Persistence of winter forage grasses in Silvopastoral Systems: dynamics of appearance and mortality of tillers under Eucalyptus sp. trees and full sunlight

Abstract

The impact of microclimatic changes caused by Silvopastoral Systems (SPS) in subtropical climates on C3 grasses persistence remains unclear, particularly concerning their effects on summer mortality and tiller growth. We hypothesized that the microclimate created by trees with different orientations in SPS would have an impact on the summer C3 grasses' persistence, as measured by the number of tillers per square meter. This study evaluated the survival of two C3 perennial grasses of different tolerance to shade (Dactylis glomerata: tolerant, Festuca arudinacea: moderately tolerant) and a C3 biannual grass typic of moist environments (Holcus lanatus) in full sunlight and SPS with tree rows oriented North-South (NS) and East-West (EW). We observed a decrease in Tiller Population Density (Tiller m− 2) for Holcus in all situations from December to April (P < 0.05) (from 2156 to 22 in NS, 2567 to 0 EW and 4667 to 533 in full sunlight). Festuca also decreased in all conditions but showed a relatively better performance (2867 to 1644 in NS, 3044 to 944 EW and 4500 to 3317 in full sunlight) and Dactylis (1933 to 2633 in NS, 2289 to 2056 EW and 3017 to 1750 in full sunlight). Results showed that Dactylis was more persistent under tree canopy, it presented lower mortality rate, especially in N-S oriented tree rows (P < 0.05). Festuca’s tiller mortality increased under reduced light, while Holcus showed higher mortality during summer, exacerbated under tree cover. These findings suggest that Dactylis could be a promising species for SPS in subtropical climates, particularly regarding summer persistence.