INVESTIGADORES
TADEY Mariana
artículos
Título:
Indirect effects of exotic grazers: livestock decreases the nutrient content of refuse dumps of leaf-cutting ants through vegetation impoverishment
Autor/es:
TADEY, M.; A. G. FARJI-BRENER
Revista:
JOURNAL OF APPLIED ECOLOGY
Referencias:
Año: 2007 p. 1209 - 1218
ISSN:
0021-8901
Resumen:
Abstract
1.
We present evidence of how exotic grazers can indirectly change the nutrient availability
on the soil surface by affecting the quality of refuse dumps of leaf-cutting ants
through changes in vegetation. Understanding the mechanisms involved in this process
is vital to propose proper control and restoration practices.
2.
In the Monte Desert of Argentina, we sampled seven paddocks with similar environmental
conditions but different stocking rates (individuals ha
1
). In each paddock
we measured grazing intensity, plant species number and cover, leaf-cutting ant nest
density, leaf-cutting ant diet and the nutrient content of the external ant refuse dumps
and of the adjacent non-nest soils. We found higher content of N, C and P in refuse
dumps than in non-nest soils, but the strength of this effect decreased with an increase
in stocking rates. As stocking rate increased, plant richness and cover, the number of plant
species harvested by ants and the nutrient content of their refuse dumps all decreased.
Nest density was not affected by stocking rates.
3.
These results suggests that livestock reduce plant richness and cover through
grazing, affecting ant diet with the subsequent alteration of the nutrient content of their
external refuse dumps. A decrease in the nutrient quality of the refuse dumps may affect
plants that establish and grow on this substrate and the rate of nutrient cycling.
4.
Synthesis and applications
. We have shown that negative effects of exotic grazers on
plants may spread throughout native insect herbivores to affect soil nutrient availability.
These results can provide useful information to prevent soil impoverishment and restore
the nutrient content of soils in this managed system. A slight reduction in stocking rates
can restore the contribution of ants to soil fertility. Additionally, refuse dumps from
paddocks with low grazing levels should be employed as fertilizer to restore soil quality
in paddocks with high grazing intensities.