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 subregional 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 data set of 541 plots located within 44 stands and 6 subregions. 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 subregions, 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.
Habitat loss and fragmentation can negatively impact the persistence of dispersal-limited lichen species with narrow niches. Rapid change in microclimate due to canopy dieback exposes species to ...additional stressors that may limit their capacity to survive and colonize. We studied the importance of old trees as micro-refuges and microclimate stability in maintaining lichen survival and diversity. The study was situated in mountain Norway spruce (
Picea abies
) forests of the Gorgany Mountains of the Ukrainian Carpathian mountain belt. Lichens were collected on 13 circular study plots (1000 m
2
). Dendrochronological methods were used to reconstruct age structure and maximum disturbance event history. A linear mixed effects model and general additive models were used to explain patterns and variability of lichens based on stand age and disturbance history for each plot. Tree age was the strongest variable influencing lichen diversity and composition. Recent (<80 years ago) severely disturbed plots were colonized only by the most common species, however, old trees (>200 years old) that survived the disturbances served as microrefuges for the habitat-specialized and/or dispersal limited species, thus epiphytic lichen biodiversity was markedly higher on those plots in comparison to plots without any old trees. Most species were able to survive microclimatic change after disturbances, or recolonize disturbed patches from surrounding old-growth forests. We concluded that the survival of old trees after disturbances could maintain and/or recover large portions of epiphytic lichen biodiversity even in altered microclimates.
Context
Distribution and connectivity of suitable habitat for species of conservation concern is critical for effective conservation planning. Capercaillie (
Tetrao urogallus
), an umbrella species ...for biodiversity conservation, is increasingly threatened because of habitat loss and fragmentation.
Objective
We assessed the impact of drastic changes in forest management in the Carpathian Mountains, a major stronghold of capercaillie in Europe, on habitat distribution and connectivity.
Methods
We used field data surveys with a forest disturbance dataset for 1985–2010 to map habitat suitability, and we used graph theory to analyse habitat connectivity.
Results
Climate, topography, forest proportion and fragmentation, and the distance to roads and settlements best identified capercaillie presence. Suitable habitat area was 7510 km
2
in 1985; by 2010, clear-cutting had reduced that area by 1110 km
2
. More suitable habitat was lost inside protected areas (571 km
2
) than outside (413 km
2
). Habitat loss of 15 % reduced functional connectivity by 33 % since 1985.
Conclusions
Forest management, particularly large-scale clear-cutting and salvage logging, have substantially diminished and fragmented suitable capercaillie habitat, regardless of the status of forest protection. Consequently, larger areas with suitable habitat are now isolated and many patches are too small to sustain viable populations. Given that protection of capercaillie habitat would benefit many other species, including old-growth specialists and large carnivores, conservation actions to halt the loss of capercaillie habitat is urgently needed. We recommend adopting policies to protect natural forests, limiting large-scale clear-cutting and salvage logging, implementing ecological forestry, and restricting road building to reduce forest fragmentation.
Determining the drivers of shifting forest disturbance rates remains a pressing global change issue. Large‐scale forest dynamics are commonly assumed to be climate driven, but appropriately scaled ...disturbance histories are rarely available to assess how disturbance legacies alter subsequent disturbance rates and the climate sensitivity of disturbance. We compiled multiple tree ring‐based disturbance histories from primary Picea abies forest fragments distributed throughout five European landscapes spanning the Bohemian Forest and the Carpathian Mountains. The regional chronology includes 11,595 tree cores, with ring dates spanning the years 1750–2000, collected from 560 inventory plots in 37 stands distributed across a 1,000 km geographic gradient, amounting to the largest disturbance chronology yet constructed in Europe. Decadal disturbance rates varied significantly through time and declined after 1920, resulting in widespread increases in canopy tree age. Approximately 75% of current canopy area recruited prior to 1900. Long‐term disturbance patterns were compared to an historical drought reconstruction, and further linked to spatial variation in stand structure and contemporary disturbance patterns derived from LANDSAT imagery. Historically, decadal Palmer drought severity index minima corresponded to higher rates of canopy removal. The severity of contemporary disturbances increased with each stand's estimated time since last major disturbance, increased with mean diameter, and declined with increasing within‐stand structural variability. Reconstructed spatial patterns suggest that high small‐scale structural variability has historically acted to reduce large‐scale susceptibility and climate sensitivity of disturbance. Reduced disturbance rates since 1920, a potential legacy of high 19th century disturbance rates, have contributed to a recent region‐wide increase in disturbance susceptibility. Increasingly common high‐severity disturbances throughout primary Picea forests of Central Europe should be reinterpreted in light of both legacy effects (resulting in increased susceptibility) and climate change (resulting in increased exposure to extreme events).
