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 ha1 (30e70% woody biomass), supporting
low stocking rates (0.2e0.3 AU ha1). 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
(2500e3800 kg DM ha1) were dominated by forbs and the least productive ones (800
e2000 kg DM ha1) were dominated by woody species, yielding an overall stocking rate of
1.2 AU ha1. 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 47e89 d during the 2017 rainy season, 50
e123 d during the transition to the dry season, and 210e290 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.

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