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  • Springer  (6)
  • Cambridge University Press  (1)
  • 1990-1994  (7)
  • 1
    Electronic Resource
    Electronic Resource
    Water and nitrogen dynamics in an arid woodland (1994)
    Springer
    Oecologia 99 (1994), S. 233-242 
    Details
    ISSN: 1432-1939
    Keywords: Cryptobiotic crust ; Desert ecology ; Nitrogen cycle ; Stable isotopes ; Water source
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Arid environments are characterized by spatial and temporal variation in water and nitrogen availability. differences in δ15N and δD of four co-occurring species reveal contrasting patterns of plant resource acquisition in response to this variation. Mineralization potential and nitrogen concentration of surface soils associated with plant canopies were greater than inter-canopy locations, and values decreased with increasing depth in both locations. Mineralization potential and nitrogen concentration were both negatively correlated with soil δ15N. The spatial variation in soil δ15N caused corresponding changes in plant δ15N such that plant δ15N values were negatively correlated with nitrogen concentration of surface soils. Plants occurring on soils with relatively high nitrogen concentrations had lower δ15N, and higher leaf nitrogen concentrations, than plants occurring on soils with relatively low nitrogen concentrations. Two general temporal patterns of water and nitrogen use were apparent. Three species (Juniperus, Pinus andArtemisia) relied on the episodic availability of water and nitrogen at the soil surface. δ15N values did not vary through the year, while xylem pressure potentials and stem-water δD values fluctuated with changes in soil moisture at the soil surface. In contrast,Chrysothamnus switched to a more stable water and nitrogen source during drought. δ15N values ofChrysothamnus increased throughout the year, while xylem pressure potentials and stem-water δD values remained constant. The contrasting patterns of resource acquisition have important implications for community stability following disturbance. Disturbance can cause a decrease in nitrogen concentration at the soil surface, and so plants that rely on surface water and nitrogen may be more susceptible than those that switch to more stable water and nitrogen sources at depth during drougnt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00627735
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  • 2
    Electronic Resource
    Electronic Resource
    Water relations of stem succulent trees in north-central Baja California (1990)
    Springer
    Oecologia 82 (1990), S. 299-303 
    Details
    ISSN: 1432-1939
    Keywords: Succulent ; C3 trees ; Capacitance ; Baja California ; Idria collumnaris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Water relations of several stem succulent trees were measured in north-central Baja California in comparisons to other growth forms in the same habitat. Our research concentrated on three stem succulent species (Idria collumnaris, Pachycormus discolor and Bursera microphylla) each with a different succulent stem morphology. The stem succulent trees had 1 to 4 kg H2O/m3 of trunk while the other trees and shrubs in the same habitat had 0.6 to 0.8 kg H2O/m3. The diurnal and seasonal variation in leaf water potential was small for the stem succulent species in comparison to deciduous and evergreen species as a consequence of the stem-water, buffering capacity. In addition, the leaf conductance of the stem succulent species was low (60 mmol m−2 s−1) and yet, the leaf conductance decreased through the day similar to adjacent evergreen and deciduous species. The leaves of the stem succulent trees lost turgor at low saturated water deficits (0.06 to 0.14), had comparatively high osmotic potentials, and high values of elastic modulus in comparison to adjacent evergreen and deciduous species. The stem acts as an important buffering mechanism allowing for the maintenance of leaf turgor in these stem succulent trees. The low transpiration rates of the stem succulent trees may be a mechanism to minimize leaf saturated water deficit and extend leaf longevity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317474
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  • 3
    Electronic Resource
    Electronic Resource
    A break in the nitrogen cycle in aridlands? Evidence from δp15N of soils (1993)
    Springer
    Oecologia 94 (1993), S. 314-317 
    Details
    ISSN: 1432-1939
