Water Relations and Alpine Timberline

Tranquillini, Walter

doi:10.1007/978-3-642-66429-8_29

Cited by 57 publications

(34 citation statements)

References 20 publications

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“…The first Picea pollen grains may have been the result of increased pollen productivity of individual local trees as a response to climate warming. Picea is more sensitive to moisture balance as compared with Pinus and Larix (Tranquillini, 1979;Huntley and Prentice, 1993) and its restriction throughout Europe during the Lateglacial has been associated with dry conditions during the growing season (Ravazzi, 2002). Between 13 400 and 13 200 cal.…”

Section: >14 700 Cal Yr Bp Pleniglacialmentioning

confidence: 99%

Late Quaternary palaeoecological and palaeoclimatological reconstruction in the Gutaiului Mountains, northwest Romania

Feurdean

Bennike

2004

J Quaternary Science

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Macrofossil, pollen, lithostratigraphy, mineral magnetic measurements (SIRM and magnetic susceptibility), loss-on-ignition, and AMS radiocarbon dating on sediments from two former crater lakes, situated at moderate altitudes in the Gutaiului Mountains of northwest Romania, allow reconstruction of Late Quaternary climate and environment. Shrubs and herbs with steppe and montane affinities along with stands of Betula and Pinus, colonised the surroundings of the sites prior to 14 700 cal. yr BP and the inferred climatic conditions were cold and dry. The gradual transition to open Pinus-Betula forests, slightly higher lake water temperatures, and higher lake productivity, indicate more stable environmental conditions between 14 700 and 14 100 cal. yr BP. This development was interrupted by cooler and drier climatic conditions between 14 100 and 13 800 cal. yr BP, as inferred from a reduction of open forests to patches, or stands, of Pinus, Betula, Larix, Salix and Populus. The expansion of a denser boreal forest, dominated by Picea, but including Pinus, Larix, Betula, Salix, and Ulmus started at 13 800 cal. yr BP, although the forest density seems to have been reduced between 13 400 and 13 200 cal. yr BP. Air temperature and moisture availability gradually increased, but a change towards drier conditions is seen at 13 400 cal. yr BP. A distinct decrease in temperature and humidity between 12 900 and 11 500 cal. yr BP led to a return of open vegetation, with patches of Betula, Larix, Salix, Pinus and Alnus and individuals of Picea. Macrofossils and pollen of aquatic plants indicate rising lake water temperatures and increased aquatic productivity already by ca. 11 800 cal. yr BP, 300 years earlier than documented by the terrestrial plant communities. At the onset of the Holocene, 11 500 cal. yr BP, forests dominated by Betula, Pinus and Larix expanded and were followed by dense Ulmus forests with Picea, Betula and Pinus at 11 250 cal. yr BP. Larix pollen was not found, but macrofossil evidence indicates that Larix was an important forest constituent at the onset of the Holocene. Moister conditions were followed by a dry period starting about 10 600 cal. yr BP, which was more pronounced between 8600 and 8200 cal. yr BP, as inferred from aquatic macrofossils. The maximum expansion of Tilia, Quercus, Fraxinus and Acer between 10 700 and 8600 cal. yr BP may reflect a more continental climate. A drier and/or cooler climate could have been responsible for the late expansion (10 300 cal. yr BP) and late maximum (9300 cal. yr BP) of Corylus. Increased water stress, and possibly cooler conditions around 8600 cal. yr BP, may have caused a reduction of Ulmus, Tilia, Quercus and Fraxinus. After 8200 cal. yr BP moisture increased and the forests included Picea, Tilia, Quercus and Fraxinus.

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Section: >14 700 Cal Yr Bp Pleniglacialmentioning

confidence: 99%

Late Quaternary palaeoecological and palaeoclimatological reconstruction in the Gutaiului Mountains, northwest Romania

Feurdean

Bennike

2004

J Quaternary Science

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“…High stress intensities were reported for tree water relations (e.g. Pisek and Larcher 1954;Larcher 1972;Tranquillini 1976;Mayr et al 2002Mayr et al , 2003b so that also Rhododendron shrubs may be affected by drought and freeze-thaw events (e.g. Sperry 2003, 2006;Mayr et al 2003a, b) unless protected by the snow cover.…”

Section: Introductionmentioning

confidence: 96%

“…Alpine areas are known to be rather humid in summer as precipitation increases with altitude while temperature and, in consequence, evaporation decreases (e.g. Tranquillini 1976;Körner 2003;Mayr 2007). However, conditions vary on a very small scale, particularly when the substrate has low water storage capacity.…”

