced the dominance of Norway spruce (Picea abies (L.) Karst.) on the landscape, increasing compositional diversity. Disturbances decreased structural diversity within stands (α diversity) and increased structural diversity between stands (β diversity). Overall, disturbance‐mediated changes in forest structure and composition dampened future disturbance activity (a reduction of up to −67%), but were not able to fully compensate for the amplifying effect of climate change. Synthesis. Our findings indicate that the recent disturbance episode at the Bavarian Forest National Park was caused by a convergence of highly susceptible forest structures with climatic conditions favourable for bark beetle outbreaks. While future climate is increasingly conducive to massive outbreaks, the emerging landscape structure is less and less likely to support them. This study improves our understanding of the long‐term legacies of ongoing bark beetle disturbances in Central Europe. It indicates that increased diversity provides an important dampening feedback, and suggests that preventing disturbances or homogenizing post‐disturbance forests could elevate the future susceptibility to large‐scale bark beetle outbreaks.
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The expected future intensification of forest disturbance as a consequence of ongoing anthropogenic climate change highlights the urgent need to more robustly quantify associated biotic responses. Saproxylic beetles are a diverse group of forest invertebrates representing a major component of biodiversity that is associated with the decomposition and cycling of wood nutrients and carbon in forest ecosystems. Disturbance-induced declines or shifts in their diversity indicate the loss of key ecological and/or morphological species traits that could change ecosystem functioning. Functional and phylogenetic diversity of biological communities is commonly used to link species communities to ecosystem functions. However, our knowledge on how disturbance intensity alters functional and phylogenetic diversity of saproxylic beetles is incomplete. Here, we analyzed the main drivers of saproxylic beetle abundance and diversity using a comprehensive dataset from montane primary forests in Europe. We investigated cascading relationships between 250 years of historical disturbance mechanisms, forest structural attributes and the taxonomic, phylogenetic and functional diversity of present-day beetle communities. Our analyses revealed that historical disturbances have significant effects on current beetle communities. Contrary to our expectations, different aspects of beetle communities, that is, abundance, taxonomic, phylogenetic and functional diversity, responded to different disturbance regime components. Past disturbance frequency was the most important component influencing saproxylic beetle communities and habitat via multiple temporal and spatial pathways. The quantity of deadwood and its diameter positively influenced saproxylic beetle abundance and functional diversity, whereas phylogenetic diversity was positively influenced by canopy openness. Analyzing historical disturbances, we observed that current beetle diversity is far from static, such that the importance of various drivers might change during further successional development. Only forest landscapes that are large enough to allow for the full range of temporal and spatial patterns of disturbances and post-disturbance development will enable long-term species coexistence and their associated ecosystem functions.
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Zusammenfassung Bergmischwälder aus Fichte (Picea abies (L.) Karst), Weißtanne (Abies alba Mill.) und Europäischer Rot-buche (Fagus sylvatica) bedecken in Europa eine Gesamtfläche von mehreren Millionen Hektar. Sie verbinden die Buchenwaldgesellschaften im Tiefland mit den fichtendominierten, alpinen Waldtypen. Aufgrund ihrer Höhenzonierung sind diese Wälder besonders von den Auswirkungen des Klimawandels betroffen. Darüber hinaus ermöglichen neue Erschließungstechniken innovative Möglichkeiten einer intensivierten Bergwaldbewirtschaftung. Da jedoch wenig über die langfristige Entwicklung der Produk-tivität dieser Waldsysteme in Europa bekannt ist, sind belastbare Informationen über Produktivität und Anpassungsmöglichkeiten erforderlich, um nachhaltige Bewirtschaftungspläne zu entwickeln. Vor die-sem Hintergrund wurden in der vorliegenden Arbeit 59 langfristige Bergmischwald-Versuchsflächen entlang eines Höhengradienten in Europa untersucht. Der periodische jährliche Volumenzuwachs (iV) auf Bestandsebene, sowie die artspezifische Produktivitätsentwicklung in den letzten 30 Jahren bilde-ten den Schwerpunkt der Untersuchung. So konnte im Rahmen der Studie erstmals eine durchschnittli-che Produktivität der gemäßigten Bergmischwälder Europas ermittelt werden (9,3 m³ha-1 a-1 über alle Bereiche hinweg). Die Entwicklung zeigt, dass die Produktivität auf Bestandsniveau in den letzten Jahr-zehnten insgesamt konstant geblieben ist. Die artenspezifische Produktivitätsanalyse zeigt, dass der iV der Fichte zu Beginn der Studie (1980) noch etwa 14 m 3 ha-1 a-1 betrug und heute knapp 11 m 3 ha-1 a-1 beträgt. Mit knapp 7 m 3 ha-1 a-1 ist der iV der Tanne der niedrigste der drei Baumarten zu Beginn der Untersuchungsperiode. Das Wachstum der Tanne steigt jedoch signifikant auf über 11 m³ha-1 a-1 und ist damit heute die produktivste Baumart in den Berg-Mischwäldern Europas. Die Buche wächst über den gesamten Untersuchungszeitraum mit einer Wachstumsrate von ca. 8,2 m³ha-1 a-1. Der Rückgang der Produktivität der Fichte in den letzten 30 Jahren konnte somit durch eine Steigerung der Produktivität der Tanne weitgehend kompensiert werden und erklärt den konstanten iV auf Bestandsebene. Folglich konstatieren wir stabile Volumenzuwächse in Bezug auf den Klimawandel. Damit scheint eine kontinu-ierliche Versorgung mit Ökosystemgütern aus Berg-Mischwäldern gewährleistet zu sein. Summary Mixed mountain forests of Norway spruce (Picea abies (L.) Karst), silver fir (Abies alba Mill.) and Euro-pean beech (Fagus sylvatica) cover a total area of several million hectares in Europe. They connect the beech forest communities in the lowlands with the spruce-dominated alpine forest types. Due