Avaliação do efeito das árvores sobre a produtividade e sobre a qualidade da pastagem no ecossistema montado: estudo de caso

Abstract

The objective of this study was to evaluate the effect of trees on pasture productivity and quality in the montadoecosystem, composed of pasture grown under holm oak trees (Quercus ilex ssp. rotundifolia Lam.), grazed by sheep. Six trees were selected, and four sampling points were georeferenced for each tree (two points outside the canopy and two under the canopy). The evolution of the pasture was recorded in the twenty four sampling points at five monitoring dates: at the end of autumn (December 2015), at the end of winter (March 2016) and then monthly during spring 2016 (April, May and June). The following pasture parameters were measured: green and dry matter production per hectare, ash, crude protein and neutral detergent fiber. Between April and May 2016 the floristic composition of the each sampling point was surveyed. The results showed: (i) higher pasture productivity outside tree canopy; (ii) higher crude protein content under tree canopy; (iii) significant differences in floristic composition, with a greater preponderance of plants from composite and legume families outside tree canopy and greater preponderance of grasses under tree canopy. This knowledge is fundamental for supporting the decision making process of the farm manager in formulating the most appropriate management strategies: animal stocking rates, rotation among grazing parcels, calculation of animal headings, soil fertilization/correction, preservation of the biodiversity of botanical species and tree density.