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  • 1985-1989  (86)
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  • 11
    Electronic Resource
    Electronic Resource
    Water use patterns of four co-occurring chaparral shrubs (1986)
    Springer
    Oecologia 70 (1986), S. 172-177 
    Details
    ISSN: 1432-1939
    Keywords: Water use ; Root distribution ; Water potential predawn ; Leaf conductance ; Quercus durata ; Heteromeles arbutifolia ; Adenostoma fasciculatum ; Rhamnus californica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mixed stands of chaparral in California usually contain several species of shrubs growing close to each other so that aerial branches and subterranean roots overlap. There is some evidence that roots are stratified relative to depth. It may be that root stratification promotes sharing of soil moisture resources. We examined this possibility by comparing seasonal water use patterns in a mixed stand of chaparral dominated by four species of shrubs: Quercus durata, Heteromeles arbutifolia, Adenostoma fasciculatum, and Rhamnus californica. We used a neutron probe and soil phychrometers to follow seasonal depletion and recharging of soil moisture and compared these patterns to seasonal patterns of predawn water potentials, diurnal leaf conductances, and diurnal leaf water potentials. Our results indicated that 1) Quercus was deeply rooted, having high water potentials and high leaf conductances throughout the summer drought period, 2) Heteromeles/Adenostoma were intermediate in rooting depth, water potentials, and leaf conductances, and 3) Rhamnus was shallow rooted, having the lowest water potentials and leaf conductances. During the peak of the drought, predawn water potentials for Quercus corresponded to soil water potentials at or below a depth of 2 m, predawn water potentials of Heteromeles/ Adenostoma corresponded to a depth of 0.75 m, and predawn water potentials of Rhamnus corresponded to a depth of 0.5 m. This study supports the concept that co-occurring shrubs of chaparral in California utilize a different base of soil moisture resources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379236
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  • 12
    Electronic Resource
    Electronic Resource
    Tissue water relations of four co-occurring chaparral shrubs (1986)
    Springer
    Oecologia 70 (1986), S. 527-535 
    Details
    ISSN: 1432-1939
    Keywords: Chaparral ; Osmotic potential ; Turgor ; Pressure-volume curve ; Dew-point hygrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Chaparral shrubs of California have a suite of morphological and physiological adaptations to withstand the prolonged summer droughts of a mediterranean climate. Not all species of chaparral have the same rooting depth and there is some evidence that those with shallow roots have tissue that is most tolerant to water stress. We tested this notion by comparing the tissue water relations of four co-occurring chaparral shrubs: Quercus durata, Heteromeles arbutifolia, Adenostoma fasciculatum, and Rhamnus californica. We used a pressure-volume technique and a dew-point hygrometer to metsure seasonal changes in osmotic potential when plant tissue was fully hydrated and osmotic potential at predawn, midday, and the turgor loss point. We also calculated seasonal changes in the minimum daily turgor potential, saturated weight/dry weight ratio of leaf tissue, and the bulk modulus of elasticity. We had information on the seasonal water use patterns and apparent rooting depths of these same four shrubs from a previous study (Davis and Mooney 1986). All evidence indicated that Rhamnus had shallow roots and Quercus deep roots. Our results indicated that the tissue water relations of our four co-occurring chaparral shrubs were not alike. Even though Rhamnus had shallow roots, it had the least xerophytic tissue. Seasonal osmotic potential and saturated weight/dry weight ratios were relatively high and bulk modulus of elasticity and minimum daily turgor potentials were low. Furthermore, even though Quercus had deep roots and experienced no seasonal water stress at our study site, its tissue water relations indicated relatively high tolerance to water stress. We conclude that seasonal drought tolerance of stem and leaf tissue of co-occurring chaparral shrubs does not necessarily correspond to rooting depth, to soil moisture resources available to the shrub, or to the degree of seasonal water stress experienced by the shrub.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379899
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  • 13
    Electronic Resource
    Electronic Resource
    Comparative water relations of adjacent california shrub and grassland communities (1985)
    Springer
    Oecologia 66 (1985), S. 522-529 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Much of the coastal mountains and foothills of central and southern California are covered by a mosaic of grassland, coastal sage scrub, and evergreen sclerophyllous shrubs (chaparral). In many cases, the borders between adjacent plant communities are stable. The cause of this stability is unknown. The purpose of our study was to examine the water use patterns of representative grasses, herbs, and shrubs across a grassland/chaparrel ecotone and determine the extent to which patterns of water use contribute to ecotone stability. In addition, we examined the effects of seed dispersal and animal herbivory. We found during spring months, when water was not limited, grassland species had a much higher leaf conductance to water vapor diffusion than chaparral plants. As the summer drought progressed, grassland species depleted available soil moisture first, bare zone plants second, and chaparral third, with one chaparral species (Quercus durata) showing no evidence of water stress. Soil moisture depletion patterns with depth and time corresponded to plant water status and root depth. Rabbit herbivory was highest in the chaparral and bare zone as indicated by high densities of rabbit pellets. Dispersal of grassland seeds into the chaparral and bare zone was low. Our results support the hypothesis that grassland species deplete soil moisture in the upper soil horizon early in the drought, preventing the establishment of chaparral seedlings or bare zone herbs. Also, grassland plants are prevented from invading the chaparral because of low seed dispersability and high animal herbivory in these regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379344