to their height zoning, these forests are particularly affected by climate change. In addition, new development techniques enable innovative possibilities for intensified mountain forest management. However, as little is known about the long-term development of the productivity of these forest systems in Europe, reliable information on productivity and adaptation options is required in order to develop sustainable management plans. Against this background, 59 long-term mixed mountain forest experimental plots along a height gradient in Europe were investigated in this study. The periodic annual volume increment (iV) at stand level as well as the species-specific productivity development over the last 30 years formed the focus of the study. For the first time, an average productivity of Europe's temperate mixed mountain forests (9.3 m³ha-1a-1 across all areas) could be determined within the framework of the study. This development shows that overall productivity at stand level has remained constant over the past decades. The species-specific productivity analysis showed that the iV of spruce at the beginning of Hilmers et al.: Zur Produktivität von Bergmischwäldern aus Picea abies, Abies alba und Fagus sylvatica in Europa DVFFA-Sektion Ertragskunde 25 Beiträge zur Jahrestagung 2018 the study (1980) was still about 14 m 3 ha-1 a-1 and today is just under 11 m 3 ha-1 a-1. With just under 7 m 3 ha-1 a-1 , the iV of fir is the lowest of the three tree species at the beginning of the study period. However , the growth of fir rises significantly to over 11 m 3 ha-1 a-1 and is therefore today the most productive tree species in the mixed mountain forests of Europe. Beech grows at a growth rate of approx. 8.2 m³ha-1 a-1 over the entire period under study. The decline in spruce productivity over the last 30 years has thus been largely compensated by an increase in fir productivity and explains the constant iV at stand level. Consequently, we observe stable volume increases in relation to climate change. This seems to guarantee a continuous supply of ecosystem goods from mixed mountain forests.
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Strong winds, fire, and subsequent forest management impact arthropod communities. We monitored the diversity and changes in the community structure of forest thrips assemblages in the context of secondary succession and anthropogenic impact. There were eight study plots that were affected to varying degrees by the mentioned disturbances that were selected in the Central European spruce (Picea abies (L.) Karst.) forests in Slovakia. The soil photoeclectors were used to obtain thrips in the study plots during two vegetation seasons. The thrips assemblages and their attributes were analyzed by non-metric multidimensional scaling (NMDS). The significant changes in community structure, composition, stratification, species richness, and diversity of thrips assemblages that were caused by natural- (wind) and human-induced disturbance (forestry and fire) were observed in our research. Our analyses revealed a clear relationship between different thrips assemblages and impacted environment. Moreover, our results indicate that silvicolous thrips species may be useful for indicating changes and disturbances in forest ecological systems.
Article
Disentangling the long-term changes in forest disturbance dynamics provides a basis for predicting the forest responses to changing environmental conditions. The combination of multidisciplinary records can offer more robust reconstructions of past forest disturbance dynamics. Here we link disturbance histories of the central European mountain spruce forest obtained from dendrochronological and palaeoecological records (fossil pollen, sedimentary charcoal, bark beetle remains and geochemistry) using a small glacial lake and the surrounding forest in the Šumava National Park (Czech Republic). Dendrochronological reconstructions of disturbance were created for 300-year-long records from 6 study plots with a minimum of 35 trees analyzed for the abrupt growth increases (releases) and rapid early growth rates, both indicative of disturbance events. High-resolution analysis of lake sediments were used to reconstruct 800-year long changes in forest composition and landscape openness (fossil pollen), past fire events (micro- and macroscopic charcoal), bark beetle occurrence (fossil bark beetle remains), and erosion episodes (geochemical signals in the sediment) potentially resulting from disturbance events. Tree-ring data indicate that disturbances occurred regularly through the last three centuries and identify a most intensive period of disturbances between 1780 and 1830 CE. Geochemical erosion markers (e.g. K, Zr, % inorganic) show greater flux of catchment sediment and soils in the periods 1250–1400 and 1450–1500 CE, before a substantial shift to a more erosive regime 1600–1850 and 1900 CE onwards. Pollen records demonstrate relatively small changes in forest composition during the last 800 years until the beginning of the 20th century, when there was decrease in Picea. Fossil bark beetle remains indicate continuous presence of bark beetles from 1620s to 1800s, and charcoal records suggest that more frequent fires occurred during the 18th century. Each of the dendrochronological, palaeoecological and sedimentological records provide a unique perspective on forest disturbance dynamics, and combined offer a more robust and complete record of disturbance history. We demonstrate that sedimentary proxies originating from the lake catchment mirror the forest disturbance dynamics recorded in the tree-rings. The multidisciplinary records likely record forest disturbances at different spatial and temporal scales revealing different disturbance characteristics. Integrating these multidisciplinary datasets demonstrates a promising way to obtain more complete understanding of long-term disturbance dynamics. However, integrating datasets with variable spatial and temporal influence remains challenging. Our results indicated that multiple disturbance factors, such as windstorms, bark beetle outbeaks and fires, may occur simultaneously creating a complex disturbance regime in mountain forests, which should be considered in forest management and conservation strategies.
