Floristic diversity and stocking rate in tropical dry forest secondary vegetation used for grazing
The natural process of ecological regeneration in tropical regions in conjunction with local livestock management practices creates grazing environments with high floristic diversity and structural complexity. Yet, these environments are being neglected despite the opportunities and benefits for domestic herbivores. Voisin grazing (VG) is better in such highly biodiverse environments, as this management system seeks to improve forage utilization by coupling forage allowance with livestock needs for forage, using small paddocks, high stock densities over short occupation periods, and allowing plants to fully recover after grazing. Floristic diversity, biomass and stocking rate were assessed in sites having tropical dry forest secondary vegetation undergoing grazing. Six sites having extensive seasonal grazing were studied by placing 10 × 10 m2 quadrats across sites to list woody species and nested 2 × 2 m2 frames for listing herbaceous vegetation. The response of vegetation to Voisin grazing (VG) was evaluated in one of the six sites (split into 15 paddocks having 400-m2 each). A total of 191 species (from all sites) including 50 potential forage species were listed. Quadrats were classified into two groups, one contained more preserved vegetation dominated by woody species, and the other a less preserved group dominated by herbaceous and shrub species. Available forage biomass across sites ranged from 1000 to 1200 kg DM ha−1 (30–70% woody biomass), supporting low stocking rates (0.2–0.3 AU ha−1). In the site where VG was implemented, most of the identified species were forage (56/58). After one year of VG, the most productive paddocks (2500–3800 kg DM ha−1) were dominated by forbs and the least productive ones (800–2000 kg DM ha−1) were dominated by woody species, yielding an overall stocking rate of 1.2 AU ha−1. Based on forage botanical composition, three groups of paddocks were identified: 1) dominated by grasses, 2) heterogeneous forage diversity, and 3) dominated by forbs and shrubs. Pastures recovered in 47–89 d during the 2017 rainy season, 50–123 d during the transition to the dry season, and 210–290 d during the 2018 dry season. Secondary vegetation provides high floristic diversity and a large number of forage plant species, but low forage yield and stocking rates. Yet, implementation of a proper grazing system such as VG gradually enhances yield and stocking rates.