Juniperus Thurifera Research Articles

Atlantic and Mediterranean synoptic drivers of central Spanish juniper growth

Atlantic and Mediterranean air masses influence the climate over the Iberian System mountain range. The relatively short instrumental records in central Spain though limit any long-term assessment of these synoptic systems. We here evaluate the potential to analyze such changes using ring width data from Juniperus thurifera trees growing in the northwestern and southeastern regions of the Iberian System, exposed to Atlantic and Mediterranean cyclonic activity, re- spectively. Comparison of tree rings with regional precipita- tion, temperature, and Palmer Drought Severity Index (PDSI) data indicates that juniper trees contain information on late springand early summer drought conditions. Calibration trials using spatially resolved, gridded climate data reveal that the northwestern sampling site is predominantly controlled by Atlantic weather, while the southeastern site mainly reflects Mediterranean climate patterns. The strength and position of the blocking Azores high during spring to early summer is of particular importance for the distinct growth reactions in the Iberian System. The climate signal is remarkably strong in the southeastern site, where we developed the longest and best- replicated juniper tree ring record of the Iberian Peninsula. Data from this site allowed the reconstruction of May-June PDSI variability back to the early eighteenth century, indicat- ing severe drought (PDSI<−9) in southeastern Spain in 1782, 1828, 1869, 1981, and 2005. The new PDSI record coheres well with historical rogation ceremony data from eastern Spain, indicating that common information on past drought events is inherent in both proxy archives.

The colonization of abandoned land by Spanish juniper: Linking biotic and abiotic factors at different spatial scales

Colonization of abandoned lands by woody vegetation may be a great opportunity for ecosystem recovery given the current and future trend of land abandonment. This may help to reverse the generalized condition of ecosystem degradation of developed countries which is an urgent need. However, ecosystem recovery in abandoned lands can be seriously limited by biotic and abiotic factors. Indentify such factors and determine the relevant spatial scales at which they operate will help to understand natural patterns of colonization of abandoned lands and may be useful to guide restoration activities. We used Spanish juniper remnant woodlands and old fields recently colonized by the species to assess the variation in post-dispersal seed predation and environmental suitability to plant recruitment. These biotic and abiotic factors are two of the most limiting for vegetation recovery in abandoned lands, at the regional and local spatial scale. We found that recruitment was controlled by factors operating at different spatial scales in a hierarchical manner along different stages of the process. The regional scale was determinant for post-dispersal seed predation and seedling abundance which was, in turn, controlled by environmental suitability at the local spatial scale. Post-dispersal seed removal was higher in old fields than in mature woodlands, hence increasing seed limitation, a pervasive constraint for plant recruitment in abandoned lands. Environmental suitability for plant recruitment did not decrease as a result of previous farming uses at the regional scale, a common pattern in areas not subjected to intensive farming practices. Abandoned lands in Mediterranean areas seem to have a strong potential for ecosystem recovery being the biotic factors (e.g. seed availability) more limiting than the abiotic ones when non-intensive farming practices have been performed. This together with predictions of increase in land abandonment in low productive areas makes old fields especially relevant from an ecosystem recovery perspective.

Drought-induced increase in water-use efficiency reduces secondary tree growth and tracheid wall thickness in a Mediterranean conifer.

In order to understand the impact of drought and intrinsic water-use efficiency (iWUE) on tree growth, we evaluated the relative importance of direct and indirect effects of water availability on secondary growth and xylem anatomy of Juniperus thurifera, a Mediterranean anisohydric conifer. Dendrochronological techniques, quantitative xylem anatomy, and (13)C/(12)C isotopic ratio were combined to develop standardized chronologies for iWUE, BAI (basal area increment), and anatomical variables on a 40-year-long annually resolved series for 20 trees. We tested the relationship between iWUE and secondary growth at short-term (annual) and long-term (decadal) temporal scales to evaluate whether gains in iWUE may lead to increases in secondary growth. We obtained a positive long-term correlation between iWUE and BAI, simultaneously with a negative short-term correlation between them. Furthermore, BAI and iWUE were correlated with anatomical traits related to carbon sink or storage (tracheid wall thickness and ray parenchyma amount), but no significant correlation with conductive traits (tracheid lumen) was found. Water availability during the growing season significantly modulated tree growth at the xylem level, where growth rates and wood anatomical traits were affected by June precipitation. Our results are consistent with a drought-induced limitation of tree growth response to rising CO2, despite the trend of rising iWUE being maintained. We also remark the usefulness of exploring this relationship at different temporal scales to fully understand the actual links between iWUE and secondary growth dynamics.

