Survival of tropical native trees in a silvopastoral system in Veracruz, Mexico.
In livestock production systems, the combination of pasture and woody perennials improves the yield and reduces the negative environmental impact. In 2006, a silvopastoral system was established at the experimental station (Posta Zootécnica: PZ) of the Universidad Veracruzana. It contained 791 native tropical trees of the following species: quickstick (Gliricidia sepium; Glse), cópite (Cordia dodecandra; Codo), West Indian elm (Guazuma ulmifolia; Guul), (Diphysa robinioides; Diro) and tihuixtle (Caesalpinia cacalaco; Caca). Starting from the second year after the trees were planted, livestock was brought into the PZ to browse on them. The objective of this study was to quantify the development and survival of five native species, 11 years after they were planted. The resulting support data was gathered from August to November 2017. Due to their specific characteristics, the survival and development of the said species is expected to be different under similar conditions. The experimental design was a series of blocks, with five treatments (species) and 156 replicates per treatment. Thirteen rows of trees were planted in a 2-ha surface, using the following repeated arrangement: Glse+Codo+Guul+Diro+Cala. The trees were planted 3 m apart from each other and the distance between rows was 5 m. Eleven years after they were planted, the specimens of each species were counted, the diameter of their trunks or main branches was measured and the height at which this measurement was carried out was recorded. The overall survival rate was 57.7% (p=0.02); there was a difference between species in the diameter of the trunk or main branch (p=0.03) and the height at which they were measured (p=0.003). Eight species of trees that had grown naturally in the system or that were planted to provide shade or serve as windbreak were identified: Indian siris (Albizia lebbeck), Australian pine (Casuarina equisetifolia), Spanish cedar (Cedrela odorata), lead tree (Leucaena leucocephala), Elephant-ear tree (Enterolobium cyclocarpum), trumpet tree (Tabebuia rosea), teak (Tectona grandis) and sea grape (Coccoloba uvifera). Native tropical trees maintain the silvopastoral system and they are available for browsing.