Abstract
La calidad del pasto en los pastizales de montaña es un factor importante para mantener o mejorar el rendimiento animal. Estudios previos han identificado atributos vegetales beneficiosos para la nutrición animal; sin embargo, poco se sabe sobre su mantenimiento en comunidades vegetales. Nuestra principal hipótesis sostiene que el pastoreo favorece a las especies con una alta capacidad de rebrote y una baja eficiencia de utilización de recursos, promoviendo así la producción de pasto de alta calidad. Para testar la hipótesis, realizamos un experimento de exclusión del pastoreo en un pastizal de la montaña atlántica, combinado con un marco teórico de respuesta-efecto basado en varios atributos vegetales y una metodología estadística apropiada para medir la contribución relativa del recambio de especies y la variabilidad intraespecífica de los atributos (ITV) tras el abandono del pastoreo. Nuestros resultados mostraron que la calidad del pasto disminuyó tras el abandono del pastoreo a corto plazo, principalmente debido al efecto de la ITV. Los efectos por recambio de especies podrían aparecer tras un período más largo de abandono si, tal y como es esperable, las gramíneas altas con tejidos de baja calidad nutritiva sustituyen a las especies de mayor calidad.
Highlights
We propose a hypothesis for the mechanism behind these changes in forage quality that is based on the tolerance strategy of the plants: grazing favors plants with high regrowth capacity and low resource utilization efficiency, promoting the production of forage with high nutritional value; grazing abandonment favors plants with the ability to compete for light and that have high resource utilization efficiency, promoting the production of low-quality forage
T. repens was clearly associated with G plots, whereas G. saxatile was associated with exclusion plots (E plots) (Figure 1)
We aimed to investigate the underlying mechanisms of grassland community response to grazing using a framework based on plant traits (Cingolani et al, 2005; Cruz et al, 2010; Deléglise et al, 2015; Moreno García et al, 2014; Pontes et al, 2010, 2007)
Summary
Cattle and small ruminants, such as sheep and goats, consume 80% of the total animal feed produced worldwide (Herrero et al, 2013). Plants use two main strategies against herbivores: avoidance (or defense) and tolerance (Díaz et al, 2007; Van Der Meijden et al, 1988) The latter, which is common in grasslands with high resource availability and long evolutionary history of grazing (Cingolani et al, 2005), favors plant species with fast regrowth rate after defoliation (Peco et al, 2017) and produces high-quality forage (Díaz et al, 2007). Herbivores enhance nitrogen (N) inputs to the soil through their urine and feces, increasing the abundance of grass species with low fiber content and high N content (Pontes et al, 2010, 2007) In this type of grassland, grazing abandonment promotes plant species that more efficiently compete for light and utilize resources (Díaz et al, 2001; McNaughton, 1984; Milchunas et al, 1988), producing forage of low nutritional value
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