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One mechanism proposed to explain high species diversity in tropical systems is strong negative conspecific density dependence (CDD), which reduces recruitment of juveniles in proximity to conspecific adult plants. Although evidence shows that plant-specific soil pathogens can drive negative CDD, trees also form key mutualisms with mycorrhizal fungi, which may counteract these effects. Across 43 large-scale forest plots worldwide, we tested whether ectomycorrhizal tree species exhibit weaker negative CDD than arbuscular mycorrhizal tree species. We further tested for conmycorrhizal density dependence (CMDD) to test for benefit from shared mutualists. We found that the strength of CDD varies systematically with mycorrhizal type, with ectomycorrhizal tree species exhibiting higher sapling densities with increasing adult densities than arbuscular mycorrhizal tree species. Moreover, we found evidence of positive CMDD for tree species of both mycorrhizal types. Collectively, these findings indicate that mycorrhizal interactions likely play a foundational role in global forest diversity patterns and structure.

Abstract Herbivorous insects alter biogeochemical cycling within forests, but the magnitude of these impacts, their global variation, and drivers of this variation remain poorly understood. To address this knowledge gap and help improve biogeochemical models, we established a global network of 74 plots within 40 mature, undisturbed broadleaved forests. We analyzed freshly senesced and green leaves for carbon, nitrogen, phosphorus and silica concentrations, foliar production and herbivory, and stand-level nutrient fluxes. We show more nutrient release by insect herbivores at non-outbreak levels in tropical forests than temperate and boreal forests, that these fluxes increase strongly with mean annual temperature, and that they exceed atmospheric deposition inputs in some localities. Thus, background levels of insect herbivory are sufficiently large to both alter ecosystem element cycling and influence terrestrial carbon cycling. Further, climate can affect interactions between natural populations of plants and herbivores with important consequences for global biogeochemical cycles across broadleaved forests.

This paper presents the correlations between two different analytical methods of assessing soil nutrient contents. Soil nutrient content measurements measured using the flame atomic absorption spectrometry (FAAS ) method, which uses barium chloride extraction, were compared with those of the now-unused Gedroiz method, which uses ammonium chloride extraction (calcium by titration, magnesium, potassium and sodium by weighing). Natural forest soils from the Ukrainian Carpathians at the localities of Javorník and Pop Ivan were used. Despite the risk of analysis errors during the complicated analytical procedure, the results showed a high level of correlation between different nutrient content measurements across the whole soil profile. This allows concentration values given in different studies to be linearly recalculated on results of modern method. In this way, results can be used to study soil’s chemical changes over time from the soil samples that were analysed in the past using labour-intensive and time-consuming methods with a higher risk of analytic error.

Abstract Carbon accounting in the land sector requires a reference level from which to calculate past losses of carbon and potential for gains using a stock-based target. Carbon carrying capacity represented by the carbon stock in primary forests is an ecologically-based reference level that allows estimation of the mitigation potential derived from protecting and restoring forests to increase their carbon stocks. Here we measured and collated tree inventory data at primary forest sites including from research studies, literature and forest inventories (7982 sites, 288,262 trees, 27 countries) across boreal, temperate, and subtropical Global Ecological Zones within Europe. We calculated total biomass carbon stock per hectare (above- and below-ground, dead biomass) and found it was 1.6 times larger on average than modelled global maps for primary forests and 2.3 times for all forests. Large trees (diameter greater than 60 cm) accounted for 50% of biomass and are important carbon reservoirs. Carbon stock foregone by harvesting of 12–52% demonstrated the mitigation potential. Estimated carbon gain by protecting, restoring and ongoing growth of existing forests equated to 309 megatons carbon dioxide equivalents per year, additional to, and higher than, the current forest sink, and comparable to the Green Deal 2030 target for carbon dioxide removals.

ABSTRACTThe radial growth of trees significantly contributes to climate change mitigation by sequestering carbon into woody biomass. Radial growth trends observed in European temperate forests during the recent period of climate warming vary between growth acceleration due to longer growing seasons and growth declines due to amplified drought stress. Assessing the spatial variation of growth trends is challenging due to the point relevance of available empirical data including forest inventories and tree-ring width chronologies. Here, we used a database of tree-ring width chronologies from 596 sites and spatial models to describe the growth trends of five tree species across the Czech Republic between 1990 and 2018. The resulting map highlights multiple sources of variation in growth trends including differences between species and prominent spatial gradients along elevation, latitude, and longitude. The knowledge of spatially explicit growth trends is essential for the adaptation of the forestry sector to ongoing climate change.

