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  • 1
    Language: English
    In: Global change biology, 2018-11, Vol.24 (11), p.5549-5559
    Description: Among forest ecosystems, the alpine treeline ecotone can be considered to be a simplified model to study global ecology and climate change. Alpine treelines are expected to shift upwards in response to global warming given that tree recruitment and growth are assumed to be mainly limited by low temperatures. However, little is known whether precipitation and temperature interact to drive long‐term Himalayan treeline dynamics. Tree growth is affected by spring rainfall in the central Himalayan treelines, being good locations for testing if, in addition to temperature, precipitation mediates treeline dynamics. To test this hypothesis, we reconstructed spatiotemporal variations in treeline dynamics in 20 plots located at six alpine treeline sites, dominated by two tree species (birch, fir), and situated along an east–west precipitation gradient in the central Himalayas. Our reconstructions evidenced that treelines shifted upward in response to recent climate warming, but their shift rates were primarily mediated by spring precipitation. The rate of upward shift was higher in the wettest eastern Himalayas, suggesting that its ascent rate was facilitated by spring precipitation. The drying tendency in association with the recent warming trends observed in the central Himalayas, however, will likely hinder an upslope advancement of alpine treelines and promote downward treeline shifts if moisture availability crosses a critical minimum threshold. Our study highlights the complexity of plant responses to climate and the need to consider multiple climate factors when analyzing treeline dynamics. Based on 20 treeline plots along an east–west precipitation gradient in the central Himalayas, this research showed that treelines shifted upward in response to recent climate warming, but their shift rates were mediated by spring precipitation. The drying tendency in association with the recent warming trends observed in the central Himalayas, however, will likely hinder an upslope advancement of alpine treelines and promote downward treeline shifts if moisture availability crosses a critical minimum threshold. Our study highlights the complexity of plant responses to climate and the need to consider multiple climate factors when analyzing treeline dynamics.
    Subject(s): Air pollution ; Alpine ecosystems ; Alpine treeline ; Altitude ; Analysis ; central Himalayas ; climate change ; Environmental aspects ; Global Warming ; Mountain ecology ; Nepal ; Plant Dispersal ; Rain ; Rain and rainfall ; Time Factors ; tree recruitment ; treeline shift ; Trees - physiology
    ISSN: 1354-1013
    E-ISSN: 1365-2486
    Source: Hellenic Academic Libraries Link
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  • 2
    Language: English
    In: The Journal of ecology, 2010-05-01, Vol.98 (3), p.592-603
    Description: 1. Long-term basal area increment (BAI) in Abies pinsapo was studied to investigate the way density-dependent factors modulate the responses of radial growth to climatic stresses in relict stands of a drought-sensitive Mediterranean fir. 2. First, we verified that spatially explicit competition predicts mean A. pinsapo BAI at our study site; i. e. it modulates the degree to which the average climate-driven potential for growth is expressed. Second, we verified that the long-term pattern of temperature predicts the long-term pattern of BAI, estimated as the main trend over a time period of 40 years. Finally, we assessed whether the intensity of tree-to-tree competition restrains the potential improvements achieved by our model of BAI when a short-term, high-frequency Stressor such as drought (inter-annual precipitation variability) is introduced. 3. We applied Dynamic Factor Analysis (DFA) to characterize regional climatic trends and to test thehypothesis that trees subjected to contrasting competition intensity may differ in their growth pattern. Significant long-term climate trends obtained by DFA were used as predictors of long-term BAI. 4. The mean BAI was mainly determined by competition, whereas growth trends obtained by DFA did not differ among dominant, suppressed and dying trees. Common trends of growth decline were strongly related to long-term, late-winter to summer temperatures, while the residuals were related to total annual precipitation, although with decreasing significance as competition increased. Our results support the contention that the reported patterns of A. pinsapo growth decline and death occur as a result of the interacting effects of both competition and climate Stressors acting at longand short-term time scales. 5. Synthesis. Long-term climatic drought stress was the main driving factor of growth decline in A.pinsapo. Moreover, trees already suffering from competition (a long-term stress) were predisposed to decline given an additional short-term stress, such as a severe drought.
