Document: JON-3-58-4

Soil resource heterogeneity in the Mojave Desert.

TITUS, J.H.* ^1,2, R.S.NOWAK ¹ and S.D.SMITH ²

University of Nevada, Reno, Reno, NV 89557 ¹
University of Nevada, Las Vegas, Las Vegas, NV 89154-4004 ²

Abstract:
Heterogeneity of soil resources was investigated in the Mojave Desert at the Nevada Test Site to better understand soil attributes of a research site that is currently being established to study the effects of global change on desert ecosystems. In the Mojave Desert, belowground resources are assumed to be spatially heterogeneous. Six soil samples were collected at each of eight sites at three locations 0.7km apart in a Larrea tridentata-Ambrosia dumosa community. The sites were as follows: mixed shrubs with no mammal burrows, mixed shrubs with mammal burrows, Larrea tridentata, Lycium pallidum, Ambrosia dumosa, Pleuraphis rigida, interspaces and washes. The following soil parameters were assessed: OM, pH, CEC, NH₄, NO₃, PO₄, K, Na, Mg, Ca, litter, particle size, and mycorrhizal inoculum potential (MIP) and spore density. Infiltration was assessed at a subset of the sites. All of the parameters differed across sites (P<0.001) with soil nutrients (except for Ca), OM and litter higher in soils collected below shrubs compared to other sites. Shrubs with mammal burrows had significantly more N (52 ppm NO₃ and 5ppm NH₄) and PO₄ (21ppm) than other sites. Wash and interspace soils contained very low N and P levels. Mg, Na, pH (8.4) and CEC were highest in Lycium soils. Ca levels were the highest in wash soils. Spore densities were low; Lycium soils contained more spores (12 spores/10g soil) than other sites (<1 spore/10g soil). Wash and interspace soils did not contain spores but had MIP values similar to the other sites indicating that mycorrhizal propagules are present. Interspace soils were fine grained and wash soils coarse grained. The presence of a shrub strongly influences soil characteristics with higher levels of nutrients and intermediate particle size distributions. Burrows increased nutrient levels. Lycium also appeared to influence soil properties with higher levels for several soil parameters particularly spores. Except for spore density, a significant location effect for all of the soil parameters occurred and interactions between site and location were common. Thus, patterns of resource heterogeneity differ greatly between nearby areas in desert ecosystems.

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This abstract is being presented at: 3:30 PM in session:
Poster Session #15: Nutrient Cycling.