Pinus Heldreichii Research Articles

Dendrochronological examination of the Assumption of the Virgin Mary orthodox church in the village of Pades, Greece

The current study is a dendrochronological analysis of the wood from the church of the Assumption of the Virgin Mary, Pades, Greece which was built towards the end of the 18th century according to historical sources. The tree-ring analysis shows that the date, 1784, given on the inscription at the main entrance of the church probably documents the year when the construction works began, and that there were several construction stages of the structural and decorative elements of the church until the early 19th century. Moreover, the oldest (reused) timber elements that were identified through the dendrochronological study date back to the first half of the 15th century and may indicate the first traces of the construction activity in and around Pades. The dendrochronological study enabled the development of three local reference chronologies for the Epirus region. The timespan for the developed chronologies for the church in Pades is: 1262–1825 for Pinus heldreichii (Bosnian pine), 1295–1854 for Pinus nigra (Black pine), and 1571–1767 for Quercus sp. (Deciduous oak).

Spatial conservation planning of forest genetic resources in a Mediterranean multi-refugial area

The Kunming-Montreal Global Biodiversity Framework recognised the urgency of taking action to conserve intraspecific genetic diversity (IGD) as an insurance against habitat degradation and environmental change. Recent work suggests that 90–99 % of IGD should be conserved to safeguard viability of future generations.Here, we addressed such a conservation issue in three forest tree species in Italy: silver fir (Abies alba Mill.), Heldreich's pine (Pinus heldreichii H. Christ), and pedunculate oak (Quercus robur L.). We used microsatellite markers to measure IGD of 36 (A. alba), 15 (P. heldreichii) and 25 (Q. robur) natural sites, including several putative glacial refugia. We developed a spatial conservation planning (SCP) analysis to quantify the genetic irreplaceability of each site and identify the minimum set coverage ensuring IGD protection. Finally, we compared SCP results with the contributions to allelic diversity within and between sites, total allelic diversity and private allelic richness.We found that between 44 % and 73 % of sites were required to conserve 90–99 % of the alleles, and that this conservation effort held even when targeting lower percentages of alleles to protect (50–75 %). Glacial refugia were often included in the minimum set coverage, confirming biogeographical expectations. Finally, sites with high genetic irreplaceability were found to have higher private allelic richness on average. These results are discussed in the light of the biogeographic history of the species studied and the current policies for the conservation of forest genetic resources.

Diversity of epiphytic lichens and allied fungi on Pinus heldreichii and P. peuce in Bulgaria

Diversity of epiphytic lichens and allied fungi on Pinus heldreichii and P. peuce in Bulgaria

Chemical profile, antioxidant and antimicrobial activity of Pinus heldreichii Christ. Distributed in Bulgaria

Pinus heldreichii Christ. (Bosnian pine), a Tertiary relict and Balkan sub-endemic, has not been comprehensively studied for its essential oil (EO) profile and bioactivity of its different plant parts. This study aimed to determine the EO yield, composition and antimicrobial activity from different parts of P. heldreichii at three different populations (mountains) in Bulgaria. Furthermore, the study assessed the antioxidant activities of plant tissue, including leaves (needles), twigs wood, male and female cones. The EOs yield from different plant parts ranged from 0.09 % (leaves) to 0.74 % (wood of twigs), with monoterpenes being the predominant class. Limonene, α-pinene, β-caryophyllene, germacrene D, β-pinene, and β-myrcene were detected in the EO extracted from all analyzed trees. However, these compounds were not found in the EO extracted from all plant parts of the same trees. Four chemical groups (chemotypes) were identified for EO from twigs, and three chemotypes were identified for EO from leaves. The chemotypes were based on the percent ratio of the main EO constituents (>5 %). Leaves tissue showed the highest values in terms of polyphenols and flavonoids, as well as higher ABTS radical scavenging activity, while the highest antimicrobial activity against Staphylococcus aureus subsp. aureus was seen in the EOs obtained from twigs. This is the first study to identify several chemotypes based on leaf and twigs EO of P. heldreichii distributed in Bulgarian flora. Furthermore, the EO of twigs tips (TT), male cones (MC), and wood of one-two-year-old twigs (WT) of the same trees were reported for the first time. The total polyphenol, flavonoid content, and radical scavenging activity of tissues of annual twigs wood and biennial twigs wood, leaf tissue, MC tissue, and the twigs tips tissue is also reported for the first time in the accessible literature. These findings highlight the potential of P. heldreichii to provide EOs with varying compositions and bioactivities, making them suitable for nutraceutical, pharmacological, and potentially food additive applications. Furthermore, the identification of chemotype accessions in this study suggests their selection for the development of new forest crop as a source for natural products with desirable composition and bioactivity.