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  • 14
    Electronic Resource
    Electronic Resource
    Comparative physiology of burned and unburned Rhus laurina after chaparral wildfire (1986)
    Springer
    Oecologia 71 (1986), S. 63-68 
    Details
    ISSN: 1432-1939
    Keywords: Rhus ; Lignotuber ; Nitrogen ; Water relations ; Fire
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Laurel Sumac (Rhus laurina) is a dominant member of the coastal chaparral community of southern California that survives periodic burning by wildfires by resprouting from a lignotuber (root crown). We investigated the physiological basis for resprouting by comparing shoot elongation, leaf nitrogen content, tissue water status, leaf conductance to water vapor diffusion, and photosynthetic rates of post-fire R. laurina to those of adjacent unburned shrubs. Resprouts had higher rates of shoot elongation, leaf conductance, and photosynthesis than mature, unburned shrubs. Leaf nitrogen contents were elevated in burned shrubs even though their leaves developed interveinal chlorosis. A comparison of soil water potential to predawn water potential indicated that roots of R. laurina remain active below 2 m during the first summer drought after wildfire. Our results support the hypothesis that lignotubers not only contain dormant buds that develop into aerial shoots after wildfire but they also supply nutrient resources that enhance shoot elongation. Because R. laurina is relatively sensitive to drought, yet very successful in its rapid recovery after fire, maintaining an active root system after shoot removal may be the primary function of the massive lignotuber formed by this species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377322
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  • 15
    Electronic Resource
    Electronic Resource
    Differential survival of chaparral seedlings during the first summer drought after wildfire (1988)
    Springer
    Oecologia 76 (1988), S. 215-221 
    Details
    ISSN: 1432-1939
    Keywords: Chaparral ; Seedling establishment ; Water stress ; Drought ; Fire
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Big Pod Ceanothus (Ceanothus megacarpus) is an obligate seeder after fire; Laurel Sumac (Rhus laurina) is primarily a resprouter after fire. Both species commonly occur together in mixed stands and are dominant members of the coastal chaparral of southern California. We compared the mean survival of post-fire seedlings of each species during the first summer drought after fire and found C. megacarpus to have a mean survival of 54% while R. laurina had a mean survival of only 0.1%. Rooting dephs were similar between species but predawn water potentials and leaf temperatures were higher for R. laurina seedlings. Leaf temperatures for R. laurina reached a mean value of 46.8° C on hot, summer days, about 5° C higher than seedlings of C. megacarpus. By the end of the first growing season, 92% of all C. megacarpus seedlings had suffered herbivory compared to only 17% of all R. laurina seedlings. Herbivory did not appear to be the immediate cause of seedling mortality. Transect data indicated that full recovery of prefire species composition and density at our study site was likely but the mode of recovery was different for the species examined. R. laurina recovered primarily by sprouting, C. megacarpus totally by seedling establishment and a third species, Adenostoma fasciculatum (chamise), by a combination of sprouting and seedling establishment. We attribute the higher mortality of R. laurina seedlings to the greater sensitivity of its tissue to water stress. It may be that differential survival of shrub seedlings and differential modes of reestablishment after fire play an important role in maintaining species diversity in the chaparral communities of coastal, southern California.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379955
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  • 16
    Electronic Resource
    Electronic Resource
    Tissue water relations of three chaparral shrub species after wildfire (1989)
    Springer
    Oecologia 80 (1989), S. 303-308 
    Details
    ISSN: 1432-1939
