Global synthesis of the temperature sensitivity of leaf litter breakdown in streams and rivers. (28th February 2017)

• Record Type: Journal Article
• Authors: Follstad Shah, Jennifer J.; Kominoski, John S.; Ardón, Marcelo; Dodds, Walter K.; Gessner, Mark O.; Griffiths, Natalie A.; Hawkins, Charles P.; Johnson, Sherri L.; Lecerf, Antoine; LeRoy, Carri J.; Manning, David W. P.; Rosemond, Amy D.; Sinsabaugh, Robert L.; Swan, Christopher M.; Webster, Jackson R.; Zeglin, Lydia H.
• Is Part Of: Global change biology. Volume 23:Number 8(2017)
• Page Start: 3064
• Page End: 3075
• Publication Date: 2017-02-28
• Subjects: activation energy -- breakdown -- carbon cycling -- climate change -- detritivore -- leaf chemistry -- metabolic theory -- microbe -- organic matter -- temperature sensitivity; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.13609
• Languages: English
• ISSNs: 1354-1013

Abstract

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 ( E a, in eV). Temperature sensitivity of litter breakdown varied among twelve plant genera for which E a could be calculated. Higher values of E a were correlated with lower‐quality litter, but these correlations were influenced by a single, N‐fixing genus ( Alnus ). E a values 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 E a was 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 E a values 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 E a values for breakdown mediated by microbes alone and microbes plus detritivores were similar at the global scale. Abstract : Warmer water enhances decomposition of organic matter in streams and rivers, but it is unclear if climate change will result in more carbon emitted to the atmosphere or transported to the ocean. We assembled over 1000 published data points on leaf litter breakdown in streams and rivers globally to assess how rates of breakdown will change with elevated temperature. Across 85 plant genera, we found that rates may increase only half as much as expected should water temperature rise by 1–4 °C. Among 12 plant genera for which temperature sensitivity could be calculated individually, higher sensitivity was correlated with lower quality litter. Similarity in the temperature sensitivity of breakdown mediated by microbes alone or microbes plus detritivores suggests the relative proportions of carbon converted to gas or transported as smaller particles will not change with elevated temperature.