Assessing earlywood-latewood proportion influence on tree-ring stable isotopes

Tree-ring stable isotopes are typically measured in latewood cellulose to mitigate potential carry-over effects from previous year storage pools. The isotopic composition of individual tree-ring segments is thought to include considerable intra-annual variability. This sampling strategy may be complicated by steep intra-annual isotope gradients that can rival the inter-annual variability, however. Consistent sampling of latewood material may not always be possible due to low sample availability or high prevalence of narrow rings or low amounts of latewood because of species-specific changes in ring width. Therefore, years that contain samples with higher portions of non-latewood (earlywood) material may influence the final chronology of isotopic variability. Here, we analyze the potential influence that changing earlywood and latewood components of individual tree rings can have on stable carbon and oxygen records from Quercus spp. and Pinus heldreichii chronologies. Analysis of stable isotopes in oak tree rings with varying amounts of latewood show no statistically significant differences in the range of isotopic composition, nor any major differences when considering the same calendric year. Similar results were found for the pine data, when comparing stable isotope measurements with earlywood-to-latewood ratio and maximum density. We argue that this simple approach should be applied to any long-term tree-ring stable isotope record in order to provide a better understanding of the potential biases that could arise from previously recorded intra-annual variability in the wood.

Ground beetle (Coleoptera: Carabidae) taxocoenoses from high-altitude Pinus peuce and Pinus heldreichii forests in Bulgaria

The sensitivity of ground beetles to changing habitat conditions makes them a good indicator of environmental change. The shift in their distribution could be used as an early warning signal for natural disturbances due to climate change. To reflect and monitor these changes, initial information is needed on carabid taxa in different high-altitude habitats, including the endemic and climate-sensitive tertiary relict coniferous forests of Pinus peuce (Macedonian pine) and Pinus heldreichii (Bosnian pine). Data on the carabid beetles in the different coniferous habitats in Bulgaria are scattered in various faunistic or taxonomic publications, and there is no exact information about their taxocoenoses in the Macedonian and Bosnian pine habitats. The present study aims to clarify the species composition and diversity patterns of ground beetles in these habitats in Bulgaria. Six sample sites were selected: five natural forest stands in the Rila Mts and Pirin Mts and one forest plantation in the Vitosha Mts. A total of 18 species and subspecies typical of forest habitats were recorded. Five of them were endemic to Bulgaria and five to the Balkan Peninsula. The most common species and the eudominant in the majority of the sample sites was Calathus metallicus aeneus. The exception was one of the Bosnian pine sample sites. Here, the dominant species was Xenion ignitum. The ground beetle species found in the studied forests were mostly zoophagous, mainly crevice or burrowing stratobionts in leaf litter, rocks and soil, a few epigeobionts, one botrobiont and one mixophytophagous geohrotobiont. The classification of the carabid taxocoenoses according to their qualitative composition showed two main clusters: the first being the carabids from the studied sites of the Vitosha and Rila Mts, and the second being the taxocoenoses from the Pirin Mts. The Bosnian pine habitats provide more favourable conditions for the high-altitude ground beetles, where they are in a state of equilibrium with higher species richness and evenness compared to those inhabiting the Macedonian pine forests. The forest communities of Pinus peuce and Pinus heldreichii in Bulgaria are of high conservation importance for the ground beetle and an even higher level of protection of these habitats is required.