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The paper discusses changes in forest-forming species in the nemoral spruce forests of the Central Forest Reserve (Tver Region, the Russian Federation). A comparison is made of the characterization of vegetation in the reserve spruce forests, carried out during the first survey of the reserve by Ya. Ya. Alekseev in 1931 (Alekseev, 1935) with the descriptions of vegetation made by the author from 2011 to 2019. It is shown that the coverage of nemoral herbs in the spruce forests of the reserve has increased over the past 90 years. In addition, three types of broadleaf trees (Tilia cordata Mill., Acer platanoides L. and Ulmus scabra Mill.) have greatly increased their abundance in the stand, most notably the linden. In recent decades, the decay of nemoral spruce forests has been taking place in the Central Forest Reserve. The birch-aspenspruce stand is not replenished with spruce renewal but is replaced by linden-maple forests. The vitality of spruce undergrowth is deteriorating. After the decay of a spruce forest, a change of the tree dominants occurs on 74% of the trial plots and the stand continues with a spruce forest on 26%. The largest part of the reserve's nemoral spruce forests arose after major disturbances 100–150 years ago (on the site of burned-out areas, hurricane windblows and cuttings). Old nemoral spruce forests were formed during the period when severe frosts prevented linden and maple from entering the stand. Currently, the coincidence of climate warming with the aging of the spruce stand and the removal of anthropogenic influence contributed to the release of maple and linden from the undergrowth into the stand and change to a spruce-deciduous forest. Under the prevailing climatic conditions, a return to the spruce forest is possible in the event of a burning out or when the climate becomes cold. The nemoral spruce forest is an ecotone type and, depending on conditions, becomes a spruce or broad-leaved forest.
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The impact of forest management on biodiversity is difficult to scrutinize along gradients of management. A step towards analyzing the impact of forest management on biodiversity is comparisons between managed and primary forests. The standardized typology of tree-related microhabitats (TreMs) is a multi-taxon indicator used to quantify forest biodiversity. We aim to analyze the influence of environmental factors on the occurrence of groups of TreMs by comparing primary and managed forests. We collected data for the managed forests in the Black Forest (Germany) and for the primary forests in the Western (Slovakia) and Southern Carpathians (Romania). To model the richness and the different groups of TreMs per tree, we used generalized linear mixed models with diameter at breast height (DBH), altitude, slope and aspect as predictors for European beech ( Fagus sylvatica (L.)) , Norway spruce ( Picea abies (L.) ) and silver fir ( Abies alba (Mill.) ) in primary and managed temperate mountain forests. We found congruent results for overall richness and the vast majority of TreM groups. Trees in primary forests hosted a greater richness of all and specific types of TreMs than individuals in managed forests. The main drivers of TreMs are DBH and altitude, while slope and aspect play a minor role. We recommend forest and nature conservation managers to focus: 1) on the conservation of remaining primary forests and 2) approaches of biodiversity-oriented forest management on the selection of high-quality habitat trees that already provide a high number of TreMs in managed forests based on the comparison with primary forests.
