Floristic associations and filtering ability of riparian vegetation strips

The analysis of lateral flow runoff of superficial nutrientsand sediments from an agricultural origin and their retentionby infiltration of riparian vegetation strips are of great importancein reducing the agricultural externalities on surface water quality.The aim of this study was to relate soil infiltration to the main biophysicalproperties of riparian environments in the Pampa Australof Argentina, defined by the composition of its plant communityand the coverage of exotic species. We explored the relationships betweenhydraulic conductivity (Ks) and aboveground, litter and rootbiomasses, organic matter concentration, terrain slope, soil bulk density,texture and electrical conductivity. We determined eight floristicassociations through the classification of 65 censuses of vegetation.Three of the associations were dominated by native grasses, threeby exotic grasses and two presented a layer of exotic willow trees incombination with native and invasive grasses. The mean Ks in soilsfrom the floristic associations with trees and from the associationsof native grasses without trees were higher than in soils from theassociations of exotic grasses without trees. Significant relationshipswere found between Ks and the soil properties that are sensitive tothe influence of vegetation, suggesting that the relationships betweenfloristic composition and infiltration could be explained partly due tocausal relationships.