Bell-shaped tree-ring responses to air temperature drive productivity trends in long-lived mountain Mediterranean pines

We investigated the dendroclimatic response of a Pinus heldreichii metapopulation distributed over a wide elevation interval (from 882 to 2143 m a.s.l.), spanning from low mountain to upper subalpine vegetation belts in the southern Italian Apennines. The tested hypothesis is that wood growth along an elevational gradient is non-linearly related to air temperature. During three years of fieldwork (2012–2015) at 24 sites, we collected wood cores from a total of 214 pine trees with diameter at breast height from 19 to 180 cm (average 82.7 ± 32.9 cm). We used a combination of tree-ring and genetic methods to reveal factors involved in growth acclimation using a space-for-time approach. Scores from canonical correspondence analysis were used to combine individual tree-ring series into four composite chronologies related to air temperature along the elevation gradient. Overall, the June dendroclimatic response followed a bell-shaped thermal niche curve, increasing until a peak around 13–14 °C. A similarly bell-shaped response was found with previous autumn air temperature, and both dendroclimatic signals interacted with stem size and growth rates, generating a divergent growth response between the top and the bottom of the elevation gradient. Increased tree growth in the upper subalpine belt was consistent with the consequences of increasing air temperature under no drought stress. A positive link was uncovered between pine growth at all elevations and April mean temperature, with trees growing at the lowest elevations showing the strongest growth response. No elevational genetic differences were found, hence long-lived tree species with small geographical ranges may reverse their climatic response between the lower and upper bioclimatic zones of their environmental niche. Our study revealed a high resistance and acclimation capability of Mediterranean forest stands, and such low vulnerability to changing climatic conditions highlights the potential to store carbon in these ecosystems for the coming decades.

Multi-proxy crossdating extends the longest high-elevation tree-ring chronology from the Mediterranean

Annually precise dating is the cornerstone of dendrochronology. The accurate crossdating of relict wood is, however, frequently challenged during early chronology periods when sample replication is typically low. Here we present a multi-proxy approach in which stable carbon (δ13C) and radiocarbon (14C) isotope data are used to evaluate and correct dating errors in the early period of the longest high-elevation tree-ring chronology from the Mediterranean Basin. The record was initially developed using 878 tree-ring width (TRW) and 192 maximum latewood density (MXD) series from living and relict Bosnian pines (Pinus heldreichii) from Mt. Smolikas in Greece to reconstruct hydroclimate and temperature variability back to the 8th century. New annually resolved and non-pooled δ13C series now suggest a re-dating of first millennium relict pine samples during a period when sample replication was too low for proper TRW and/or MXD crossdating. The associated correction shifts the start of the Mt. Smolikas chronology from 575 back to 468 CE, a change independently confirmed by wiggle-matching annual 14C data along the 774/775 CE cosmic event. Our study demonstrates the importance of independent age validation for robust chronology development and shows how multi-proxy crossdating can improve dating success during periods of low sample replication.

Bioregionalization of Albania: Mismatch between the flora and the climate suggests that our models of Southern European bioregions are in need of a revision

