PARENT SESSION
Poster Session #5: Soil Ecology.
Monday, August 6, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall
120
Harvester ants and soil nutrients: Effects of colony age and size on nitrogen storage.
Wagner, Diane1, Jones, Jeremy2, Gordon, Deborah3, 1 2 3
ABSTRACT- Harvester ants are common in arid areas of North America. Colonies can live 15-20 years, during which they deposit organic materials, such as seed husks and waste products, near the nest. We studied how the storage of soil mineral nitrogen (nitrate and ammonium) changes in ant nest soils as colonies age. The study was conducted on a harvester ant population (Pogonomyrmex barbatus) in which all colony ages are known. Nest mound size was positively related to colony age, indicating that as colonies grow older, they affect a greater soil area. The concentration of mineral nitrogen in ant nest soils (80.7 &uscript;g/g) was 10-fold higher, on average, than that of control soils sampled several meters away (8.8 &uscript;g/g). Mineral nitrogen storage in ant nest soils, relative to controls, increased with colony age, suggesting that nutrients accumulate in ant nest soils over time. In addition, the difference in nitrogen concentration between nest and control soils in individual colonies increased from one sampling year to the next, as would be expected if nutrients accumulated in ant nests as colonies age. When colonies die, nutrient-rich nest sites can be colonized by plants. The results suggest that changes in age structure, as well as density, could have important effects on the distribution of soil nutrients over space.
KEY WORDS: Deserts, Soils, Nitrogen, Ants