Tree and meadow production under birch silvopastoral system: fertilization, seed mixture and tree density effect

摘要

The combination of tree and pasture production has been recently promoted by the European Union as an agroforestry system type. Pasture production under trees produces annual farm outputs which promote long term rural population stabilisation comparedwith exclusively forest systems. At the same time, the presence of a tree increases the long term value of the land. The objective of this study was to evaluate the effect of two different tree densities, seed mixtures and fertilization on annual meadowproduction after 9 years of a silvopastoral system. The tree species was birch (Betula alba L.) established at two densities (2500 and 833 tree ha~(-1)). Fertilization regimes included no fertilization and mineral inputs. Initial seed mixtures includedcocksfoot (Dactylis glomerata) and perennial ryegrass (Lolium perenne) together with white and red clover (Trifolium repens and T. pratense). The results showed a significant effect of fertilization, seed mixture and tree density on meadow production. Meadow production was not reduced over time in spite of tree canopy development, which makes birch more suitable for meadow production when compared with radiate pine (Pinus radiata). Fertilization had a major effect at the start of the experiment in termsof modifying annual meadow production. However, by the end of the experiment its effect was modified by tree density and previous seed mixture.