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This report provides an overview of the forest vegetation and the status of its conservation in Romania. Due to a large range of climates and soils, and a long-lasting postglacial vegetation history, the Romanian forests are highly diverse and species-rich ecosystems. Approximately 150 natural types of forest ecosystems have been described. Seven zonal forest formations were distinguished: (1) forest steppes and dry oak forests; (2) forests with Oriental hornbeam (Carpinus orientalis); (3) forests with oaks (Quercus spp.) and hornbeam (Carpinus betulus); (4) beech forests: Fagus sylvatica and Fagus sylvatica mixed forests; (5) beech-fir (Abies alba)-spruce (Picea abies) mixed mountain forests; (6) spruce forests; (7) subalpine shrubland with dwarf pine (Pinus mugo subsp. mugo). On extreme sites, azonal forests occur, dominated by (8) black pine (Pinus nigra subsp. banatica); (9) Scots pine (Pinus sylvestris); (10) Carpathian larch (Larix decidua subsp. carpatica) and stone pine (Pinus cembra); (11) valuable broadleaf species, including maple (Acer spp.), ash (Fraxinus spp.), elm (Ulmus spp.), linden (Tilia spec). Along water courses with periodical inundations, riparian forests and shrublands occur, dominated by (12) black alder (Alnus glutinosa); (13) grey alder (A. incana); (14) tamarisk (Myricaria germanica) pioneer copse; (15) pioneer forest with poplar (Populus spp.) and willow (Salix spp.); (16) riparian hardwood forest with oak, elm (Ulmus spp.), ash (Fraxinus spp.). In the EU countries virgin (primeval) and old growth forests account for less than 3% of the total forest area. Most alarming is the situation of temperate virgin and old-growth forest. About 80% of them are situated in the Carpathians, mainly formed by beech, fir, and spruce. Estimations of virgin and quasi-virgin, old-growth forests in Romania range between 150,000 and 200,000 ha. Between 2001 and 2019 about 350,000 ha disappeared through illegal and legal logging. Legislation in Romania demands that production forests have to be managed sustainably, and virgin forests have to be protected. Romanian forests are also subject to European law, such as the Habitats and Birds Directives. However, there is a severe lack of enforcement at all administration levels, even in National Parks. Sanctioning activities by the EU authorities are hardly visible. It follows: (1) It must be in the interest of all of Europe to preserve and protect the last large areas of primeval forest in Europe. (2) The community of EU countries, the Parliament and the European Commission must provide clear guidelines and care for their implementation, connected with attractive, secure and long-term funding programs (compensation for non-use). (3) At a regional level, new creative ideas and concrete initiatives must integrate wilderness areas into regional value creation concepts. [ABSTRACT FROM AUTHOR]

Despite decreasing sequencing costs, whole‐genome sequencing for population‐based genome scans for selection is still prohibitively expensive for organisms with large genomes. Moreover, the repetitive nature of large genomes often represents a challenge in bioinformatic and downstream analyses. Here, we use in‐depth transcriptome sequencing to design probes for exome capture in Swiss stone pine (Pinus cembra), a conifer with an estimated genome size of 29.3 Gbp and no reference genome available. We successfully applied around 55,000 self‐designed probes, targeting 25,000 contigs, to DNA pools of seven populations from the Swiss Alps and identified >160,000 SNPs in around 15,000 contigs. The probes performed equally well in pools of the closely related species Pinus sibirica; in both species, more than 70% of the targeted contigs were sequenced at a depth ≥40× (number of haplotypes in the pool). However, a thorough analysis of individually sequenced P. cembra samples indicated that a majority of the contigs (63%) represented multi‐copy genes. We therefore removed paralogous contigs based on heterozygote excess and deviation from allele balance. Without putatively paralogous contigs, allele frequencies of population pools represented accurate estimates of individually determined allele frequencies. We show that inferences of neutral and adaptive genetic variation may be biased when not accounting for such multi‐copy genes. Without individual genotype data, it would have been nearly impossible to recognize and deal with the problem of multi‐copy contigs. We advocate to put more emphasis on identifying paralogous loci, which will be facilitated by the establishment of additional high‐quality reference genomes. [ABSTRACT FROM AUTHOR]

Graphical abstract Image 1 Highlights • Higher ozone concentrations at high altitude mountain sites than low altitude sites. • Correlation between ozone concentration and foliar symptoms observed for Pinus cembra. • Percentages of foliar ozone symptoms decreased significantly between 2000 and 2016. • Significant increase of crown defoliation of Pinus cembra between 2000 and 2016. [ABSTRACT FROM AUTHOR]

The Swiss stone Pine (Pinus cembra L.) is an alpine species, fairly commonly occurring in the Alps and the Carpathians, close to the timberline. Natural sites of the Swiss stone pine in Poland are found exclusively in the Tatra Mountains, within the area of the Tatra National Park (TNP). In 2017, the health status of the needles of P. cembra was determined and their mycological analysis was carried out. As a result, 11 species of fungi were isolated from the needles showing disease symptoms, manifested by various shades of discoloration. The most frequently observed species was Fusarium oxysporum. It probably does not bring on disease symptoms, but may affect the development of other frequently isolated species (such as Sydowia polyspora, Lophodermium sp. and Lophodermium conigenum) that are pathogenic to Pinus spp. [ABSTRACT FROM AUTHOR]

Climate sensitivity of populations at the margins of their distribution range is of key importance to understand species’ responses to future warming conditions. Pinus cembra is of particular interest being a typical high-elevation taxon, spread with mostly scattered populations within its actual range, but still overlooked in traditional dendrochronological researches due to low tree-ring variability and climate sensitivity. With a different approach, we analyzed time series of xylem anatomical traits, split into intra-ring sectors, and used daily climate records over 89 years (1926-2014) aiming to improve the quality and time resolution of the climate/growth associations. From nine trees growing at their altitudinal limit and on 1.5 × 106 tracheids, we measured ring width (MRW), cell number per ring, lumen area (LA), and cell-wall thickness (CWT). We then computed correlations with monthly and fortnightly climate data. Late-spring and summer temperature emerged as the most important factors. LA and especially CWT showed a stronger temperature response than MRW, starting in mid-May and early June, respectively. CWT also evidenced the longest period of correlations with temperature and a significant difference between latewood radial and tangential walls. Analysis of xylem anatomical traits at intra-ring level and the use of daily temperature records proved to be useful for high resolution and detailed climate/growth association inferences in Pinus cembra. [ABSTRACT FROM AUTHOR]

The seasonal course of xylem sap parameters (electrical conductivity EC, potassium concentration [K+], and pH) of three conifers (Pinus cembra, Picea abies, and Larix decidua) growing at the alpine timberline was monitored. We also looked into possible effects of [K+] and pH on the difference in hydraulic conductivity (Δks). In all studied species, EC, [K+], and pH varied considerably over the year, with pH ranging between 7.3 (February) and 5.8 (June) and [K+] changing between 0.4 (January) and 2.5 mM (June). The Δks was overall low with positive values during winter (up to +20%) and negative values in summer (-15% in August). Samples perfused with alkaline solutions showed higher Δks. Xylem sap parameters in all conifers under study were surprisingly variable over the year thus indicating either effects upon seasonal changes in environmental factors or active adjustments, or both. Although Δks values over the year were minor, observed induction of Δks by high pH might indicate a role for hydraulic adjustment in harsh winter periods. [ABSTRACT FROM AUTHOR]

