Size and connectivity of upslope runoff-source areas modulate the performance of woody plants in Mediterranean drylands

Feedbacks between vegetation spatial pattern and resource redistribution from bare areas (sources) to vegetation patches (sinks) are considered critical to the functioning of dryland ecosystems. However, experimental fieldworks testing the underlying assumptions and quantifying the feedbacks involved are very scarce. We hypothesized that the size and surface conditions of the upslope runoff-source areas control the transfer of resources to the downslope vegetation patch, and thereby vegetation performance. In a restored semiarid woodland in Alicante, SE Spain, we investigated the performance of planted shrubs (Olea europaea and Pistacia lentiscus) in response to the size, upslope length, internal connectivity and soil surface properties of their respective upslope runoff-source areas (drainage microcatchments). Growth of O. europaea seedlings increased with drainage microcatchments size, whilst their water–stress level decreased with the upslope hillslope length. Lower plant density and higher bare-soil connectivity within the respective microcatchments improved the performance of O. europaea seedlings. Seedling survival was much lower for P. lentiscus than for O. europaea, and growth and water–stress of alive P. lentiscus seedlings showed no significant relationships with any of the microcatchment properties assessed. Survival of P. lentiscus seedlings increased with hillslope length upslope the seedling location. Overall, results point to the interplay between the size and connectivity of the bare-soil upslope interpatch and the relative location on the hillslope as the most relevant control factors for seedling performance. Observed linkages between source–sink dynamics and plant performance provide valuable information for improving the design of conservation and restoration actions in semiarid lands. Copyright © 2014 John Wiley & Sons, Ltd.