An assessment of cellulose filters as a standardized material for measuring litter breakdown in headwater streams

Abstract

AbstractThe decay rate of cellulose filters and associated chemical and biological characteristics were compared with those of white oak (Quercus alba) leaves to determine whether cellulose filters could be a suitable standardized material for assessing deciduous leaf breakdown in headwater streams. The comparison was done across reaches draining mixed deciduous forest and post‐coal mining catchments, in natural and constructed channels, and ranged in flow duration from ephemeral to perennial. Decay rates of leaves and filters were predicted to differ at a given site, but the decay rates and associated characteristics of leaf and filter litterbags would be positively related. Filter decay rates did not differ across channel type or flow permanence class. Oak leaves decayed ca 2·5× faster than cellulose filters and there was no relationship between decay rates (R2 = 0·02). Ergosterol concentration, total invertebrate density, shredder density, total invertebrate biomass and taxa richness were significantly higher in oak litterbags than in filter litterbags across four sampling dates over 306 days. The biomass of invertebrate shredders colonizing litterbags did not differ between the substrate types. The C:N content was higher for filters than for oak leaves, but the mean difference between substrates decreased by ∼10‐fold over the 306‐day study. In contrast, mean differences in ergosterol concentration between substrates increased threefold over the study. Although characteristics associated with filter litterbags were positively related to those of oak leaf litterbags, most relationships had low explanatory power (R2⩽0·3); however, stronger relationships existed for total invertebrate density, shredder density and taxa richness (R2 = 0·78). Although a standardized material would be useful for incorporating litter breakdown in stream assessments, because of the strong differences in decay rate and associated characteristics, we cannot recommend cellulose filters as a suitable substrate to represent the natural breakdown of leaf material. Published in 2010. This article is a US Government work and is in the public domain in the USA.