Seasonal And Diurnal Changes In Water Relations Parameters In Evergreen Chaparral Shrubs

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ISBN 13 :
Total Pages : 228 pages
Book Rating : 4.:/5 (55 download)

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Download or read book Temporal and Spatial Variability of Seed Weight, Water Relations, and Carbon Translocation in Ceanothus Shrubs of the California Chaparral written by and published by . This book was released on 1996 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: Patterns of variation in seed weight, water potential, and carbon translocation were investigated in Ceanothus shrubs of San Diego County, California. Four Ceanothus species (greggii, leucodermis, foliosus, and palmeri) showed seed weight differences among species, individuals, and branches. Among-branch patterns in C. greggii were shrub-specific rather than aspect-dependent. The most likely explanation was differential parental allocation among branches, but other genetic, physiological, and architectural effects may be involved. Seed weight variation may spread the risk of total seedling failure after fire. Diurnal and seasonal water potential measures among C. greggii shrubs differed in all seasons. Measures within shrubs were only uniform at predawn. Minimum water potentials occurred before solar noon in winter and spring, but increasingly later in the afternoon in summer and fall as the drought progressed. Differences within canopies were greatest in early morning and late afternoon, and seasonally largest in spring and summer, and least in fall. Canopy response to the solar track was modified seasonally by atmospheric moisture demand and soil water availability. Differentials were not thought to affect growth. Single branches of C. greggii shrubs were repeatedly labeled with 14CO2 from July to May. Label fixed in fall was translocated to shoots all around the canopy in winter coinciding with the initiation of new leaf growth after drought-relieving rains. In spring, virtually all newly fixed label was used for growth, reproduction, and maintenance, but it was not translocated to other shoots. No direction-specific, within-canopy spatial patterns of translocation were observed. Assimilation and storage in fall may be one reason chaparral shrubs maintain open stomates at low water potentials. Shrub-scale variations in soil depth and quality likely play a large role in determining among-shrub differences. The mostly overlooked spatial and temporal patterns within shrubs illustrate the complexity of canopy interaction with diurnal and seasonal changes in environmental variables. Canopy-wide patterns clearly present problems for extrapolation from the leaf to the whole-plant level and need further study.