Post-fire vegetation change and bird use of a salt marsh in coastal Argentina

Abstract

Vegetation structure is an integral component of avian habitat selection. Therefore, structure changes caused by management practices can influence avian communities. The salt marshes of the pampas region of Argentina have experienced an increase in fire use as a management tool to improve cattle forage and to avoid accidental fires. A spring burn of 200 ha of salt marsh in Mar Chiquita Biosphere Reserve, Argentina, in September 1995, allowed us to compare the response of birds associated with two vegetation communities, one dominated by Spartina densiflora (Spartina marsh) and another dominated by Juncus acutus (Juncus marsh) from one month to one year post-burn. We recorded changes in plant species composition and vegetation structure (height and cover) at 40 days after the burn and every season for the subsequent year. Fire reduced total cover of both plant communities. Juncus marsh recovered pre-burn structure and bird community by one year post-fire. However, Spartina marsh recovery was incomplete in that period. Relative abundances of bird species that used unburned Juncus marsh were similar to those in burned Juncus marsh in the spring period one year after the burn. Plant height at the burned Spartina marsh did not reach that of the unburned Spartina in 12 months; red-capped wren-spinetail (Spartonoica maluroides), a rare tall-grass-dependent species, settled burned parcels at lower relative abundances than in unburned babitat. Because species that first use the burned patches are very common and widespread in other habitats, and excessive burning may reduce available habitat for endangered or rare species, prescribed burns should be avoided in this region.