The substantial volume of timber recovered from the aftermath of the eruption of Vesuvius in 79 AD offers a valuable resource for gaining insights into the timber trade during Roman times. Silver fir ...emerges as the dominant species in construction within the Vesuvian region. While this species once thrived more abundantly along the Apennines, it now exists only in small, isolated groups, raising the possibility that the Romans contributed to its scarcity. Nevertheless, the origins of the substantial quantity of silver fir wood discovered in Pompeii, Herculaneum, and the surrounding areas remain unclear. This study examines 35 wood samples obtained during the excavation of the Moregine site, an ancient commercial port located a mere 600 m to the south of Pompeii's walls. Dendrochronological analysis successfully dated 19 out of the 35 samples. Despite silver fir not being the ideal species for dendroprovenancing analysis, certain observations can be made regarding its likely foreign origin. The correlation with chronologies of different species of Central European origin, the presence of species such as spruce/larch among the structural material and the existence of different groups among the material analysed are strong indications that demonstrate the foreign origin of at least some of the timber. Dendrochronological data further support that the wood trade played a strategically significant role in the economy of ancient Rome.
•Abies alba is able to grow and regenerate under meso-Mediterranean conditions.•Mediterranean silver fir decadal tree ring width trends follow European patterns.•Lowland silver firs are very ...sensitive to water shortage and summer drought.•Drought summers impact the growth in the current season but not in the following.•Silver fir confirms its potential to thrive at the warm edge of its distribution.
The potential ecological envelope of silver fir (Abies alba Mill.) based on its present distribution suggests a high suitability for moist rather than warm and dry environments. This contrasts with paleoecological evidence reporting its former presence at low elevations under meso-Mediterranean conditions. In this study, we evaluated the growth performance of silver fir at low elevation (20–60 m a.s.l.) under meso-Mediterranean climatic conditions in Tuscany (central Italy). We conducted a dendroecological analysis on Abies alba trees along a geomorphological gradient (from depression to upper slope conditions). Climate-growth relationships were assessed by means of correlations, response functions, pointer years, and superposed epoch analysis.
Silver fir was found to grow and regenerate well in these stands mixed with evergreen (e.g., Quercus ilex L.) and thermophilous deciduous Mediterranean tree species (e.g., Q. cerris L.). Summer drought was the most growth-influencing factor, with immediate (i.e., current season) negative impacts on tree-ring widths (TRW). No significant impacts were observed in the four years following extreme summer droughts, but the TRW series (which started between the 1930s and 1950s) showed a growth decline since the mid-1990s that is likely drought-related.
Our results show that, provided there is a sufficiently large soil water holding capacity, silver fir provenances exist which are able to withstand Mediterranean summer droughts, can naturally and regularly regenerate in these systems, and may even dominate over typical meso-Mediterranean species. As long as annual precipitation is not too low (i.e., >850 mm) and summer drought conditions not too extreme (i.e., less than three months), silver fir has thus the potential to thrive under warm Mediterranean conditions.
•ECMF communities of native A. alba and alien A. grandis were assessed.•Studied fir species harboured high and comparable number of ECMF symbionts.•ECMF community composition of tested firs differed ...substantially.•The weak effect of provenances on ECMF communities was determined.•Both fir species hosted ECMF species of conservation concern.
Our study contributes to the understanding of the diversity of ectomycorrhizal fungal (ECMF) communities of native A. alba and alien A. grandis in provenance trials situated in lowland and montane regions in Poland (Central Europe). Ectomycorrhizal fungi were identified directly from field-collected root tips using PCR- and Sanger-sequencing-based methods. We found that the studied fir species had relatively high and comparable ECMF species richness (66 and 69 fungal taxa on A. grandis and A. alba, respectively). Twenty-six taxa were associated with both hosts and 83 taxa were found uniquely on one or the other fir species. The ECMF community composition and structure of A. alba and A. grandis differed substantially both at the species and the phylogenetic lineage levels. Soil parameters such as total nitrogen, magnesium and potassium content and C/N ratio appeared moderately but significantly correlated with the ECMF community assembly of both firs. The provenance of the host tree species did not appear to be a strong factor in structuring the ECMF communities. This was found despite the low number of common ECMF species and relatively high number of unique species among the individual provenances of both fir species. The results of the study suggest that locally based specificity in host–fungal communities is likely a contributing factor in the outcome of provenance trials. We posit that much insight into the role of tree provenances in shaping ECMF communities will be gained by further exploring this area of research. On the surveyed experimental forest sites of A. alba and A. grandis, fungal species of conservation concern – particularly those that were endangered and rare – have been reported. Our findings imply that tree species planted outside their natural range serve as ecologically important species because they may act as an excellent reservoir of ECMF diversity, a factor of importance in functioning forest ecosystems.
