title: Microbial carbon mineralization in tropical lowland and montane forest soils of Peru.
abstract: Climate change is affecting the amount and complexity of plant inputs to tropical forest soils. This is likely to influence the carbon (C) balance of these ecosystems by altering decomposition processes e.g., "positive priming effects" that accelerate soil organic matter mineralization. However, the mechanisms determining the magnitude of priming effects are poorly understood. We investigated potential mechanisms by adding (13)C labeled substrates, as surrogates of plant inputs, to soils from an elevation gradient of tropical lowland and montane forests. We hypothesized that priming effects would increase with elevation due to increasing microbial nitrogen limitation, and that microbial community composition would strongly influence the magnitude of priming effects. Quantifying the sources of respired C (substrate or soil organic matter) in response to substrate addition revealed no consistent patterns in priming effects with elevation. Instead we found that substrate quality (complexity and nitrogen content) was the dominant factor controlling priming effects. For example a nitrogenous substrate induced a large increase in soil organic matter mineralization whilst a complex C substrate caused negligible change. Differences in the functional capacity of specific microbial groups, rather than microbial community composition per se, were responsible for these substrate-driven differences in priming effects. Our findings suggest that the microbial pathways by which plant inputs and soil organic matter are mineralized are determined primarily by the quality of plant inputs and the functional capacity of microbial taxa, rather than the abiotic properties of the soil. Changes in the complexity and stoichiometry of plant inputs to soil in response to climate change may therefore be important in regulating soil C dynamics in tropical forest soils.
authors.affiliation: Centre for Ecology & Hydrology, Lancaster Environment Centre Lancaster, UK.
authors.forename: Jeanette
authors.initials: J
authors.lastname: Whitaker
authors.affiliation: Soil and Ecosystem Laboratory, Lancaster Environment Centre, Lancaster University Lancaster, UK.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Ostle
authors.affiliation: Centre for Ecology & Hydrology, Lancaster Environment Centre Lancaster, UK.
authors.forename: Niall P
authors.initials: NP
authors.lastname: McNamara
authors.affiliation: School of Geosciences, University of Edinburgh Edinburgh, UK.
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Nottingham
authors.affiliation: Centre for Ecology & Hydrology, Lancaster Environment Centre Lancaster, UK.
authors.forename: Andrew W
authors.initials: AW
authors.lastname: Stott
authors.affiliation: Faculty of Life Sciences, The University of Manchester Manchester, UK.
authors.forename: Richard D
authors.initials: RD
authors.lastname: Bardgett
authors.affiliation: Seccion Química, Pontificia Universidad Católica del Perú Lima, Peru ; School of Geography and the Environment, Environmental Change Institute, University of Oxford Oxford, UK.
authors.forename: Norma
authors.initials: N
authors.lastname: Salinas
authors.affiliation: Facultad de Ciencias Biologicas, Universidad Nacional de San Antonio Abad Cusco, Peru.
authors.forename: Adan J Q
authors.initials: AJ
authors.lastname: Ccahuana
authors.affiliation: School of Geosciences, University of Edinburgh Edinburgh, UK.
authors.forename: Patrick
authors.initials: P
authors.lastname: Meir
keywords: cloud forest; decomposition; ecosystem function; microbial community composition; priming; respiration; soil organic matter