Sustainable dry forest management for cattle ranching: The effects of deschampado practices on the shrub layer and the light environment in comparison to roller chopping

Abstract

The Chaco region, faces land cover changes due to agricultural and cattle ranching intensification. Silvopastoral practices employ roller chopping, in which the shrub layer is completely removed. Disturbance triggers vegetation successional processes and promotes shrub recolonization. Roller chopping only removes aerial organs, so some species resprout, which can modify their architecture. Searching for sustainable alternatives, participative approaches introduced “deschampado”, which involves a low-intensity intervention, and sowing shade-tolerant fodder grasses. The study aims to compare roller chopping and deschampado, regarding the changes in cover, composition and architecture of the shrub layer, and the variations in the light environment produced by them. We hypothesized that deschampado causes a minimal disturbance, thus maintaining shrub layer characteristics and a light environment similar to unmanaged forests. The study was conducted in the Semiarid Chaco Pilot Site (Salta, Argentina). Two sites were selected: Puesto el Quirquincho (roller chopping), and Puesto La China (deschampado). The both sites included control forest and managed areas. We defined six plots of 250 m2 per site. Vegetation cover, shrub layer composition and shrub architecture were assessed. The light environment was characterized using hemispheric photographs. We also measured production of M. maximus in deschampado. Roller-chopped plots showed increased bare soil (8.92%) and reduced shrub (56.74%) and tree cover (13.2%). Deschampado plots maintained near-100% shrub cover, 35.5% tree cover and lacked bare soil. Herbaceous cover was higher in both treatments (∼70%) compared to controls. In the shrub layer, Salta triflora and Sarcotoxicum salicifolium relative abundance decreased, Castela coccinea disappeared and Parkinsonia praecox appeared in roller-chopped plots. Shrubs from roller chopping had a greater number of stems, were shorter, had a smaller crown diameter (50%), and a greater length (50%) and number (5-fold) of thorns than their control, while those from the deschampado were more similar to their control. Roller chopping increased transmitted radiation in 57% and canopy opening in 50%, and reduced leaf area index; while deschampado maintained transmitted radiation similar to unmanaged forests. The disturbance produced by roller chopping facilitates shrub recolonization, with changes in composition and architecture of shrub layer. In contrast, deschampado, as it implies a low disturbance, maintains shrub layer and light conditions similar to unmanaged forests. The study highlights the ecological consequences of these practices, emphasizing the potential of deschampado as a more sustainable alternative for maintaining forest structure and ecosystem services while allowing fodder production in dry forests.