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Disturbances have been recognized as a key factor shaping the species composition, structure and dynamics of natural forest ecosystems. In Europe, where forests driven by spontaneous processes have survived in relic form, knowledge about natural disturbance regimes is still fragmentary. To expand this knowledge, we reconstructed stand-level growth and analyzed the spatio-temporal pattern of release signals in the increment chronologies of individual trees as indicators of disturbance events in the Western Carpathians (Central Europe). The study was carried out in five old-growth forests formed by Fagus sylvatica L., Abies alba Mill. and Picea abies (L.) H. Karst. Depending on the stand, the analyses included tree-ring series of 84–193 trees sampled over areas of 5.9–13.6 ha and aimed at determining (1) the spatio-temporal pattern of disturbance severity over the last two centuries, (2) whether disturbances have been synchronized in time across the study sites and (3) whether disturbances have induced pulsed dynamics of stand development manifested as fluctuations in radial tree increment at the level of entire stands. In the period 1850–2010, the percentage of decades with the proportion of released trees < 10, 10–20, 20–30 or more than 30% was 38, 41, 14 and 7%, respectively, and no instances of severe disturbances simultaneously impacting an extensive area and releasing the vast majority of trees were found. The release events were only weakly synchronized at the between-stand level. The spatial distribution of released trees varied over the decades, with a shift toward spatial independence for the most severe disturbances. At the stand level, the interchanging periods of increasing/decreasing tree growth lasted between 24 and 36 years, with the exception of one stand in which this period lasted 54 years. The revealed fluctuations in tree growth attributable to changes in stand density were relatively small and accounted on average for 7% of the total variation in annual tree increments. This suggests that local level disturbances introduce structural heterogeneity and strongly modify tree growth, but at the stand level, their effect is dispersed and causes only minor fluctuations. An over-dispersion of decadal release frequencies compared to the random model and spatial correlation of disturbing events on the one hand, and the lack of extensive disturbances, frequent occurrence of multiple releases in tree life histories, and small fluctuations in the reconstructed growth at the stand level on the other hand, suggest a disturbance regime which goes beyond random processes in a strict sense and is thus not entirely compatible with the classical model of gap-phase stand dynamics.
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Catastrophic wind disturbances under climatic changes are causing major economic impacts and ecological changes that can persist for decades. Bark beetle (Coleoptera: Curculionidae) population and community dynamics are often linked to such wind disturbances at several spatial and temporal scales ranging from damage to individual trees to large-scale windthrow that may prompt multiyear outbreaks on the landscape scale. In this chapter, we discuss how catastrophic wind disturbances and ensuing biological legacies enhance bark beetle populations, particularly in the context of climatic changes. The high level of variability at the tree, stand, and landscape levels created by windstorms generally has positive consequences for eruptive bark beetle species, particularly in Europe. Poststorm timber salvaging to alleviate pest burdens may push biotic elements, especially those dependent on coarse woody debris and forest gaps, into different successional pathways. Climate change is undoubtedly influencing the interactions between these two major disturbance agents by increasing their intensity and severity levels and altering landscape characteristics with feedback loops. In the Anthropocene, predictive modeling of network interactions between multiple abiotic and biotic disturbances and stressors will be critical for effective mitigation, forest restoration, and sustainable forestry practices in a rapidly changing world.
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The aim of the study was to compare a patch-mosaic pattern in the old-growth forest stands developed in various climate and soil conditions occurring in different regions of Poland. Based on the assumption, that the patch-mosaic pattern in the forest reflect the dynamic processes taking place in it, and that each type of forest ecosystem is characterized by a specific regime of natural disturbances, the following hypotheses were formulated: (i) the patches with a complex structure in stands composed of latesuccessional, shade-tolerant tree species are more common than those composed of early-successional, light-demanding ones, (ii) the patch-mosaic pattern is more heterogeneous in optimal forest site conditions than in extreme ones, (iii) in similar site conditions differentiation of the stand structure in distinguished patches is determined by the successional status of the tree species forming a given patch, (iv) the successional trends leading to changes of species composition foster diversification of the patch structure, (v) differentiation of the stand structure is negatively related to their local basal area, especially in patches with a high level of its accumulation. Among the best-preserved old-growth forest remaining under strict protection in the Polish national parks, nineteen research plots of around 10 ha each were selected. In each plot, a grid (50 × 50 m) of circular sample subplots (with radius 12,62 m) was established. In the sample subplots, species and diameter at breast height of living trees (dbh ≥ 7 cm) were determined. Subsequently, for each sample subplot, several numerical indices were calculated: local basal area (G), dbh structure differentiation index (STR), climax index (CL) and successional index (MS). Statistical tests of Kruskal- Wallis, Levene and Generalized Additive Models (GAM) were used to verify the hypotheses. All examined forests were characterized by a large diversity of stand structure. A particularly high frequency of highly differentiated patches (STR > 0,6) was recorded in the alder swamp forest. The patch mosaic in the examined plots was different – apart from the stands with a strongly pronounced mosaic character (especially subalpine spruce forests), there were also stands with high spatial homogeneity (mainly fir forests). The stand structure in the distinguished patches was generally poorly related to the other studied features. Consequently, all hypotheses were rejected. These results indicate a very complex, mixed pattern of forest natural dynamics regardless of site conditions. In beech forests and lowland multi-species deciduous forests, small-scale disturbances of the gap dynamics type dominate, which are overlapped with less frequent medium-scale disturbances. In more difficult site conditions, large-scale catastrophic disturbances, which occasionally appear in communities formed under the influence of gap dynamics (mainly spruce forests) or cohort dynamics (mainly pine forests), gain importance.
