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  • 1
    Electronic Resource
    Electronic Resource
    The relationship between freezing tolerance and thermotropic leaf movement in five Rhododendron species (1991)
    Springer
    Oecologia 87 (1991), S. 63-71 
    Details
    ISSN: 1432-1939
    Keywords: Leaf curling ; Leaf angle ; Water relations ; Rhododendron ; Freezing tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Leaf movement kinetics in five species of Rhododendron were studied in response to leaf temperature, leaf freezing point, and leaf water deficit. There was a gradient in the degree of leaf curling among species in the following order from the greatest curling to the least curling: Rhododendron catawbiense, R. maximum, R. minus, R. macrophyllum, R. ponticum. Those species found to be tolerant of winter conditions had the most intense leaf movements (both curling and angle) while those species with minimal cold tolerance had limited or no leaf movements. Leaf curling occurred at leaf temperatures above the tissue freezing points in all species. Athough leaf angle was influenced by leaf turgor, general tissue desiccation was not the ultimate cause for thermotropic leaf curling in any species tested. Those species with the greatest leaf curling and angle movements had the highest osmotic potential, the lowest water deficit at the turgor loss point, and the lowest symplastic water fraction. These data suggest that there is a trade off in Rhododendron leaf physiology between cold tolerance (due to leaf movements) and water stress tolerance (due to turgor maintenance mechanisms).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00323781
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  • 2
    Electronic Resource
    Electronic Resource
    Stem photosynthesis in Psorothamnus spinosus (smoke tree) in the Sonoran desert of California (1989)
    Springer
    Oecologia 79 (1989), S. 193-197 
    Details
    ISSN: 1432-1939
    Keywords: Stem ; Photosynthesis ; Desert ; Plant stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Stem photosynthetic responses to environmental parameters were investigated with Psorothamnus spinosus in the Sonoran Desert of California. Light saturation of stem photosynthesis was equal to maximum midday summer irradance (1600–2000 μmol·m-2·s-1). The optimum temperature for stem photosynthesis was 39°C, and lower stem temperatures (27–35°C) caused significant decreases (up to 50%) in stem photosynthesis. Positive stem photosynthesis was maintained up to 51°C. Stem photosynthesis was relatively insensitive to increasing vpd up to 5 kPa; However, stem conductance decreased by 25% at a vpd of 5 kPa. At vpd greater than 5 kPa stem photosynthesis decreased relatively more than that of stem conductance causing a decrease in water use efficiency and an increase an intercellular carbon dioxide concentration. Maximum stem photosynthetic rates were low (6.2–10.6 μmol·m-2·s-1) on a stem surface area, but, stem photosynthetic rates of young shoots were substantially higher (19.5–33.3 μmol· m-2·s-1) on a projected area basis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00388478
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  • 3
    Electronic Resource
    Electronic Resource
    Phenology, productivity, and nutrient accumulation in the post-fire chaparral shrub Lotus scoparius (1981)
    Springer
    Oecologia 50 (1981), S. 217-224 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Lotus scoparius is a drought-deciduous shrub which is an early and abundant colonizer of sites following fire in southern California chaparral. Productivity, seasonal nutrient concentrations, nutrient accumulations and phenology were studied in a 4-year-old burn site in Adenostoma chaparral in which L. scoparius had established 49% cover. Net aboveground primary production for L. scoparius was 105 g m-2 y-1; leaves accounted for 40% of the annual production. The true increment to biomass was only 17 g m-2 y-1; 83% of the net production entered the litter layer or standing dead components. In response to the Mediterranean climatic regime, most of the annual net production and plant activity occurred from May through June when photoperiod and temperatures were favorable and moisture was available. In July leaf abscission occurred in response to the summer drought conditions. Correlation and principal component analysis suggested consistent seasonal behavior in the foliar concentrations of N, P, Zn, and Mn. Nitrogen, P, K, and Zn were strongly reabsorbed from leaf tissues before abscission. Calcium, Mg, and Fe formed a second functional group of elements which increased in concentration throughout leaf maturation and which were not reabsorbed from senescing foliage. The seasonal pattern of nitrogen-containing organic compounds (chlorophylls and proteins) was most associated with the leaf phenology and water stress. The rapid growth of Lotus scoparius plays a role in conserving nutrients that might be lost through runoff and erosion after fire in the chaparral.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00348041
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  • 4
    Electronic Resource
    Electronic Resource
    Summer water relations of the desert phreatophyte Prosopis glandulosa in the Sonoran Desert of southern California (1981)
    Springer
    Oecologia 50 (1981), S. 271-276 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Prosopis is a genus of phreatophytic trees inhabiting hot deserts and semiarid grasslands of the world. Although desert trees are exposed to unusual environmental temperature and water stress, few investigations have evaluated their water relations. This is particularly true for Prosopis species growing in areas where a large portion of their water use comes from ground water. Water relations components for Prosopis glandulosa were studied at Harper's Well, near the Salton Sea, California during the summer months of 1980. Maximum temperatures (49° C), irradiance (2,000 μE/m2/sec), and vapor pressure deficit (5.3 kPa) were reached in July. During this time Prosopis glandulosa predawn xylem pressure potentials were below-3.0 MPa. Prosopis glandulosa at Harper's Well is able to maintain open stomata during high temperatures, high vapor pressure deficit and at low estimated turgor pressure. Leaf resistance measurements indicate that stomata are open primarily in the morning, but may reopen in the afternoon in trees with greater water resources. Osmotic potentials of juvenile shoots were higher (-1.0 to-2.5 MPa) than mature shoots (-3.5 MPa). Estimated turgor potential remained low (0.1–0.2 MPa) during the morning and early afternoon. Estimated turgor pressure increased from August to September as temperatures and vapor pressure deficit decreased. Leaf conductance was strongly associated with leaf vapor pressure deficit and estimated turgor potential but poorly associated with xylem pressure potential. Prosopis stomata seem to be uncoupled from tissue water potential until-4.8 MPa is reached.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00348050