Abstract One mechanism proposed to explain high species diversity in tropical systems is strong negative conspecific density dependence (CDD), which reduces recruitment of juveniles in proximity to conspecific adult plants. Although evidence shows that plant-specific soil pathogens can drive negative CDD, trees also form key mutualisms with mycorrhizal fungi, which may counteract these effects. Across 43 large-scale forest plots worldwide, we tested whether ectomycorrhizal tree species exhibit weaker negative CDD than arbuscular mycorrhizal tree species. We further tested for conmycorrhizal density dependence (CMDD) to test for benefit from shared mutualists. We found that the strength of CDD varies systematically with mycorrhizal type, with ectomycorrhizal tree species exhibiting higher sapling densities with increasing adult densities than arbuscular mycorrhizal tree species. Moreover, we found evidence of positive CMDD for tree species of both mycorrhizal types. Collectively, these findings indicate that mycorrhizal interactions likely play a foundational role in global forest diversity patterns and structure.

In this paper, we examined the degree to which inherent spatial structure in soil properties influences the outcomes of machine learning (ML) approaches to predicting soil spatial variability. We compared the performances of four ML algorithms (support vector machine, artificial neural network, random forest, and random forest for spatial data) against two non-ML algorithms (ordinary least squares regression and spatial filtering regression). None of the ML algorithms produced residuals that had lower mean values or were less autocorrelated over space compared with the non-ML approaches. We recommend the use of random forest when a soil variable of interest is weakly autocorrelated (Moran’s I 0.4). Overall, this work opens the door to a more consistent selection of model algorithms through the establishment of threshold criteria for spatial autocorrelation of input variables.

The formation of spatial pedocomplexity in forested landscapes is an issue that has not yet been comprehensively resolved. This study analysed the effects of tree disturbances on the spatial variability of soil chemical properties in order to explain the spatial pedocomplexity in one of the oldest forest reserves in Europe. A total of 1545 sites over an area of 74 ha were assessed in terms of soil taxonomy, morphology, and profiles. We quantified the spatial autocorrelation of soil chemical properties and analysed the effects of soil disturbance regimes on soil chemical properties in both the surface and subsurface layers using geostatistics and redundancy analysis, respectively. A paired difference test revealed that the factors involved in the soil formation of the two layers are different. The neoformation of the surface layer proceeds rapidly after soil disturbance and, therefore, some formerly disturbed surface layers become mature above immature subsurface layers. The effect of tree disturbances on soil chemical properties was significant for totally decomposed treethrows. Treethrow density partially explained the variation in soil chemical properties in both layers, but even more so in the subsurface layer. This study further elucidates the impact of treethrows on soils and shows that they are an important driver of soil spatial pedocomplexity.

Increasing growing season temperatures and the seasonal redistribution of precipitation due to climate change have recently been recorded across the globe. Simultaneously, increases of severe droughts and windstorm frequency have also been documented. However, the impacts of climate change on tree growth performance and fitness might largely differ among coexisting species. Consequently, ongoing temperature increases could lead to extensive changes in tree species compositions in many forest biomes including temperate mountain forests. In this study we used an extensive dataset of 2824 cored trees of three species from two sites, and parameterized a purely climate driven process-based model (Vaganov–Shaskin) to simulate the growth dynamics and climatic limitations of coexisting Picea abies, Fagus sylvatica and Abies alba in two of the oldest mountain forest reserves in Central Europe (the Boubín and Žofín Primeval Forests). We assumed that the species composition reflects climatic growth limitations, and considered between-site differences in mean temperature due to elevation as a model of future climate change effects on mountain forests. Our results show a complexity of site- and species-specific responses of Central European forests to climate change. Over the last 70 years, the proportion of F. sylvatica in Central European natural forests has increased at the expense of conifers. During the investigated period, we observed an increase in the growth rates of the studied species mainly at the higher elevation site, while for the lower elevation site there was increasing intensity of moisture limitation. Despite being the most moisture-limited species, P. abies showed the highest simulated growth rates. In contrast, A. alba was the least moisture limited of all considered species. Given its recent proportion in the forest species composition and intermediate drought resistance, we anticipate the future expansion of F. sylvatica in Central European mountain forests.