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Forest succession is an ecological phenomenon that can span centuries. Although the concept of succession was originally formulated as a deterministic sequence of different plant communities by F. Clements more than a century ago, nowadays it is recognized that stochastic events and disturbances play a pivotal role in forest succession. In spite of that, forest maps and management plans around the world are developed and focused on a unique “climax” community, likely due to the difficulty of quantifying alternative succession pathways. In this research, we explored the possibility of developing a Markov Chain model to study multiple pathway succession scenarios in mixed forests of western red cedar, hemlock and Pacific silver fir on northern Vancouver Island (western Canada). We created a transition matrix using the probabilities of change between alternative ecological stages as well as red cedar regeneration. Each ecological state was defined by the dominant tree species and ages. Our results indicate that, compared to the traditional Clementsian, deterministic one-pathway succession model, which is unable to replicate current stand distribution of these forests in the region, a three-pathway stochastic succession model, calibrated by a panel of experts, can mimic the observed landscape distribution among different stand types before commercial logging started in the region. We conclude that, while knowing the difficulty of parameterizing this type of models, their use is needed to recognize that for a given site, there may be multiple “climax” communities and hence forest management should account for them.
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A forest stand is a community where the interactions between trees and surroundings, result in a wide range of growth patterns that are also reflected in the stand biomass. The primordial features of stand structure description are structure (even-aged or uneven-aged) and composition (pure or mixed). The variability in structure and composition is high and it is reflected in the variability of growth and biomass as they are influenced by the interactions among individuals, nutrient and water uptake, light absorption, forest microclimate, density and tree distribution in space, and time. Trees’ interactions in forest stands are complex and species traits and proportions are determinant to the growth and biomass patterns. Stand structure determines forest biomass and its sustainability in space and time. Overall it can be said the more diverse stands (mixed) enable higher biomass in space, higher variability in tree’s dimensions (uneven-aged) enable more constant biomass and time, and more complex structures (mixed uneven-aged) can store more biomass in space and time. The biomass sustainability is enhanced by short regeneration periods, by complementarity of species traits, by spatial arrangements promoting complementarity, by silvicultural practices of high frequency and low severity, by maintaining the harvest intensity at a growth resilience level, by the increase of length of the harvest cycles and by the maintenance of, at least, part of the residues to promote the biomass reallocation to the soil.
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Background Assessing functional diversity to identify its spatial patterns and drivers is an important step towards understanding the adaptive capacity of ecosystems to environmental change. However, until now, these mechanisms were poorly understood in the temperate forests of northeastern China, which prevented the development of new management methods aimed at increasing functional trait diversity and thus ecological resilience. Methods In this study, we mapped functional diversity distributions using a Kriging Interpolation Method. A specific random forest model approach was adopted to test the importance ranking of 18 variables in explaining the spatial variation of functional diversity. Three piecewise structural equation models (pSEMs) with forest types as random effects were constructed for testing the direct effects of climate, and the indirect effects of stand structure on functional diversity across the large study region. Specific causal relationships in each forest type were also examined using 15 linear structural equation models. Results Although environmental filtering by climate is important, stand structure explains most of the functional variation of the forest ecosystems in northeastern China. Our study thus only partially supports the stress-dominance hypothesis. Several abundant species determine most of the functional diversity, which supports the mass ratio hypothesis. Conclusions Our results suggest that forest management aimed at increasing structural complexity can contribute to increased functional diversity, especially regarding the mixing of coniferous and broad-leaved tree species.
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The ontogenic forest life cycle of regeneration, maturation, senescence and death is a common starting point for the conceptualization of developmental pathways in forest ecosystems. Nonetheless, the usefulness of this framework under natural stand dynamics in small tree collectives formed by individuals with overlapping and weakly synchronised life cycles is not evident. This research investigated empirical relationships between local structural attributes linked with biomass accumulation, mortality in the canopy zone, the occurrence of undercanopy trees and structural heterogeneity quantified in small spatial scales and compared them with anticipations derived from the theoretical ontogenic life cycle model. The material was collected in six old-growth, mixed-species and mixed-aged forests consisting of European beech (Fagus sylvatica L.), silver fir (Abies alba Mill.) and Norway spruce (Picea abies (L.) H. Karst.) and situated in the central Dinaric Mts. (Bosnia and Herzegovina) and Western Carpathians (southern Poland). In each of the stands, a dense grid of circular plots with a radius of 7 and 15 m was established on an area of about 10 ha, and all live (d1.3 ≥ 7 cm) and dead trees (d1.3 ≥ 20 cm) growing within the plots were registered. The analyses indicated that the relationships between local basal areas of live and dead trees are very weak. Ambiguous relationships between the basal area of live and dead trees and the density of undercanopy trees, the high level of structural heterogeneity in small stand patches, and the tendency towards increasing structural heterogeneity with increasing biomass accumulation suggest that the life cycle model based on the sequence of ontogenic phases is a poor projection of the local developmental pathways in the studied ecosystem. The high level of structural heterogeneity found in small stand patches corroborated the alternative hypothesis that the mortality of canopy trees in most cases releases younger or suppressed individuals with delayed growth and only sporadically leads to the formation of a canopy opening reaching the forest floor. A general framework for an alternative model based on stochastic backward shifts was proposed. It emphasizes the diversity of possible developmental trajectories and assumes that the death of a canopy tree shifts local basal area and frequently also structural heterogeneity backwards on the developmental pathway. Depending on the pre-disturbance situation and the kind of disturbance factor, stochastic backward shifts may lead to different “states” in the space of structural attributes.