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  • 5
    Electronic Resource
    Electronic Resource
    Seasonal and diurnal leaf movements of Rhododendron maximum L. in contrasting irradiance environments (1985)
    Springer
    Oecologia 65 (1985), S. 296-302 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Leaf orientation (azimuth and angle) and leaf curling were measured seasonally and diurnally on Rhododendron maximum L. under an evergreen and a deciduous canopy. The microclimatic conditions under the evergreen canopy (mixed pine and hemlock) were characterized by lower irradiance but similar temperature, and vapor pressure deficit (vpd) to that under the deciduous canopy (mixed oak and maple). Under both canopies irradiance was more intense during winter months. On a seasonal basis leaf angle was closer to horizontal under the evergreen canopy but there was no difference between leaf curling in the two sites. Stomatal conductance was higher under the deciduous canopy but stomata were closed in the winter (following canopy abscission) under the evergreen and deciduous canopies even during warm winter days. Leaf water potentials were lower in the winter and Rhododendron maximum had higher leaf water potentials under the evergreen canopy. Significant association between mean leaf angle and curling index were found above a mean leaf angle of 70°. Leaf curling was highly associated with leaf temperature where 0° C was a critical value stimulating leaf curling. Leaf angle was linearly related to leaf temperatures above 0° C although this relationship was different under the two canopy types as a result of differing irradiance or differing water potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379233
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  • 6
    Electronic Resource
    Electronic Resource
    The influence of photoperiod on drought induction of dormancy in Lotus scoparius (1982)
    Springer
    Oecologia 53 (1982), S. 79-83 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Many species of plants in Mediterranean climate regions have evolved deciduousness, causing reduced leaf area during the long summer drought characteristic of Mediterranean climates. This summer deciduous growth form has been considered a plant adaptation in Mediterranean regions allowing survival during periods of extreme water stress. Many studies have suggested the ecological importance of this growth form but few studies have examined the physiological stimulus for deciduousness. Previous data indicate that abscission in Lotus scoparius (a mediterranean California deciduous species) is influenced by both photoperiod and water stress in a complex manner. Here the physiological basis of long day enhanced leaf fall during water stress is investigated. Examination of water potential components indicate an osmotic adjustment with incresing water stress which enables the maintenance of turgor at lower water potentials. Osmotic adjustment in plants grown under long photoperiods was greater than that in short photoperiods. Therfore, long day enhanced abscission during water stress was not due to a greater susceptability to turgor loss during long days. Rather, long day treatment caused these plants to initiate dormancy (as indicated by soluble protein concentrations) during the onset of water stress. The dormant condition could not be released by subsequent release from water stress. Apparently, Lotus scoparius has evolved a photoperiodic control (presumably through growth regulators) over the initiation of dormancy during water stress. The adaptive significance of this photoperiodic control over the leaf abscission response to water stress relates to the variable climate of Mediterranean regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377139
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  • 7
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    Atlantic origin of observed and modelled freshwater anomalies in the Nordic Seas (2014)
    Springer Nature
    Details
    Publication Date: 2014-10-31
    Description: Nature Geoscience 7, 801 (2014). doi:10.1038/ngeo2259 Authors: Mirjam Sophia Glessmer, Tor Eldevik, Kjetil Våge, Jan Even Øie Nilsen & Erik Behrens Between 1965 and 1990, the waters of the Nordic Seas and the subpolar basins of the North Atlantic Ocean freshened substantially. The Arctic Ocean also became less saline over this time, as a consequence of increasing runoff, but it is not clear whether flow from the Arctic Ocean was the main source of the Nordic Seas salinity anomaly. As a region of deep-water formation, the Nordic Seas are central to the Atlantic meridional overturning circulation, but this process is inhibited if the surface salinity is too low. Here we use the instrumental record of Nordic Seas hydrography, along with a global ocean–sea-ice model hindcast simulation, to identify the sources and magnitude of freshwater that has accumulated in the Nordic Seas since 1950. We find that the freshwater anomalies within the Nordic Seas can mostly be explained by less salt entering the southern part of the basin with the relatively saline Atlantic inflow, with seemingly little contribution from the Arctic Ocean. We conclude that hydrographic changes in the Nordic Seas are primarily related to changes in the Atlantic Ocean. We infer that if the Atlantic inflow and Nordic Seas both freshen similarly, this would render the Atlantic meridional overturning circulation relatively insensitive to Nordic Seas freshwater content.
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Springer Nature
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  • 8
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    Carbon limitation leads to suppression of first year oak seedlings beneath evergreen understory shrubs in Southern Appalachian hardwood forests (2005)
    Springer
    Details
    Publication Date: 2005-02-01
    Print ISSN: 1385-0237
    Electronic ISSN: 1573-5052
    Topics: Biology
    Published by Springer
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  • 9
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    Analysis of interactions between the invasive tree-of-heaven (Ailanthus altissima) and the native black locust (Robinia pseudoacacia) (2005)
    Springer
    Details
    Publication Date: 2005-03-01
    Print ISSN: 1385-0237
    Electronic ISSN: 1573-5052
    Topics: Biology
    Published by Springer
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  • 10
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    Summer water relations of the desert phreatophyte Prosopis glandulosa in the Sonoran Desert of southern California (1981)
    Springer
    Details
    Publication Date: 1981-01-01
    Print ISSN: 0029-8549
    Electronic ISSN: 1432-1939
    Topics: Biology
    Published by Springer
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