Section: Introductionmentioning

confidence: 99%

Hydraulic plasticity and limitations of alpine Rhododendron species

et al. 2010

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In the European Alps, Rhododendron ferrugineum grows in silicate regions while Rhododendron hirsutum is restricted to limestone areas. At geologically mixed sites, also hybrids (Rhododendron × intermedium) can occur. We hypothesised that hydraulic properties would vary with the species' habitat requirements. Key hydraulic parameters (vulnerability to drought-induced embolism, stomata regulation) and related wood characteristics as well as diurnal courses of water potential (Ψ) and stomatal conductance were analysed on plants growing on a silicate, a limestone and a geologically mixed site. Highest embolism resistance[Ψ at 50% loss of conductivity (Ψ (50)), -3.24 ± 0.18 MPa] and the highest safety margin between the Ψ at stomata closure (Ψ (SC) at 10% of maximal leaf conductance) and Ψ (50) were observed in R. hirsutum at the limestone site (1.57 MPa). Like in R. ferrugineum, hydraulic parameters indicated less resistance at the geologically mixed site. Highest Ψ (50) (-1.95 ± 0.12 MPa), corresponding to wide conduits and a reduced conduit wall reinforcement, was found in R. × intermedium. Diurnal courses indicated a rapid stomata closure in response to low Ψ in R. hirsutum and R. × intermedium. The plasticity in drought adaptation of R. hirsutum corresponds to its ability to colonise dry limestone areas. In contrast, hydraulic limitations of R. × intermedium may explain restrictions to rather moist sites. This study provides insight into the role of xylem hydraulics and stomata regulation in shrub water relations, interspecific and site-specific differences in drought adaptation, as well as effects of hybridisation on plant hydraulics.

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“…The latter study was carried out at the alpine timberline where up to 130 freeze-thaw events per winter (Groß et al, 1991;Mayr et al, 2003aMayr et al, , 2003bMayr et al, , 2006 and frost drought (Michaelis, 1934;Pisek and Larcher, 1954;Larcher, 1972;Tranquillini, 1976Tranquillini, , 1980 with extremely low c (Mayr et al, 2003a(Mayr et al, , 2003b occur. The conditions at the alpine timberline led to conductivity losses of up to 100%, while in the studies of Sperry et al (1994) as well as Sparks et al (2001), relatively low embolism rates were observed.…”

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confidence: 99%

Embolism Formation during Freezing in the Wood ofPicea abies

et al. 2006

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Freeze-thaw events can cause embolism in plant xylem. According to classical theory, gas bubbles are formed during freezing and expand during thawing. Conifers have proved to be very resistant to freeze-thaw induced embolism, because bubbles in tracheids are small and redissolve during thawing. In contrast, increasing embolism rates upon consecutive freeze-thaw events were observed that cannot be explained by the classical mechanism. In this study, embolism formation during freeze-thaw events was analyzed via ultrasonic and Cryo-scanning electron microscope techniques. Twigs of Picea abies L. Karst. were subjected to up to 120 freeze-thaw cycles during which ultrasonic acoustic emissions, xylem temperature, and diameter variations were registered. In addition, the extent and cross-sectional pattern of embolism were analyzed with staining experiments and Cryo-scanning electron microscope observations. Embolism increased with the number of freeze-thaw events in twigs previously dehydrated to a water potential of 22.8 MPa. In these twigs, acoustic emissions were registered, while saturated twigs showed low, and totally dehydrated twigs showed no, acoustic activity. Acoustic emissions were detected only during the freezing process. This means that embolism was formed during freezing, which is in contradiction to the classical theory of freeze-thaw induced embolism. The clustered pattern of embolized tracheids in cross sections indicates that air spread from a dysfunctional tracheid to adjacent functional ones. We hypothesize that the low water potential of the growing ice front led to a decrease of the potential in nearby tracheids. This may result in freezing-induced air seeding.

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Water Relations and Alpine Timberline

Cited by 57 publications

References 20 publications

Late Quaternary palaeoecological and palaeoclimatological reconstruction in the Gutaiului Mountains, northwest Romania

Late Quaternary palaeoecological and palaeoclimatological reconstruction in the Gutaiului Mountains, northwest Romania

Hydraulic plasticity and limitations of alpine Rhododendron species

Embolism Formation during Freezing in the Wood ofPicea abies

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