In paleoecology, the function of biomass as a fire driver has become a focus of attention in cold ecosystems, and concerns have been raised about climate in this context. Little is known about the fire frequency and fire-plant relationships during glaciation when woodlands were limited and the climate was cold., Fire history and tree biomass were reconstructed from sedimentary charcoal and macroremains, respectively, archived in lake sediments from the western Alps. Two nunataks were investigated, both with lacustrine sediments covering the last 21 000 yr at least., During the Last Glacial Maximum ( LGM) and the Lateglacial, fires occurred only on the nunatak sheltering woody plants. Cembra pine ( Pinus cembra) and larch ( Larix decidua) survived above glaciers during the LGM, thus evidencing a biological refugium and supporting the nunatak theory., We highlighted a long-term relationship between fires and dominant trees over the last 21 000 yr, where fire frequencies track the global climate and the local changes in tree biomass. Glacial climate (dry, cold) does not rule out fires. Fuel load and composition were significant fire drivers, with cembra pine dominating during colder periods with rare fires, and larch during the warmer Holocene with frequent fires. These findings increase knowledge of fire ecology in cold environments, and open perspectives in tree population genetics by considering new areas of tree glacial refugia in Europe. [ABSTRACT FROM AUTHOR]

A syntaxonomical statistical analysis of 110 phytocoenological relevés of the Western Carpathians Norway spruce-Arolla pine and Arolla pine phytocoenoses was performed. Resulting six relevé aggregates were evaluated at the rank of association. Two major groups of Arolla pine woodlands were distinguished following strong floristical differences and classified at the rank of alliances: non-carbonate group -- Homogyno alpinae-Pinion cembrae (associations: Homogyno alpinae-Pinetum cembrae, Mylio taylorii-Pinetum cembrae, Prenantho purpureae-Pinetum cembrae, Cembro-Piceetum) and carbonate group -- Calamagrostio variae-Pinion cembrae (associations: Seslerio tatrae-Pinetum cembrae, Cystopterido montanae-Pinetum cembrae). [ABSTRACT FROM AUTHOR]

We here analyze the tree-ring series from 42 high-altitude sites in a region of the European Alps centered over the 1° × 1° grid cell 46°N 10°E to reconstruct the summer temperature signal using an approach based on site chronologies and only on trees that are highly sensitive to temperature (HSTT). For the forest sites of Larix decidua Mill ., Picea abies Karst., and Pinus cembra L., we find that HSTT trees, representing 33 %, 25 % and 27.5 % of all trees in the dataset, respectively, are growing larger tree-rings in recent periods (since approximately 1935 AD) compared with the other trees in the region. The temperature reconstruction based on the HSTT chronology is consistent with other reconstructions already available in the European Alps, well preserves the long-term temperature variability and suggests lower summer temperatures than those derived from the chronology avgALL (based on the entire dataset) during the periods 1725-1800 AD and 1845-1910 AD. Since 1935, the HSTT reconstruction is more efficient than the avgALL in recording the recent temperature trends. Overall, we stress the importance of testing for the presence of HSTT trees at each site, as their incidence may influence the temperature reconstructions as much as the other known factors related to, e.g., site characteristics, tree age and species sensitivity. HSTT trees may enhance the long-term climate signal for performing reliable climate reconstructions because they reduce potential biases derived from non-climatic influences on tree growth. Our results can further help to avoid the divergence problem with the instrumental records, particularly for those periods where the avgALL curve shows a tendency to smooth the long-term summer temperature signal. [ABSTRACT FROM AUTHOR]

Forest fires are controlled by local (vegetation, aspect, elevation, land uses) and regional (climate) factors. The role of these factors remains poorly assessed on centennial to millennial time scales. Here, we investigate fire and vegetation history in five subalpine sites over the past 8000 years to determine when, how, and why there were differences in fire regimes. We focus on time and aspect separately and account for vegetation composition. There are no significant differences in the fire return intervals among sites (~290 years between two fires). The rise of fire frequency from its lowest values (1.5 fires.1000 yr) at 8000-7000 years before present (yrBP) to its highest at 4000-3000 yrBP (5 fires-1000 yr) is well explained by the high temperatures and low precipitation of the Holocene, both leading to better conditions for fire ignition and spread. From 8000 yrBP, climate is likely the main factor driving the fire frequency on the north-facing sites, which contained mixed Larix decidua- Pinus cembra vegetation; whereas south-facing sites, dominated by the flammable P. cembra and broadleaved trees, appear to be driven by local features, including land use. A shift in the main drivers occurs at 4000 yrBP, when local processes start to control burning activity at all sites. Forest clearance for land use might have directly increased fire frequency, but has also helped to suppress fires through fuel limitation. During the last four millennia, land use likely altered the natural climate-vegetation-fire system mainly by converting forests to grassland by pastoral practices, thus leading to less fire and making the fire-vegetation-climate relationships more complex. [ABSTRACT FROM AUTHOR]

In alpine regions, elevational gradients in environmental parameters are reflected by structural and functional changes in plant traits. Elevational changes in plant water relations have also been demonstrated, but comparable information on root hydraulics is generally lacking. We analyzed the hydraulic efficiency (specific hydraulic conductivity k, entire root system conductance K) and vulnerability to drought-induced embolism (water potential at 50 % loss of conductivity Ψ) of the roots of Pinus cembra trees growing along an elevational transect of 600 m. Hydraulic parameters of the roots were compared with those of the stem and related to anatomical traits {mean conduit diameter ( d), wall reinforcement [( t/b)]}. We hypothesized that temperature-related restrictions in root function would cause a progressive limitation of hydraulic efficiency and safety with increasing elevation. We found that both root k and K decreased from low (1600 m a.s.l.: k 5.6 ± 0.7 kg m s MPa, K 0.049 ± 0.005 kg m s MPa) to high elevation (2100 m a.s.l.: k 4.2 ± 0.6 kg m s MPa, K 0.035 ± 0.006 kg m s MPa), with small trees showing higher K than large trees. k was higher in roots than in stems (0.5 ± 0.05 kg msMPa). Ψ values were similar across elevations and overall less negative in roots ( Ψ −3.6 ± 0.1 MPa) than in stems ( Ψ −3.9 ± 0.1 MPa). In roots, large-diameter tracheids were lacking at high elevation and ( t/b) increased, while d did not change. The elevational decrease in root hydraulic efficiency reflects a limitation in timberline tree hydraulics. In contrast, hydraulic safety was similar across elevations, indicating that avoidance of hydraulic failure is important for timberline trees. As hydraulic patterns can only partly be explained by the anatomical parameters studied, limitations and/or adaptations at the pit level are likely. [ABSTRACT FROM AUTHOR]

The levels of variation and genetic diversity of offspring of randomly selected old mother trees in four marginal populations of the Pinus cembra in the Tatra Mountains were analyzed. Twenty-four isozyme loci were analyzed (nine of them were monomorphic). The analyzed offspring of Swiss stone pine showed highly diverse polymorphism at the levels of both provenances and individual families (the offspring of one mother tree). The mean observed heterozygosity was low and very similar to that of other Carpathian populations. The genetic diversity (mean F = 11%) between the four provenances was higher than that observed for populations from the Carpathian Mountains and the Alps. The genetic uniqueness (high genetic richness and diversity) of the analyzed Tatra populations of P. cembra as a whole and particular tree stands requires protection because of their valuable contribution to the species total genetic diversity (gene pool). [ABSTRACT FROM AUTHOR]