Biota–soil interactions in natural ecosystems are the subject of considerable research. Our hypothesis is that individual trees play a significant role through biomechanical and biochemical disturbances affecting soil formation in temperate forests, resulting in a complex spatial pattern of disturbance regimes and a close relationship between disturbance histories and soil units. In Žofínský Prales (Czech Republic) – the fourth oldest, continuously protected reserve in Europe and the first site of global research network SIGEO (Smithsonian Institution Global Earth Observatories) in continental Europe – we compared extensive dendrochronological, soil and pit–mound microtopography data both temporally and spatially from an area of anthropogenically unaffected 42 ha collected from 2008–2012. These data sets differ in terms of information complexity and length of memory: tree cores contain complex information about the disturbance history of the past 350 years, footprints of disturbances from the uprooting of a specific tree can persist 1700 years, and soils represent an extensive composite phenotype that has been developing for at least the entire postglacial period (10 500 years). On average, 6.18–13.41% of the canopy on individual soil units was disturbed per decade. Even though the "backbone" of key events in the development of the forest ecosystem remained the same (e.g. the 1870s, 1880s and 1980s), the internal structure of disturbance history often differed among soil units; the most exceptional were Gleysols and Histosols, where important feedback from soil to trees was expected. However, the characteristics of treethrow dynamics as well as the frequencies of stronger releases in core series also significantly differed along a gradient of terrestrial soil weathering and leaching (Haplic Cambisols – Dystric Cambisols – Entic Podzols – Albic Podzols). These results suggest the existence of several disturbance regimes within the forest, controlling fine-scale pedodiversity.

The pine stand in the Havraní Skála locality in the Bohemian Switzerland National Park was affected by an extensive mixed-severity wildfire in summer 2006. The fire severity, fire type and fire extent were assessed by various fire severity measures collected in the field (mean bole char height on stems on sample plots, content of oxidizable C and total N at a soil depth of 0-5 cm), as well as by classification and filtering of green canopy cover from time series of aerial photographs acquired before the fire (2005), soon after the fire (2006) and one year after the fire (2007). The specific image analyses made it possible to uncover the spatial and temporal pattern of the stand defoliation. The central part of the site was mainly affected by the crown fire and thus defoliated substantially right during the fire. On the contrary, the peripheral part of the site was mostly affected by low-severity ground fire and therefore defoliated progressively one year later. All the fire severity measures used were well related.

Based on a map of potential natural vegetation (PNV), actual vegetation was studied in the Mramor locality (106.4 ha). A total of 188 relevés were examined using stratified random sampling. A comparison was made between trends in vegetation variability throughout the entire locality and variability within the defined PNV units. The stratification of the locality according to PNV units was only partly representative of the main trends in vegetation variability, especially at ecologically distinctive sites. On the other hand, in areas with a relatively limited ecological gradient, the sites were "oversampled". The variability of plant communities within PNV units was high. The results of this case study suggest that the need for delineation of PNV units which are homogeneous in terms of production, site and phytocoenosis is overestimated. This delineation neither corresponds to the characteristics of actual ecosystems nor is necessary for the application of a PNV system. A more suitable unit for the development of such a system would be, for example, forest type series.

Since the mid-1970's, the landscape around the confluence of the Morava and Dyje rivers has undergone substantial changes related to the drop of water table caused by water management measures undertaken on both ri-vers. Periodical spring floods are among the phenomena lost due to ameliorations. In this study, the reaction of forest ecosystems to the decrease in soil moisture is assessed on the basis of changes in species composition of the herb layer as well as of the known requirements of individual recorded taxa and the entire herb synusiae for the water content of soils. The results confirm that the species with the greatest demand for water disappear over time. The tendency of decreasing Ellenberg indicator values of the herb layers within the phytocoenological relevés is obvious also with the consideration of the influence of different numbers of species recorded on the same plots in different years of the survey. The changes are most visible in the dampest habitats, while elevated sites, so-called "hrudy", tend to be most stable. The intensity of vegetation changes increases in direct proportion to the altitude of the sites. The process of changes in some habitats caused by the alteration of the water regime has to be separated from the changes in the vegetation structure, which are easier to observe optically. The limiting factor of their development in the given conditions is the forest wildlife. After the elimination of wildlife's influence, the woody species synusia differentiates in height. A qualitative shift is represented by the recession of the formerly dominant Quercus robur on the main level, and its gradual replacement by other species. The impact of changes going on in the woody synusia on selected characteristics of the herb layer are included in the analyses.