Main biotic drivers of tree growth in a developing Juniperus thurifera stand in central Spain

Over the last few decades, abandonment of traditional management practices in Spain has led to widespread stand densification and has favoured the expansion of some forest species that previously exhibited more restricted ranges. Spanish juniper (Juniperus thurifera L.) woodlands are experiencing this phenomenon due to agricultural land abandonment and a decrease in the livestock pressure. Yet the main drivers underlying stand structure and dynamics at this novel scenario are poorly understood. In this study, we investigate the main biotic drivers of tree growth in a high-density stand of the dioecious J. thurifera at an early developmental stage (mean tree age of 32, ca. 50 years after land abandonment). Tree growth was measured by coring 299 individuals of different reproductive classes (male, female and non-reproductive). Neighbourhood models were used to assess the relative importance of tree size and neighbourhood competition on tree growth of each reproductive class in the study plot. We found that tree size had the strongest effect on tree growth, whereas the effect of intraspecific competition was negligible. We observed differences in growth patterns among reproductive classes along trunk diameter sizes. Thus, at smaller sizes, the three reproductive classes presented identical patterns of growth. However, at bigger sizes, females were the fastest growing individuals, followed by males and non-reproductive individuals. Overall, our results suggest that in young J. thurifera monospecific forests, where self-thinning processes may have not undergone yet, tree size and the reproductive class could play a relatively more important role than competition as drivers of tree growth. These findings constitute new information which contributes to understanding growth dynamics at early developmental stages in this dioecious species. Furthermore, our results provide guidelines for silvicultural managing, suggesting that at these young juniper stands thinning would likely not translate into enhanced growth on remnant trees.

Physico-mechanical properties of Spanish juniper wood considering the effect of heartwood formation and the presence of defects and imperfections

Aim of study: Determining the main physical and mechanical properties of Spanish juniper wood from Soria (Spain) considering the effects of heartwood formation and the presence of defects and imperfections; and comparing the resulting characteristics with similar existing data for other regional softwood species of commercial interest. Area of study: Berlanga de Duero (Soria, Castilla y León), Spain.Material and Methods: Wood physico-mechanical performance was determined by Spanish UNE standards in order to provide proper comparisons to other regional softwood species. An individual tree representing average plot characteristics was selected in all eight 10 m radius circular plots that were established well-representing the heterogeneity of this woodland. The age of every tree was determined reading the number of growth rings at the base of each sampled tree. Every physico-mechanical property was assessed at least 4 times for every wood sample type (sapwood and heartwood, whether clear or with the presence of defects) of each tree. Two-way ANOVA was run to assess significant differences in the results. Post hoc all pairwise comparisons were performed using Tukey's test (p &lt; 0.05).Research highlights: Spanish juniper wood resulted harder than other regional commercial conifers, and showed semi-heavyweight heartwood and lightweight sapwood; whereas shrinkage figures remarked its great dimensional stability. The high presence of knots within heartwood made it even heavier, harder, and more resistant to compression parallel to grain. A commercial use of this rare precious wood may contribute to juniper forests preservation in the frame of forest sustainable management plans. Key words: heartwood effect; Juniperus thurifera L.; physico-mechanical wood properties; wood classification; wood defects.

Remarkable Bark-Dwelling Species in a Hautes-AlpesJuniperus thuriferaL. Forest with the New Finding for France ofDidymodon johansenii(R.S.Williams) H.A.Crum

One of the most famous incense juniper (Juniperus thurifera L.) forest of western Alps, Saint-Crepin site, has been floristically surveyed focusing on corticolous assemblages. New data regarding the occurrence of Didymodon johansenii (R.S.Williams) H.A.Crum, a species newly recorded for France, Pseudoleskeella tectorum (Funck ex Brid.) Kindb. ex Broth., Orthotrichum crenulatum Mitt, and Orthotrichum vittii F.Lara, Garilleti et Mazimpaka are provided. The floristic originality of incense juniper's bark is underlined.

