Pine afforestation affects key primary producers in mountain grassland streams in Córdoba, Argentina

Abstract

We evaluated changes in benthic algal community in grassland mountain streams converted to exotic pine afforestation. Three headwater streams draining grasslands and three draining plantations of Pinus elliottii were selected in a semiarid mountain watershed (Córdoba, Argentina). Hydraulic and physicochemical variables were recorded and benthic algal samples were collected in each stream at two hydrological periods (high and low flow). Light intensity was lower in afforested streams. Community composition differed between grassland and afforested streams. Algal abundance and richness, richness of chlorophytes and cyanobacteria, and the indicator taxa were reduced in afforested streams. Diversity, evenness and biomass were higher in the high water period but did not differ between riparian vegetation types. The observed changes in benthic algal attributes may have implications in ecosystem functioning because of the central role that algal biofilms play in the productivity of these fluvial systems, as sources of food, energy and oxygen.