The Roles of Competition and Facilitation in Producing Zonation Along an Experimental Flooding Gradient: a Tale of Two Tails with Ten Freshwater Marsh Plants

Plant zonation is conspicuous in wetlands. The cause frequently assumed to be the direct physiological effects of physical factors (termed ‘stress’), however many experiments show that competition and facilitation also patterns. We conducted a field experiment with freshwater marsh emergent plants test causes along single stress gradient: flooding duration. constructed an experimental wetland ten levels ensure environmental conditions represented full range potential levels, from never flooded continually flooded. planted common varied ecology duration gradient. grew them alone mixture for three years measured changes minimum maximum limits, mode distribution, interaction importance. distribution did not shift, whether species were grown or neighbours. found strong under low stress. no high Flooding controlled lower limits plants. intense enough eliminate half within growing seasons. Our showed stresses, but facilitation, controls macrophytes gradient, at least Models guiding restoration need include as well flood causal factors, facilitation.