Phenology in winter‐deciduous relict Mediterranean forests as a tool to understand their adaptation to climatic seasonal cycles

Winter deciduous forests signify a relict ecosystem that survives restricted to microclimatic zones of high mountains in the western Mediterranean Basin and they are well represented in the southern Iberian Peninsula (Sierra Nevada, Spain). Given the scarce knowledge of their phenological behaviour, the aim of this work was to obtain the annual phenophasic sequencing and phenophasic indexes, at both species and plant community level and to determine its phenological functional groups (FG). Phenophase sequencing, phenophasic patterns and indexes have been determined considering the winter functionality of most species. As methodology was initially implemented for typically Mediterranean vegetation, new vegetatives and reproductives phenophases have been proposed. The majority of the studied taxa showed their activity concentrated between April and June, coinciding with the rise in temperatures and when rainfall is maintained, while winter is generally a non‐phenophasic activity season mainly due to low temperatures and frequent frosts. The annual phenophasic characterisation of the forest and its comparison with other Mediterranean ecosystems highlighted that the maximum vegetative phenophasic activity occurs in spring, as do evergreen forests. In contrast, the maximum reproductive activity takes place between spring and early autumn but, in evergreens, it occurs throughout the year. The maximum active phenophasic period of the plant (APS) was achieved in spring due to optimal environmental conditions in terms of temperature and humidity, while the minimum values were achieved from late autumn through late winter (December, January and February) due to unfavourable environmental conditions. In the deciduous forest, the phenophasic duration of reproductive functions predominated over vegetative functions and this is typical of Mediterranean forests and mainly of deciduous tree species. Four functional groups were identified: FG1 – early and prolonged foliation and dispersal; FG2 – very short dispersal and fructification; FG3 – very long‐lasting foliation and fruiting, FG4 – long foliation.