PARENT SESSION
Poster Session #5: Soil Ecology.
Monday, August 6, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall

The effects of harvester ants on nitrogen storage in Mojave Desert soils.

Jones, Jeremy¹, Wagner, Diane², ^{1 2}

ABSTRACT- Harvester ants transport seeds to their colonies and deposit debris near their nests, thereby redistributing organic matter and potentially impacting nutrient cycles in arid-land ecosystems. We examined the influence of the harvester ant, Pogonomyrmex rugosus, on soil nitrogen storage at two study sites in the Mojave Desert of southern Nevada. At the two sites, mean organic matter storage in ant nest soils ranged from 37.6 to 41.8 mgAFDM/gSoil and was significantly greater than both soils from under the dominant plant taxa (24.1 to 34.0 mgAFDM/gSoil) and soils from bare patches (13.6 to 20.6 mgAFDM/gSoil). Accumulation of inorganic nitrogen in ant nest soils was even more pronounced. At the Boulder City study site, mean inorganic nitrogen (nitrate + ammonium) storage in colony soils (130 &uscript;gN/gSoil) was two-fold greater than in soils under the dominant plant species (Larrea tridentata, 63 &uscript;gN/gSoil; Ambrosia dumosa, 56 &uscript;gN/gSoil) and 20-fold greater than in bare soils (6.4 &uscript;gN/gSoil). Similarly, at the Kane Springs study site, mean inorganic nitrogen storage in ant nest soils (48 &uscript;gN/gSoil) was nearly six-fold greater than under the dominant plant species (a bunch grass, Pleuroraphis ridiga, 8.4 &uscript;gN/gSoil) and nine-fold greater than in bare soils (5.2 &uscript;gN/gSoil). Harvester ants play an important role in deserts by creating nutrient-rich patches. This nutrient heterogeneity likely affects seedling recruitment and plant species distributions.

KEY WORDS: Deserts, Soils, Nitrogen, Ants