Inherent variation of functional traits in winter and summer leaves of Mediterranean seasonal dimorphic species: evidence of a ‘within leaf cohort’ spectrum

Leaf morphological, physiological and biochemical traits tend to vary in a coordinated manner as described by the Leaf Economics Spectrum (LES). Nevertheless, some aspects, such as how the leaf trait variation sources affect LES predictions, are still little investigated.

In a recent study published in AoB PLANTS, Puglielli and Varone test whether leaf trait variations within different leaf cohorts could alter the LES. A database on leaf morphological and physiological traits from different leaf cohorts of Cistus spp. was built by collecting data from literature. These species are seasonal dimorphic shrubs with two well-defined leaf cohorts during a year: summer leaves and winter leaves. Traits investigated included leaf mass area, leaf thickness, leaf tissue density, net photosynthetic rate and nitrogen content. The results of the study suggest that different leaf cohorts of evergreen seasonal dimorphic species display significant differences from the LES. Moreover, they show that species characterized by an extended leaf production during a growing season, such as evergreens, can shift from a more competitive to a more stress tolerant strategy during a single growing season. This provides a new framework to better investigate evergreens’ future responses to the major drivers of global climate change. This is particularly important considering that functional differences among leaf flushes formed at different times during a growing season are expected to increase due to global climate change.