Plastic bimodal growth in a Mediterranean mixed-forest of Quercus ilex and Pinus halepensis.

• Intra- and inter-annual growth are compared in Quercus ilex and Pinus halepensis. • Pinus halepensis shows a longer growing season and a marked bimodal growth pattern. • Quercus ilex shows a facultative bimodal growth that could be unimodal under drought conditions. • The VS-Lite2 model detects intra- and inter-specific differences in growth response to climate. • Intra- and inter-annual growth patterns are crucial to understand tree-growth responses and species coexistence. Mediterranean tree species have evolved to face seasonal water shortages, but may fail to cope with future increases in drought frequency and intensity. We investigated stem radial increment dynamics in two typical Mediterranean tree species, Aleppo pine (Pinus halepensis), a drought-avoiding species, and holm oak (Quercus ilex), a drought-tolerant species, in a mixed forest and on contrasting slope aspects (south- and north-facing). Intra- and inter-annual growth patterns were modelled using the VS-Lite2 model for each tree species and slope-aspect. Both species showed a bimodal growth pattern, with peaks coinciding with favourable conditions in spring and autumn. A bimodal growth pattern is always observed in P. halepensis , while in Q. ilex is facultative, which suggests different strategies adopted by these species to cope with summer drought. More specifically, trees on south-facing slope showed a more evident bimodal pattern and more intra-annual density fluctuations. In recent decades, the intensity of both growth peaks has diminished and drifted away due to the increased summer drought. The VS-Lite2 model reveals a niche partitioning between both species. Differences in growing season's length and timings of growth peaks in both species are relevant for their coexistence and should be considered for estimating mixed-forest responses under climate change scenarios. [ABSTRACT FROM AUTHOR]