title: Litter decay controlled by temperature, not soil properties, affecting future soil carbon.
abstract: Widespread global changes, including rising atmospheric CO2concentrations, climate warming and loss of biodiversity, are predicted for this century; all of these will affect terrestrial ecosystem processes like plant litter decomposition. Conversely, increased plant litter decomposition can have potential carbon-cycle feedbacks on atmospheric CO2levels, climate warming and biodiversity. But predicting litter decomposition is difficult because of many interacting factors related to the chemical, physical and biological properties of soil, as well as to climate and agricultural management practices. We applied13C-labelled plant litter to soil at ten sites spanning a 3500-km transect across the agricultural regions of Canada and measured its decomposition over five years. Despite large differences in soil type and climatic conditions, we found that the kinetics of litter decomposition were similar once the effect of temperature had been removed, indicating no measurable effect of soil properties. A two-pool exponential decay model expressing undecomposed carbon simply as a function of thermal time accurately described kinetics of decomposition. (R2= 0.94; RMSE = 0.0508). Soil properties such as texture, cation exchange capacity, pH and moisture, although very different among sites, had minimal discernible influence on decomposition kinetics. Using this kinetic model under different climate change scenarios, we projected that the time required to decompose 50% of the litter (i.e. the labile fractions) would be reduced by 1-4 months, whereas time required to decompose 90% of the litter (including recalcitrant fractions) would be reduced by 1 year in cooler sites to as much as 2 years in warmer sites. These findings confirm quantitatively the sensitivity of litter decomposition to temperature increases and demonstrate how climate change may constrain future soil carbon storage, an effect apparently not influenced by soil properties.
authors.affiliation: Agriculture & Agri-Food Canada (AAFC) Research & Development Centre, Central Experimental Farm, Ottawa, ON, K1A 0C6, Canada.
authors.forename: Edward G
authors.initials: EG
authors.lastname: Gregorich
authors.affiliation: AAFC Research & Development Centre, Lethbridge, AB, T1J 4B1, Canada.
authors.forename: Henry
authors.initials: H
authors.lastname: Janzen
authors.affiliation: AAFC Research & Development Centre, Lethbridge, AB, T1J 4B1, Canada.
authors.forename: Benjamin H
authors.initials: BH
authors.lastname: Ellert
authors.affiliation: AAFC Research & Development Centre, Saskatoon, SK, S7H 5A8, Canada.
authors.forename: Bobbi L
authors.initials: BL
authors.lastname: Helgason
authors.affiliation: Agriculture & Agri-Food Canada (AAFC) Research & Development Centre, Central Experimental Farm, Ottawa, ON, K1A 0C6, Canada.
authors.forename: Budong
authors.initials: B
authors.lastname: Qian
authors.affiliation: AAFC Research & Development Centre, Fredericton, NB, E3B 4Z7, Canada.
authors.forename: Bernie J
authors.initials: BJ
authors.lastname: Zebarth
authors.affiliation: AAFC Research & Development Centre, Quebec, QC, G1V 2J3, Canada.
authors.forename: Denis A
authors.initials: DA
authors.lastname: Angers
authors.affiliation: AAFC Research & Development Centre, London, ON, N5V 4T3, Canada.
authors.forename: Ronald P
authors.initials: RP
authors.lastname: Beyaert
authors.affiliation: AAFC Research & Development Centre, Harrow, ON, N0R 1G0, Canada.
authors.forename: Craig F
authors.initials: CF
authors.lastname: Drury
authors.affiliation: AAFC Research & Development Centre, Morden, MB, R6M 1Y5, Canada.
authors.forename: Scott D
authors.initials: SD
authors.lastname: Duguid
authors.affiliation: AAFC Research & Development Centre, Indian Head, SK, S0G 2K0, Canada.
authors.forename: William E
authors.initials: WE
authors.lastname: May
authors.affiliation: AAFC Research & Development Centre, Swift Current, SK, S9H 3X2, Canada.
authors.forename: Brian G
authors.initials: BG
authors.lastname: McConkey
authors.affiliation: Department of Renewable Resources, University of Alberta, Edmonton, AB, T6G 2H1, Canada.
authors.forename: Miles F
authors.initials: MF
authors.lastname: Dyck
mesh_terms: D002170:Canada; D002244:Carbon; D057231:Climate Change; D017753:Ecosystem; D012987:Soil / Q000737:chemistry*; D013696:Temperature
chemical_list: D012987:Soil; D002244:Carbon
keywords: agriculture; carbon cycling; climate change; litter decomposition; temperature