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Bark beetle outbreaks have had major impacts on Norway spruce forests in Europe. The large majority of these forests are located in areas under forest management; thus, few studies have investigated outbreak-driven spruce mortality patterns unaffected by humans. Our study examined spruce mortality resultant from a beetle outbreak in a high-elevation, unmanaged forest over a 17-year span. We analyzed three tree-level survivorship and DBH datasets collected during pre-, mid-, and post-outbreak conditions to evaluate long-term mortality dynamics. We measured changes in mortality severity, topographic and stand structure characteristics, and stand complexity using ANOVAs, and we assessed five topographic and stand structure mortality predictors by employing boosted regression trees. Our results showed that though spruce mortality increased significantly over time, such increases were disproportionate with spatial synchrony. Moreover, the outbreak did not significantly alter the living stand structure and had little effect on stand complexity, exhibiting the effects of an outbreak that spread throughout the forest without causing major stand-level damage. Larger trees at higher elevations on south-facing slopes were targeted most frequently, particularly during the later stages of the outbreak. Aspect, elevation, and slope were the best predictors of mortality, demonstrating moderate forecasting ability. We showed that bark beetle outbreaks can operate on patch-scale gradients, affecting microhabitat conditions, without resulting in sweeping, stand-altering mortality. Small-scale outbreaks may increase forest resilience against more severe outbreaks in the future by creating canopy gaps that facilitate regeneration, which leads to more complex age and size structures within the stand.
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The species-energy hypothesis predicts that more productive areas support higher species richness. Conversely, when resources are reduced, species richness is reduced. Empirical tests of whether extinctions are predominantly caused by environmental constraints or competitive exclusion are lacking. We experimentally reduced dead wood to c. 15% of the initial amount after a major windstorm and examined changes in assembly mechanisms by combining trait-based and evolutionary species dissimilarities of eight taxonomic groups, differing in their dependence on dead wood (saproxylic/non-saproxylic). Species richness and assembly mechanisms of non-saproxylic taxa remained largely unaffected by removal of dead wood. By contrast, extinctions of saproxylic species were caused by reversing the predominant assembly mechanisms (e.g. increasing importance of competitive exclusion for communities assembled through environmental filtering or vice versa). We found no evidence for an intensification of the predominant assembly mechanism (e.g. competitive exclusion becoming stronger in a competitively structured community).
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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. © 2015, National Research Council of Canada. All rights Reserved.
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In many parts of the world forest disturbance regimes have intensified recently, and future climatic changes are expected to amplify this development further in the coming decades. These changes are increasingly challenging the main objectives of forest ecosystem management, which are to provide ecosystem services sustainably to society and maintain the biological diversity of forests. Yet a comprehensive understanding of how disturbances affect these primary goals of ecosystem management is still lacking. We conducted a global literature review on the impact of three of the most important disturbance agents (fire, wind, and bark beetles) on 13 different ecosystem services and three indicators of biodiversity in forests of the boreal, cool- and warm-temperate biomes. Our objectives were to (i) synthesize the effect of natural disturbances on a wide range of possible objectives of forest management, and (ii) investigate standardized effect sizes of disturbance for selected indicators via a quantitative meta-analysis. We screened a total of 1958 disturbance studies published between 1981 and 2013, and reviewed 478 in detail. We first investigated the overall effect of disturbances on individual ecosystem services and indicators of biodiversity by means of independence tests, and subsequently examined the effect size of disturbances on indicators of carbon storage and biodiversity by means of regression analysis. Additionally, we investigated the effect of commonly used approaches of disturbance management, i.e. salvage logging and prescribed burning. We found that disturbance impacts on ecosystem services are generally negative, an effect that was supported for all categories of ecosystem services, i.e. supporting, provisioning, regulating, and cultural services (P < 0.001). Indicators of biodiversity, i.e. species richness, habitat quality and diversity indices, on the other hand were found to be influenced positively by disturbance (P < 0.001). Our analyses thus reveal a 'disturbance paradox', documenting that disturbances can put ecosystem services at risk while simultaneously facilitating biodiversity. A detailed investigation of disturbance effect sizes on carbon storage and biodiversity further underlined these divergent effects of disturbance. While a disturbance event on average causes a decrease in total ecosystem carbon by 38.5% (standardized coefficient for stand-replacing disturbance), it on average increases overall species richness by 35.6%. Disturbance-management approaches such as salvage logging and prescribed burning were neither found significantly to mitigate negative effects on ecosystem services nor to enhance positive effects on biodiversity, and thus were not found to alleviate the disturbance paradox. Considering that climate change is expected to intensify natural disturbance regimes, our results indicate that biodiversity will generally benefit from such changes while a sustainable provisioning of ecosystem services might come increasingly under pressure. This underlines that disturbance risk and resilience require increased attention in ecosystem management in the future, and that new approaches to addressing the disturbance paradox in management are needed. © 2015 The Authors. Biological Reviews published by John Wiley & Sons Ltd on behalf of Cambridge Philosophical Society.