Climate change has been linked to increasing forest disturbance rates and large‐scale disturbance histories are needed to assess how disturbance legacies modulate climate–disturbance dynamics. Historical disturbance rates (c. 1750–2000), reconstructed with tree cores collected from primary Picea abies forests throughout Central‐Eastern Europe, have exhibited moderate sensitivity to drought extremes; developmental feedbacks are important determinants of a forest's responsiveness to climate‐induced events. Widespread increases in forest age have occurred throughout the 20th century and these developmental patterns, in addition to climate change, are responsible for the severity of recent disturbances.
Protect old-growth forests in Europe now Mikolāš, Martin; Piovesan, Gianluca; Ahlström, Anders ...
Science (American Association for the Advancement of Science),
05/2023, Volume:
380, Issue:
6644
Journal Article
Basic ecological theory suggests that a tradeoff between competitiveness and stress tolerance dictates species range limits at regional extents. However, empirical support for this key theory remains ...deficient because the necessary spatial and temporal coverage and scalability of field observations has rarely been achieved. We harnessed an extensive dendroecological network (> 22 000 tree‐ring samples from 816 forest inventory plots) to disentangle competition‐limited from climate‐limited growth in both overstory and understory trees. Growth synchrony among trees thereby served as an integral metric of climate sensitivity, an approach that we justify in supplementary analyses of growth responses to temperature, precipitation, and the standardized precipitation‐evapotranspiration index. Sampling plots were arranged along elevational climate and vegetation gradients throughout the Carpathian Mountains, ranging from mixed‐species lowland forests to coniferous forests at high elevations. With mixed‐effect modelling, we also identified non‐climatic factors (stand characteristics, species diversity, and disturbance history) that modulate spatial patterns in the growth rate and synchrony of European beech Fagus sylvatica and Norway spruce Picea abies. Beech exhibited reduced growth and increased climate sensitivity towards higher elevations but performed better when species diversity was higher. The growth of spruce increased towards its lower range boundary, but understory cohorts grew poorly under interspecific competition. Overall, climate sensitivity was lower in more productive stands with benign climatic conditions and in recently disturbed sites with reduced stand density. These contrasting performances at mid‐elevations where the two species overlap (900–1300 m a.s.l.) reflect their evolutionary history, which enables them to be competitive (beech) or cold‐stress tolerant (spruce). This history will affect interactions between the two species under climate warming and shape macroecological patterns in the Carpathian ecoregion and likely other parts of Europe. Our findings point to a growing advantage of competitively stronger species in montane and subalpine vegetation zones.
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.
Context
A comprehensive understanding of how rapidly changing environments affect species gene flow is critical for mitigating future biodiversity losses. While recent methodological developments in ...landscape ecology and genetics have greatly advanced our understanding of biodiversity conservation, they are rarely combined and applied in studies.
Objectives
We merged multifaceted landscape habitat modelling with genetics to detect and design biological corridors, and we evaluated the importance of habitat patches to test corridor efficacy for gene flow in a fragmented landscape. We examined an isolated population of an endangered umbrella species, the capercaillie (
Tetrao urogallus
), in the Western Carpathians; they have experienced habitat deterioration and accompanying population declines in recent decades.
Methods
To detect spatial patterns of genetic distances, we combined and optimized resistance surfaces using species distribution modelling, structural and functional connectivity analyses, multivariate regression approaches, and Moran’s eigenvector maps at hierarchical scales.
Results
Larger habitat patches had better gene flow among them, and we confirmed a broken metapopulation network characterised by a pattern of isolation by the environment. Distance to human settlements explained landscape genetic patterns better than other environmental and landscape features, M
ax
E
nt
resistance, C
onefor
resistance surfaces, and the pairwise Euclidean distances among individuals. The closer individuals were to settlements, the more pronounced were the effects of logging and other negative factors on their connectivity.
Conclusions
Merging multifaceted landscape habitat modelling with genetics can effectively test corridor efficacy for gene flow, and it represents a powerful tool for conservation of endangered species.
