Nutrients stimulate leaf breakdown rates and detritivore biomass: bottom-up effects via heterotrophic pathways |
| |
Authors: | Jennifer L Greenwood Amy D Rosemond J Bruce Wallace Wyatt F Cross Holly S Weyers |
| |
Institution: | (1) Present address: Department of Biological Sciences, 247 Brehm Hall, University of Tennessee at Martin, Martin, TN 38238, USA;(2) Institute of Ecology, University of Georgia, Athens, GA 30602, USA;(3) Institute of Ecology and Department of Entomology, University of Georgia, Athens, GA 30602, USA;(4) Present address: Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071, USA;(5) Present address: USGS, 1289 Mc D Drive, Dover, DE 19901, USA |
| |
Abstract: | Most nutrient enrichment studies in aquatic systems have focused on autotrophic food webs in systems where primary producers
dominate the resource base. We tested the heterotrophic response to long-term nutrient enrichment in a forested, headwater
stream. Our study design consisted of 2 years of pretreatment data in a reference and treatment stream and 2 years of continuous
nitrogen (N) + phosphorus addition to the treatment stream. Studies were conducted with two leaf species that differed in
initial C:N, Rhododendron maximum (rhododendron) and Acer rubrum (red maple). We determined the effects of nutrient addition on detrital resources (leaf breakdown rates, litter C:N and microbial
activity) and tested whether nutrient enrichment affected macroinvertebrate consumers via increased biomass. Leaf breakdown
rates were ca. 1.5 and 3× faster during the first and second years of enrichment, respectively, in the treatment stream for
both leaf types. Microbial respiration rates of both leaf types were 3× higher with enrichment, and macroinvertebrate biomass
associated with leaves increased ca. 2–3× with enrichment. The mass of N in macroinvertebrate biomass relative to leaves tended
to increase with enrichment up to 6× for red maple and up to 44× for rhododendron leaves. Lower quality (higher C:N) rhododendron
leaves exhibited greater changes in leaf nutrient content and macroinvertebrate response to nutrient enrichment than red maple
leaves, suggesting a unique response by different leaf species to nutrient enrichment. Nutrient concentrations used in this
study were moderate and equivalent to those in streams draining watersheds with altered land use. Thus, our results suggest
that similarly moderate levels of enrichment may affect detrital resource quality and subsequently lead to altered energy
and nutrient flow in detrital food webs.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. |
| |
Keywords: | Detritus Headwater stream Leaf quality Nutrient enrichment Stream macroinvertebrates |
本文献已被 PubMed SpringerLink 等数据库收录! |
|