Contributions of Leaf-Cutting Ants to Soil Fertility: Causes and Consequences

FARJI-BRENER, ALEJANDRO GUSTAVO; TADEY, MARIANA

Soil Fertility

Nova Science Publishers

Lugar: New York; Año: 2009; p. 81 - 91

Leaf-cutting ants modify soil fertility through two mechanisms. First, the building, enlargement, and maintenance of ant nests affect soil structure, porosity and density. Second, leafcutters collect and concentrate vegetal material inside their nests to maintain their fungus culture, the food for most of the colony. As a result of this process, ants generate a huge quantity of organic waste that is deposited in nest cavities or dumps on the soil surface. This organic waste show high nutrient content. The content of organic Carbon, Nitrogen, Potassium, Phosphorous, and Magnesium was, in average, between 20 and 50 times greater in refuse dumps compare to adjacent, non-nest soils. The process of waste deposition, thus, notably increases the nutrient content of the soils around nests. Consequently, plants in nest areas often show more abundance, growth rate, foliar and root biomass, and reproduction rate than plants outside nest areas. This positive effect on plants scale-up and affect the structure of vegetation assemblages and the balance between trees and herbs at landscape scale. Several factors affect the contribution of leaf-cutting ants to soil fertility. Particularly, extreme weather, low abundance of palatable vegetation for leafcutters, competition with introduced mammalian herbivores and frequent fires reduce ant foraging rates, nest abundance, and therefore the production of organic waste. Since leaf-cutting ant activity and nest density is strongly dependent on the availability of pioneer or ruderal plant species, the strength of their contribution to soil fertility could be more important in early successional environments and disturbed habitats. Ant-nest areas should be especially protected because they are hot spot of plant diversity and core of plant succession. From a restoration point of view, the nutrient-rich refuse dumps can be employed as a natural, free-access and ecologically sustainable fertilizer to improve soil fertility in degraded areas.