This study quantified the effect of soil warming on sap flow density (Qs) of Pinus cembra L. at the treeline in the Central Tyrolean Alps. To enhance soil temperature we installed a transparent roof construction above the forest floor around six trees. Six other trees served as controls in the absence of any manipulation. Roofing enhanced growing season mean soil temperature by 1.6, 1.3 and 1.0 °C at 5, 10 and 20 cm soil depth, respectively, while soil water availability was not affected. Sap flow density (using Granier-type thermal dissipation probes) and environmental parameters were monitored throughout three growing seasons. During the first year of treatment, no warming effect was detected on Qs. However, soil warming caused Qs to increase significantly by 11 and 19% above levels in control trees during the second and third year, respectively. This effect appeared to result from warming-induced root production, a reduction in viscosity and perhaps an increase also in root hydraulic conductivity. Hardly affected were leaf-level net CO2 uptake rate and conductance for water vapour, so that water-use efficiency stayed unchanged as confirmed by needle δ13C analysis. We conclude that tree water loss will increase with soil warming, which may alter the water balance within the treeline ecotone of the Central Austrian Alps in a future warming environment. [ABSTRACT FROM AUTHOR]

The asexual form of the fungus Mycosphaerella attacks most species of pine trees and produces major damage in the woody nursery. This pathogen has had only seven years after the first infection in Tanzania to reach nurseries in central or eastern Africa. Global losses resulting from epidemics in the world were major. There were losses of 67% to Pinus radiata trees 7-8 years of age in California, total losses of P. ponderosa trees in most eastern states of the United States of America and 40% loss of trees P. flexilis in Montana (Taylor, Schwandt, 1998). Within this paper observations were performed in the laboratory and in the field, determinations were made based on symptoms and morphological characteristics of the fungus. To achieve these observations and measurements samples were taken every ten days for three months from The Botanical Garden of Iasi, from the species Pinus nigra and Pinus cembra damaged by Dothistroma septosporum. [ABSTRACT FROM AUTHOR]

In Europe, most of the alpine timberline ecotone has been altered by human activities and climate change. Hence, mountain forests are of the highest conservation interest. Here, we screened 25 populations of Swiss stone pine ( Pinus cembra L.) from the Carpathians and the Alps, using a set of ten microsatellite primers to assess the relative conservation value of populations sampled in Polish and Slovak Tatra National Parks, where potential extinction risk is the highest within the Carpathian range. Although endangered, with small and fragmented populations, P. cembra in the Tatra Mts. shows high levels of allelic richness ( AR = 5.0) and observed heterozygosity ( H = 0.554). Our results suggest that anthropogenic habitat fragmentation has had little impact on DNA variation of Swiss stone pine in the Tatra Mts. However, the effects of changing conditions on the genetic structure may occur with a substantial time delay due to the long life span of P. cembra. Moreover, inbreeding depression may occur in the next generations, since we found inbreeding ( F = 0.063) and elevated coancestry coefficient ( θ = 0.062) in all populations. Also a shallow pattern of genetic differentiation between populations was found, indicating recent fragmentation of a common gene pool that formerly occupied a larger range. Therefore, the Tatra Mts. can be considered as a single conservation unit. Based on our results, we suggest possible conservation activities for Swiss stone pine both in Poland and Slovakia. [ABSTRACT FROM AUTHOR]

Mating systems have long been recognized as key factors determining genetic structure within and between populations. Outcrossing promotes genetic diversity and gene flow between populations, while inbreeding, on the other hand, decreases recombination rates, facilitating fixation of co-adapted genes. In small populations, selfing moderates pollen limitation because of low mate availability, but at the cost of increased inbreeding depression. These conflicts are of more than theoretical interest; they are critical for the management of endangered species. In order to help designing conservation strategies for the management of the gene pool of fragmented populations of Pinus cembra, a protected species in Poland, we have characterized pollen flow and mating structure using nuclear microsatellite markers. We demonstrated that P. cembra in the studied stands of the Tatra Mts. is characterized by an average outcrossing rate ( t) of 0.72. Unlike with the existing approaches, using the newly developed Bayesian method, we found that population size and seasonal variation had confounding effects on outcrossing rates. In concordance with predictions, large populations showed significantly higher outcrossing rates ( t = 0.89) than smaller ones ( t = 0.51). Temporal variation revealed in the outcrossing rate might be linked with masting behavior of the species. On the other hand, we showed that outcrossing rates were not associated with a trunk diameter of a mother tree. Our study also demonstrated that biparental inbreeding is a significant component of mating system. However, we further show that pollen dispersal follows a fat-tailed distribution (with the average dispersal distance of 1,267 m) so that at least some long-distance pollen dispersal must be occurring. Overall, we conclude that the high inbreeding (both selfing and mating between relatives) found in P. cembra buffers for pollen limitation. We argue that small, isolated stands can be at risk of gene pool erosion, despite the potential for long-distance pollen and seed dispersal. [ABSTRACT FROM AUTHOR]

Genetic differentiation of scattered populations at neutral loci is characterized by genetic drift counteracted by the remaining gene flow. Populations of Pinus cembra in the Carpathian Mountains are isolated and restricted to island-like stands at high-elevation mountain ranges. In contrast, paleobotanical data suggest an extended early Holocene distribution of P. cembra in the Carpathians and its surrounding areas, which has contracted to the currently disjunct occurrences. We analyzed the genetic variation of 11 Carpathian populations of P. cembra at chloroplast and, in part newly developed, nuclear microsatellites. Both marker types revealed low levels of genetic differentiation and a lack of isolation by distance, reflecting the post-glacial retraction of the species to its current distribution. Stronger effects of genetic drift were implied by the higher genetic differentiation found for haploid chloroplast than for diploid nuclear markers. Moreover, we found no association between the values of population genetic differentiation for the two marker types. Several populations indicated recent genetic bottlenecks and inbreeding as a consequence of decline in population sizes. Moreover, we found individuals in two populations from the Rodnei Mountains that strikingly differed in assignment probabilities from the remaining specimens, suggesting that they had been introduced from a provenance outside the studied populations. Comparison with Eastern Alpine P. cembra and individuals of the closely related Pinus sibirica suggests that these individuals presumably are P. sibirica. Our study highlights the importance of the maintenance of sufficiently large local population sizes for conservation due to low connectivity between local occurrences. [ABSTRACT FROM AUTHOR]

Whole-tree water use of nine Pinus cembra trees was estimated in the treeline ecotone of the Central Austrian Alps. Sap flow density using Granier-type thermal dissipation probes and environmental parameters was monitored along an elevational gradient from the forest limit up to treeline and finally mediating the krummholz limit throughout two growing seasons. Normalized sap flow density ( Q) was significantly correlated with solar radiation ( R) and vapor pressure deficit ( D) throughout the treeline ecotone. Multiple regression analysis indicated that at the forest limit and at treeline, D had a similar effect on Q than R. At the krummholz limit by contrast, D had a greater effect on Q than R due to partially stomatal closure and wind-induced clustering of the needles, which impaired their response to available irradiance. Whole-tree water use scaled to crown surface area estimated for an entire growing (172 days) declined from 449 mm at the forest limit to 274 mm at treeline and was 251 mm at the krummholz limit, which is within the values estimated for other European forest ecosystems. Nevertheless, the observation above the forest limit in the central Tyrolean Alps tree transpiration scaled to crown surface area is comparable to the water use of adjacent low-stature vegetation, which should also be taken into account when forecasting potential effects of global change on the water balance of the treeline ecotone. [ABSTRACT FROM AUTHOR]

