PLANT FUNCTIONAL TYPES IDENTIFICATION IN THE LOWER PARANÁ RIVER

MORANDEIRA, NATALIA; BORRO, MARIA MARTA; GONZALEZ TRILLA, GABRIELA; SALVIA, MARÍA MERCEDES; MADANES, NORA; KANDUS, PATRICIA

Orlando

Congreso; 9 th INTECOL International Wetlands Conference "WETLANDS IN A COMPLEX WORLD"; 2012

Large wetlands of temperate South American floodplains are mostly covered by herbaceous plants, which are expected to be adapted to a wide range of water availability and hydroperiods. While few species usually dominate at any particular location, at landscape and regional scales there is a large number of plant species, probably with functional redundancy. Plant Functional Types (PFT) relying on a shared set of key structural and functional traits, promise to be a tool to assess wetland environmental conditions. Beside traditional vegetation surveys and phytosociological descriptions, this approach may synthesize the complexity of wetland plant communities with less emphasis on taxonomy. We aimed to identify PFTs within the herbaceous plant communities of the Lower Paraná floodplain. We also evaluated the spatial association between dominant PFTs and environmental conditions determined by geomorphic setting, topographical position and soil condition. In 47 sites stratified into distinct geomorphic settings and topographical positions, we estimated mean species coverage using Braun-Blanquet cover-abundance scale in three 1m2 plots. Sub-surface soil samples (two layers, ca.0-25 and 25-45 cm depth) and plant community biomass were also collected in the plots. In each site, we randomly selected 5 adult individuals of each dominant species for trait recording. The data matrix had 53 plant observations x 20 functional and structural traits. Plant traits values were standardized and in order to avoid trait redundancy we excluded those significantly correlated with each other. The remaining 8 independent traits were: presence of hollow stems, plant height, number of leaves, leaf thickness (mm), leaf area (mm2), leaf specific area (mm2/g), leaf perimeter/length, total leaf nitrogen content (%N of dry weight). Through cluster analysis (Gower distance measure, Ward linkage method) we classified plant populations into 10 PFTs. The traits that better discriminated PFTs were plant height, number of leaves, %N, leaf perimeter/length and leaf area. Morpho-ecological growth types were well discriminated: 5 PFTs were predominantly of broad-leaved species (mainly Polygonaceae, Asteraceae and Onagraceae), 4 of graminoid species (mainly Poaceae) and one PFTs of a sedge species (Cyperaceae). Two broad-leaved PFTs with distinct structural features had high N foliar content (and high phosphorus content). Multiple regression models suggest that both N and P leaf content could be explained by P content in the first soil layer, plant community biomass and belonging or not to Poaceae family. Contrary to our expectations, PFTs distribution was not related to geomorphic setting. However, 4 PFTs dominated only low or high topographic positions, which would be closely related to water table level dynamics and water permanence.