Assessing impact of eucalyptus plantations on benthic macroinvertebratecommunities by a litter exclusion experiment

Abstract

To test whether leaf litter from eucalyptus plantations affects stream macroinvertebrate communities, we manipulated litterinputs into a small headwater tributary of the Agüera stream (northern Spain) running under mixed deciduous forests. Threecontiguous 50 m long reaches were used: the upstream reach was left as a control (site C), whereas the two downstream siteswere covered by 1 mm mesh nets to avoid natural litter inputs, and twice a month received litter collected at a deciduous forest(site D, mid) or a eucalyptus plantation (site E, downstream). Benthic Surber samples were taken from the three sites before andafter the treatment and density, biomass and structure of the community were compared. Density and biomass of macroinvertebratesdid not differ among sites before the treatment. Total density and biomass of macroinvertebrates increased in all the sitesduring the experimental period but most considerably at the site were deciduous forest inputs were simulated (station D). At theend of the experiment shredders were significantly less abundant at site E (eucalyptus) than at site D (deciduous). In addition,shredder density and biomass per total organic matter amount and per total leaf amount became higher at site D. In conclusion,these results suggest a subtle negative impact of eucalyptus litter on stream macroinvertebrate communities, especially on shredders.