We analysed the floristic subdivisions of Albania by hierarchical clustering of all the vascular plant species of Albania over a grid of 25 km cells, adapting data from the Vascular Species Distribution Atlas in Albania of ( Barina Z (ed.) (2017) Distribution atlas of vascular plants in Albania. Hungarian Natural History Museum, Budapest). We identified the principal axes of variation of the flora and the bioclimatic variables that explain it. We also analysed the bioclimate of Albania by means of a self-organizing map (SOM) of the main climatic variables and the application of the global bioclimatic model of Rivas-Martínez. We compared the analysis based on the flora with that based on the bioclimate. The results divided Albania into eight floristic units corresponding to the main vegetation types (Carpinus orientalis woodlands, Quercus cerris woodlands, Quercus petraea and Fagus sylvatica woodlands, Quercus coccifera woodlands, Quercus coccifera and Quercus ithaburensis woodlands, Pinus heldreichii woodlands, alpine vegetation of North Albania, and alpine vegetation of eastern Albania). Two main trends of variation can be recognized: four elevational belts, strongly correlated with average July temperature, and a north–south subdivision, weakly correlated with annual rainfall and thermal excursion. The bioclimatic analysis (SOM and Rivas-Martínez model) resolves and adds detail to the axis of the elevational belts but cannot discern the north–south subdivision apart from the high mountains. We obtained a division into eight floristic units ordered according to two gradients: four elevational belts, each in turn subdivided into a north-central and a southern province. These two gradients seem to have a broader meaning in Southern Europe, particularly the north–south subdivision at about 30° latitude. The partial mismatch between the bioclimate and the flora indicates that bioclimatic models of Europe are in need of a revision and suggests that the history, in addition to the present-day climate (for instance, the vegetation of the last glacial maximum), can play a role in shaping the biogeography of Southern Europe.

Structural properties of pure and mixed bosnian pine stands on Mt. Zeletin

The subject of this research are stands of bosnian pine in the area of the mountain massif Visitor with Zeletin in Montenegro. Considering the fact that these forests are unexplored, due to their small area and the absence of economic interest (the strictest protection regime), the research task of this paper is to conduct an adequate research of one of the most preserved white-bark pine populations in this areas in structural and partly production terms. The bosnian pine stands on Mt. Zeletin belong to two management units: FMU ?Pisevska Reka - Zeletin? and FMU ?Kutska Reka? which occupy an area of 160 ha. The research included the accessible parts of sections 2/b, 3/a, 5/a, 28/a and 28/s, in which 8 sample plots (SP) of an 30 ar area each were established (4 SP in pure and 4 SP in mixed stands). The SPs are vertically distributed between 1,550 and 1,850 m a.s.l. In pure stands, the average number of trees (for 4 SPs) is 723 pcs?ha-1, the basal area is 74 m2?ha-1, and the volume is 529 m3?ha-1, which are considered high values given the conditions in which these stands have developed. In mixed stands, the numerical elements show significantly higher values: the number of trees is 875 pcs?ha-1, the basal area is 87 m2?ha-1 and the volume is 721 m3?ha-1. A high degree of correlation was found between the values of volumes (unweighted and weighted) and the values of dominant heights. The mixed stands reveal a more heterogeneous structural development. Bosnian pine trees cluster at short distances, which is probably the result of a struggle for survival in highly unfavorable conditions. As these stands are subjected to spontaneous development over a long period of time, their research provides the opportunity to get to know more about bosnian pine ecology. Considering its modest requirements towards habitat conditions, bosnian pine has considerable advantages when choosing a species for afforestation of the most unfavorable sites.

Historical ecology identifies long-term rewilding strategy for conserving Mediterranean mountain forests in south Italy.