Soil development mediated by traditional practices shape the stand structure of Spanish juniper woodland

Aim of study: Assessing the effect of soil development on the stand structure of a Spanish juniper forest traditionally shaped by livestock browsing and wood extraction. Area of study: Berlanga de Duero (Soria, Castilla y León), Spain.Material and Methods: A stand inventory served to record stand structure. Tree age, height, DBH, basal area, and overbark volume were determined in each plot. Results were pooled considering two well-differentiated degrees of soil evolution. One-way ANOVAs (and Tukey’s test) and regressions between growth parameters were performed to assess significant differences between growth performances on both types of soils. Research highlights: Deeper soils yielded significant higher plant density and stand stock figures than stony shallower profiles despite the intense past livestock activity in the area; and single tree-size was also significantly greater. Non-significant differences were found for merchantable junipers age (≈120-160 years). Wood extraction and livestock browsing should be limited on shallower soils to allow soil and forest evolution; as well as to preserve the genetic pool better adapted to hardest growing conditions.Keywords: livestock browsing; forest development; Juniperus thurifera L.; soil evolution; stand stock.

Different growth sensitivity to climate of the conifer Juniperus thurifera on both sides of the Mediterranean Sea

Mediterranean plants cope with cold wet winters and dry hot summers, with a drought gradient from northwest to southeast. Limiting climatic conditions have become more pronounced in the last decades due to the warming trend and rainfall decrease. Juniperus thurifera L., a long-lived conifer tree endemic to the western Mediterranean region, has a disjunct distribution in Europe and Africa, making it a suitable species to study sensitivity to climate in both sides of the Mediterranean Basin. Tree-ring width chronologies were built for three J. thurifera stands at Spain (Europe) and three in Morocco (Africa) and correlated with monthly temperature and precipitation. The temporal stability of climate-growth relationships was assessed using moving correlations; the drought effect on growth was calculated using the monthly standardized precipitation-evapotranspiration index (SPEI) at different temporal scales. In the wettest stands, increasing spring temperature and summer precipitation enhanced growth, while in the driest stands, growth was enhanced by higher spring precipitation and lower summer temperature. The climate-growth correlations shifted during the twentieth century, especially since the 1970s. Particularly noticeable is the recent negative correlation with previous autumn and winter precipitation in the wettest stands of J. thurifera, probably related with an effect of cloud cover or flooding on carbon storage depletion for next year growth. The driest stands were affected by drought at long time scales, while the wettest stands respond to drought at short time scales. This reveals a different strategy to cope with drought conditions, with populations from drier sites able to cope with short periods of water deficit.

Does plant colour matter? Wax accumulation as an indicator of decline in Juniperus thurifera

The photosynthesis in evergreen trees living in Mediterranean ecosystems is subjected to multiple climatic stresses due to water shortage and high temperatures during the summer and to low temperatures during the winter. Mediterranean perennials deploy different photoprotective mechanisms to prevent damage to the photosynthetic system. Wax accumulation in leaves is a primary response which by enhancing light scattering in the leaf surface reduces incident radiation in the mesophyll. The existence of high variability in wax accumulation levels between coexisting individuals of a species has a visual effect on colour that provides distinguishable green and glaucous phenotypes. We explored this variability in a Mediterranean evergreen tree Juniperus thurifera (L.) to evaluate the impact of epicuticular wax on optical and ecophysiological properties and on the abundance of photoprotective pigments throughout an annual cycle. Because of light attenuation by waxes, we expected that glaucous phenotypes would lower the need for photoprotective pigments. We evaluated the effect of phenotype and season on reflectance, defoliation levels, photochemical efficiency and photoprotective pigment contents in 20 green and 20 glaucous junipers. Contrary to our expectations, the results showed that glaucous trees suffered from a diminution in photochemical efficiency, but there was no reduction in photoprotective pigments. Differences between glaucous and green phenotypes were greater in winter, which is the most stressful season for this species. Glaucous individuals also showed the highest levels of leaf defoliation. The lower photochemical efficiency of glaucous trees, together with higher defoliation rates and equal or greater number of physiological photoprotective mechanisms, suggests that in spite of wax accumulation, glaucous trees suffer from more severe stress than green ones. This result suggests that changes in colouration in Mediterranean evergreens may be a decline indicator.

Minimum wood density of Juniperus thurifera is a robust proxy of spring water availability in a continental Mediterranean climate

AbstractAimThe Mediterranean Basin is considered to be a climate‐change hotspot, for which rising temperatures and associated aridification have been forecast. Such trends could affect the performance and growth of conifers in these drought‐prone areas. We evaluated whether radial growth and wood density can act as proxy measures of precipitation and drought in a Mediterranean conifer.LocationIberian Juniperus thurifera forests in northern and eastern Spain.MethodsWe sampled 10 stands encompassing J. thurifera's distributional area. We related four annually resolved tree‐ring variables (earlywood and latewood width, and maximum and minimum wood density) to climatic factors (temperature, precipitation and drought index) for the period 1951–2000. We then analysed the spatial and temporal patterns of those associations.ResultsOf all the four tree‐ring variables analysed, minimum wood density presented the strongest response to climate. Higher values of minimum wood density were related to drier spring conditions, particularly in the most xeric sites, confirming that a drought‐induced reduction in the radial expansion of tracheids increases earlywood density.Main conclusionsMinimum wood density is a biogeographically meaningful proxy of spring water availability for the Mediterranean conifer J. thurifera.

