Fire influence on vegetation structure in north Patagonia rangelands

BRAN, D., G. CECCHI, L. GHERMANDI, J. AYESA, C. LOPEZ AND C. GITTINS

Cape Town, South Africa

Conferencia; IV Southern Connections Conference; 2004

Wildfires are frequent in north Patagonia, mainly in two regions: sSub-andean grasslands and eastern “Monte” shrublands.  In both regions fires and grazing may play an important role in vegetation structure. We carried out studies in two regions with the aim of knowing the post fire vegetation dynamics and grazing interactions. .   The first study site, a sub-andean grassland dominated by Stipa speciosa and Festuca pallescens, is located in Estancia San Ramon (mean annual temperature: 7,4ºC, mean annual precipitation: 580 mm,) and was affected by a fire in January 1999.  The second study site is located in Estación Vintter eastern “Monte”, a shrubland dominated by Larrea sp. and Condalia microphylla with Stipa tenuis in herbaceous layer (mean annual temperature: 15.2ºC, mean annual precipitation: 270 mm) and was affected by a fire in January 2001. In both sites burned areas were evaluated using Landsat-TM images., We carried out field studies assessing burn severity, grasses and shrubs resprouting capability, and early post-fire succession,.   According to our first results and  land use knowledge, we propose that in thesub-andean grassland, fire and grazing affect sinergically the relationship between dominant grasses, favouring Stipa speciosa.  This suggests that grazing and recurrent fires have spread Stipa speciosa grasslands over Festuca pallescens grasslands.  In the”Monte” region, fire and grazing seems to have opposite direction in the relationship between shrubs and grasses.  Fire would benefit grasses, and grazing benefits shrubs, so that history and intensity of these disturbances can explain different vegetation structure.