In the context of global decline in old-growth forest, historical ecology is a valuable tool to derive insights into vegetation legacies and dynamics and develop new conservation and restoration strategies. In this cross-disciplinary study, we integrate palynology (Lago del Pesce record), history, dendrochronology, and historical and contemporary land cover maps to assess drivers of vegetation change over the last millennium in a Mediterranean mountain forest (Pollino National Park, southern Italy) and discuss implications in conservation ecology. The study site hosts a remnant beech-fir (Fagus sylvatica-Abies alba) mixed forest, a priority habitat for biodiversity conservation in Europe. In the 10th century, the pollen record showed an open environment that was quickly colonized by silver fir when sociopolitical instabilities reduced anthropogenic pressures in mountain forests. The highest forest cover and biomass was reached between the 14th and the 17th centuries following land abandonment due to recurring plague pandemics. This rewilding process is also reflected in the recruitment history of Bosnian pine (Pinus heldreichii) in the subalpine elevation belt. Our results show that human impacts have been one of the main drivers of silver fir population contraction in the last centuries in the Mediterranean, and that the removal of direct human pressure led to ecosystem renovation. Since 1910, the Rubbio State Forest has locally protected and restored the mixed beech-fir forest. The institutions in 1972 for the Rubbio Natural Reserve and in 1993 for Pollino National Park have guaranteed the survival of the silver fir population, demonstrating the effectiveness of targeted conservation and restoration policies despite a warming climate. Monitoring silver fir populations can measure the effectiveness of conservation measures. In the last decades, the abandonment of rural environments (rewilding) along the mountains of southern Italy has reduced the pressure on ecosystems, thus boosting forest expansion. However, after four decades of natural regeneration and increasing biomass, pollen influx and forest composition are still far from the natural attributes of the medieval forest ecosystem. We conclude that long-term forest planning encouraging limited direct human disturbance will lead toward rewilding and renovation of carbon-rich and highly biodiverse Mediterranean old-growth forests, which will be more resistant and resilient to future climate change.

Essential oil composition of Pinus heldreichii Christ., P. peuce Griseb., and P. mugo Turra as a function of hydrodistillation time and evaluation of its antimicrobial activity

Pinus heldreichii and P. peuce are Balkan endemics, Tertiary relicts, while Pinus mugo is an edificator in the phytocenoses in the Alpine mountain range. The chemical profile and essential oil (EO) yield and composition of these three species as a function of distillation time (DT) was the subject of this study. The working hypothesis was that EO of P. heldreichii, P. peuce and P. mugo would produce EO with dissimilar composition and antimicrobial activity at different DT. The EO yields in the controls were 0.4% for P. heldreichii, 1.3% for P. peuce and 1.08% for P. mugo. During the first 0–15 min interval of the distillation, up to 70% of the total EO was extracted in P. heldreichii, 53.85% in P. peuce and 54.63% in P. mugo. Overall, the EO of the three species had relatively constant compositional profile at the different DTs, which contradicts the working hypothesis. Most of the quantitative differences in the main components were determined. The EO obtained from 0 to 15 min DT interval had the following major compounds: limonene (76.9%−77.0%) and α-pinene (12.47%−15.54%) in P. heldreichii; α-рinene (34.26–43.75%), limonene (19.2%−22.2%), and β-рinene (9.24%−11.48%) in P. peuce; and α-pinene (16.48%−17.84%), α-phellandrene (23.06–23.76%), and β-phellandrene (28.12%−28.79%) in P. mugo. The obtained results of EO from the three studied species are a prerequisite for obtaining EO with a certain, desired composition while reducing the distillation duration and saving energy and time. The tested EOs demonstrated significant antimicrobial activity against Escherichia coli.

Seed germination traits of Pinus heldreichii in two Greek populations and implications for conservation

Seed germination traits were assessed on Pinus heldreichii H. Christ, a Tertiary relict, high-elevation Mediterranean pine, endemic in the western Balkan Peninsula and southern Italy; it is naturally grown at the northern Greece mountains, but also found in shrubby form above the timberline. Closed and mature cones were collected (October) for three consecutive years from Pindos Range and Mt. Olympus populations. Cone and seed morphological traits were recorded along with the seedling cotyledon number. Seed germination tests were performed under various ecologically meaningful temperatures and light regimes; climate change effects on seed germination and seedling development were assessed based on two climate scenarios. Final seed germination was moderate (~55%) on both, untreated seed lots at most favourable conditions (15 and 20 °C). Although cold stratification is not an absolute requirement, seed germination rate and final percentage are promoted by both a month of cold stratification (at least 30 or 45 days) and white light. The predicted climate change suggests that a prolonged drought period (>3 months) might turn out by the end of the century in the populations studied. Although the temperature increase might not have significant effects in the germination window of the species. The rainfall decrease will inevitably expose the young seedlings to the summer drought, thus increasing the potential mortality rate. Both ex situ (e.g., germplasm conservation) and in situ measures of conservation are recommended for the species survival in Greece, with a particular focus on the populations established at lower altitudes.