The uniqueness of limestone soil-forming substrate was assessed with respect to the classification of forest ecosystems. 50 soil profiles from the Bohemian Karst were studied and the results were confronted with previously published works from other karst areas. The evaluation of soil profiles was based on a macroscopic description, on the results of chemical and physicochemical analyses, and on a micromorphological study. The carbonate bedrock was a cause of specific genesis of soils in these sites - both recent and relict ones (terrae calcis). However, it does not always condition the unique characteristics of these sites whose differentiation would call for an a priori special edaphic category. Unique geochemical characteristics of the substrate are modified on the gradient of advanced pedogenesis (Holocene up to mid-Pleistocene soils were assessed) by a very intensive soil-forming process connected with the impact of allochthonous, mostly aeolian material. Two possible approaches were designed for the classification of these sites: (i) wider conception - distinction of the basic edaphic category with small limitations for the quality of soil-forming substrate, (ii) narrower conception - limestone edaphic category with a number of limitations to distinguish this edaphic category.

In 2002 a study focused on the evaluation of height and density of expanding natural regeneration of Fraxinus excelsior L. (FE) was carried out on Velká hora Hill, a locality in the Bohemian Karst (Český kras). The examined area is located in Karlštejn National Nature Reserve and takes up around 31 ha. The parent rock is limestone. The expansion depends on soil and exposition conditions and relates to the water balance gradient. FE reached the highest densities (up to 6,000 individuals/400 m2) on Velká hora's peak plateau on medium-deep, heavy-textured decarbonized soils. The lowest expansion (508 individuals/400 m2) was found on slopes fully exposed to south (S) with water retention capacity lower than 20 mm. In total, the average density was 1,190 individuals/400 m2. FE natural regeneration reached the highest average heights (around 210 cm) on Fageto-Quercetum illimerosum mesotrophicum, the smallest heights on Carpineto-Aceretum saxatile. Average height in the locality was 47 cm. No relation was found between FE natural regeneration height or density and the distance of a fertile specimen. The distance exceeded 70 m only in 3.4%. FE seeds could be detected almost everywhere at the area. FE is capable to establish itself on any location of the studied locality except ecologically extreme parts of rock steppe without forest and Fagus sylvatica L. stands occupying S slopes. On less favourable sites it is capable to use the protection of other tree species and as a low growing tree it can eventually dominate the site. In more favourable conditions it expands on the whole area, where it can dominate the undergrowth already at 1-m height. If the forest sites are left to natural development, a distinctive change in the tree species composition could take place in a short time period. Such a change could have an essential impact on light conditions, energy flux and species composition of plant and animal communities.

The study focuses on selected forest site units on water uninfluenced sites on limestone in Bohemian Karst. The species composition of phytocoenoses, their potential production and soil properties were assessed. Studied forest site complexes are correctly determined and they provide important information from the aspect of planning and practical nature conservation management. It is necessary to specify the criteria of categoria calcaria in detail, since it is often difficult to distinguish it from categoria mesotrophica. Water retention capacity of soils, a criterion often neglected so far, presents a useful view of forest site water budget and it is a suitable criterion in forest site classification.