Relationships between the flammability properties of a given plant and its chances of survival after a fire still remain unknown. We hypothesize that the bark flammability of a tree reduces the potential for tree survival following surface fires, and that if tree resistance to fire is provided by a thick insulating bark, the latter must be few flammable.We test, on subalpine tree species, the relationship between the flammability of bark and its insulating ability, identifies the biological traits that determine bark flammability, and assesses their relative susceptibility to surface fires from their bark properties. The experimental set of burning properties was analyzed by Principal Component Analysis to assess the bark flammability. Bark insulating ability was expressed by the critical time to cambium kill computed from bark thickness. Log-linear regressions indicated that bark flammability varies with the bark thickness and the density of wood under bark and that the most flammable barks have poor insulating ability. Susceptibility to surface fires increases from gymnosperm to angiosperm subalpine trees. The co-dominant subalpine species Larix decidua (Mill.) and Pinus cembra (L.) exhibit large differences in both flammability and insulating ability of the bark that should partly explain their contrasted responses to fires in the past. [ABSTRACT FROM AUTHOR]

Identifying the factors controlling tree mortality is key to understanding the effects of ongoing global change on treeline movement and species composition. One potentially significant but little studied factor that impacts the formation of treelines is mortality caused by snow fungi. We studied the mortality patterns of Pinus cembra, a typical treeline species of the Central Alps of Switzerland, in two plantations located on opposite slopes of the Dischma valley (Northeast [NE] and Southwest [SW]) above the current treeline. In 1975, 33,000 P. cembra trees were planted at the NE site and 550 trees at the smaller SW site. All trees have been periodically monitored for survival since then. After 30 years, only ca. 5% of all P. cembra trees survived in both plantations. Two species of pathogenic snow fungus, Gremmeniella abietina and Phaciclium infestons, were major mortality agents for saplings. High rates of infection by Gremmeniella corresponded to late snowmelt and high ratios of rainfall to temperature. High rates of infection by Phacidium corresponded to earlier snowmelt and were spatially associated with P. cembra mature trees that had been present in the area before the time of planting. We provide experimental evidence that snow fungi are a primary cause of sapling tree mortality at treeline. Although additional evidence from different geographic regions and more natural treeline distributions is needed, our results suggest that the prevalence of snow fungi may prevent establishment of trees above the current treeline at present, and under future climate scenarios. [ABSTRACT FROM AUTHOR]

Recent studies on non-structural carbohydrate (NSC) reserves in trees focused on xylem NSC reserves, while still little is known about changes in phloem carbohydrate pools, where NSC charging might be significantly different. To gain insight on NSC dynamics in xylem and phloem, we monitored NSC concentrations in stems and roots of Pinus cembra (L.) and Larix decidua (Mill.) growing at the alpine timberline throughout 2011. Species-specific differences affected tree phenology and carbon allocation during the course of the year. After a delayed start in spring, NSC concentrations in L. decidua were significantly higher in all sampled tissues from August until the end of growing season. In both species, NSC concentrations were five to seven times higher in phloem than that in xylem. However, significant correlations between xylem and phloem starch content found for both species indicate a close linkage between long-term carbon reserves in both tissues. In L. decidua also, free sugar concentrations in xylem and phloem were significantly correlated throughout the year, while a lack of correlation between xylem and phloem free sugar pools in P. cembra indicate a decline of phloem soluble carbohydrate pools during periods of high sink demand. [ABSTRACT FROM PUBLISHER]

Abstract: Cumulative ozone uptake (COU, mmolm−2) and O3 flux (FO3, nmolm−2 s−1) were related to physiological, morphological and biochemical characteristics of field-grown mature evergreen Norway spruce [Picea abies (L.) Karst.], Cembran pine [Pinus cembra L.], and deciduous European larch [Larix decidua Mill.] trees at treeline. The threshold COU causing a statistically significant decline in photosynthetic capacity (A max) ranged between 19.6mmolm−2 in current-year needles of evergreen conifers and 22.0 6mmolm−2 in short-shoot needles of deciduous L. decidua subjected to exposure periods of ≥84 and ≥43 days, respectively. The higher O3 sensitivity of deciduous L. decidua than of evergreen P abies and P. cembra was associated with differences in FO3 and specific leaf area (SLA), both being significantly higher in L. decidua. FO3 was 5.9nmolm−2 s−1 in L. decidua and 2.7nmolm−2 s−1 in evergreen conifers. Species-dependent differences were also related to detoxification capacity expressed through total surface area based concentrations of reduced ascorbate and α-tocopherol that both increased with SLA. Findings suggest that differences in O3 sensitivity between evergreen and deciduous conifers can be attributed to foliage type specific differences in SLA, the latter determining physiological and biochemical characteristics of the treeline conifers. [Copyright &y& Elsevier]

The chemical composition and the antioxidant and antimicrobial effects of the essential oils of Pinus cembra L. needles and twigs were investigated in this study. The chemical composition was analyzed using both the GC and GC--MS techniques. α-Pinene (69.14 %) was the major constituent of the needle essential oil while the twig essential oil was characterized by a high content of limonene+β-phellandrene (40.97 %) and α-pinene (24.94 %). The needle and twig essential oils showed weak DPPH radical scavenging effects. In the antimicrobial assays, both essential oils showed high activity against Sarcina lutea and Staphylococcus aureus but no activity against Bacillus cereus, Escherichia coli and Pseudomonas aeruginosa. The needle and twig essential oils had similar antimicrobial effects against Sarcina lutea. The twig essential oil was more active against S. aureus than the needle essential oil and also exhibited a moderate activity against Candida albicans. [ABSTRACT FROM AUTHOR]

Background and Aims: In contrast to the wealth of information on sap flow characteristics of forest trees at low-elevation sites, knowledge is scarce for trees within the treeline ecotone. Thus, our aim was to identify environmental controls on water loss in P. cembra trees at the treeline. Methods: Three isolated individuals were equipped with thermal dissipation probes for monitoring sap flow density (QS ). A Jarvis-type model and multiple linear regression, with irradiance and vapour pressure deficit as explanatory variables, were applied to compare predicted and measured sap flow density. Results: Both models successfully predicted measured QS . The Jarvis model tended to underestimate QS values by 25% on average, as compared with an underestimate of 8% by multiple linear regression analysis. The multiple linear regression analysis also allowed discrimination between effects of irradiance (RS ) and vapour pressure deficit (D) on QS , indicating that RS (ß-coefficient = 0.70) had a greater effect on QS than D (ß-coefficient = 0.25). Whole-tree water loss scaled to ground surface area (1.9 ± 0.5 mm d−1) was within the range reported for adjacent low-stature vegetation. Conclusions: The results suggest that the multiple linear regression approach is superior to the non-linear Jarvis-type model, as this approach allows discrimination between the effects of RS and the effects of D on QS . [ABSTRACT FROM PUBLISHER]