Discovering the Unknown History of the Utilization of Pinus heldreichii in Wooden Structures by Means of Dendroarchaeology: A Case Study from Metsovo (Northern Greece)

(1) Background: Pinus heldreichii is a long-living tree subalpine species commonly used for climate reconstruction. Nevertheless, its potential for dendroarchaeology and dating of historical timber remains unknown. In Metsovo and in the surrounding area of Pindus National Park (Northern Greece) it is commonly used for the construction of buildings and wooden objects and artifacts. (2) Methods: We examined timber found in historical buildings within the study area and we tried to date it using local reference chronologies of Bosnian and Black pines. (3) Results: Bosnian pine chronologies can be used to date timber from historical buildings, while they can also be used as reference chronologies against Black pines, giving very high cross-dating values. Therefore, and since the macroscopic identification of the two species’ timber is impossible, the analysis of wood anatomy is necessary to distinguish the two species in the case of historical wood. (4) Conclusions: The current paper presents the first application of dendroarchaeology for Bosnian pine and highlights the potential of the species in studying cultural heritage and the human past.

First record of rare boreal-alpine waxcap Hygrocybe calciphila (Hygrophoraceae, Agaricales) in Southeastern Europe

Hygrocybe calciphila, an uncommon species of the genus was found for the first time in Southeastern Europe in forests of Pinus heldreichii in Bulgaria. Description and illustrations of the finding are presented. The European distribution of the species is summarized and briefly discussed, with emphasis on the scarce previous findings in Southern Europe.

Assessment of the decorative qualities of species of the genus Pinus L. in the conditions of the European part of Russia

The paper presents the results of a study of the decorativeness of pines, which are actively grown on the territory of the European part of Russia. Decorativeness is based on the visual perception of plant habitus. The state of the habitus depends on the genotype and adaptive characteristics in certain growing conditions. The study examined 25 decorative features of 56 species. 24 traits were related to vegetative and generative organs. 1 trait was assessed by the method of weight taxonomy as an indicator of originality of all species for 24 traits. Studies have shown that the total score on a 100-point scale of decorativeness in the studied pines varies from 40 in Pinus heldreichii Chirst and Pinus waschoensis Mason & Stockwell to 68 in Pinus patula Schltdl. & Cham. The research results can be applied when choosing species for cultivation on landscaping objects to increase their aesthetic appeal.

Mediterranean old-growth forests exhibit resistance to climate warming

Old-growth mountain forests represent an ideal setting for studying long-term impacts of climate change. We studied the few remnants of old-growth forests located within the Pollino massif (southern Italy) to evaluate how the growth of conspecific young and old trees responded to climate change. We investigated two conifer species (Abies alba and Pinus leucodermis) and two hardwood species (Fagus sylvatica and Quercus cerris). We sampled one stand per species along an altitudinal gradient, ranging from a drought-limited low-elevation hardwood forest to a cold-limited subalpine pine forest. We used a dendrochronological approach to characterize the long-term growth dynamics of old (age > 120 years) versus young (age < 120 years) trees. Younger trees grew faster than their older conspecifics during their juvenile stage, regardless of species. Linear mixed effect models were used to quantify recent growth trends (1950–2015) and responses to climate for old and young trees. Climate sensitivity, expressed as radial growth responses to climate during the last three decades, partially differed between species because high spring temperatures enhanced conifer growth, whereas F. sylvatica growth was negatively affected by warmer spring conditions. Furthermore, tree growth was negatively impacted by summer drought in all species. Climate sensitivity differed between young and old trees, with younger trees tending to be more sensitive in P. leucodermis and A. alba, whereas older F. sylvatica trees were more sensitive. In low-elevation Q. cerris stands, limitation of growth due to drought was not related to tree age, suggesting symmetric water competition. We found evidence for a fast-growth trend in young individuals compared with that in their older conspecifics. Notably, old trees tended to have relatively stable growth rates, showing remarkable resistance to climate warming. These responses to climate change should be recognized when forecasting the future dynamics of old-growth forests for their sustainable management.

