Growth and foliar d super(15)N of a Mojave desert shrub in relation to soil hydrological dynamics

• Published in: Journal of arid environments 2010-11, Vol.74 (11), p.1569-1571
• Main Authors: Hamerlynck, E P, McAuliffe, J R
• Format: Article
• Language: English
• Subjects: Alluvial deposits; Aridity; Availability; Canopies; Deposition; Desert environments; Horizon; Hydrology; Larrea tridentata; Soil (material)
• ISSN: 0140-1963
• DOI: 10.1016/j.jaridenv.2010.06.001

Soil matric potential (q sub(matric)) was modeled for two years at four sites with different soil profile characteristics. Canopy volumes and foliar super(15)N ratios (d super(15)N) of Larrea tridentata were related to average soil water availability (q sub(matric)) and the modeled duration of available soil water (consecutive days q sub(matric) > -6.0 MPa). Weakly developed soils on young (Holocene) alluvial deposits had the longest duration (129 d) and highest q sub(matric) (-1.8 MPa), compared to soils with moderate horizon development in intermediate-aged (late Pleistocene) deposits (80 d, -4.3 MPa) and in soils with strong horizons on old (mid-late Pleistocene) deposits (20 d, -3.2 MPa). Plant canpoy volume was highest in weakly developed soils (2.23 m super(3) c 0.342 SE) than in moderately or strongly developed older soils (0.57 m super(3) c 0.082 SE; 0.56 m super(3) c 0.123 SE, respectively). The fourth site possessed possessed a soil with a silt- and clay-rich horizon beneath a strong stone pavement, and had the shortest, most water-limited regime (13 d; -5.5 MPa) and smallest plant canopies (0.46 m super(3) c 0.073 SE). Foliar d super(15)N variation was better explained by average q sub(matric) (R super(2) = 0.69; p , 0.001) than duration of available soil water (R super(2) = 0.49; p , 0.001). Together, these findings suggest soil hydrological regimes establish thresholds for plant growth, and plant N-dynamics are tightly coupled to desert soil hydrological characteristics.