• A complex of factors at different spatial scales affects beech growth response. • The variability in responses to an identical event implies uncertainty in reconstructing disturbance histories. • A detailed examination of all important parameters of the growth reaction is suggested. Despite improvements of dendrochronological techniques in many forest ecosystems, studies describing the growth responses of trees following disturbance events including comprehensive data on factors and processes behind tree-growth release are rare, especially for European temperate forests, limiting the interpretation and generalization of dendroecological studies. Here we examine the effect of key factors on the growth reaction of Fagus sylvatica L. to disturbances in 8 old-growth forests in the Czech Republic, independently dated using three different data sources – tree censuses, dendrochronology and historical aerial photographs. Using 117 increment cores, we studied four parameters of radial tree-growth surrounding canopy gaps: magnitude, duration, abruptness and response shift, in relation to factors of different spatial scales, i.e. tree-, gap- and stand-level variables. Our results indicate that the beech growth response to gap formation strongly differs across a complex of factors at diverse spatial levels, frequently occurring in noteworthy interactions. A positive trend for the gap size * radiation interaction in the analysis of magnitude was found, suggesting that the effect of gap area differs among topographical features. As for duration and abruptness, the interaction of distance and mortality mode was identified, indicating a longer and more gradual reaction along with increasing distance of the cored tree from the gap centre, varying by the type of the gap maker's death. In addition, an altitudinal gradient was found to predict the magnitude of growth changes and the time interval between the disturbance and the reaction of nearby trees. Surprisingly, the diameter of the surviving trees was not a good predictor of radial growth, with a significant positive relationship to just abruptness. An effect of locality was not observed, facilitating the broad applicability of our findings across a wide range of beech-dominated temperate forests. Our results emphasize the general limits of dendrochronological data in disturbance spatial pattern studies, as indicated by the considerable variability in the responses of neighbouring trees to identical disturbance event. A detailed examination of the growth reaction, considering not only the response magnitude but also other important parameters, plays a key role in the precision of detecting growth releases as well as in reducing the sample size required for summary disturbance history evaluations. In focusing on this issue we believe we contribute to future dendroecological research by demonstrating the need for more precise disturbance history evaluations. [ABSTRACT FROM AUTHOR]

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. We established 184 plots (mostly 1000 m 2 ) in 14 primary mountain Norway spruce forests in the Western Carpathians. On each plot we surveyed live and dead trees and regeneration, and cored around 25 canopy trees. Disturbance history was reconstructed by examining individual tree growth trends. The study plots were further aggregated into five groups based on disturbance history (severity and timing) to evaluate and explain its influence on forest structure. These ecosystems are characterized by a mixed severity disturbance regime with high spatiotemporal variability in severity and frequency. However, periods of synchrony in disturbance activity were also found. Specifically, a peak of canopy disturbance was found for the mid-19th century across the region (about 60% of trees established), with the most important periods of disturbance in the 1820s and from the 1840s to the 1870s. Current stand size and age structure were strongly influenced by past disturbance activity. In contrast, past disturbances did not have a significant effect on current tree density, the amount of coarse woody debris, and regeneration. High mean densities of regeneration with height >50 cm (about 1400 individuals per ha) were observed. Extensive high severity disturbances have recently affected Central European forests, spurring a discussion about the causes and consequences. We found some evidence that forests in the Western Carpathians were predisposed to recent severe disturbance events as a result of synchronized past disturbance activity, which partly homogenized size and age structure and made recent stands more vulnerable to bark beetle outbreak. Our data suggest that these events are still part of the range of natural variability. The finding that regeneration density and volume of coarse woody debris were not influenced by past disturbance illustrates that vastly different past disturbance histories are not likely to change the future trajectories of these forests. These ecosystems currently have high ecological resilience to disturbance. In conclusion, we suggest that management should recognize disturbances as a natural part of ecosystem dynamics in the mountain forests of Central Europe, account for their stochastic occurrence in management planning, and mimic their patterns to foster biodiversity in forest landscapes. [ABSTRACT FROM AUTHOR]

Because of some arbitrary decisions in recent dendrochronological research on forest disturbance histories, describing the actual growth responses of trees to disturbance events is still an issue of great importance. This is even more important in temperate beech-dominated old-growth forests driven by fine-scale disturbances, where a majority of growth pulses occur close to the arbitrary threshold of release detection. Recognizing this limitation, we provide a new empirically-based release detection criterion on the basis of actual reactions of trees to independently dated disturbance events interconnecting three data sets – tree censuses, dendrochronology and historical aerial photographs. The growth response of Fagus sylvatica L. was studied in detail in relation to the canopy position of surviving trees as well as regional climate responses, using 280 increment cores extracted in 8 old-growth forests in the Czech Republic. Cluster and bootstrap analysis resulted in distinguishing 2 ecoregions with site-specific growth patterns and plasticity. A boundary line (BL) method was applied to the identification and quantification of release, providing a new curve for F. sylvatica regionally valid in the mountainous regions of Central Europe. During the period investigated (1970s–1990s) 7% of trees experienced no reaction, despite clear evidence of canopy disturbances in both aerial photographs and tree censuses. 25% of growth changes were attributed to regional-scale environmental factors, in particular climate and air pollution. The magnitude of the growth response varied significantly among canopy positions, with subcanopy trees released from suppression experiencing the most intense growth rates, and individuals under permanent suppression showing a negligible response. Considering these differences we empirically inferred new criteria, subdivided into two categories according to disturbance intensity. Pulses falling within the 25–63% of the boundary line are classified as weak releases while pulses exceeding 63% of the BL are identified as major. Still, our results imply relatively high uncertainty in the detection of disturbance using dendrochronology, which can be troubled particularly in spatial analysis of past disturbances. We believe that our empirically-derived criteria represent a substantial contribution to further dendroecology research, with broad applicability to a wide range of beech-dominated temperate forests. [ABSTRACT FROM AUTHOR]