Understanding the interplay between environmental factors contributing to treeline formation and how these factors influence different life stages remains .a major research challenge. We used an afforestation experiment including 92 000 trees to investigate the spatial and temporal dynamics of tree mortality and growth at treeline in the Swiss Alps. Seedlings of three high-elevation conifer species (Larix decidua, Pinus mugo ssp. uncinata, and Pinus cembra) were systematically planted along an altitudinal gradient at and above the current treeline (2075 to 2230 m above sea level [a.s.l.]) in 1975 and closely monitored during the following 30 years. We used decision-tree models and generalized additive models to identify patterns in mortality and growth along gradients in elevation, snow duration, wind speed, and solar radiation, and to quantify interactions between the different variables. For all three species, snowmelt date was always the most important environmental factor influencing mortality, and elevation was always the most important factor for growth over the entire period studied. Individuals of all species survived at the highest point of the afforestation for more than 30 years, although mortality was greater above 2160 m a.s.l., 50-100 m above the current treeline. Optimal conditions for height growth differed from those for survival in all three species: early snowmelt (ca. day of year 125-140 [where day 1 is 1 January]) yielded lowest mortality rates, but relatively later snowmelt (ca. day 145-150) yielded highest growth rates. Although snowmelt and elevation were important throughout all life stages of the trees, the importance of radiation decreased over time and that of wind speed increased. Our findings provide experimental evidence that tree survival and height growth require different environmental conditions and that even small changes in the duration of snow cover, in addition to changes in temperature, can strongly impact tree survival and growth patterns at treeline. Further, our results show that the relative importance of different environmental variables for tree seedlings changes during the juvenile phase as they grow taller. [ABSTRACT FROM AUTHOR]

As an efficient seed-disperser, Eurasian nutcrackers (Nucifraga caryocatactes) generally consume and hoard mature, edible pine seeds for future use. In 2009, when the Arolla pine, Pinus. cembra, produced a mast-crop, we investigated cones discarded by nutcrackers. Most cones were only partly eaten and some mature seeds remained in the distal part. This was in contrast to years of lower seed production when nearly all seeds were harvested from the majority of cones. To determine whether nutcracker cone-discarding behaviour maximised intake rate, seed kernels and the aborted seeds rate were measured from the different cone parts. In 2009, seeds from cone-tops were on average 17% lighter than in the base and middle sections, and the proportion of aborted seeds in the top part was 81% higher than in the other sections. There was no difference in seed mass and proportion of aborted seeds in cone-tops of intact cones and cones handled by nutcrackers. Regarding each cone as a patch, cone discarding behaviour can be considered as an optimal cone-leaving rule, maximising rate of energy-intake, supporting the Marginal Value Theorem. Hence, we suggest that increased food abundance leads to more selective seed harvesting in nutcrackers. [ABSTRACT FROM AUTHOR]

Winter frost resistance (WFR), midwinter frost hardening and frost dehardening potential of Pinus cembra L. were determined in situ by means of a novel low-temperature freezing system at the alpine timberline ecotone (1950 m a.s.l., Mt Patscherkofel, Innsbruck, Austria). In situ liquid nitrogen (LN2)-quenching experiments should check whether maximum WFR of P. cembra belonging to the frost hardiest conifer group, being classified in US Department of Agriculture climatic zone 1, suffices to survive dipping into LN2 (−196 °C). Viability was assessed in a field re-growth test. Maximum in situ WFR (LT50) of leaves was <− 75 °C and that of buds was less (−70.3 °C), matching the lowest water contents. In midwinter, in situ freezing exotherms of leaves, buds and the xylem were often not detectable. Ice formed in the xylem at a mean of −2.8 °C and in leaves at −3.3 °C. In situ WFR of P. cembra was higher than that obtained on detached twigs, as reported earlier. In situ LN2-quenching experiments were lethal in all cases even when twigs of P. cembra were exposed to an in situ frost hardening treatment (12 days at −20 °C followed by 3 days at −50 °C) to induce maximum WFR. Temperature treatments applied in the field significantly affected the actual WFR. In January a frost hardening treatment (21 days at −20 °C) led to a significant increase of WFR (buds: −62 °C to <− 70 °C; leaves: −59.6 °C to −65.2 °C), showing that P. cembra was not at its specific maximum WFR. In contrast, simulated warm spells in late winter led to premature frost dehardening (buds: −32.6 °C to −10.2 °C; leaves: −32.7 to −16.4 °C) followed by significantly earlier bud swelling and burst in late winter. Strikingly, both temperature treatments, either increased air temperature (+10.1 °C) or increased soil temperature (+6.5 °C), were similarly effective. This high readiness to frost harden and deharden in winter in the field must be considered to be of great significance for future winter survival of P. cembra. Determination of WFR in field re-growth tests appears to be a valuable tool for critically judging estimates of WFR obtained on detached twigs in an ecological context. [ABSTRACT FROM AUTHOR]

Abstract: This paper examines fourteen fossil pollen datasets from Romania. It aims to investigate the temporal and spatial variability in the range distribution and abundance of three forest taxa, Pinus, Picea abies, and Quercus, during the Holocene. This is essential for understanding their current status in the forests of Eastern Europe, the conditions under which they arose, and the timing and processes responsible for their variability. Results from this synthesis do not indicate any apparent time lag in the establishment of Pinus diploxylon type (Pinus sylvestris and Pinus mugo), Pinus cembra, P. abies, and Quercus across Romania within the limits of the dating resolution. However, the onset of the mass expansion of P. abies was not uniform, spreading earlier from sites in the western and north-western Carpathians (11,000–10,500 yr BP) than in the east (10,000 yr BP). We found that sites from the western, north-western, and northern Carpathians contained higher abundances of P. abies, whilst Quercus was in higher abundances in sites from the east, but there was no regional distinctiveness in the abundance of Pinus across the study area. However, P. diploxylon type was found in much higher abundance than P. cembra. Additionally, results indicate a greater proportion of Pinus (mainly P. diplxylon type) at high elevations, P. abies at mid to high elevations, and Quercus at low elevations (<500 m). The dominance of Pinus in the early Holocene boreal forest is likely the legacy of its local glacial refugia, fast life history strategies, high stress tolerance, and large habitat availability. In contrast, Pinus exhibited poor competitive abilities and was quickly replaced with P. abies and temperate deciduous taxa after 10,500 yr BP. P. abies has persisted in large abundances at higher elevations (above 1000 m) until the present day, as a result of good competitive abilities, and resilience to climate change and disturbance. The long-term dominance of P. abies appears to have been spatially constrained, as populations below ca 1000 m were replaced by Fagus sylvatica from ca 4000 years ago, Recently, Pinus (mainly P. sylvestris) and P. abies have both experienced range expansions a consequence of forest management. Quercus is the only continental deciduous tree that has maintained high abundance throughout the whole Holocene. Members of this genus demonstrated high resilience to climate change and disturbance; following a period of decline it was capable of recovery during subsequent intervals of warm conditions or disturbance. [Copyright &y& Elsevier]