•Silver fir trees were accurately mapped at individual tree level in a mixed forest.•LiDAR and hyperspectral data were combined as input for one-class classification.•Species-specific traits were ...identified to capture the main morphological difference between silver fir and Norway spruce.
Mapping a specific tree species at individual tree level across landscapes using remote sensing is challenging, especially in forests where co-occurring tree species exhibit similar characteristics. In Central European mixed forests, silver fir and Norway spruce have been identified as a pair of coniferous tree species with similar spectral and structural characteristics, typically leading to a major misclassification error in mapping studies. Here, we aimed to accurately map individual silver fir trees in a spruce-dominated natural forest in the Bavarian Forest National Park using integrated airborne hyperspectral and LiDAR data. To accomplish this goal, we extracted a set of relevant spectral and structural features from the hyperspectral and LiDAR data and used them to build machine learning classification models. Specifically, we compared the performance of three one-class classification algorithms (i.e. one-class support vector machine, biased support vector machine, and maximum entropy) for mapping individual silver fir trees. Our results showed that the biased support vector machine classifier yielded the highest mapping accuracy, with the area under the curve for positive and unlabeled samples (puAUC) achieving 0.95 (kappa 0.90). We found that the intensity value of 95th percentile of normalized tree height and the percentage of first returns above 2 m high were the most influential structural features, capturing the main morphological difference between silver fir and Norway spruce at the top tree crown. We also found that the wavebands at 700.1 nm, 714.5 nm, and 1201.6 nm were the most robust spectral bands, which are strongly affected by chlorophyll and foliar water content. Our study suggests that discovering links between spectral and structural features captured by different remotely sensed data and species-specific traits can significantly improve the mapping accuracy of a focal species at the individual tree level.
The future performance of native tree species under climate change conditions is frequently discussed, since increasingly severe and more frequent drought events are expected to become a major risk ...for forest ecosystems. To improve our understanding of the drought tolerance of the three common European temperate forest tree species Norway spruce, silver fir and common beech, we tested the influence of climate and tree‐specific traits on the inter and intrasite variability in drought responses of these species. Basal area increment data from a large tree‐ring network in Southern Germany and Alpine Austria along a climatic cline from warm‐dry to cool‐wet conditions were used to calculate indices of tolerance to drought events and their variability at the level of individual trees and populations. General patterns of tolerance indicated a high vulnerability of Norway spruce in comparison to fir and beech and a strong influence of bioclimatic conditions on drought response for all species. On the level of individual trees, low‐growth rates prior to drought events, high competitive status and low age favored resilience in growth response to drought. Consequently, drought events led to heterogeneous and variable response patterns in forests stands. These findings may support the idea of deliberately using spontaneous selection and adaption effects as a passive strategy of forest management under climate change conditions, especially a strong directional selection for more tolerant individuals when frequency and intensity of summer droughts will increase in the course of global climate change.
