Native palms and trees mediate drought impacts on dry neotropical pastures.
Abstract
Dry forests are the most threatened biome across the global tropics. Despite their massive conversion into agricultural landscapes, local farmers often retain disperse trees and palms within grazing pastures. Understanding how on-farm tree cover in the dry neotropics impacts the environmental and productive functions of pastures is key for biodiversity conservation and the development of climate-resilient production systems. We studied tree composition of 23 dry cattle pastures in Yucatan, Mexico. We assessed the effects of palms, N2-fixing trees and non-N2-fixing trees on microsite environmental conditions, bare soil cover and the performance of grasses and woody plants in their understory during the dry and wet seasons of 2018 and 2019. We found that 45% of the total pool of tree species of the native dry forest is conserved in the pastures of Yucatan. Palms were the most abundant overstory functional group with a relative abundance of 45%, followed by N2-fixing trees and non-N2-fixing trees with 33% and 22%. Palms and trees ameliorated the impact of seasonal drought on grasses but slowed down their recovery during the wet season. Palms had overall higher positive effects on grass greenness and height than N2-fixing trees and non-N2-fixing trees and these effects were higher during the driest season. Palms decreased bare soil less than trees. Shrubs and tree seedlings tended to increase in the understory of all functional groups as the canopies of palms and trees became denser. Synthesis and applications. Climate warming and the alteration of precipitation regimes are expected to compromise pasture and cattle productivity worldwide. 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. A larger appreciation and understanding of the facilitative effects of remnant palms and trees on pastures during seasonal droughts may help developing more climate-resilient livestock systems that maintain productivity during dry conditions while contributing also to tree biodiversity conservation.