The chemical constituents and biological activity of Pinus cembra L. (Pinaceae), native to the Central European Alps and the Carpathian Mountains, are not well known. The aim of the present work was to examine the phenolic content, antioxidant and antimicrobial effects of hydromethanolic extracts of Pinus cembra L. bark and needles. Bark extract had higher concentrations of total phenolics (299.3 vs. 78.22 mg gallic acid equivalents/g extract), flavonoids (125.3 vs. 19.84 mg catechin equivalents/g extract) and proanthocyanidins (74.3 vs. 12.7 mg cyanidin equivalents/g extract) than needle extract and was more active as a free radical scavenger, reducing agent and antimicrobial agent. The EC50 values in the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline- 6-sulfonic acid) diammonium salt (ABTS) and reducing power assays were 71.1, 6.3 and 26 μg/mL for bark extract and 186.1, 24 and 104 μg/mL for needle extract, respectively. In addition, needle extract showed ferrous ions chelating effects (EC50 = 1,755 μg/mL). The antimicrobial effects against Staphylococcus aureus, Sarcina lutea, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans were assessed by the agar diffusion method. Both extracts (4 mg/well) were active against all the microorganisms tested; bark extract showed higher inhibition on all strains. These results indicate that Pinus cembra L. bark and needles are good sources of phytochemicals with antioxidant and antimicrobial activities. [ABSTRACT FROM AUTHOR]

Tree-ring width and glacier mass balance are two highly sensitive climatic proxies which are often used as indicators of biological and geophysical changes in high-altitude ecosystems. Tree-ring data have been widely used to reconstruct past temperatures and also to reconstruct past glacier mass balance. Here we show that tree-ring chronologies from a high-altitude Pinus cembra L. dendroclimatic network and glaciers from the same region in the European Alps have non-stationary responses to air temperature, and have also been responding non-proportionally to temperature extremes in recent decades. Both ring-width chronologies and the mass-balance series of some glaciers from the same region have shown an increasing sensitivity to summer (JJA) temperatures. Our results demonstrate that the sensitivity to climate of tree-ring chronologies and glacier mass balance may change over time and has been increasing in recent decades, posing some limitations to tree-ring-based glacier mass-balance reconstruction. Moreover, we found these reconstructions in the European Alps are more reliable for large rather than for small glaciers, and may not be able to reveal years of extreme ablation that could have occurred in the past. [ABSTRACT FROM AUTHOR]

The article presents a study on the diversity pattern of Swiss stone pine, Pinus cembra L. along the Carpathian range. The range characteristics of nine Swiss stone pine populations were analyzed using six chloroplast DNA microsatellites (cpSSR). The study revealed that the most diverse populations can be found in the Retezat Mountains in South Carpathians and the High Tatras, while the diversity of population decreases towards Eastern Carpathian.

Abstract: Seed predation and dispersal are key processes in the survival and distribution of plant species. Many animals cache seeds for later consumption, and, failing to recover some of these seeds, act as seed dispersers, influencing post-dispersal seed and seedling survival. Both animal and plant benefit from scatterhoarding and natural selection of seed characteristics and adaptations of seed predators (and dispersers) is one of the most important examples of co-evolution and mutualism. We studied the producer–consumer Arolla pine (Pinus cembra)–red squirrel (Sciurus vulgaris) system in a subalpine forest in the Italian Alps. Arolla pine produced large seed-crops (masting) at irregular intervals, followed by years with poor or moderate seed production. Squirrel density fluctuated in synchrony with the food resource, eliminating the time-lag normally present when resources are produced in pulses. In all years except 2009 (a mast-crop year), all Arolla pine cones were harvested (their seeds consumed and/or cached) by September to late October by different species. Both squirrels and nutcrackers (Nucifraga caryocatactes) fed on seeds, and their relative pre-dispersal predation rates (on cones in the canopy) differed between years. Overall, nutcrackers consumed more seeds between July and October than squirrels, but in 1 year squirrels took the largest number of seeds. Pre-dispersal seed predation by squirrels tended to be lower in years with large seed-crop size and there was a positive correlation, over the entire study period, between density of recovered hoards and Arolla pine seed density of the previous year. We conclude that (i) squirrels and nutcrackers are important pre-dispersal seed predators and seeds dispersers; (ii) squirrels are also post-dispersal seed predators, and (iii) the proportion of cached seeds consumed by squirrels increased with the size of the Arolla pine seed-crop, suggesting that red squirrel is a conditional mutualistic scatterhoarder of Arolla pine seeds. [Copyright &y& Elsevier]

Abstract: A pollen study at Survilly (2235m asl, 06° 49′ 12″ E, 45° 59′ 24″ N), a small peatbog located on the Anterne mountain (Upper-Arve Valley, French north-western Alps) highlights the local role of human activities in Holocene vegetation dynamics of the currently treeless subalpine belt and the consecutive resumption of erosion. As early as 8890 cal. years BP (±122), Pinus cembra grew close to the site. Grasslands without shrubs were established at around 4624±86 cal. years BP. Due to human activities, spruces extended little after 3600 cal. BP. The intense grazing that resulted in the current alpine meadows goes back to 1436 cal. years BP (±81). After 4624 cal. BP three clay layers show that from this period, the erosion became as active as during the first steps of the colonization of the vegetation prior to 10,050 cal. BP. During peat growth only a millimetre of clay at the end of the 9400–9050 cal. BP climatic event was recorded. [ABSTRACT FROM AUTHOR]

Abstract: Global environmental changes observed during recent decades are likely to have had an impact on the distribution of species. Currently, silver fir (Abies alba) is becoming established in the subalpine forests of the west central Alps at elevations higher than 2000m a.s.l.; prior to the 1970s its upper altitudinal limit was 2000m. Several hypotheses could explain this recent expansion of the upper tree-limit. Silver fir regeneration could be linked (1) to land-use changes or (2) to current climatic warming. Using dendrochronology, the age structure of 31 forest plots containing at least one silver fir was examined in order to elucidate the population dynamics of subalpine communities. This allowed us to decipher the timing of fir regeneration in relation to the mean age of the stands examined and of the other tree-canopy species present. The majority of the firs germinated sporadically since 1950, before the regional temperature increase. The pattern of fir recruitment did not appear to relate to altitude, but followed a pattern characteristic of secondary succession. The age structures identified showed an exponential increase in tree-density during the 20th century; the stands were first dominated by Larix decidua during the 18th and 19th centuries, and then by Pinus cembra during the 20th century. In most stands, fir regeneration occurred after Larix and before P. cembra dominated, following a similar pattern to Picea abies regeneration. The number of local inhabitants and temperature both exhibited a negative relationship with fir tree recruitment, thus supporting the land-use change hypothesis. There has been a significant upward shift of the altitudinal range of fir, amounting to an increase of about 300m since 1950. This followed the abandonment of low-productivity land. This trend is likely to continue during the 21st century, because of new agricultural and forestry practices which involve limited intervention in low-productivity areas and may be because of the effects of global warming. [Copyright &y& Elsevier]