    Keywords: Chaparral ; Osmotic potential ; Turgor ; Pressure-volume curve ; Dew-point hygrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We compared the tissue water relations among resprouts and seedlings of three chaparral species during the first summer drought after wildfire. Two of the species, Rhus laurina and Ceanothus spinosus recover after fire by a combination of resprouting and seedling establishment (facultative resprouters), whereas a third species, Ceanothus megacarpus recovers by seedling establishment alone (obligate seeder). Our objectives were to document any differences in tissue water characteristics that might arise between resprouts and seedlings and to test the hypothesis that seedlings of obligate seeders develop more drought tolerant characteristics of their tissues than seedlings of facultative resprouters. We found that resprouts had much higher predawn values of water potential, osmotic potential, and turgor potentials than seedlings. Predawn turgor potentials of resprouts were 1.5 MPa through July and August when turgor potentials for seedlings remained near 0 MPa. During summer months, midday water potentials were 2 to 3 MPa higher for resprouts than seedlings and midday conductances of resprouts were two to five fold greater than those of seedlings. Even though resprouts did not experience severe water stress like seedlings, their tissue water characteristics, as determined by pressure-volume curve analyses, were similar by the peak of the drought in August. Further-more, the tissue water characteristics of seedlings from the obligate seeder, C. megacarpus, were similar to those of facultative resprouters — R. laurina, and C. spinosus. We attribute the observed differences in plant water status between resprouts and seedlings to differences in rooting depths and access to soil moisture reserves during summer drought. We conclude that the higher growth rates, photosynthetic performance, and survivorship of postfire resprouts are primarily a result of higher water availability to resprouting tissues during summer months. It appears that the greater seedling survivorship during summer drought observed for the obligate seeder, C. megacarpus, is not associated with more favorable tissue water characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379031
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  • 17
    Electronic Resource
    Electronic Resource
    Recovery patterns of three chaparral shrub species after wildfire (1989)
    Springer
    Oecologia 80 (1989), S. 309-320 
    Details
    ISSN: 1432-1939
    Keywords: Chaparral ; Seedling survival ; Root depth ; Rhus ; Ceanothus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In a mature, even aged stand of mixed chaparral, Rhus laurina (facultative resprouter) had consistently higher water potentials and deeper roots than Ceanothus spinosus (facultative resprouter) and Ceanothus megacarpus (obligate seeder). For two years following a wildfire, the same stand of chaparral had resprouts with higher survivorships, predawn water potentials, stomatal conductances, photosynthetic rates and shoot elongation rates than seedlings. Supplemental irrigation of seedlings during summer months removed differences between resprouts and seedlings suggesting that the cause of such differences was limited water availability to the shoot tissues of seedlings. After two years of postfire regrowth, mean seedling survivorship for the obligate seeder (C. megacarpus) was 42%, whereas seedling survivorship for facultative resprouters was only 18% (C. spinosus) and 0.01% (R. laurina). Our results are consistent with the hypothesis that lack of resprouting ability among obligate seeders is offset by an enhanced ability to establish seedlings after wildfire, allowing obligate seeders to maintain themselves in mixed populations through many fire cycles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379032
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  • 18
    Electronic Resource
    Electronic Resource
    The oscillator strength of theC 2 Swan bands (1985)
    Springer
    The European physical journal 321 (1985), S. 75-77 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Litetimes of six individual rotational levels in theν=0 vibrational level of the3 π g state of C2 were measured by monitoring the fluorescent decay after pulsed laser excitation. A value of 92±5 ns was obtained, 25% lower than previous measurements. The corresponding oscillator strength for the Swan (0-0) band isf 00=0.032±0.002, in agreement with recent theoretical work.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01411947
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  • 19
    Electronic Resource
    Electronic Resource
    Stability criteria for swirl flows with free surfaces (1986)
    Springer
    Zeitschrift für angewandte Mathematik und Physik 37 (1986), S. 597-607 
    Details
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Description / Table of Contents: Résumé Un écoulement tourbillonnaire admettant une surface libre est susceptible de présenter des instabilités du type centrifuge, capillaire et Rayleigh-Taylor. Notre travail étend les critères de stabilité obtenus par Rayleigh et Synge respectivement pour des fluides parfaits et visqueux aux cas des configurations à surface libre.
    Notes: Abstract A swirl flow with a free surface is susceptible to centrifugal, capillary, and Rayleigh-Taylor instabilities. The present work extends the stability criteria of Rayleigh and Synge for inviscid and viscous fluids, respectively, to free-surface configurations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00945432
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  • 20
    Electronic Resource
    Electronic Resource
    Dilepton and trilepton production by antineutrinos and neutrinos in neon (1985)
    Springer
    The European physical journal 29 (1985), S. 15-28 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A sample of over 25,000 fully measured neutrino and antineutrino charged current interactions in BEBC includes 192 dilepton candidates. The prompt signal after subtraction of background is 41 ±7µ+ e -, 35±7µ+µ- events from $$\bar v$$ interactions, and 32±7µ-µ+ events from ν interactions. There are 2 trileptons, µ-µ- e + and µ-µ-µ+. Results are compared with other experimental data and with the standard model. Limits to prompt like sign µ+ e +, µ+µ+ and µ-µ- signals are given and compared with other experiments and with theoretical calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01571374
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