Horizontal growth: An overlooked dimension in plant trait space

By mainly focusing on leaves and roots, functional ecology has been omitting an important dimension of plant form and function. Horizontal spacers (rooting stems and roots with adventitious shoots) have an important role in competition, multiplication, foraging, and resprouting. In this report, we provide overview of what is known about the functions of horizontal rooting stems and how such horizontal spacers affect plant performance and community functions. To date, horizontal spacers have been considered only in studies restricted to specific biomes, growth forms, or regions. Consideration of their functions in broader contexts will improve our understanding of plant strategies.