Fostering native palms and trees to increase resilience of cattle rangelands to drought

Ivan Raniero Hernández-Salmerón and Milena Holmgren, Wildlife Ecology and Conservation, Wageningen University, Wageningen, Netherlands, Julie Eliene Hernández-Salmerón, Biology, Wilfrid Laurier University, Waterloo, Canada, Francisco Javier Solorio Sánchez, Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Yucatán, Mérida, Canada

Background/Question/Methods
Despite their massive conversion into agricultural landscapes, local farmers across the neotropics often retain disperse trees and palms within grazing paddocks. Understanding how farmers manage on-farm tree cover and how these decisions impact the environmental and productive functions of pastures is key for biodiversity conservation and the development of climate-resilient production systems. We conducted field surveys in Yucatan, Mexico to study tree composition in cattle pastures and their effects on the performance of grasses, the microbial diversity of grass rhizosphere and the behavior of cattle during dry and wet seasons. We also performed a meta-analysis to compare our local results with other dry rangelands around the world.
Results/Conclusions
Scatter trees and especially palm trees ameliorated the impact of seasonal drought on grasses but slowed down their recovery during the wet season. The overall higher positive effects of palms on grass performance might be related to both smaller canopy density (<40%) and host-plant interactions belowground. After sequencing 104,900 OTUs obtained from 16S rRNA region V3-V4, we found that the rhizosphere of grasses under palm trees harbors a richer and more diverse bacterial community (Shannon H’ =7.8, AMOVA =0.007) than the rhizosphere of grasses in the open (Shannon = 7.5). On-farm tree cover also influences cattle behavior. Animals actively look for dense tree shade for ruminating or idling. Our results show that fostering the maintenance of a diversity of native palms and trees has positive effects on the functioning of cattle pastures, especially during dry periods. This may help developing more climate-resilient livestock systems that maintain productivity and animal welfare while contributing also to biodiversity conservation.