Genetic Diversity and Differentiation of Juniperus thurifera in Spain and Morocco as Determined by SSR

Juniperus thurifera L. is an important tree endemic to the western Mediterranean basin that it is able to grow in semi-arid climates. It nowadays exhibits a disjunct distribution pattern, occurring in North Africa, Spain, France and the Italian Alps. The Strait of Gibraltar has acted as an efficient barrier against gene flow between African and European populations, which are considered different subspecies by some authors. We aimed at describing the intraspecific genetic diversity of J. thurifera in populations from the Iberian Peninsula and Morocco and the phylogeographical relationships among these populations. The ploidy level of J. thurifera was examined and eleven nuclear microsatellites (nSSRs) developed for J. thurifera were assessed for genotyping this species. Six nSSRs were polymorphic and subsequently used to assess the genetic diversity and structure of the studied populations. Genotyping of the tetraploid J. thurifera using nuclear microsatellites supports the separation of Moroccan and Spanish populations into two genetically differentiated groups that correspond to the proposed subspecies africana and thurifera. High values of within population genetic diversity were found, that accounted for 90% of the total genetic variance, while population structure was weak. The estimators of genetic diversity were higher in populations of Spain than in populations of Morocco pointing for a possible loss of genetic diversity during the spread of this species to Africa from Europe.

Large‐scale features affect spatial variation in seed dispersal by birds in juniper woodlands

AbstractFruit–frugivore interactions have received great attention from evolutionary, ecological and applied perspectives. However, despite the fact that large‐scale approaches may offer new insights on fruit–frugivore interactions, little work has been devoted to exploring the factors shaping large‐scale variation of seed dispersal. This paper studies the spatial variation in seeds regurgitated within pellets by wintering thrushes (genus Turdus) in a set of 26 Spanish juniper (Juniperus thurifera) woodlands scattered along a latitudinal gradient during two winters of contrasting cone and bird abundance. It explicitly explores whether pellet rain variation among woodlands was related to changes in vegetation cover, temperature, day length duration and bird abundance. Top regression models in the Akaike information criterion framework explained 34 % and 70 % of variance in pellet numbers in low and high crop and bird abundance years, respectively. In both winters, the spatial variation in pellets correlated to thrush abundance and day length duration. Pellet abundance linked to cone distribution only in the year of high crop, in which many migratory, extra‐Iberian thrushes arrived to exploit the resource. Strong dependence of seed dispersion on large‐scale features affecting bird numbers (e.g. the arrival of extra‐Iberian migratory birds) and feeding behaviour (e.g. latitudinal variation in day length duration) suggests a primary role for variables acting at large scale on this mutualistic interaction.

Spanish juniper gain expansion opportunities by counting on a functionally diverse dispersal assemblage community

Seed dispersal is typically performed by a diverse array of species assemblages with different behavioral and morphological traits which determine dispersal quality (DQ, defined as the probability of recruitment of a dispersed seed). Fate of ecosystems to ongoing environmental changes is critically dependent on dispersal and mainly on DQ in novel scenarios. We assess here the DQ, thus the multiplicative effect of germination and survival probability to the first 3 years of life, for seeds dispersed by several bird species (Turdus spp.) and carnivores (Vulpes vulpes, Martes foina) in mature woodland remnants of Spanish juniper (Juniperus thurifera) and old fields which are being colonized by this species. Results showed that DQ was similar in mature woodlands and old fields. Germination rate for seeds dispersed by carnivores (11.5%) and thrushes (9.12%) was similar, however, interacted with microhabitat suitability. Seeds dispersed by carnivores reach the maximum germination rate on shrubs (16%), whereas seeds dispersed by thrushes did on female juniper canopies (15.5) indicating that each group of dispersers performed a directed dispersal. This directional effect was diluted when survival probability was considered: thrushes selected smaller seeds which had higher mortality in the seedling stage (70%) in relation to seedlings dispersed by carnivores (40%). Overall, thrushes resulted low-quality dispersers which provided a probability or recruitment of 2.5%, while a seed dispersed by carnivores had a probability of recruitment of 6.5%. Our findings show that generalist dispersers (i.e., carnivores) can provide a higher probability of recruitment than specialized dispersers (i.e., Turdus spp.). However, generalist species are usually opportunistic dispersers as their role as seed dispersers is dependent on the availability of trophic resources and species feeding preferences. As a result, J. thurifera dispersal community is composed by two functional groups of dispersers: specialized low-quality but trustworthy dispersers and generalist high-quality but opportunistic dispersers. The maintenance of both, generalist and specialist dispersers, in the dispersal assemblage community assures the dispersal services and increases the opportunities for regeneration and colonization of degraded areas under a land-use change scenario.

