Over-yielding in temperate silvopastures: a meta-analysis
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Over-yielding in temperate silvopastures: a meta-analysis Gabriel J. Pent
Received: 12 November 2019 / Accepted: 16 April 2020 Ó The Author(s) 2020
Abstract Over-yielding in an intercropping system occurs when the productivity of the intercrop exceeds the overall productivity of the systems managed in segregation. The objective of this systematic review was to calculate the over-yielding of silvopastures compared to open pastures and forests, timber plantations, or orchards managed separately. A literature search was completed for comparisons of the productivity of these practices in temperate regions. Data collected from these studies included mean yields of timber or non-timber forest products, forages, and livestock, as well as the characteristics of the study site. Silvopasture practices improve the productivity of land typically managed separately for pasture or trees by 42–55%, depending on whether the productivity of the pastures is measured by livestock or forage output, respectively. In most cases, overyielding occurred despite a reduction in individual forage, livestock, or tree productivity in the silvopastures. Calculating confidence intervals around these means was not feasible because standard errors were largely not reported or available. Some assumptions were made about the actual productivity of timber or non-timber forest products. This work illustrates the
G. J. Pent (&) Shenandoah Valley Agricultural Research and Extension Center, Virginia Polytechnic Institute and State University, 128 McCormick Farm Circle, Raphine, VA, USA e-mail: [email protected]
significant level of over-yielding that may be achieved by integrating trees, forages, and livestock into a single production system. Keywords Silvopasture Yield Production Forage Livestock Tree
Introduction Integrating trees with pastures for livestock is an intensive practice (Sharrow et al. 2009). The manager of such a combination must protect trees from potential damage by livestock, but also periodically prune or thin the trees to maintain enough forage production in the understory to sustain a herd or flock of animals (Robinson and Clason 2000; Lehmkuhler et al. 2003). When water is scarce during droughts, established trees may vigorously compete with the forages for water resources (Karki and Goodman 2015), although this may not result in a reduction in forage growth under some conditions (DeBruyne et al. 2011). In a similar way, competition for light may reduce forage growth underneath trees when the days are short or when the sky is overcast for prolonged periods of time (Feldhake et al. 2005). To sustain longterm forage production and persistence, the manager must alter the livestock stocking management typically employed in open pastures to apply appropriately
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to the silvopastures (Belesky 2005a, b; Neel and Belesky 2017). Besides managing competitive interactions between the components of these complex systems, the manager must be well versed in the care an
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