Copyright of Annals of Forest Science (EDP Sciences) is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Proactive management should be applied within a forest conservation context to prevent extinction or degradation of those forest ecosystems that we suspect will be affected by global warming in the next century. The aim of this study is to estimate the vulnerability under climate change of a localized and endemic tree species Pinus cembra that occurs in the alpine timberline. We used the Random Forest ensemble classifier and available bioclimatic and ecological data to model present and future suitable areas for P. cembra and estimate its current and future vulnerability. Future projections for years 2020, 2050 and 2080 were simulated using two IPCC Special Report on Emission Scenarios run under four global climate models. The suitability model described the optimal environmental conditions for P. cembra. Model scores (κ =0.77, sensitivity=0.99 and specificity=0.80) are robust. The main factors defining the model were Kira''s warmth index and summer temperatures. Results show that there is potential for P. cembra to regenerate and persist in currently suitable areas. Future trends analysis suggested a cumulated mean loss of suitable areas of between 53% and 72% for different scenarios. All modeled projections predicted an upslope shift of the optimally suitable P. cembra belt and no downslope shift. We discuss environmental factors/plant interactions, the theoretical assumptions behind the model, model strengths and limitations, and we highlight the conservative traits of our analysis. The results suggest that forest management practices will play a fundamental role in the conservation of P. cembra habitats in the Alps. [Copyright &y& Elsevier]

This paper presents and discusses the use of soil charcoal analysis (pedoanthracology) to reconstruct past forest dynamics in a larch forest of the upper Guil valley (French Alps, Queyras). We also discuss the role of anthropogenic fire in forest dynamics. The radiocarbon dates from this site demonstrate that arolla pine (Pinus cembra) and larch were present in the area since 7566-7673 cal. BP and 5934-6123 cal. BP, respectively. The identification of a piece of charcoal to fir (Abies alba) dated to 5734-5908 cal. BP suggests that this species was present at 1980 m a.s.l. since c. 6000 cal. BP and had a higher ecological tolerance than previously assumed. The cover of larch forests has increased since the second half of the Holocene because of anthropogenic practices (eg, clearing with fire, cattle grazing). However, today, owing to the abandonment of pastoral practices, the arolla pine has become dominant, which greatly modifies the forest structure and the landscape. [ABSTRACT FROM AUTHOR]

The study presented here from the southern French Alps demonstrates the reliability of soil charcoal analysis for the study of Holocene past treeline positions. The occurrence of charcoal in mineral soils along transects from 1950 m up to 2920 m demonstrates the role of fire in the establishment of the present vegetation patterns. The abrupt decrease of charcoal concentration at about 2400-2600 m (which varies across the study sites) corresponds to the modern transition between subalpine forest and alpine tundra. Charcoal particles formed in situ provide high spatial-resolution data for the reconstruction of past forest and treeline changes. Soil charcoal analysis indicated that: (1) treeline was 300 m higher around 6800 cal. BP than today; and (2) the uppermost forest belt up to 2810 m was colonized by larch (Larix decidua Mill.) and arolla pine (Pinus cembra L.). This pine is present today but patchily distributed: it is absent from the three areas studied. Radiocarbon dates, ranging from c. 6800 cal. BP to the modern period, along with historical and archaeological data, suggest that the present pattern of the uppermost forest belt, and the patchy distribution of arolla pine in the studied area are the results of anthropogenic fire (mainly agropastoral activities). The question of global warming consequences on treelines in this part of the French Alps is discussed. [ABSTRACT FROM AUTHOR]

High altitude alpine ecosystems are likely to be highly sensitive to future climate change. Understanding long-term tree stand dynamics may be a key requirement for forecasting such changes. Here, we present a high resolution record of paleobotanical macroremains covering the last 11 700 years, from a small subalpine pond situated in the inner French Alps, at 2035 m a.s.l. The early presence of larch (Larix decidua), arolla pine (Pinus cembra) and birch (Betula) at this elevation, just after the end of the Younger Dryas cold transition, suggests the occurrence of either glacial tree-refugia located nearby in the northwestern Alps, or a previously unrecorded early and rapid tree migration. The 8200 cal. BP cooling event is characterized by a rapid and limited expansion of mountain pine (Pinus mugo/uncinata type).Mixed stands of larch, birch and arolla pine established at 8300 cal. BP and were present through the mid Holocene. After the Holocene climatic optimum, at 5600 cal. BP, recurrent fires led to the development of highly dynamic and more diversified forests, with larch, birch, arolla pine, mountain pine and fir (Abies alba). Natural and anthropogenic disturbances, e.g., fires, avalanches, slash-and-burn and other agricultural practices, influenced subsequent vegetation until the last millennium when tree-pasture established around the lake. The data indicate that the vegetation was progressively dominated by open larch woodland from 4000 years ago, and was clearly established during the Middle Ages (1250 cal. BP) up to the nineteenth century, when land began to be abandoned. The modern vegetation, dominated by larch and arolla pine and resulting from land abandonment, tends to resemble the communities that occurred from 8300 to 4000 cal. BP, before the postulated anthropogenic alteration of subalpine forest ecosystems. The plant macroremains analysis provides a unique and precise record of stand-to-local vegetation composition and dynamics that can bridge paleoecology and forest management. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a new method for the standardisation of tree-ring series, which attempts to remove the age effect from the low-frequency variations in the series. standardisation techniques based on the biological growth trend (RCS) only remove the trend linked to the age of the tree. However, in some trees, the trend is substantially different from the regional curve, and when the site fertility is not taken into account, the standardisation process may induce significant biases in the RCS standardised curve. An artificial neural network is used here to estimate an adaptive regional growth curve (ARGC) model. For each population or group of populations, the predictors are, in addition to the age (used by RCS) of each ring, the initial and the maximum growth rates (measured by the ring increments) of each tree. We have compared this method to the RCS method, using 20 Pinus cembra sites covering the Southern French Alps. The results show that the ARGC standardisation performs better for growth trend analysis and, by inference, for climate reconstruction. [Copyright &y& Elsevier]

Anticipated future climate changes are expected to significantly influence forest ecosystems, particularly in treeline ecotones. Climate change will have both direct and indirect effects on the future distribution of alpine tree species, some of which will be positive and others negative. Although increased temperatures are on the whole likely to have a positive impact on growth and distribution of Swiss stone pine (Pinus cembra L.), indirect effects that influence seed dispersal may threaten the population viability of species. The complexity of the interrelations between climatic and non-climatic factors demands further research, which should include long-term monitoring. [ABSTRACT FROM AUTHOR]

Recently a divergence between tree-ring parameters from temperature-limited environments and temperature records has been observed worldwide but comprehensive explanations are still lacking. From a dendroclimatic analysis performed on a high-altitude tree-ring network of Pinus cembra (L.) in the Central Italian Alps we found that site aspect influences non-stationary growth-climate relationships over time. A general increasing divergence between ring width and the summer temperature record (J–A) has been observed especially for chronologies from SW-facing slopes, whereas chronologies from N-facing sites showed stable relationships over time. The monthly analysis revealed that the decrease in sensitivity was mostly accounted for by the changes in the relationships with June temperature (decreasing correlations especially for S- and W-facing site chronologies), whereas trees from N-facing sites showed an increasing sensitivity to July temperatures. Our data suggest that at high altitudes, low temperatures at the beginning of the growing season no longer limit growth. We also found that our temperature-sensitive trees did not linearly respond in radial growth to the extreme heat event of summer 2003, and formed an annual ring of average width, resulting in a strong divergence from the temperature record. Our findings underline the importance of site ecology for tree-ring based climate reconstructions using temperature-sensitive ring-width chronologies, and may help in solving the ‘divergence problem’. [ABSTRACT FROM AUTHOR]