Juniper Structures in Western Mediterranean Vernacular Architecture: Ongoing Research

This research highlights the constructive features of Juniperus thurifera timber visible in the Western Mediterranean (from the island of Sardinia to Morocco). The use of this material is above all related to vernacular and traditional architecture, in the coastal areas as well as in the interior of the analyzed countries. An initial taxonomy of its use presents us with the issue of understanding the main structural performance of this type of timber, focusing in particular on its structural use and behavior. The results, visible throughout the research, are related to the resistance of the timber and its performance. On the other hand, this raw material is valued in vernacular architecture because of its strength when exposed to sea water or harsh weather conditions. Juniper beams and pillars are the most frequent solutions, but the use of branches and roots is also common, as the research demonstrates. In this framework, the text underlines the results of the research based on a geographical survey of juniper as a construction material, and on the first attempts to study its mechanical performance.

Species abundance and migratory status affects large-scale fruit tracking in thrushes (Turdus spp.)

The mutualistic interactions between fruit-producing plants and seed-dispersing birds may be disrupted by the difficulties involved in tracking fruit resources, which are often patchily distributed in space and time. As a consequence, the strength of this interaction will rely on the ability of birds to distribute numbers according to the spatiotemporal patterning of the resource. This paper tests if wintering thrushes (Turdus) track inter-winter and inter-site changes of cone abundance in an area that encompasses the main range of the Spanish Juniper Juniperus thurifera in the Iberian highlands. We test whether the regional abundance and migratory status of birds affect this fruit-tracking process. Analyses were approached by using the habitat matching rule, a null model applied to explore the effect of spatiotemporal change of resources on bird distribution. All species followed inter-winter food variation over the study area but under-matched the changes. The strength of this bird–plant interaction increased with the regional abundance of individual species. When thrushes were analyzed according to their migratory status, migratory species (Turdus pilaris, T. iliacus, and T. philomelos) tracked the resource better than sedentary ones (T. viscivorus and T. merula). This suggests that in a time of rapid environmental change any reduction of vagrant and abundant migratory thrushes could weaken the strength of this bird–plant interaction.

Growth and carbon isotopes of Mediterranean trees reveal contrasting responses to increased carbon dioxide and drought

Forest dynamics will depend upon the physiological performance of individual tree species under more stressful conditions caused by climate change. In order to compare the idiosyncratic responses of Mediterranean tree species (Quercus faginea, Pinus nigra, Juniperus thurifera) coexisting in forests of central Spain, we evaluated the temporal changes in secondary growth (basal area increment; BAI) and intrinsic water-use efficiency (iWUE) during the last four decades, determined how coexisting species are responding to increases in atmospheric CO2 concentrations (C(a)) and drought stress, and assessed the relationship among iWUE and growth during climatically contrasting years. All species increased their iWUE (ca. +15 to +21%) between the 1970s and the 2000s. This increase was positively related to C(a) for J. thurifera and to higher C(a) and drought for Q. faginea and P. nigra. During climatically favourable years the study species either increased or maintained their growth at rising iWUE, suggesting a higher CO2 uptake. However, during unfavourable climatic years Q. faginea and especially P. nigra showed sharp declines in growth at enhanced iWUE, likely caused by a reduced stomatal conductance to save water under stressful dry conditions. In contrast, J. thurifera showed enhanced growth also during unfavourable years at increased iWUE, denoting a beneficial effect of C(a) even under climatically harsh conditions. Our results reveal significant inter-specific differences in growth driven by alternative physiological responses to increasing drought stress. Thus, forest composition in the Mediterranean region might be altered due to contrasting capacities of coexisting tree species to withstand increasingly stressful conditions.

