How do riparian woody seedlings survive seasonal drought

• Published in: Oecologia Vol. 164; no. 3; pp. 579 - 590
• Main Authors: Stella, John C, Battles, John J
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Berlin/Heidelberg : Springer-Verlag 01.11.2010; Springer; Springer-Verlag; Springer Nature B.V
• Subjects: Analysis; Animal and plant ecology; Animal, plant and microbial ecology; Applied sciences; Aquatic resources; Arid regions; Arid zones; Biological and medical sciences; Biomass; Biomedical and Life Sciences; Buildings. Public works; California; Climate; Cottonwood and willow; Dehydration; Desiccation; Drawdown; Drought; Drought resistance; Droughts; Dry season; Ecology; ecophysiology; Ecosystem; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; General aspects; Hydraulic constructions; Hydrology/Water Resources; Leaves; Life Sciences; PHYSIOLOGICAL ECOLOGY - ORIGINAL PAPER; Plant growth; Plant Leaves - growth & development; Plant Leaves - metabolism; Plant Leaves - physiology; Plant Roots - growth & development; Plant Roots - metabolism; Plant Roots - physiology; Plant Sciences; Plant Shoots - growth & development; Plant Shoots - metabolism; Plant Shoots - physiology; Plants; Populus - growth & development; Populus - metabolism; Populus - physiology; Populus fremontii; Ratios; Regression Analysis; Relative abundance; Riparian forests; River flow; River flow control. Flood control; River regulation; River regulations; Rivers; Root growth; Sago; Salicaceae; Salix - growth & development; Salix - metabolism; Salix - physiology; Salix gooddingii; Sand bars; Seasons; Seedlings; Seedlings - growth & development; Seedlings - metabolism; Seedlings - physiology; Semiarid lands; Species Specificity; Stress, Physiological; Trees; Water - metabolism; Water Movements; Water stress; Water table; Water tables; Water use; water use efficiency; California; USA, California; USA, California, San Joaquin Basin; Drought stress; Water use efficiency; River regulation; Ecophysiology; Cottonwood and willow; Riparian; Seasonal variation; Riverflow control; Plant juvenile growth stage; Drought; Water stress; Survival
• ISSN: 0029-8549; 1432-1939
• DOI: 10.1007/s00442-010-1657-6

In semi-arid regions, a major population limitation for riparian trees is seedling desiccation during the dry season that follows annual spring floods. We investigated the stress response of first-year pioneer riparian seedlings to experimental water table declines (0, 1 and 3 cm day⁻¹), focusing on the three dominant cottonwood and willows (family Salicaceae) in California's San Joaquin Basin. We analyzed growth and belowground allocation response to water stress, and used logistic regression to determine if these traits had an influence on individual survival. The models indicate that high root growth (>3 mm day⁻¹) and low shoot:root ratios (<1.5 g g⁻¹) strongly predicted survival, but there was no evidence that plants increased belowground allocation in response to drawdown. Leaf δ¹³C values shifted most for the best-surviving species (net change of +3.5 per mil from −30.0 ± 0.3 control values for Goodding's willow, Salix gooddingii), implying an important role of increased water-use efficiency for surviving water stress. Both S. gooddingii and sandbar willow (S. exigua) reduced leaf size from controls, whereas Fremont cottonwood (Populus fremontii) sustained a 29% reduction in specific leaf area (from 13.4 to 9.6 m² kg⁻¹). The functional responses exhibited by Goodding's willow, the more drought-tolerant species, may play a role in its greater relative abundance in dry regions such as the San Joaquin Basin. This study highlights the potential for a shift in riparian forest composition. Under a future drier climate regime or under reduced regulated river flows, our results suggest that willow establishment will be favored over cottonwood.