SEASONAL ANALYSIS OF AQUATIC AND TERRESTRIAL INVERTEBRATE SUPPLY TO STREAMS WITH GRASSLAND AND DECIDUOUS RIPARIAN VEGETATION

Abstract

Aquatic and terrestrial invertebrate supply was measured across eight streams with contrasting riparian vegetation (grassland, open-canopy deciduous and closed-canopy deciduous) in County Mayo, Ireland, in 2002. Benthic invertebrates were collected from Surber samples, drifting aquatic and terrestrial invertebrates were collected in drift traps, aerial terrestrial invertebrates were collected on sticky traps and soil-surface-dwelling invertebrates were collected in pitfall traps. Season had greatest influence on aquatic invertebrate supply, whereas riparian vegetation type had a greater influence on terrestrial invertebrate supply to streams. Benthic invertebrate abundance tended to be lowest in summer while, in contrast, aquatic invertebrate drift was significantly higher. Terrestrial invertebrate drift was greatest in open-canopy streams. Aerial terrestrial invertebrate densities were greater in canopied streams in spring but were greater in grassland streams in summer. Biomass, however, was lowest in grassland streams in spring and summer. Soil-surface invertebrate abundances did not differ among riparian types, but canopied streams were associated with wingless groups while grassland streams were associated with winged groups that may be easily dislodged by wind and rain. !!c:/3b2win/remove.batRiparian influences on the abundance and composition of invertebrate supply to streams are discussed.