Exploring the past of Mavrovouni forest in the\xa0Pindus Mountain range (Greece) using tree rings of Bosnian pines

Key messageLong Bosnian pine chronologies from different mountains are shaped by different climatic parameters and can help identify past drought events and reconstruct landscape histories.We developed a 735-year-long Pinus heldreichii chronology from the southern distribution limit of the species, expanding the available database of long Bosnian pine chronologies. Tree-ring growth was mainly positively correlated with growing degree days (GDD: r1950–2018 = 0.476) while higher temperatures during both winter and growing season also enhanced growth (TWT: r1950–2018 = 0.361 and TGS: 0.289, respectively). Annual precipitation, during both calendar and water years, had a negative but weaker impact on annual tree growth. The newly developed chronology correlates well with chronologies developed from the neighboring mountains. The years with ring width index (RWI) lower than the average were found to correspond to cool years with dry summers. Still, the newly developed chronology was able to capture severe drought events, such as those in 1660, 1687, and 1725. Several old living trees had internal scars presumably caused by fires. Therefore, old mature trees could be used for fire history reconstruction in addition to climate reconstruction. Although the presence of lightning scars indicates an important natural agent of fire ignition, human activities associated with animal grazing could also be an underlying reason for fires in the region.

Stable Isotopes in Tree Rings of Pinus heldreichii Can Indicate Climate Variability over the Eastern Mediterranean Region

A long-term context is important for understanding past climatic variability. Although tree-ring widths (TRWs) are widely used as a proxy for reconstructing past climate, the use of annually-resolved values of δ13C and δ18O tree-ring stable isotopes (TRSIs) is increasing and may provide further valuable information. Here, we present a 487-year-long TRW chronology and 240-year-long TRSI chronology for Bosnian pine (Pinus heldreichii H. Christ) and compare them to each other. We demonstrate that both δ13C and δ18O values are better proxies for temperature, precipitation, and drought than TRW. The correlations between these climate parameters and TRSIs are strongest for the combined summer (JJA) period. The results of temporal and spatial field correlation indicate that TRSI chronologies are stable, reliable proxies for JJA precipitation reconstruction over the whole Balkan Peninsula and surrounding eastern Mediterranean region. However, the stability of the temperature signal of the both δ13C and δ18O chronologies declines after the 1950s. Our work supports the emerging evidence that TRSI data track climate variability more accurately than a conventional TRW approach and can be subsequently used for the reconstruction of past climate.

Tree Growth Variability of Pinus heldreichii at Tree-Line Locations in Kosovo

It is well-known that tree growth at the upper treeline is controlled by low temperatures and limited seasonal growth. The study’s objective was to investigate the climate warming effects on Bosnian pine (BP; Pinus heldreichii Christ.) growth during the 20th century. We hypothesized that, like all the other drought-stressed conifers growing on tree-line locations, BP responds significantly to climate factors that control their growth. Three natural forest stands of BP were selected in Prevalla, Decan and Koritnik. The cores were taken from 98 dominant and co-dominant BP trees at breast height with no sign of human interference. The tree-ring widths were measured at 0.001 mm precision, with a LINTAB 6 (RINNTECH, Heidelberg) system and TSAP-Win Scientific software. A set of three BP tree-ring width chronologies were developed by trees spread on a typical mountain slope at elevations ranging from 1815 to 1945 m above sea level. The tree-ring chronologies from three sites showed significant correlation and this agreement decreased with the distance between sites. The length of the master chronologies varies among sites ranging from 176 years (Koritnik) to 541 years (Decani). The tree growth was controlled by a common climatic signal (local temperatures) and drought during midsummer across the investigated sites. These results confirm the assumption that tree growth at tree-line sites is controlled by low temperatures and drought conditions during the midsummer.