There are hundreds of scientific papers dealing with the issues of biodiversity and extinction debt in temperate forests, both of which are partly related to the absence of deadwood. Some studies have derived habitat thresholds for deadwood (according to species, size, spatial distribution) as baselines for management recommendations. But a majority of studies have one important knowledge gap – how long does it take for deadwood to decompose? To derive the residence time of deadwood, we used a 40-year time series of 4 censuses in European lowland hardwood temperate forests. The deadwood residence of 2252 logs of 5 main tree species was calculated using Bayesian Survival Trajectory Analysis. Pedunculate oak ( Quercus robur ) had the longest residence time, with the largest logs decomposing for an average of 62 years. Next was narrow-leaved ash ( Fraxinus angustifolia ) with a residence time of about 42 years. Field maple ( Acer campestre ) and hornbeam ( Carpinus betulus ) had a similar residence time – with the largest logs averaging 37–39 years. Elm ( Ulmus sp.) had the fastest decomposition of large-sized logs – estimated at 24 years. Generally, small-sized logs of all investigated species decomposed quickly. Conversely, large-sized logs of hornbeam and ash decomposed as quickly as their intermediate-sized logs. Large-sized logs of elm decayed even faster than intermediate-sized logs. An analysis of the position of field maple logs during decomposition showed that those decomposing in the air or in water decomposed slower than logs “on the ground”, with a half-life of 40 years (compared to 28 years on the ground) and a residence time of 54 years (44 years on the ground). Our results suggest that the management of deadwood should focus on (i) leaving the largest logs, which took the longest time to reach advanced decay stages, and (ii) a diversified approach regarding the individual residence time of different tree species. [ABSTRACT FROM AUTHOR]

Questions Uncertainty in detecting disturbance histories has long been ignored in dendrochronological studies in forest ecosystems. Our goal was to characterize this uncertainty in relation to the key parameters of forest ecosystems and sample size. In addition, we aimed to provide a method to define uncertainty bounds in specific forest ecosystems with known parameters, and to provide a required (conservative) minimal sample size to achieve a pre-defined level of uncertainty if no actual key forest parameters are known. Location Training data were collected from Žofínský Prales (48°40′N, 14°42′E, 735–830 m a.s.l., granite, Czech Republic). Methods We used probability theory and expressed uncertainty as the length (the difference between the upper and lower bounds) of the 95% confidence interval. We studied the uncertainty of (i) the initial growth of trees – if they originated under canopy or in a gap; and (ii) the responses to disturbance events during subsequent growth – on the basis of release detection in the radial growth of trees. These two variables provide different information, which together give a picture of the disturbance history. While initial growth date the existence of a gap in a given decade (recent as well as older gaps are included), release demonstrates the moment of a disturbance event. Results With the help of general mathematical deduction, we have obtained results valid across vegetation types. The length of a confidence interval depends on the sample size, proportion of released trees in a population, as well as on the variability of tree layer features (e.g., crown area of suppressed and released trees). Conclusions Most studies to date have evaluated the initial growth of trees with higher uncertainty than for canopy disturbed area. The length of the 95% confidence interval for detecting initial growth has been rarely shorter than 0.1 (error ± 5%) and has mostly been much longer. To reach 95% confidence interval length of 0.1 (error ± 5%) when detecting the canopy disturbed area, at least 485 tree cores should be evaluated in studied time period, while to reach a 0.05 interval length (error ± 2.5%) at least 1925 tree cores are required. Our approach can be used to find the required sample size in each specific forest ecosystem to achieve pre-defined levels of uncertainty while detecting disturbance history. [ABSTRACT FROM AUTHOR]