Intraspecific trait variability: Herbs are not just small trees

Intraspecific trait variability has been identified as a possible reason why the trait-based approach in functional ecology is not as predictive as we would like. However, sources of intraspecific variability are not only largely acknowledged responses to the environmental gradients, but also the intrinsic effects due to seasonal and ontogenetic development. Yet, the effect of seasonal and ontogenetic development on intraspecific trait variability has not been as theoretically predicted or studied so far as it would deserve. In this opinion paper, we follow recent theoretical predictions on the ontogenetic development of a key functional trait capturing plant economics - leaf mass per area (LMA,) and contribute to the debate on whether general predictions based and demonstrated on trees hold true also for herbs. While plant height, the position of leaves in the canopy, and the whole plant leaf area are suggested to be important drivers of LMA in trees, we propose seasonal development, bud preformation, meristem size, and amount of carbohydrate storage to be crucial for intraspecific trait variability in temperate herbs.