Long-Term Tree Regeneration of Fragmented Agroforestry Systems Under Varying Climatic Conditions

DÍAZ, MARIO; SÁNCHEZ-MEJÍA, TERESA; MORÁN-LÓPEZ, TERESA

Frontiers in Ecology and Evolution

Frontiers Media S.A.

Año: 2021 vol. 9

2296-701X

Iberian dehesas and montados are agroforestry systems protected by the EuropeanHabitats Directive due to high levels of biological diversity associated to their savannahlike structure. Tree scattering in dehesas, montados and other agroforestry systemsis, however, known to compromise tree regeneration, although recent work suggeststhat it may protect tree populations from climate warming by alleviating plant-plantcompetition. We analyze how climatic conditions, tree isolation and their interactionsinfluence the outcomes of regeneration stages, from flower production to early seedlingestablishment, using data gathered during the long-term monitoring (2001?2018) ofca. 300 Holm oak Quercus ilex trees located in central Spain. Holm oak reproductiveeffort, predispersal seed losses, and early seedling recruitment were sensitive toclimate change, especially to year-round drought. Effort and early seedling recruitmentdecreased, while abortion and predispersal seed predation increased, with higherdrought intensity. Spring warming increases pollination effectiveness, but had no furthereffect on acorn crops. Forest clearing seemed to have little scope to ameliorate thesenegative effects, as shown by weak or no interactive effects between the spatialconfiguration of trees (cover or isolation) and climate variables (spring temperature ordrought intensity). Forest opening aimed at decreasing adult tree mortality under climatechange scenarios would then have little or no effects on tree recruitment. Landscapescale rotations alternating shrub encroachment and thinning along periods adapted tochanging climate are proposed as the main management option to preserve both oakforests and dehesas in the long term.