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Insect outbreaks constitute major disturbances and global climate changes are expected to increase their frequency and severity. In Canada, an increase in outbreak severity of the jack pine budworm is expected as a consequence of more frequent droughts associated with climate changes. In this study, the impact of jack pine budworm defoliation on radial growth was assessed on two host species: jack pine (Pinus banksiana Lamb.) and scots pine (Pinus sylvestris L.). Standard tree-ring chronologies were developed for each host species in thirteen plantations established in the early 20th century and located in Spruce Woods Provincial Forest (central Canada). Radial growth suppressions caused by jack pine budworm defoliation were identified using a host and non-host comparison and calibrated against historical outbreak records. Five periods of major growth suppression were identified (1956–1958, 1966–1968, 1974–1977, 1979–1980 and 1984–1986) that matched historical jack pine budworm outbreaks. An annual tree-ring signature made up of a tree ring with thin latewood followed by a narrow ring most often characterized these growth suppressions. The occurrence of missing rings also increased during outbreaks. Based on the timing of suppression, jack pine was the initial host with scots pine often showing a one year lag in suppression. However, scots pine may be more sensitive to jack pine budworm defoliation as indicated by the abundance of missing rings during outbreak years. In the study area, jack pine budworm outbreaks were generally associated with the occurrence of dry summers and cool May temperatures. No outbreak occurred in the study area since the mid-1980s. The occurrence of droughts that were not synchronized with cool May temperatures suggests that warmer springs associated with climate changes could alter the phenological synchrony between the jack pine budworm and its host trees species. Future research should attempt to (i) relate the results of this study to natural forest stands where management practices (and non-native tree species) have not influenced the natural jack pine budworm population dynamics, (ii) assess the spatial dynamics of these outbreaks using a network of tree-ring chronologies and (iii) reconstruct outbreaks prior to historical surveys. Such research would help develop a better understanding of insect population dynamics and subsequent impacts on both European and North American forests under future climate changes.
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Support resilience and promote carbon storage, say Silvano Fares and colleagues.
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In November 2004, the Alžbeta windstorm hit the mountainous areas of northern and central Slovakia. The most affected area was Tatra National Park, where downslope wind damaged 12,000 ha of forest, mostly Norway spruce (Picea abies [L.] Karst.). In the areas with the highest level of nature conservation, about 165,000 m 3 of damaged wood was left uncleared. These uncleared sites triggered a serious bark beetle outbreak, where Ips typographus (L.) was among the dominant species. The aim of our work was to quantify and map forest damage resulting from this windstorm and subsequent insect outbreak in Tatra National Park. The objective of this article is also to present simple geographic information system (GIS) techniques available to forest managers for the detection and mapping of bark beetle infestations. The infested areas were studied using GIS and a series of color-infrared aerial photographs taken in 2005– 2009. More than 50% of all damage was recorded within 300 m, and more than 75% within 500 m, of uncleared windthrow sites. Based on our findings, we propose reinforcing post-disaster monitoring with an emphasis on (1) data acquisition and processing and (2) management of I. typographus outbreaks. For instance, we recommend using 300-m phytosanitary buffer zones in mountain spruce forests to prevent substantial beetle invasion from uncleared windthrow into adjacent stands.
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Global change is increasingly challenging the sustainable provisioning of ecosystem services to society. Addressing future uncertainty and risk has therefore become a central problem of ecosystem management. With risk management and resilience-based stewardship, two contrasting approaches have been proposed to address this issue. Whereas one is concentrated on anticipating and mitigating risks, the other is focused on fostering the ability to absorb perturbations and maintain desired properties. While they have hitherto been discussed largely separately in the literature, I here propose a unifying framework of anticipating risks and fostering resilience in ecosystem management. Anticipatory action is advocated when the predictability of risk is high and sufficient knowledge to address it is available. Conversely, in situations in which predictability and knowledge are limited, resilience-based measures are paramount. I conclude that, by adopting a purposeful combination of insights from risk and resilience research, we can make ecosystem services provisioning more robust to future uncertainty and change.