    Subject(s): Abies pinsapo ; adaptive capacity ; Analysis ; Animal and plant ecology ; Animal, plant and microbial ecology ; basal area increment ; Biological and medical sciences ; Climate ; Climate change ; Climate models ; climatic change ; competition ; Death ; Drought ; Droughts ; Dynamic Factor Analysis ; Ecological competition ; Forest ecology ; Forestry ; Fundamental and applied biological sciences. Psychology ; General aspects ; General forest ecology ; Generalities. Production, biomass. Quality of wood and forest products. General forest ecology ; Global warming ; Human ecology ; linear mixed models ; Mortality ; Plant-climate interactions ; Precipitation variability ; Rain and rainfall ; Statistics ; Tree growth ; Trees ; vulnerability
    ISSN: 0022-0477
    E-ISSN: 1365-2745
    Source: JSTOR Life Sciences
    Source: JSTOR Arts & Sciences I
    Source: Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals
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  • 3
    Language: English
    In: Trees (Berlin, West), 2014-09-03, Vol.28 (6), p.1737-1750
    Description: Key message The retrospective analysis of wood anatomical features evidences how a long-term deterioration of hydraulic performance and carbon use portend drought-induced mortality in Scots pine. Widespread episodes of drought-induced tree mortality are predicted to become more frequent as climate becomes warmer and drier. Nevertheless, growth trends and their links to changes in wood anatomy before tree dies are still poorly understood. Wood anatomical features provide valuable information that can be extracted to infer the mechanisms leading to tree death. In this study, we characterize drought-induced mortality affecting two Scots pine ( Pinus sylvestris ) sites (Prades and Arcalís) located in the North Eastern Iberian Peninsula. Co-occurring now-dead and living Scots pine trees were sampled and their wood anatomical features were measured and compared. We aimed to detect differences in anatomical features between living and dead trees, and to infer past physiological performances that might have determined their subsequent death or survival. Now-dead trees showed lower tracheid and resin duct production, and smaller radial lumen diameters than co-occurring living trees. At the more xeric Prades site, these anatomical differences were larger and chronic, i.e. were observed over the three studied decades, whilst they were less pronounced at the other, more mesic Arcalís site, where tree mortality episodes were more recent. This indicates that dead trees’ hydraulic conductivity was severely affected and that carbon investment in xylem formation and resin duct production was constrained prior to tree death. Our findings show that both hydraulic deterioration and low carbon allocation to xylem formation were associated to drought-induced mortality in Scots pine. Nevertheless, the temporal dynamics of these processes differed between populations as a function of site climatic conditions.
    Subject(s): Agriculture ; Analysis ; Biomedical and Life Sciences ; Dendroclimatology ; Droughts ; Forestry ; Health aspects ; Hydrogeology ; Investments ; Life Sciences ; Mortality ; Original Paper ; Physiological aspects ; Plant Anatomy/Development ; Plant Pathology ; Plant Physiology ; Plant Sciences ; Tree Rings
    ISSN: 0931-1890
    E-ISSN: 1432-2285
    Source: Alma/SFX Local Collection
    Source: ProQuest Central
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  • 4
    Language: English
    In: Journal of biogeography, 2014-06, Vol.41 (6), p.1105-1114
    Description: Aim The 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. Location Iberian Juniperus thurifera forests in northern and eastern Spain. Methods We 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. Results Of 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 conclusions Minimum wood density is a biogeographically meaningful proxy of spring water availability for the Mediterranean conifer J. thurifera.
    Subject(s): Animal and plant ecology ; Animal, plant and microbial ecology ; Biological and medical sciences ; Climate ; Climate proxy ; Climatic changes ; conifer ; Dendroclimatology ; dendroecology ; Drought ; Earlywood ; Fundamental and applied biological sciences. Psychology ; General aspects ; Growth rings ; Herbivores ; Juniperus thurifera ; Latewood ; Mediterranean climate ; Paleoclimatology ; Pine trees ; Plant–environment relationships ; Precipitation ; Precipitation (Meteorology) ; Proxy ; Seasons ; Spain ; Specific gravity ; Synecology ; Tracheids ; Water ; Wood density
    ISSN: 0305-0270
    E-ISSN: 1365-2699
    Source: JSTOR Life Sciences
    Source: Hellenic Academic Libraries Link
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  • 5
    Language: English
    In: Trees (Berlin, West), 2009-03-20, Vol.23 (4), p.787-799
    Description: This study analyses how coexisting evergreen and deciduous oaks adjust their phenology to cope with the stressful Mediterranean summer conditions. We test the hypothesis that the vegetative and reproductive growth of the winter deciduous ( Quercus faginea Lam.) is more affected by summer drought than that of the evergreen [ Quercus ilex L. subsp. ballota (Desf.) Samp.]. First, we assessed the complete aboveground phenology of both species during two consecutive years. Shoot and litter production and bud, acorn and secondary growth were monitored monthly. Second, we identified several parameters affected by summer conditions: apical bud size, individual leaf area (LA), leaf mass per area (LMA) and acorn yield in both species, and leaf-fall in Q. faginea ; and analysed their variation over 10 years. Q. ilex performed up to 25% of shoot growth and most leaf development during summer, whereas Q. faginea completed most of both phenophases during spring. Secondary growth was arrested in summer under drought conditions. Approximately, 30–40% of bud and 40–50% of acorn growth was undertaken during summer in both species. Summer drought related to differences in LA, LMA and leaf senescence, but not to acorn yield. Both species had similar year-to-year patterns of acorn production, though yields were always lower in Q. faginea . Bud size decreased severely in both species during extremely dry years. In Q. ilex, bud size tended to alternate between years of large and small buds, and these patterns were followed by opposite trends in stem length. In Q. faginea , bud size was more stable through time. Q. ilex was more phenologically active during summer than Q. faginea , indicating a higher tolerance to drought. Furthermore, bud and fruit growth (the only two phenophases that both species performed during summer) were more severely affected by summer drought in Q. faginea than in the evergreen. The differential effects of summer drought on key phenophases for the persistence (bud growth) and colonization ability (fruit production) of both species may have consequences for their coexistence.
