Incidencia del fuego en un gradiente altitudinal de las sierras del centro de la Argentina

Abstract

In mountain ecosystems, vegetation distribution along elevation has been traditionally interpreted in terms of the decreasing temperature from base to top, but wildfires may co-vary with the elevation gradient, also playing an important role. In the mountains of central Argentina (500-2800 m a. s. l.) wildfires are one of the main disturbances, which may have an important role in shaping vegetation dynamics along elevation. However, to date, no study described the fire pattern along the elevation gradient. We compared fire incidence among five elevation intervals using an 18-year spatially explicit fire database derived from remote sensing. For each interval, we discarded unburnable areas and calculated fire incidence per year as the percentage of burned area. Fire incidence showed a hump-shaped pattern along the elevation gradient. The highest fire incidence occurred at intermediate elevations, in the 1301-1700 m and 901-1300 m intervals, 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 incidence observed at intermediate elevations is consistent with a sharp increase in the cover of grasslands above 900 m a. s. l., with an associated reduction in forest occupation. Towards higher elevations, the lower fire incidence is consistent with the presence of topographic breaks, greater proportion of unburnable surfaces that work as firebreaks and moister conditions. The greater fire incidence observed at intermediate elevations may be limiting forest expansion in those areas. At higher elevations the low forest cover may be explained by a combination of fire and livestock pressure. Our study is the first to show how fire incidence varies along the complete elevation gradient, bringing an important tool to understand vegetation distribution and plan future conservation and restoration strategies.

Flora vascular de las montañas de Córdoba (Argentina): características y distribución de las especies a través del gradiente altitudinal

“…El paisaje de estas montañas se encuentra dominado por un complejo mosaico de diferentes fisonomías y ensambles florísticos que varían a través del gradiente altitudinal y de los gradientes geográficos. Estas variaciones, además de asociarse con cambios en los factores ambientales, también se relacionan con la presencia de disturbios antropogénicos y con la invasión de especies exóticas leñosas (Cingolani et al, 2004(Cingolani et al, , 2008Giorgis et al 2011aGiorgis et al , 2016Tecco et al, 2016;Argañaraz et al, 2020). Este último proceso, generalmente se desencadena en las zonas más bajas y con el tiempo se expande hacia mayores elevaciones (Giorgis et al, 2011a(Giorgis et al, , 2016(Giorgis et al, , 2017Tecco et al, 2016).…”

“…Por arriba de este último límite, son prominentes en el paisaje las comunidades dominadas por Poa stuckertii, Deyeuxia hieronymi y/o Lachemilla pinnata, así como por la especie leñosa Polylepis australis (Cabido & Acosta, 1985Cingolani et al, 2003;Cabido et al, 2018). Entre ambos pisos existe un ecotono complejo que denominamos "piso de transición", siguiendo a Argañaraz et al (2020).…”

“…La composición florística de estas montañas es muy heterogénea y su variación está fuertemente asociada al gradiente altitudinal (Cabido et al, 1991;Acosta et al, 1992;Cantero et al, 2001Cantero et al, , 2011Giorgis et al, 2017;Oyarzabal et al, 2018;Arana et al, 2021). Este gradiente no solo involucra cambios en la temperatura y las precipitaciones, sino también en la incidencia de fuegos (Argañaraz et al, 2020), herbivoría (Argibay & Renison, 2018;Marcora et al, 2018) y en el estado de avance de la mayoría de las especies exóticas invasoras desde zonas bajas y centros poblados (Giorgis et al, 2011a(Giorgis et al, , 2016.…”

Floristic patterns of the neotropical forests, savannas and scrublands with Trithrinax campestris (Arecaceae) in central Argentina

“…Following Argañaraz et al (2015a) and Argañaraz et al (2020) the fire history frequency was characterized for the 92 sampling sites.Time series of Landsat TM, ETM+, and OLI images (30 m of spatial resolution), covering the study area, acquired between 1999 and 2018 were used. This fire database was derived automatically using ABAMS (Automatic Burned Area Mapping Software), a tool based on the algorithm proposed by Bastarrika et al (2011) and updated versions implemented in Google Earth Engine.…”

“…Similar patterns of higher species diversity reflecting habitat heterogeneity have been reported elsewhere in the world for different types of vegetation (Whittaker 1960;Coblentz and Riiters 2004;Kreft and Jetz 2007) and specifically for communities rich in palm species (Guimarães et al 2002;Resende et al 2013). An additional factor influencing local species richness may be the physiognomy of vegetation which, is the results of complex feedback between climate, topography and disturbance (i.e., fire and grazing) (Giorgis et al 2017;Argañaraz et al 2020). Vegetation types comprised in Cluster 1 exhibited higher tree canopy cover and the differences in their canopy openness could determine gradients of light affecting the distribution of species.…”