What makes a good neighborhood? Interaction of spatial scale and fruit density in the predator satiation dynamics of a masting juniper tree

Spatio-temporal variability in fruit production (masting) has been regarded as a key mechanism to increase plant fitness by reducing seed predation. However, considerably more effort has been devoted into understanding the consequences of temporal rather than spatial variations in fruit crop for plant fitness. In order to simultaneously evaluate both components, we quantify fruit production and pre-dispersal damage by three arthropod species (mites, chalcid wasps and moths) in the Spanish juniper (Juniperus thurifera) during 3 years in a spatially explicit context. Our aims were to assess (1) the interaction between fruit production and pre-dispersal fruit damage by arthropods, (2) the potential interference or competition between arthropods, and (3) the form of the phenotypic selection exerted by arthropods on fruit traits considering the spatial context. Arthropods damaged a substantial fraction of fruits produced by Spanish juniper with levels of damage showing sharp inter-annual variations. Fruit damage by mites was negatively related to yearly fruit crop and positively correlated at individual trees fruiting in consecutive years. Increased interspecific interference was an additional consequence of reduced fruit availability during small crop years. During a masting year, fruit damage by less mobile species such as mites was negatively affected by tree crop size, and no spatial structure was observed for mite damage. The incidence of chalcid wasps was low, so the spatial pattern of seed predation was unclear, and no preferences for fruit or seed traits were detected. Conversely, moths selected larger fruits and their incidence on trees was spatially aggregated up to 20 m, with predation levels being negatively affected by fruit abundance at the patch level, suggesting a positive density-dependent effect of neighbors on fruit output. These results highlight the importance of including the spatial component to understand complex species interactions at local scales.

Sphinctrina paramerae, a new Mediterranean lichenicolous species with non-septate spores

AbstractThe new species, Sphinctrina paramerae, is proposed. Characteristics of ascospores (size, morphology and ornamentation), apothecia (morphology, size and chemical reactions) and ecological features revealed significant differences between S. paramerae and the currently known species of Sphinctrina with non-septate ascospores. The new species grows on Pertusaria paramerae, epiphytic on the bark of Juniperus thurifera, which occurs on well-exposed areas of parameras in the Iberian high plateau and other montane Mediterranean areas.

Intensity and timing of warming and drought differentially affect growth patterns of co-occurring Mediterranean tree species

Climate change involves warmer temperatures, altered precipitation patterns, increased climatic variability and, in Mediterranean regions, increased frequency and severity of droughts. Tree species may show different growth responses to these components of climatic change, which may trigger changes in forest composition and dominance. We assessed the influence of recent climatic changes on secondary growth of mature trees from four species co-occurring in a Mediterranean continental forest: Quercus ilex, Quercus faginea, Pinus nigra and Juniperus thurifera. We used dendrochronology to relate radial-growth variables [earlywood and latewood widths, basal area increment (BAI)] to annual and seasonal climatic variables for the period 1977–2007. Our results showed that Q. faginea BAI has declined, whereas J. thurifera BAI has increased over time while Q. ilex and P. nigra have maintained their growth rates. Growth was mainly favored by higher precipitations and tree size for all species. Reduced growth during extremely dry years was observed for all study species, but all of them except Q. faginea recovered their growth levels 2 years after drought. Our findings illustrate how the effects of climatic changes on growth should include analyses of seasonal climatic trends and extreme events such as severe droughts. We conclude that the seasonal timing of warming and precipitation alterations leading to drought events caused contrasting effects on growth of co-occurring Mediterranean tree species, compromising their future coexistence.

Morphological differentiation supports the genetic pattern of the geographic structure of Juniperus thurifera (Cupressaceae)

Juniperus thurifera is an important component of woodland communities of dry sites within the West Mediterranean region and is characterised by a strongly disjunctive geographic range. Two subspecies were recognised, subsp. thurifera in Europe and subsp. africana in Africa. The aim of the study was the comparison of phenetic diversity to the pattern of AFLP geographic differentiation of the species described in the literature. The examination of phenetic diversity was based on the biometrical analysis of 17 populations using 12 morphological characters of cone and seed. The differences among populations were analysed using Student’s t test, analysis of discrimination, UPGMA agglomeration and hierarchical analysis of variance. The majority of morphological characters differentiated at a statistically significant level between populations and between J. thurifera subsp. thurifera and subsp. africana. Three groups of populations were detected using multivariate statistical analyses. The first, well separated, is subsp. africana, while the following two concern subsp. thurifera. The morphological differentiation of populations appeared similar to that described on the AFLP. The Gibraltar Straight appeared to be the most important barrier.