Floristic enrichment of the understory increases forage production and carrying capacity of temperate silvopastoral systems

Abstract

In silvopastoral systems, the use of land for multiple purposes diversifies economic income and improves the stability of the system. If shading levels are medium or high, cattle production is often limited by the absence of one or more forage components of the herbaceous layer (such as perennial grasses). In the present study, we hypothesized that perennial C₃ cover is a major determinant of cattle production because pasture cover throughout the year is higher and more persistent than that of annuals C₃ and thus forage productivity is more stable over time. Therefore, we studied the introduction of orchardgrass into a silvopastoral system of the Paraná River Delta (Argentina) and estimated forage production and carrying capacity of the enriched grassland. Between March 2013 and December 2014, we measured forage production and cover in four paired stands either sown (S) or not sown (NS) with C₃ grasses by successive harvests of the herbaceous component. The contribution of the different plant functional types to annual forage production was separated across seasons and livestock potential was estimated through carrying capacity. S stands had 105% higher annual forage production than NS stands (S: 2.546 vs. NS: 1.240 kg ha⁻¹ y⁻¹, p = 0.037), with forage species (C₃, C₄, orchardgrass, Fabaceae) contributing 98.8% to total biomass. The greatest forage production gap between S and NS stands was in winter (S: 594 vs. NS: 23 kg ha⁻¹ 90 day⁻¹), when carrying capacity increased ten times in S stands. This is the first research in the area that describes grassland composition and forage production in the understory of plantations, with substantial improvements in livestock carrying capacity of silvopastoral systems.