Where are Europe's last primary forests? Sabatini, Francesco Maria; Burrascano, Sabina; Keeton, William S. ...
Diversity & distributions,
October 2018, Volume:
24, Issue:
9/10
Journal Article
Peer reviewed
Open access
Aim: Primary forests have high conservation value but are rare in Europe due to historic land use. Yet many primary forest patches remain unmapped, and it is unclear to what extent they are ...effectively protected. Our aim was to (1) compile the most comprehensive European-scale map of currently known primary forests, (2) analyse the spatial determinants characterizing their location and (3) locate areas where so far unmapped primary forests likely occur. Location: Europe. Methods: We aggregated data from a literature review, online questionnaires and 32 datasets of primary forests. We used boosted regression trees to explore which biophysical, socio-economic and forest-related variables explain the current distribution of primary forests. Finally, we predicted and mapped the relative likelihood of primary forest occurrence at a 1-km resolution across Europe. Results: Data on primary forests were frequently incomplete or inconsistent among countries. Known primary forests covered 1.4 Mha in 32 countries (0.7% of Europe's forest area). Most of these forests were protected (89%), but only 46% of them strictly. Primary forests mostly occurred in mountain and boreal areas and were unevenly distributed across countries, biogeographical regions and forest types. Unmapped primary forests likely occur in the least accessible and populated areas, where forests cover a greater share of land, but wood demand historically has been low. Main conclusions: Despite their outstanding conservation value, primary forests are rare and their current distribution is the result of centuries of land use and forest management. The conservation outlook for primary forests is uncertain as many are not strictly protected and most are small and fragmented, making them prone to extinction debt and human disturbance. Predicting where unmapped primary forests likely occur could guide conservation efforts, especially in Eastern Europe where large areas of primary forest still exist but are being lost at an alarming pace.
•We assess the association between forest disturbance history and current structure.•Carpathian spruce forests illustrate multiple pathways of structural development.•Complex structure is associated ...as much with disturbance as it is with stand age.•Unmanaged forests can inform adaptive management intended to foster resilience.
Mixed-severity disturbance regimes are prevalent in temperate forests worldwide, but key uncertainties remain regarding the variability of disturbance-mediated structural development pathways. This study investigates the influence of disturbance history on current structure in primary, unmanaged Norway spruce (Picea abies) forests throughout the Carpathian Mountains of central and eastern Europe, where windstorms and native bark beetle outbreaks are the dominant natural disturbances. We inventoried forest structure on 453 plots (0.1ha) spanning a large geographical gradient (>1,000km), coring 15–25 canopy trees per plot for disturbance history reconstruction (tree core total n=11,309). Our specific objectives were to: (1) classify sub-hectare-scale disturbance history based on disturbance timing and severity; (2) classify current forest structure based on tree size distributions (live, dead, standing, downed); (3) characterize structural development pathways as revealed by the association between disturbance history and current forest structural complexity. We used hierarchical cluster analysis for the first two objectives and indicator analysis for the third. The disturbance-based cluster analysis yielded six groups associated with three levels of disturbance severity (low, moderate, and high canopy loss) and two levels of timing (old, recent) over the past 200years. The structure-based cluster analysis yielded three groups along a gradient of increasing structural complexity. A large majority of plots exhibited relatively high (53%) or very high (26%) structural complexity, indicated by abundant large live trees, standing and downed dead trees, and spruce regeneration. Consistent with conventional models of structural development, some disturbance history groups were associated with specific structural complexity groups, particularly low-severity/recent (very high complexity) and high-severity/recent (moderate complexity) disturbances. In other cases, however, the distribution of plots among disturbance history and structural complexity groups indicated either divergent or convergent pathways. For example, multiple disturbance history groups were significantly associated with the high complexity group, demonstrating structural convergence. These results illustrate that complex forest structure – including features nominally associated with old-growth – can be associated as much with disturbance severity as it is with conventional notions of forest age. Because wind and bark beetles are natural disturbance processes that can induce relatively high levels of tree mortality while simultaneously contributing to structural complexity and heterogeneity, we suggest that forest management plans allow for the stochastic occurrence of disturbance and variable post-disturbance development trajectories. Such applications are especially appropriate in conservation areas where biodiversity and forest resilience are management objectives, particularly given projections of increasing disturbance activity under global change.
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