Late Holocene fire regime reconstruction and vegetation dynamics of southern Monte desert region

Abstract

This work presents the first Monte desert palaeofire record from an ephemeral northern Patagonia pond called Bajo de la Quinta (40° 55′ 42″S; 64° 20′ 19″W). The aims of this study are (1) to reconstruct past fire regime changes related to vegetation variability during the last 4000 cal yrs BP for the southern Monte region; (2) to discuss the importance of climatic versus anthropogenic control of fire regime at different periods; and (3) to integrate these results with other fossil pollen sequences located in North Patagonia (between 39° and 43°S), to infer centennial to millennial-scale changes in vegetation, linked to major palaeoclimatic variability. Long-scale fire-vegetation changes have characterised the southern Monte desert modifying vegetation intra-community patches distribution. The heterogeneous two-phase mosaic shrubland distribution is more resilient to fire at centennial to millennial scales than homogeneous high vegetation coverage. Southern Monte desert presents current fire regime characteristics since the last two centuries, which may be related to livestock introduction and the subsequent increase in human-induced- fires and changes in biomass availability. Also, the use of the composite Nothofagus pollen abundance index and the comparison between sequences located along the west-east precipitation gradient of North Patagonia (between 39° and 43°S), suggests synchronous but in opposite direction humidity availability long term changes affecting vegetation and fire behavior in Northern Patagonia during the Late Holocene.