title: Global synthesis of the temperature sensitivity of leaf litter breakdown in streams and rivers.
abstract: Streams and rivers are important conduits of terrestrially derived carbon (C) to atmospheric and marine reservoirs. Leaf litter breakdown rates are expected to increase as water temperatures rise in response to climate change. The magnitude of increase in breakdown rates is uncertain, given differences in litter quality and microbial and detritivore community responses to temperature, factors that can influence the apparent temperature sensitivity of breakdown and the relative proportion of C lost to the atmosphere vs. stored or transported downstream. Here, we synthesized 1025 records of litter breakdown in streams and rivers to quantify its temperature sensitivity, as measured by the activation energy (Ea, in eV). Temperature sensitivity of litter breakdown varied among twelve plant genera for which Eacould be calculated. Higher values of Eawere correlated with lower-quality litter, but these correlations were influenced by a single, N-fixing genus (Alnus). Eavalues converged when genera were classified into three breakdown rate categories, potentially due to continual water availability in streams and rivers modulating the influence of leaf chemistry on breakdown. Across all data representing 85 plant genera, the Eawas 0.34 ± 0.04 eV, or approximately half the value (0.65 eV) predicted by metabolic theory. Our results indicate that average breakdown rates may increase by 5-21% with a 1-4 °C rise in water temperature, rather than a 10-45% increase expected, according to metabolic theory. Differential warming of tropical and temperate biomes could result in a similar proportional increase in breakdown rates, despite variation in Eavalues for these regions (0.75 ± 0.13 eV and 0.27 ± 0.05 eV, respectively). The relative proportions of gaseous C loss and organic matter transport downstream should not change with rising temperature given that Eavalues for breakdown mediated by microbes alone and microbes plus detritivores were similar at the global scale.
authors.affiliation: Environmental and Sustainability Studies/Department of Geography, University of Utah, Salt Lake City, UT, 84112, USA.|Department of Watershed Sciences, Utah State University, Logan, UT, 84322, USA.
authors.forename: Jennifer J
authors.identifier: 0000-0001-8287-5035
authors.initials: JJ
authors.lastname: Follstad Shah
authors.affiliation: Department of Biological Sciences, Florida International University, Miami, FL, 33199, USA.
authors.forename: John S
authors.initials: JS
authors.lastname: Kominoski
authors.affiliation: Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC, 27695, USA.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Ardón
authors.affiliation: Division of Biology, Kansas State University, Manhattan, KS, 66506, USA.
authors.forename: Walter K
authors.initials: WK
authors.lastname: Dodds
authors.affiliation: Department of Experimental Limnology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), 16775, Stechlin, Germany.|Department of Ecology, Berlin Institute of Technology (TU Berlin), Ernst-Reuter-Platz 1, 10587, Berlin, Germany.
authors.forename: Mark O
authors.initials: MO
authors.lastname: Gessner
authors.affiliation: Climate Change Science Institute and Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
authors.forename: Natalie A
authors.initials: NA
authors.lastname: Griffiths
authors.affiliation: Department of Watershed Sciences, Utah State University, Logan, UT, 84322, USA.
authors.forename: Charles P
authors.initials: CP
authors.lastname: Hawkins
authors.affiliation: Pacific Northwest Research Station, US Forest Service, Corvallis, OR, 97331, USA.
authors.forename: Sherri L
authors.initials: SL
authors.lastname: Johnson
authors.affiliation: Université de Toulouse, UPS, INP, CNRS, EcoLab (Laboratoire d'Écologie Fonctionnelle et Environnement), 31062, Toulouse, France.
authors.forename: Antoine
authors.initials: A
authors.lastname: Lecerf
authors.affiliation: Environmental Studies Program, The Evergreen State College, Olympia, WA, 98505, USA.
authors.forename: Carri J
authors.initials: CJ
authors.lastname: LeRoy
authors.affiliation: School of Environment and Natural Resources, Ohio State University, Columbus, OH, 43210, USA.
authors.forename: David W P
authors.initials: DWP
authors.lastname: Manning
authors.affiliation: Odum School of Ecology, University of Georgia, Athens, GA, 30602, USA.
authors.forename: Amy D
authors.initials: AD
authors.lastname: Rosemond
authors.affiliation: Department of Biology, University of New Mexico, Albuquerque, NM, 87131, USA.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Sinsabaugh
authors.affiliation: Department of Geography and Environmental Systems, University of Maryland-Baltimore County, Baltimore, MD, 21250, USA.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Swan
authors.affiliation: Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA, 24061, USA.
authors.forename: Jackson R
authors.initials: JR
authors.lastname: Webster
authors.affiliation: Division of Biology, Kansas State University, Manhattan, KS, 66506, USA.
authors.forename: Lydia H
authors.initials: LH
authors.lastname: Zeglin
mesh_terms: D029661:Alnus; D002244:Carbon / Q000737:chemistry*; D057231:Climate Change; D017753:Ecosystem; D018515:Plant Leaves; D045483:Rivers; D013696:Temperature
chemical_list: D002244:Carbon
keywords: activation energy; breakdown; carbon cycling; climate change; detritivore; leaf chemistry; metabolic theory; microbe; organic matter; temperature sensitivity