Natural regeneration of native woodlands in drylands subjected to disturbances: A basis for their ecological restoration

Abstract

Dry woodlands are increasingly threatened by anthropogenic disturbances, which may affect their regeneration and compromise ecosystem resilience. If regeneration potential is low, ecological restoration can promote recovery. This study aimed to evaluate the effect of fires and roller-chopping on the regeneration of native dryland forests used for livestock grazing, taking the “algarrobo” (Neltuma flexuosa) woodlands in southern Mendoza, Argentina, as a case study. We expected fires to promote shrub encroachment, while roller-chopping would lead to a more open vegetation structure, favoring herbaceous species, reducing algarrobo recruitment, and species richness in both cases, with a synergistic effect between fires and roller-chopping. We selected 31 sites with contrasting disturbance histories, including woodlands subjected to different fire recurrence, roller-chopping, or their combination, and undisturbed sites. At each site, we recorded the number and size of vegetation patches, forest structure, sapling abundance, species richness, and composition. Generalized Linear Models (GLM) analyzed the effects of disturbance on sapling abundance, patch size, and number, and species richness. A Detrended Correspondence Analysis (DCA) was used to examine the influence of disturbance on species composition. Shrub cover increased in both burned sites and those affected by both disturbances. Sapling abundance was significantly reduced in burned sites, although this effect was less pronounced when combined with roller-chopping. Our results suggest a trend towards post-disturbance shrub invasion and a negative impact of fire on sapling abundance and species composition. High fire recurrence has a detrimental effect on the number of tree saplings. Selective roller-chopping could be integrated into sustainable forest management and restoration strategies of burned forests.