Causes of decline and silver fir (
Abies alba Mill.) mortality in Central Europe have been controversially discussed for a long time. This contribution details a comprehensive dendroecological ...investigation of two basic and alternative hypotheses that explain the decline by either climatic influences or by SO
2 pollution as the primary factors. Growth reduction between the 1960s and 1980s as well as the recovery of growth during recent decades have be seen as a response to complex interactions of multiple factors. Herein, we undertake a multidisciplinary evaluation of a broad database, representing the long-term growth of 1010 firs from 51 sites, long-term climate records as well as data assessing the long-term pollution situation in Southern Germany. The results provide clear evidence that SO
2-immissions play a key role in decline and that tree growth corresponds with the regional and temporal pattern of SO
2 pollution. Calculations with a new complex growth model indicate that tree-ring widths of fir at many sites were more influenced by SO
2 than by any other growth-determining factor during the second half of the last century. Strongest coherence between measured and modelled ring widths are found if – in addition to temperature, available soil water content, heavy frost events and long-term growth trends – the site-specific trend of SO
2 pollution is included. Both the immediate response to SO
2 pollution and the quick recovery of fir since the beginning of the 1980s after the decrease of SO
2 emissions indicate a direct impact of SO
2 in gaseous form and not via the soil in terms of soil acidification. Tree-ring widths document that radial growth response occurs at air concentrations above 10
μg
SO
2
m
−3 (annual average), which can be thought of as a critical threshold for silver fir health. Since the beginning of the 1980s, increasing growth trends have been observed which predominantly result from decreased SO
2 pollution in most parts of Central Europe, although climate change, fertilization by nitrogen deposition and a reduced tree-to-tree competition are also relevant factors. The drastic reduction of SO
2 emission during the recent decades significantly improved the environmental conditions for fir. Consequently, an increased cultivation of silver fir on suitable sites is recommended.
Limited resource availability may influence the competitive impact of overstory trees on forest floor vegetation. This study aimed to examine how different site types (poor, moderate, rich) and ...precipitation conditions (low or high) affect the microsite preferences of shade-tolerant silver fir (Abies alba Mill.) regeneration. The spatial relationships between overstory trees and juvenile fir seedlings were compared across six forest communities typical of Central Europe, in which silver fir co-occurs with Scots pine, Norway spruce, and broadleaved species. The analyzed microsite variables included the density of seed trees, distance-dependent and species-specific metrics of overstory tree influence, forest floor vegetation coverage, organic ectohumus layer thickness, local canopy openness and light conditions. Effects of overstory trees, ectohumus layer depth and gap fraction on seedling densities varied with site type. Dependent on precipitation level, both negative (competition) and positive (facilitation) influences of overstory trees on regeneration was observed dependent on precipitation level. As the local basal area of overstory trees increased, the density of silver fir seedlings decreased in the conifer stands on the poor site with low precipitation but increased in the conifer stands on the rich site with high precipitation. In the low-precipitation sites, the microsite preferences of fir seedlings varied between site types. Species-specific effects also were found for the overstory. In the poor low-precipitation site, the negative influence of overstory pines was weaker than that of overstory firs. Conversely, in the rich high-precipitation site, the positive influence of overstory spruces was stronger than that of overstory firs. Irrespective of the precipitation level, in forests with broadleaved species, the influence of overstory trees was less pronounced. The study discusses the mechanisms underlying the observed regeneration patterns and implications for natural regeneration techniques for silver fir depending on site conditions.
•Site conditions alter microsite preferences of fir regeneration.•Competition predominates on poor and dry sites, while facilitation is common on rich and moist sites.•The influence of overstory trees on regeneration varies between overstory species.
Embryogenic tissues of Abies alba Mill. were cryopreserved using the slow-freezing approach. Four cell lines were incubated for 24 h on a medium with 0.5 M sorbitol and pre-treated with 5% DMSO. ...Subsequently, the tissues were frozen at a cooling rate of 1 °C min-1 to -40 °C and transferred to liquid nitrogen for 72 hours. After thawing in a water bath at 40 °C, the tissues were cultivated on a proliferation medium. All tested lines recovered, but variations in regrowth frequencies across cell lines were noticed (91.66 to 100%). The recovered tissues showed similar features to the control 2 (non-pre-treated and non-cryopreserved tissues). In the accumulation of fresh and dry mass, no statistically significant differences were observed between cryopreserved cultures and control 2. The cryopreserved tissues produced cotyledonary somatic embryos capable of germination. Microscopic observations revealed considerable structural changes as a consequence of the cryopreservation procedure. The long vacuolated suspensor cells were disrupted, and mostly the meristematic cells of the embryonal region survived. The typical bipolar structure of early somatic embryos has been regained during the post-thaw period. Differences in cryotolerance across cell lines were also observed.