    Subject(s): Agriculture ; Biomedical and Life Sciences ; Drought ; Droughts ; Forestry ; Life Sciences ; Original Paper ; Phenology ; Plant Anatomy/Development ; Plant Pathology ; Plant Physiology ; Plant Sciences
    ISSN: 0931-1890
    E-ISSN: 1432-2285
    Source: Alma/SFX Local Collection
    Source: ProQuest Central
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  • 6
    Language: English
    In: Global change biology, 2020-02, Vol.26 (2), p.e1-e3
    Description: This article is a response to Zang et al., 26, 322–324.
    Subject(s): Benchmarking ; Droughts ; Ecology ; Ecosystem ; Water
    ISSN: 1354-1013
    E-ISSN: 1365-2486
    Source: Hellenic Academic Libraries Link
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  • 7
    Language: English
    In: Proceedings of the National Academy of Sciences - PNAS, 2016-04-19, Vol.113 (16), p.4380-4385
    Description: The alpine treeline is commonly regarded as being sensitive to climatic warming because regeneration and growth of trees at treeline generally are limited by low temperature. The alpine treelines of the Tibetan Plateau (TP) occur at the highest elevations (4,900 m above sea level) in the Northern Hemisphere. Ongoing climatic warming is expected to shift treelines upward. Studies of treeline dynamics at regional and local scales, however, have yielded conflicting results, indicating either unchanging treeline elevations or upward shifts. To reconcile this conflict, we reconstructed in detail a century of treeline structure and tree recruitment at sites along a climatic gradient of 4 °C and mean annual rainfall of 650 mm on the eastern TP. Species interactions interacted with effects of warming on treeline and could outweigh them. Densification of shrubs just above treeline inhibited tree establishment, and slowed upward movement of treelines on a time scale of decades. Interspecific interactions are major processes controlling treeline dynamics that may account for the absence of an upward shift at some TP treelines despite continued climatic warming.
    Subject(s): alpine treeline ; Biological Sciences ; Climate change ; Climatic changes ; Continental interfaces, environment ; Densification ; Ecological research ; Environmental aspects ; Forest dynamics ; Forests ; Global Warming ; interspecific competition ; Models, Biological ; Ocean, Atmosphere ; Picea - physiology ; Sciences of the Universe ; Temperature ; Tibet ; Tibetan Plateau ; treeline dynamics ; Trees
    ISSN: 0027-8424
    E-ISSN: 1091-6490
    Source: JSTOR Life Sciences
    Source: HighWire Press (Free Journals)
    Source: Hellenic Academic Libraries Link
    Source: PubMed Central
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  • 8
    Language: English
    In: Theoretical and applied climatology, 2014-08-26, Vol.121 (3-4), p.571-579
    Description: 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, respectively. Comparison of tree rings with regional precipitation, temperature, and Palmer Drought Severity Index (PDSI) data indicates that juniper trees contain information on late spring and 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, indicating 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.
