Summary1. Oak savannas are biodiversity-rich landscapes allowing sustainable livestock production throughout the world. The long-term persistence of these ecosystems critically depends on the regeneration of the tree layer. Nevertheless, studies addressing the mechanisms involved for conservation planning are of limited value because they tend to focus on single explanatory factors. 2. We evaluated the combined effect of biotic and abiotic factors on recruitment of holm oak Quercus ilex in the Mediterranean savannas of western Spain. Transition probabilities from flower to seed to the established seedling were estimated in grazed, shrub-encroached and cropped plus fenced habitats in two consecutive years. 3. Trees in cropped habitats produced more female flowers and larger acorn crops in both years. The physiological condition of trees was better in cropped habitats and worst in shrub-encroached plots. Overall, resource-mediated effects overrode the effects of biotic damage on tree fecundity in all habitats. 4. Acorn survival and seedling establishment were higher in cropped and shrub-encroached plots, though in cropped plots saplings are predictably destroyed by subsequent grazing and ⁄ or by mechanical treatment used to restart the cropping cycle. 5. Complete regeneration failure was found in 6 out of 24 possible management scenarios, mostly in the presence of large vertebrate herbivores. However, even low positive cumulative transition probabilities between life stages exceeded a safe threshold for early regeneration. 6. Synthesis and applications. Natural early recruitment of oak savannas can be achieved through various management regimes. These include cereal cropping in fenced plots (provided established saplings were not subsequently destroyed) or shrub encroachment in undergrazed or livestockexcluded plots. Among these, natural recruitment after encroachment is a cost-effective tool as compared to artificial plantation.

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Dehesas are extant multi-purpose agroforestry systems that consist of a mosaic of widely-spaced scattered oaks (Quercus ilex L.) combined with crops, pasture or shrubs. We aimed to clarify the role of trees in dehesas of CW Spain focussed on the analysis of treeunderstorey interactions. Spatial variability of resources (light, soil moisture and fertility), microclimate, fine roots of both herbaceous plants and trees and forage yield was measured. Additionally, we compared the nutritional and physiological status, growth and acorn production of oaks in cropped (fodder crop), grazed (native grasses) and encroached (woody understorey) dehesa plots. Significant light interception by trees was limited to the close vicinity of the trees, with very low reduction away from them. Both microclimate and soil fertility improved significantly in the trees vicinity, irrespective of soil management. Soil moisture varied very few with distance from the trees, as a result of the extended root system of oaks. Root systems of trees and herbs did not overlap to a great extent. Crop production was higher beneath trees than beyond the trees in unfertilised plots and foliar nutrient content of oaks did not increase significantly with crop fertilisation, indicating that trees and crops hardly compete for nutrients. Moreover, trees benefited from the crop or pasture management: trees featured a significantly improved nutritional and physiological status, a faster growth and a higher fruit productivity than trees growing in encroached or forest plots.