Abstract
Iberian dehesas and montados are agroforestry systems protected by the European Habitats Directive due to high levels of biological diversity associated to their savannah-like structure. Tree scattering in dehesas, montados and other agroforestry systems is, however, known to compromise tree regeneration, although recent work suggests that it may protect tree populations from climate warming by alleviating plant-plant competition. We analyze how climatic conditions, tree isolation and their interactions influence the outcomes of regeneration stages, from flower production to early seedling establishment, using data gathered during the long-term monitoring (2001–2018) of ca. 300 Holm oak Quercus ilex trees located in central Spain. Holm oak reproductive effort, predispersal seed losses, and early seedling recruitment were sensitive to climate change, especially to year-round drought. Effort and early seedling recruitment decreased, while abortion and predispersal seed predation increased, with higher drought intensity. Spring warming increases pollination effectiveness, but had no further effect on acorn crops. Forest clearing seemed to have little scope to ameliorate these negative effects, as shown by weak or no interactive effects between the spatial configuration of trees (cover or isolation) and climate variables (spring temperature or drought intensity). Forest opening aimed at decreasing adult tree mortality under climate change scenarios would then have little or no effects on tree recruitment. Landscape-scale rotations alternating shrub encroachment and thinning along periods adapted to changing climate are proposed as the main management option to preserve both oak forests and dehesas in the long term.
Highlights
Increasing tree mortality associated to drought events (Jump et al, 2017) and to introduced pests (Roy et al, 2014) is threatening forests worldwide
Data on reproductive effort and predispersal propagule losses were gathered for 145 trees, 103 in dehesa, and 42 in nearby forest sites to uncover the larger local variation of tree spatial arrangements in dehesas
Predispersal seed losses, and early seedling recruitment were sensitive to climate change
Summary
Increasing tree mortality associated to drought events (Jump et al, 2017) and to introduced pests (Roy et al, 2014) is threatening forests worldwide. Several recent papers conclude that forest thinning can be an efficient management option to deal with the negative effects of global change on tree growth and mortality (Ruiz-Benito et al, 2013; Astigarraga et al, 2020). Climate Effects on Agroforestry Sustainability regeneration deficits of tree populations (Pulido et al, 2001; 2010; Gibbons et al, 2008; Morán-López et al, 2016c), so that management actions directed to increase tree survival and growth may indirectly compromise forest survival by reducing tree recruitment. Knowledge on the interactions between climatic drivers and the forests structures resulting from management are essential to develop management practices aimed at ensuring the maintenance of tree populations under global change scenarios (Valladares et al, 2014). Regeneration is strongly determined by the processes occurring in the early stages of seed production, dispersal, and early seedling survival (Schupp et al, 2010; Johnson et al, 2014)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
