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Mixed systems of agriculture incorporating combinations of trees and crops have formed key elements of the landscape of Europe throughout historical times, and many such systems continue to function in the present day. In many cases they represent formerly widespread traditional systems in decline and a number have already become extinct or exist only in a threatened state. The causes are both practical and economic. The agricultural subsidy regime within the European Union is presently unfavourable towards silvoarable practices, which has been a major factor in their recent decline. The silvoarable systems of Europe can be split into two classes according to location -northern Europe and the Mediterranean. The latter contains not only a greater area of silvoarable cultivation, but also a greater diversity of systems due to the broader range of commercial tree and crop species grown. In general, the systems of northern Europe are limited by light, whilst those of the Mediterranean are limited by the availability of water. Mixed systems of agriculture present an opportunity for future European rural development and have the potential to contribute towards the increased sustainability of agriculture and enhancement of biodiversity, whilst preserving landscapes that are both culturally important and aesthetically pleasing. A better understanding of the legacy of traditional silvoarable systems, combined with the formulation of a consistent definition and specific European policy towards them will be invaluable in ensuring that the benefits of mixed agriculture are fully exploited in the future.

Abstract. Single species and bivariate distribution patterns in a semi‐arid shrubland in southeastern Spain, dominated by the tall leguminous shrub Retama sphaerocarpa, were investigated by second‐order spatial analysis based on Ripley's K‐function. Shrubs were significantly clumped because of a strong association of dwarf shrubs, mostly Artemisia barrelieri, under the canopy of Retama. Retama shrubs were randomly distributed, but when different size‐classes were analysed separately, the pattern changed from significantly clumped to random and then to regular with increasing canopy diameter, suggesting increasing intraspecific competition with shrub size. Artemisia was significantly clumped at all scales because of aggregation under the canopy of large Retama shrubs. The association between the species became stronger with increasing canopy diameter of Retama shrubs, suggesting that facilitation prevailed over interspecific competition because of niche separation in different tiers, both above and below ground. Retama shrub size thus determined both the type of pattern for its own size class and tier, and the scale and intensity of the association with its understorey shrubs.

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Yield-SAFE: a parameter-sparse process-based dynamic model for predicting resource capture, growth and production in agroforestry systems. Ecological Engineering 29: 419-433.