Effects of surface and sub-surface soil horizons on the seasonal performance of Larrea tridentata (creosotebush).

Hamerlynck, Erik P.; Mcauliffe, Joseph R.; Smith, Stanley D.

1. In warm arid and semiarid environments, the accumulation of clay minerals produces increasingly well developed soil horizons with the passage of time. Differences in the strength of development of two prominent soil horizons, silt- and clay-rich surface vesicular (Av), and clay-enriched subsurface argillic (Bt), may strongly influence the amount and seasonal continuity of plant-available water and the physiological activity of long-lived desert shrubs. Three sites were selected on an alluvial piedmont (bajada) in the Mojave Desert that varied in surface and subsurface horizon development. The first site, a deep deposit of stabilized dune sand, entirely lacked soil horizon development. The second site had a well developed surface stone pavement and underlying Av horizon, but lacked an argillic horizon in the sandy subsoil. The third had a well developed surface pavement and Av horizon, and a deeper, well developed clay-rich argillic horizon. Seasonal water potential and gas-exchange responses of the evergreen desert shrub Larrea tridentata [DC.] Cov., and volumetric soil water content (θ), were measured monthly in 1996 on these three soils in order to test the hypothesis that desert pavements, Av and subsurface Bt horizons differentially affect the effectiveness and utilization of seasonal precipitation. 2. Predawn and midday water potentials (Ψ[sub pd] and ψ[sub mid]), net photosynthetic rates (A[sub net]), and stomatal conductances (g[sub s]) in L. tridentata were highest in the deep, sandy dune soils lacking horizons that could restrict surface and subsurface infiltration. Plants growing in these soils also showed no physiological response to summer precipitation events. Following a single large precipitation event during the growing season (3·8 cm), the water potentials, A[sub net] and g[sub s] in L. tridentata were similar in the first (sand dune) and second (pavement and Av horizon) sites. However, plant performance on these so...

SOIL ecology; CREOSOTE bush; PLANT ecophysiology; ECOPHYSIOLOGY

Functional Ecology, 2000, Vol 14, Issue 5, p596

0269-8463

Academic Journal

10.1046/j.1365-2435.2000.t01-1-00469.x