Thresholds and alternative states in neotropical dry forest in response to fire severity, 2005-2018

Neotropical xerophytic forest ecosystems evolved with fires that shaped their resilience to disturbance events. We asked if there is evidence for a fire severity threshold causing an abrupt transition from a forest to an alternative shrub thicket state in the presence of typical post-fire management. We studied a heterogeneous wildfire event to assess medium-term effects (11 years) of varying fire severity in a xerophytic Caldén forest (Prosopis caldenia) in La Pampa province, central Argentina. We conducted field vegetation surveys in patches that were exposed to low (LFS), medium (MFS), and high (HFS) fire severities, but had similar pre-fire woody canopy cover. Satellite images were used to quantify fire severity using a delta Normalized Burning Ratio (dNBR) and to map pre-fire canopy cover. The structure and composition of woody and herbaceous vegetation was measured during the 2017-18 growing season (September to March) in areas affected by different severities of the 2006 wildfire.