Fire incidence along an elevation gradient in the mountains of central Argentina

ARGAÑARAZ JUAN P; CINGOLANI AM; BELLIS, LM; GIORGIS, MA

ECOLOGÍA AUSTRAL

ASOCIACIÓN ARGENTINA DE ECOLOGÍA

Lugar: Buenos Aires; Año: 2020

0327-5477

In mountain ecosystems, vegetation distributionalong elevation has been traditionally interpreted in terms of the decreasingtemperature from base to top, but wildfires may co-vary with the elevationgradient, also playing an important role. In the mountains ofcentral Argentina (500-2800 m a.s.l.) wildfires are one of the main disturbances,which may have an important role in shaping vegetation dynamics alongelevation. However, to date no study has described the fire patternalong the elevation gradient. We compared fireincidence among five elevation intervals using an 18-year spatiallyexplicit fire database derived from remote sensing. For each interval, wediscarded unburnable areas and calculated fire incidence per year as thepercentage of burned area. Fire incidence showed ahump-shaped pattern along the elevation gradient. The highest fire incidenceoccurred at intermediate elevations, in the 1301-1700 m and 901-1300 mintervals, with averages of 3.2 and 2.7% of the area being burned annually,respectively. The lowest fire incidence occurred at the lowest interval (500 -900 m), with 1.3% being burned annually on average. The greater fire incidenceobserved at intermediate elevations is consistent with a sharp increase in the cover of grasslands above 900 m a.s.l., with an associatedreduction in forest occupation. Towardshigher elevations, the lower fire incidence is consistent with the presence oftopographic breaks, greater proportion of unburnable surfaces that work asfirebreaks and moister conditions. The greater fire incidence observed atintermediate elevations may be limiting forest expansion in those areas. Athigher elevations the low forest cover may be explained by a combination offire and livestock pressure. Our study is the first to show how fire incidencevaries along the complete elevation gradient, bringing an important tool tounderstand vegetation distribution and plan future conservation and restorationstrategies