Aim To characterize the genetic structure and diversity of Pinus cembra L. populations native to two disjunct geographical areas, the Alps and the Carpathians, and to evaluate the rate of genetic differentiation among populations. Location The Swiss Alps and the Carpathians. Methods We screened 28 populations at three paternally inherited chloroplast simple sequence repeats (cpSSRs) for length variation in their mononucleotide repeats. Statistical analysis assessed haplotypic variation and fixation indices. Hierarchical analysis of molecular variance (AMOVA), Mantel test, spatial analysis of molecular variance (SAMOVA) andbarrier analyses were applied to evaluate the geographical partitioning of genetic diversity across the species’ range. Results Haplotypic diversity was generally high throughout the natural range of P. cembra, with the mean value substantially higher in the Carpathians ( H = 0.53) than in the Alps ( H = 0.35). The isolated Carpathian populations showed the highest haplotype diversity among the populations originating from the High Tatras (Velka Studena Dolina) and South Carpathians (Retezat Mountains). AMOVA revealed that only 3% of the total genetic variation derived from genetic differentiation between the two mountain ranges. Differentiation among Carpathian populations was higher ( FST = 0.19) than among Alpine populations ( FST = 0.04). Low, but significant, correlation was found between the geographical and genetic distances among pairs of populations ( r = 0.286, P < 0.001). SAMOVA results revealed no evident geographical structure of populations.barrier analysis showed the strongest differentiation in the eastern part of the species’ range, i.e. in the Carpathians. Main conclusions The populations of P. cembra within the two parts of the species’ range still share many cpDNA haplotypes, suggesting a common gene pool conserved from a previously large, continuous distribution range. Carpathian populations have maintained high haplotypic variation, even higher than Alpine populations, despite their small population sizes and spatial isolation. Based on our results, we emphasize the importance of the Carpathian populations of Swiss stone pine for conservation. These populations comprise private haplotypes and they may represent a particular legacy of the species’ evolutionary history. [ABSTRACT FROM AUTHOR]

1. Changes in the frequency and intensity of disturbances are expected to occur during the coming decades as a consequence of climatic changes. Mountain forests are sensitive to climate variability, disturbances and changes in human activities; this is particularly true for subalpine forests located close to the limits of tree-growth. Here we test the role of surface fires on the structure and the dynamics of a subalpine forest compared to a control stand not affected by fire events for at least two centuries. 2. The fire events are deduced from fire scars, the age-structure from tree-ring counting, regeneration from sapling and seedling counts, necromass from the volume of woody debris, and the understorey structure from shrub and herb cover, height and biomass. Land-use history is assessed from livestock and human inventories. 3. Four surface fires occurred during the last 200 years in the burned stand. Tree density is greater in the burned stand, and, even 50 years after the last fire, burning could still be having a positive effect on regeneration density. Land-use history, mainly grazing by cattle and sheep, explains the modern forest structure through its promotion of Larix decidua. The understorey composition is the same within the two stands, suggesting a rapid recovery of dwarf shrubs ( Rhododendron ferrugineum and Vaccinium myrtillus) after the latest fire, which coincided with the final change in land-use. The exception is V. vitis-idaea cover, which is higher in the control stand. The removal of livestock in the 1940s indirectly triggered a decline in L. decidua regeneration, which was formerly promoted by grazing and trampling. Conversely, Pinus cembra seedlings have begun to establish during the last 70 years. 4. Synthesis. Expansion of forests dominated by P. cembra is expected during the 21st century, unless current global warming leads to a significant and lethal increase in fire frequency, that is, a reduction of fire-return intervals, which would reduce the number of sexually mature trees. The re-introduction of grazing could maintain the mixed subalpine forests, whereas surface fires would alter the woody debris load, promoting greater regeneration of L. decidua and P. cembra. [ABSTRACT FROM AUTHOR]

Copyright of Annals of Forest Science (EDP Sciences) is the property of EDP Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Xylem conduits increase in size from the apex downwards. While conduit tapering in the stem has often been reported to converge towards a common pattern among all plants, information on conduit tapering in small plants and roots is extremely scarce. We selected 10 small trees (height < 3 m) of Pinus cembra L. and Larix decidua Miller along an altitudinal gradient and measured diameter and conduit dimensions along stems and roots in the last annual ring. Sections of 10 µm were cut from wooden disks taken at different heights in the stem and in the roots and then stained with safranine. Slides were observed under a microscope, the lumen areas of conduits were measured and mean hydraulic diameters (Dh) calculated. Dh increased from stem tip (Dh at 1 cm from the apex averaged 10.75 µm; s = 2.33) to base (Dh from 20.70 to 30.54 µm), following a power trajectory (i.e., Dh = a·Lb, with L being the distance from the tip). Such degrees of conduit tapering may have a considerable effect in minimizing the hydraulic constraints. Despite trees at the treeline being older and smaller than in the subalpine forest (age: 28–70 years at the treeline; 18–39 years in the subalpine forest), conduit tapering did not differ significantly between sites, suggesting that tree height is the main factor controlling the basipetal increase in conduit lumens. In the roots, the increase in conduit dimensions continued towards their tips, even more steeply than in the stem. The widest conduits were measured around the root tips (around 40 µm). Conduit tapering resulted as a stable structural feature in small plants as well as in tall trees. [ABSTRACT FROM AUTHOR]

The effect of needle damage on the release rate of Masson pine ( Pinus massoniana Lamb.) volatiles was examined. Needles were continuously damaged by mechanical damage (MDP) or by feeding of pine caterpillar ( Dendrolimus punctatus) larvae (LFP); undamaged pine was used as a control (UDP). Volatiles were collected before damage, and at 16, 24, 40, 48, 64, 72, 88 and 96 h post-damage, and analyzed. The analyses revealed that 19 compounds identified as constitutive volatiles from UDP were terpenes and green leaf odors. The release rate of volatiles from MDP or LFP was higher than that from UDP. At 96 h post-damage, emission from MDP or LFP returned to the same level as that of UDP. Some volatiles, including sabinene, ocimene, limonene-1,2-epoxide, linalool, linalool acetate, germacrene d-4-ol, farnesol, and ( E)-4,8-dimethyl-1,3,7-nonatriene were induced by mechanical damage and/or larval attack. Furthermore, the release rate of linalool acetate, farnesol, or ( E)-4,8-dimethyl-1,3,7-nonatriene from LFP was higher than that from MDP. Based on an exact estimation of the proportion of damaged pine needles, a significant linear correlation between the release rate of total volatiles identified and the proportion of damaged needles was found in the case of LFP but not MDP. [ABSTRACT FROM AUTHOR]

This paper reports the results of research carried out in the Roseg Valley (Lower Engadine, Switzerland) that examines debris-flow Ian typology, debris-flow activity, and the impact of debris flows on forest vegetation. Depositional landforms from debris flows were subdivided according to their degree of geomorphological hazard. An inventory of debris-flow fans and a detailed geomorphological, vegetational, and dendrochronological study of two of them was undertaken. The dendrochronological analysis allowed dating of historical events and reconstruction of their recent evolution. By dating scars and growth anomalies on Larix decidua Mill. and Pinus cembra L., 24 debris-flow events were identified on the Misaun fan and 16 on the Tschierva fan, and differences in their distribution due to drainage basin characteristics identified. Fans chosen for this investigation are crossed by a hiking trail that is frequently used by tourists during the summer season. A qualitative hazard and risk evaluation were undertaken. This approach contributes to hazard assessment on fans, and may also be applied in other environmental contexts (e.g., in trail planning). [ABSTRACT FROM AUTHOR]