Comparison of leaf processing rates under different temperature regimes in three headwater streams

Abstract

1. We studied the effects of different temperature regimes on leaf litter processing in three forested Appalachian headwater streams of different pH (mean pH = 4.2, 6.5, 7.5). 2. We compared leaf breakdown rates, microbial biomass and macroinvertebrate shredder density and biomass between two 12‐week processing periods (October–January and November–February) in each stream. Leaf processing rates were calculated both as k (day–1) and kd (degree day–1). 3. There were no significant differences in processing rates (k day–1) between the two study periods for any leaf species in any stream. The average difference in temperature between the two study periods was 175 degree days. Shredder density was significantly higher during the earlier study period on 40% of the sample dates, but shredder biomass was not significantly different between the two study periods. ATP concentration was significantly higher during the early study period for 60% of the sample dates. 4. More significant differences in these variables (shredder density and biomass, ATP concentration) were seen among the three study streams than between the two study periods. This indicates that in this study other factors, particularly stream pH, contributed more to processing rate variation than did differences in thermal regime.

Diversity of Fungi, Bacteria, and Actinomycetes on Leaves Decomposing in a Stream

“…The decay rates of maple and oak leaves we determined are comparable to those reported from other studies which also found oak leaves to be processed more slowly than maple leaves (47,53). The exponential decay model explained 69 and 61% of the variability for maple and oak leaves, respectively, in our study.…”

Chronic exposure to pentavalent arsenic of larval leopard frogs (Rana pipiens): bioaccumulation and reduced swimming performance

“…This is probably the reason that no significant effect on survival was observed in this study. Bioaccumulation of As has been observed in amphibians at some contaminated field sites (Rowe et al 1996;Clark et al 1998;Roe et al 2005). In this study, As concentrations in the metamorphs were significantly elevated only in the 150, 500, and 1,000 lg l -1 treatments, ranging between 1.7 and 5.3 mg kg -1 dry mass.…”

Organic matter breakdown and ecosystem metabolism: functional indicators for assessing river ecosystem health

“…See ''Water temperature'' below Gessner et al 1998, Mathuriau and Chauvet 2002, but see Chergui and Pattee 1991 Depends on rate of invertebrate shredding Baldy et al 1995, Jonsson et al 2001, but see Grac¸a et al 2001Fabre and Chauvet 1998, Fleituch 2001 See ''Nutrients'' below Pozo 1993 Invertebrate density or leaf abrasion higher in riffles Meyer 1980, Smith 1986, Casas 1996 Invertebrate densities lower or anaerobic Reice 1974 Higher invertebrate density Rounick and Winterbourn 1983 Crayfish very important, but fish might reduce shredder activity Rosemond et al 1998, Usio 2000, Konishi et al 2001, Schofield et al 2001 Microorganisms most responsive to temperature; if invertebrate density is high in cold season, leaf decay is faster Webster and Benfield 1986, Bunn 1988, Garden and Davies 1988, 1989, McArthur et al 1988, Short and Smith 1989, Lopez et al 2001, Menendez et al 2003 Lower invertebrate density or anaerobic conditions Reice 1974, Triska and Buckley 1978, Herbst 1980, Meyer 1980, Chauvet 1988, Chergui and Pattee 1990, Rader et al 1994, Niyogi et al 2003 Reduced invertebrate or microorganism activity Allard and Moreau 1986, Collier and Winterbourn 1987, Garden and Davies 1989, Griffith and Perry 1994, Rowe et al 1996, Dangles and Gu...…”