Multilevel responses of emergent vegetation to environmental factors in a semiarid floodplain

Wetland emergent vegetation of Tablas de Daimiel National Park (Central Spain), mainly composed by Cladium mariscus, Phragmites australis and Typha domingensis, was studied to test if population responses to environmental factors were invariant to scaling-up conditions from the single plant to the entire wetland. While the significance of the main controlling, abiotic factors (wetland location, sedimentary and water nitrogen and phosphorus, water level, duration of flooding) was that of earlier studies, the importance of them changed along with the level of plant organization. Our study showed that multiple effects occurred in the responses of helophyte populations to abiotic factors, and that these responses appeared to depend upon the level of observation involved, showing positive ( Typha biomass and sedimentary phosphorus), negative ( Cladium biomass and sedimentary phosphorus, Cladium large patch growth and total phosphorus), delayed (landscape cover of Phragmites and Cladium and water level of the previous year), saturation ( Cladium biomass and water level), threshold (small patch growth rate of Cladium and water level of the previous month) and non-linear (landscape cover of Phragmites and Cladium and total phosphorus in water) effects.