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  • Coloniser species  (1)
  • Mediterranean climate  (1)
  • Mediterranean shrublands  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Effects of soil disturbance, fire and litter accumulation on the establishment of Cistus clusii seedlings (1997)
    Springer
    Plant ecology 131 (1997), S. 207-213 
    Details
    ISSN: 1573-5052
    Keywords: Coloniser species ; Dormancy ; Drought ; Fire ; Impermeable seeds coats ; Mediterranean climate ; Seed germination ; Temperature fluctuations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cistus clusii is an early successional shrub, the most drought-resistant species of Cistus which colonises perturbed areas in the southern Iberian Peninsula and regenerates entirely from seeds after a fire. Some of the factors controlling germination and seedling establishment were examined in a field experiment in which we tested the effect of soil disturbance, fire, and litter accumulation on seedling emergence. In a first experiment, soil disturbance and fire were applied to plots in the field with a factorial design in April 1992. In a second experiment, we measured the effect of adding C. clusii litter. The number of seedlings, annual plants and grasses, and the coverage of mosses were recorded in 1993 and 1994. Soil disturbance increased the number of C. clusii seedlings almost seven-fold but did not change the number of grasses, annual plants nor moss cover. Fire significantly increased the number of C. clusii seedlings only in combination with soil disturbance, and it did not affect the presence of annuals, grasses nor moss cover. Litter increased the number of C. clusii seedlings in the following two years. Overall, soil disturbance as a single factor had the most significant effect on seedling emergence, though plots disturbed and treated with fire had the highest number of seedlings, implying that germination of C. clusii seeds was enhanced by processes that alter the hard seed coat and break the physical dormancy imposed by the testa. In addition, recruitment of C. clusii was dependent on rainfall, as drought significantly reduced the number of seedlings appearing in winter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009779820845
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Dynamics of cohorts of cladodes and related effects on reproduction in the shrub Retama sphaerocarpa in semi-arid south-eastern Spain (2000)
    Springer
    Plant ecology 146 (2000), S. 105-115 
    Details
    ISSN: 1573-5052
    Keywords: Canopy dynamics ; Mediterranean shrublands ; Photosynthetic stems ; Semi-arid shrublands ; Seed production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in the size and age structure of the canopy of the leguminous shrub Retama sphaerocarpa in semi-arid south-eastern Spain were investigated by monitoring growth and survivorship of cladodes (photosynthetic stems) on marked shoots over a period of 26 months. Three basic morphological types of cladodes – long shoots, short shoots, and secondary short shoots – were distinguished. The canopy of the shrubs contained three annual cohorts of cladodes in spring and summer. The number and size of shoots produced each year was highly variable and was apparently related to the amount of rainfall during the preceding cool season. The spring cohort of 1994 produced only 37% of cladodes compared with 1993. Two cohorts of shoots were actually initiated in spring and late summer of each year, but the second cohort produced only 2–12% of the number of cladodes compared with the spring cohort. The proportions of the different cohorts in the canopy changed rapidly from April to August, but only slowly during the remainder of the year when only two annual cohorts remained after extensive litterfall in late summer. This late summer litterfall caused a substantial reduction in green canopy area (40–50%) which was achieved mainly be shedding of one year old cladodes. The life expectancy of cladodes decreased with increasing order of their morphological type from 850 ± 25 days in long shoots to 563 ± 4 days and 546 ± 9 days in short shoots and second order short shoots, respectively. Flowering and fruiting took place from May to July, almost exclusively on one year old cladodes, and coincided with the maximum development of the canopy. Flowering intensity was high in 1994, when individual shoots supported a mean number of approximately 150 flowers. Shoots produced an average of 12.6 ± 0.6 and 5.3 ± 1.0 fruits per shoot in 1993 and 1994, respectively. Most of the annual fruit crop (80–90%) was shed during litterfall in late summer. A proportion of 10–20% was retained in the canopy for up to 12 months, however, with some fruits persisting for more than 22 months.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009817100422
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    Paper (German National Licenses)
    Fulltext
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