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Duncan, R.P. (1989). An evaluation of errors in tree age estimates based on increment cores in kahikatea (Dacrycarpus dacrydioides). New Zealand Natural Sciences 16: 31-37. Twelve kahikatea (Dacrycarpus dacrydioides) discs were used to assess the likely errors associated with estimating tree age from growth ring counts in increment cores. Two major sources of error were examined: (1) Failure of the increment core to pass through the tree's chronological centre. A geometric model is developed for estimating the distance to the chronological centre in cores where the arcs of the inner rings are visible. The mean percentage error from 84 cores that passed within 50 mm of the chronological centre was ± 35% corresponding to a mean absolute error of ± 21 years. The majority of this error is due to growth rate differences between the missing radius and the measured part of the core. (2) Missing rings. The average age underestimate from 48 cores due to missing rings was 13%. A significant correlation between radius length and age under estimate (r = 0.81) suggests that sampling along the longest radii will reduce this error. The average age underestimate due to missing rings from cores located along the longest radii of the twelve samples was 3%.
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Much of our understanding of natural forest dynamics in the temperate region of Europe is based on observational studies in old-growth remnants that have emphasized small-scale gap dynamics and equilibrium stand structure and composition. Relatively little attention has been given to the role of infrequent disturbance events in forest dynamics. In this study, we analyzed dendroecological data from four stands and three windthrow patches in an old-growth landscape in the Dinaric Mountains of Bosnia and Herzegovina to examine disturbance history, tree life history traits, and compositional dynamics. Over all stands, most decades during the past 340 years experienced less than 10% canopy loss, yet each stand showed evidence of periodic intermediate-severity disturbances that removed > 40% of the canopy, some of which were synchronized over the study area landscape. Analysis of radial growth patterns indicated several life history differences among the dominant canopy trees; beech was markedly older than fir, while growth patterns of dead and dying trees suggested that fir was able to tolerate longer periods of suppressed growth in shade. Maple had the fastest radial growth and accessed the canopy primarily through rapid early growth in canopy gaps, whereas most beech and fir experienced a period of suppressed growth prior to canopy accession. Peaks in disturbance were roughly linked to increased recruitment, but mainly of shade-tolerant beech and fir; less tolerant species (i.e., maple, ash, and elm) recruited successfully on some of the windthown sites where advance regeneration of beech and fir was less abundant. The results challenge the traditional notions of stability in temperate old-growth forests of Europe and highlight the nonequilibrial nature of canopy composition due to unique histories of disturbance and tree life history differences. These findings provide valuable information for developing natural disturbance-based silvicultural systems, as well as insight into maintaining less shade-tolerant, but valuable broadleaved trees in temperate forests of Europe.
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QuestionsWhat are the spatial patterns of adult trees and recruits in natural Picea abies forests? How are these patterns related to each other? Does the relationship differ before and after stand-replacing disturbance? What are the ecological processes behind these spatial patterns? LocationMountain Picea abies forests in the Sumava Mts. (Bohemian Forest), Czech Republic, affected by a high-severity outbreak of bark beetle (Ips typographus) that caused large-scale dieback of the forest canopy. Methods We measured the spatial coordinates and heights of all recruits and the coordinates and DBH of all adult trees in nine plots across a wide range of recruit densities. We distinguished pre- and post-disturbance recruits, trees killed by the disturbance and trees already dead before it. To analyse spatial relationship among these groups, we used univariate and bivariate pair-correlation functions. To provide further insight into the mechanisms behind the observed patterns, we fitted Thomas and Matern point processes to the observed data. ResultsRecruits formed tight clusters (2-9m), whereas trees were distributed randomly or weakly clustered at short distances (1-2m). Both pre-disturbance and post-disturbance recruits were highly clustered (cluster radii<2m) around trees before and after the stand-replacing disturbance. This fine-scale pattern was likely driven by a combination of: (1) seed accumulation in tree wells during winter; (2) nurse effects of tree trunks extending the vegetation period, suppressing competitive vegetation and enhancing nutrient supply from decomposed litter; and (3) suitable seedbeds on some decaying wood. The Thomas point process fitted the observed pattern of decreasing recruit density with increasing distance from mature trees better than the Matern process. Conclusions Tree spatial pattern in mountain P.abies forests showed high resilience to stand-replacing disturbance. After a self-thinning of recruits tightly clustered around parental trees, their spatial pattern will mirror the pattern of trees that formed the stand before the disturbance. This memory' of tree spatial patterns is an important biological legacy and should be viewed as a fundamental property of natural P.abies forests.
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We connected tree-census and dendrochronological research data (74.2 ha) in order to answer the following questions: How do we apply an individual-based approach, which allows us to abandon the traditional patch model, in the research of disturbance history through spatial scales? What is the disturbance history of the natural forest? How do we understand the influence of the Kyrill storm, which affected the reserve on 18 January 2007? How does the disturbance history in dendrochronological records correspond to real disturbances?
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A methodology is proposed for developing a disturbance chronology in stands by identifying the probable date of canopy accession for each sample tree. Canopy disturbance intensity is defined as the percentage of sample trees with canopy accession events in each decade. Rotation periods for disturbances of various intensities are calculated from the chronology. The method was evaluated using 893 increment cores from 70 plots in northern hardwood stands of W Upper Michigan. Average disturbance rate for all plots and decades was 5.7-6.9% of land area per decade, with an implied average canopy tree residence time of 145-175 yr. -from Authors
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