•Browsing only buds vs. a large part of the annual leader shoot was crucial.•Within-tree browsing intensity on Abies alba saplings was lower in Fagus-dominated forests.•Due to selective browsing, ...lightly browsed saplings grew better than unbrowsed ones.•Strong browsing on leader shoots contributes to shifts in the species’ growth ranking.•Surveying within-tree browsing intensity is recommended to accurately estimate browsing impacts.
Ungulate densities and browsing have increased over the past decades in many forests in Europe. Browsing on tree saplings is a selective process dependent on forest type. This study tested whether the impacts of browsing are altered by differences in tree vigour and within-tree browsing intensity (browsing only buds vs. browsing a large part of the annual leader shoot), and if these effects are modulated by forest type.
The growth rate and within-tree browsing intensity of leader shoots were investigated for different height classes and species compositions at 18 sites (each with 14–64 plots) in spring before budburst and at 6 sites in autumn. The sites were situated in northeast Switzerland and comprised four major forest types that had Abies alba regeneration. Linear mixed-effects models were fitted for the relative growth rate of Abies and for the ratio of the relative growth rate of Abies to the relative growth rate of Picea abies.
More Abies saplings were present in Fagus-dominated forests than in Fagus-Abies or Picea-Abies forests, and within-tree browsing intensity on their leader shoots was lower. Lightly browsed Abies saplings grew better than those that were not browsed, which in turn grew better than strongly browsed saplings. This pattern, which occurred irrespective of forest type, was caused by selective browsing on vigorously growing trees and led to a greater impact of strong browsing in comparison to light browsing on the growth of Abies saplings.
The ratio of the relative growth rate of Abies to Picea was altered by within-tree browsing intensity, forest type and soil depth. Generally, this ratio was highest in shallow soiled Fagus-dominated forests after light browsing and lowest in Fagus-Abies forests after strong leader shoot browsing, indicating a browsing-induced shift in the relative difference in growth rate between species towards Picea in Fagus-Abies and Picea-Abies forests but not in Fagus-dominated forests.
Because the main factor influencing the growth of Abies saplings was the amount of tissue loss on the leader shoots (bud vs. entire or large parts of leader shoots), browsing inventories neglecting to assess the within-tree browsing intensity are not recommended. The within-tree browsing intensity of leader shoots is a simple but objective measurement that should be used in forest regeneration inventories of Abies for improving estimates of the impact of ungulate browsing.
•Advance regeneration was studied after the 2014 ice storm and the 2017 windstorm.•Rapidly light-exposed stands and regularly managed mixed stands were compared.•Quantum yield was measured three ...years after each large-scale disturbance.•Increased light on damaged plots negatively affected fir and favoured deciduous trees.•Ice storm caused more damage and slower recovery than windstorm.
Physiological response to rapid light exposure due to canopy disintegration in young beech, fir, Norway spruce and sycamore trees was measured in three consecutive years after the severe ice storm in 2014 and after windthrow in 2017. Nitrogen amount (Ntot), maximum assimilation response to light (Amax) and quantum yield (Φ) were measured in three categories of different light intensities under closed canopy with indirect site factor (ISF) < 15%, at the forest edge (15% <ISF < 25%) and in the open (ISF > 25%). Tree responses with number of seedlings per hectare were compared between damaged and undamaged sites, with young trees gradually adapting to light conditions in the two years following the two disturbance events.
Nitrogen levels were in the optimal range for all species studied. Rapid exposure to elevated light reduced efficiency in fir and increased efficiency in beech and especially sycamore. No differences in response were observed in spruce. Assimilation efficiency, where both tree species were equal, shifted towards shade. Recovery was similar for all species studied after both disturbances: better after the windstorm, compared to the ice storm, indicating the severity of the event. Reductions in seedling numbers followed the pattern observed for physiological traits.
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