    Subject(s): Analysis ; Aquatic Pollution ; Atmospheric Protection/Air Quality Control/Air Pollution ; Atmospheric Sciences ; Automobile drivers ; Climatology ; Droughts ; Earth and Environmental Science ; Earth Sciences ; Original Paper ; Precipitation (Meteorology) ; Rites, ceremonies and celebrations ; Waste Water Technology ; Water Management ; Water Pollution Control
    ISSN: 0177-798X
    E-ISSN: 1434-4483
    Source: Academic Search Ultimate
    Source: Alma/SFX Local Collection
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  • 9
    Language: English
    In: Forests, 2021-03-23, Vol.12 (3), p.381
    Description: Background and Objectives—Coexisting tree and shrub species will have to withstand more arid conditions as temperatures keep rising in the Mediterranean Basin. However, we still lack reliable assessments on how climate and drought affect the radial growth of tree and shrub species at intra- and interannual time scales under semi-arid Mediterranean conditions. Materials and Methods—We investigated the growth responses to climate of four co-occurring gymnosperms inhabiting semi-arid Mediterranean sites in northeastern Spain: two tree species (Aleppo pine, Pinus halepensis Mill.; Spanish juniper, Juniperus thurifera L.) and two shrubs (Phoenicean juniper, Juniperus phoenicea L.; Ephedra nebrodensis Tineo ex Guss.). First, we quantified the intra-annual radial-growth rates of the four species by periodically sampling wood samples during one growing season. Second, we quantified the climate–growth relationships at an interannual scale at two sites with different soil water availability by using dendrochronology. Third, we simulated growth responses to temperature and soil moisture using the forward, process-based Vaganov‒Shashkin (VS-Lite) growth model to disentangle the main climatic drivers of growth. Results—The growth of all species peaked in spring to early summer (May–June). The pine and junipers grew after the dry summer, i.e., they showed a bimodal growth pattern. Prior wet winter conditions leading to high soil moisture before cambium reactivation in spring enhanced the growth of P. halepensis at dry sites, whereas the growth of both junipers and Ephedra depended more on high spring–summer soil moisture. The VS-Lite model identified these different influences of soil moisture on growth in tree and shrub species. Conclusions—Our approach (i) revealed contrasting growth dynamics of co-existing tree and shrub species under semi-arid Mediterranean conditions and (ii) provided novel insights on different responses as a function of growth habits in similar drought-prone regions.
    Subject(s): 21st century ; Aridity ; Cavitation ; Climate ; Dendrochronology ; dendroecology ; Drought ; Environmental assessment ; Ephedra ; Ephedra nebrodensis ; Growth patterns ; Growth rate ; Gymnosperms ; Juniperus phoenicea ; Juniperus thurifera ; Moisture content ; Pine ; Pinus halepensis ; Plant species ; Precipitation ; Shrubs ; Soil moisture ; Soil temperature ; Soil water ; Species ; Spring (season) ; Summer ; Trees ; Trends ; Water availability
    ISSN: 1999-4907
    E-ISSN: 1999-4907
    Source: DOAJ Directory of Open Access Journals - Not for CDI Discovery
    Source: ProQuest Central
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  • 10
    Language: English
    In: The New phytologist, 2010-01-01, Vol.185 (2), p.471-480
    Description: Seasonal radial-increment and xylogenesis data can help to elucidate how climate modulates wood formation in conifers. Few xylogenesis studies have assessed how plastic xylogenesis is in sympatric conifer species from continental Mediterranean areas, where low winter temperatures and summer drought constrain growth. Here, we analysed intra-annual patterns of secondary growth in sympatric conifer species (Juniperus thurifera, Pinus halepensis and Pinus sylvestris). Two field sites (xeric and mesic) were evaluated using dendrometers, microcores and climatic data. A bimodal pattern of xylogenesis characterized by spring and autumn precipitation and subsequent cambial reactivation was detected in J. thurifera at both study sites and in P. halepensis at the xeric site, but was absent in P. sylvestris where growth was largely controlled by day length. In the xeric site J. thurifera exhibited an increased response to water availability in autumn relative to P. halepensis and summer cambial suppression was more marked in J. thurifera than in P. halepensis. Juniperus thurifera exhibited increased plasticity in its xylogenesis pattern compared with sympatric pines, enabling this species to occupy sites with more variable climatic conditions. The plastic xylogenesis patterns of junipers in drought-stressed areas may also provide them with a competitive advantage against co-occurring pines.
    Subject(s): Adaptation, Physiological ; cambium ; Climate ; Cold Temperature ; Conifers ; Dehydration ; Droughts ; Growth rings ; Juniperus ; Juniperus - growth & development ; Juniperus thurifera ; Mediterranean climate ; Mediterranean climates ; Photoperiod ; Pine trees ; Pinus ; Pinus - growth & development ; Pinus halepensis ; Pinus sylvestris ; Plant Stems - growth & development ; Rain ; Rain and rainfall ; Seasons ; Tracheids ; Tree growth ; Wood - growth & development ; Xylem ; Xylem - growth & development
    ISSN: 0028-646X
    E-ISSN: 1469-8137
    Source: JSTOR Life Sciences
    Source: Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals
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