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Large near-surface nitrate pools in soils capped by desert pavement in the Mojave Desert, California

¹ Soil & Water Sciences Program, Department of Environmental Sciences, University of California–Riverside, Riverside, California 92521-0424, USA
² University of California Cooperative Extension, Inyo-Mono Counties, 207 West South Street, Bishop, California 93514, USA
³ Soil & Water Sciences Program, Department of Environmental Sciences, University of California–Riverside, Riverside, California 92521-0424, USA

View larger version (64K): [in this window] [in a new window]   Figure 1. Photographs of (A) desert pavement landscape in Pinto Basin including nondesert pavement patches around shrubs ("shrub islands") and sampling excavations at PB1 and PB2 (PB—Pinto Basin), (B) desert pavement overlying soil at PB1, and (C) soil without desert pavement near shrub at PB2. Desert pavement forms a tight mosaic that severely impedes infiltration, while lack of pavement and extensive animal burrowing under shrubs (creosote bush, Larrea tridentata) produce a highly permeable soil. In (A), PB1 and PB2 are 38 m apart and the creosote bush is 1 m high. In (B) and (C), scale tape is marked in 10 cm increments.

View larger version (23K): [in this window] [in a new window]   Figure 2. Map showing sampled locations in southeastern California. FM—Fry Mountains, CV—Cima volcanic field, PB—Pinto Basin.

View larger version (21K): [in this window] [in a new window]   Figure 3. Nitrate-N (NO3-N) and chloride (Cl–) concentration profiles for soils with (CV1, PB1, FM1) and without (CV2, PB2, FM2) desert pavement at locations indicated in Figure 2. Values are for water extracts of fine earth fraction (<2 mm diameter). Sites represent a variety of common geomorphic settings in southeastern California, including a 580,000-yr-old lava flow (CV), an alluvial fan (PB), and a mountain range (FM).

View larger version (20K): [in this window] [in a new window]   Figure 4. Conceptual model of near-surface hydrology leading to NO3– distribution patterns in desert pavement landscape.