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United States Department of Agriculture (USDA) 2002

THE EFFECT OF HARVESTER ANT NESTS ON NITROGEN CYCLING IN ARID RANGELAND SOILS

Harvester Ant Nests Nitrogen Rangeland

United States Department of Agriculture (USDA) Research, Education & Economics Information System (REEIS)

Titre : THE EFFECT OF HARVESTER ANT NESTS ON NITROGEN CYCLING IN ARID RANGELAND SOILS

Identification : ALKR-2003-05062

Pays : Etats Unis

Durée : Nov 1, 2002 à Aug 31, 2004

Domaine : Soil, Plant, Water, Nutrient Relationships ; Rangelands and grasslands, general ; 0110 - Soil ; Insects ;

Partenaire : UNIVERSITY OF ALASKA FAIRBANKS,AK 99775

Objectifs
The goal of this research is to understand the effects of a common, soil-dwelling animal species on nutrient cycling and long-term soil quality. The study focuses on the role of the harvester ant (Pogonomyrmex) in arid grassland and shrublands in the Mojave and Chihuahuan Deserts, easily degraded habitats of concern to both ranchers and environmentalists. Of particular concern is nitrogen, which limits primary productivity in North American deserts when water is available, and which is particularly subject to loss in hot, dry, grazed lands. Since receiving this grant, we have made substantial progress toward our goal.
Using a combination of field and laboratory experiments, we have found the following. (1) Ant nests are extremely nutrient-rich, containing much higher concentrations of a soil nutrients than even soils under vegetation (Wagner & Jones in prep.). (2) Ant activity increases the nutrient content of soils in a linear fashion over the 15-20 year lifespan of the colony, underscoring the importance of animal population age structure to ecosystem function (Wagner & Jones, in review). (3) Rates of mineralization and nitrification are significantly higher in ant nest soils than in soils of other microsites (Wagner & Jones in prep.). (4) Surface soils of ant nests are lost to erosion at a lower rate than those in interspaces. (5) Denitrification can occur at appreciable rates in Mojave Desert ant nest soils and under plants when water is available. Controls on denitrification vary among microsites : C limits denitrification in ant nest soils, while N limits denitrification under vegetation.
Our objectives for the last year of the project (2002-2003, no-cost extension year) are as follows. (1) Complete an ongoing field experiment measuring microsite-specific rates of organic matter decomposition at 2 Mojave study sites. As the link between organic matter accretion and mineralization, decomposition is an extremely important factor in understanding the role of ants in nutrient cycling. (2) Continue ongoing work to compare microbial respiration and biomass in major microsites (ant nests, under vegetation, bare soils). The differences in nitrogen transformation rates that we have detected in the past 3 years strongly suggest that ant nests alter the microbial community. We wish to test this hypothesis in order to understand the effects of ant nests on soil biodiversity and function. (3) Compare the biodiversity of soil bacteria present in each of the major microsites at each of the two Mojave desert sites. (4) Continue to synthesize, write, and submit results for publication.

Présentation : USDA

Page publiée le 26 octobre 2015, mise à jour le 30 octobre 2017