    Keywords: δ15N ; Cryptobiotic crusts ; Deserts ; Nitrogen cycling ; Rayleigh distillation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the content and isotopic composition of nitrogen within soils of a juniper woodland and found that a cryptobiotic crust composed of cyanobacteria, lichens, and mosses was the predominant source of nitrogen for this ecosystem. Disturbance of the crust has resulted in considerable spatial variability in soil nitrogen content and isotopic composition; intercanopy soils were significantly depleted in nitrogen and had greater abundance of 15N compared to intra-canopy soils. Variations in the 15N/14N ratio for inter- and intra-canopy locations followed similar Rayleigh distillation curves, indicating that the greater 15N/14N ratios for inter-canopy soils were due to relatively greater net nitrogen loss. Coverage of cryptobiotic crusts has been reduced by anthropogenic activities during the past century, and our results suggest that destruction of the cryptobiotic crust may ultimately result in ecosystem degradation through elimination of the predominant source of nitrogen input.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317104
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  • 4
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    A break in the nitrogen cycle in aridlands? Evidence from ?p15N of soils (1993)
    Springer
    Details
    Publication Date: 1993-06-01
    Print ISSN: 0029-8549
    Electronic ISSN: 1432-1939
    Topics: Biology
    Published by Springer
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  • 5
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    Water and nitrogen dynamics in an arid woodland (1994)
    Springer
    Details
    Publication Date: 1994-01-01
    Print ISSN: 0029-8549
    Electronic ISSN: 1432-1939
    Topics: Biology
    Published by Springer
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  • 6
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    Water relations of stem succulent trees in north-central Baja California (1990)
    Springer
    Details
    Publication Date: 1990-03-01
    Print ISSN: 0029-8549
    Electronic ISSN: 1432-1939
    Topics: Biology
    Published by Springer
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  • 7
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    Relations of carbon isotope discrimination and other physiological traits to yield in common bean (Phaseolus vulgaris) under rainfed conditions (1994)
    Cambridge University Press
    Details
    Publication Date: 1994-04-01
    Description: SUMMARYAlthough direct selection for seed yield under water deficit can result in genetic gains in the common bean (Phaseolus vulgaris L.), progress could be enhanced through selection for additional traits that are related to underlying mechanisms of adaptation to water deficit. Carbon isotope discrimination (Δ) has received considerable attention as an indicator of water use efficiency and adaptation to water deficit. To test the utility of Δ as a selection criterion, Δ and other traits were measured in F2 and F3 generations of a nine-parent diallel grown under rainfed conditions at two locations in Colombia with contrasting soil types. An irrigated trial was also conducted at one location. Significant (P 0·05) differences among parents, F2 and F3 were found for carbon isotope discrimination (Δ), leaf optical density (OD), leaf nitrogen (N) and potassium (K) concentrations, relative duration of pod-filling period (RDPF), shoot dry weight (SDW) and harvest index (HI). Effect of location and water regime and their interactions with genotype were also frequently significant. Heritability estimates, determined by regressing the F3 on the F2, ranged from 0·11±011 (S.E.) to 0·33 ±0·10 for OD, 0·22 ± 0·07 to 0·44±0·09 for N, 0·04±0·05 to 0·29±0·08 for K, 0·40 ± 0·08 to 0·43 ± 0·15 for RDPF and 0·30±0·22 to 1·00±0·24 for SDW. All values for Δ and HI did not differ significantly from zero. Correlations between seed yield and OD and RDPF were negative, whereas those with N, K, SDW, and HI were positive. For all traits, mean square values for general combining ability (GCA) were usuall significant and larger than those for specific combining ability (SCA). All significant GCA effects for Δ for ‘Rio Tibagi’, ‘San Cristobal 83’ and ‘Apetito’ were negative, while those for ‘Bayo Rio Grande’, ‘Bayo Criollo del Llano’, ‘Durango 222’ and BAT1224 were positive. Although Δappears unsuitable as an indirect criterion for selection for yield under water deficit, further study of genotypes exhibiting contrasting values of A might reveal differences in mechanisms of adaptation to water deficits, thus leading to other selection criteria or identification of valuable parental lines.
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Cambridge University Press
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