title: Effects of soil warming and nitrogen addition on soil respiration in a New Zealand tussock grassland.
abstract: Soil respiration (RS) represents a large terrestrial source of CO2 to the atmosphere. Global change drivers such as climate warming and nitrogen deposition are expected to alter the terrestrial carbon cycle with likely consequences for RS and its components, autotrophic (RA) and heterotrophic respiration (RH). Here we investigate the impacts of a 3°C soil warming treatment and a 50 kg ha(-1) y(-1) nitrogen addition treatment on RS, RH and their respective seasonal temperature responses in an experimental tussock grassland. Average respiration in untreated soils was 0.96±0.09 μmol m(-2) s(-1) over the course of the experiment. Soil warming and nitrogen addition increased RS by 41% and 12% respectively. These treatment effects were additive under combined warming and nitrogen addition. Warming increased RH by 37% while nitrogen addition had no effect. Warming and nitrogen addition affected the seasonal temperature response of RS by increasing the basal rate of respiration (R10) by 14% and 20% respectively. There was no significant interaction between treatments for R10. The treatments had no impact on activation energy (E0). The seasonal temperature response of RH was not affected by either warming or nitrogen addition. These results suggest that the additional CO2 emissions from New Zealand tussock grassland soils as a result of warming-enhanced RS constitute a potential positive feedback to rising atmospheric CO2 concentration.
authors.affiliation: School of Biological Sciences, University of Canterbury, Christchurch, New Zealand; Landcare Research, Lincoln, New Zealand.
authors.forename: Scott L
authors.initials: SL
authors.lastname: Graham
authors.affiliation: Landcare Research, Lincoln, New Zealand.
authors.forename: John E
authors.initials: JE
authors.lastname: Hunt
authors.affiliation: Landcare Research, Lincoln, New Zealand.
authors.forename: Peter
authors.initials: P
authors.lastname: Millard
authors.affiliation: Landcare Research, Lincoln, New Zealand.
authors.forename: Tony
authors.initials: T
authors.lastname: McSeveny
authors.affiliation: School of Biological Sciences, University of Canterbury, Christchurch, New Zealand; Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot, Berkshire, United Kingdom.
authors.forename: Jason M
authors.initials: JM
authors.lastname: Tylianakis
authors.affiliation: Landcare Research, Lincoln, New Zealand.
authors.forename: David
authors.initials: D
authors.lastname: Whitehead
mesh_terms: D001272:Atmosphere; D018533:Biomass; D002245:Carbon Dioxide / Q000032:analysis / Q000737:chemistry*; D065948:Grassland; D008962:Models, Theoretical; D009520:New Zealand; D009584:Nitrogen / Q000737:chemistry*; D012621:Seasons; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D013696:Temperature; D014867:Water / Q000032:analysis
chemical_list: D012987:Soil; D014867:Water; D002245:Carbon Dioxide; D009584:Nitrogen