title: Environmental and microbial factors influencing methane and nitrous oxide fluxes in Mediterranean cork oak woodlands: trees make a difference.
abstract: Cork oak woodlands (montado) are agroforestry systems distributed all over the Mediterranean basin with a very important social, economic and ecological value. A generalized cork oak decline has been occurring in the last decades jeopardizing its future sustainability. It is unknown how loss of tree cover affects microbial processes that are consuming greenhouse gases in the montado ecosystem. The study was conducted under two different conditions in the natural understory of a cork oak woodland in center Portugal: under tree canopy (UC) and open areas without trees (OA). Fluxes of methane and nitrous oxide were measured with a static chamber technique. In order to quantify methanotrophs and bacteria capable of nitrous oxide consumption, we used quantitative real-time PCR targeting the pmoA and nosZ genes encoding the subunit of particulate methane mono-oxygenase and catalytic subunit of the nitrous oxide reductase, respectively. A significant seasonal effect was found on CH4 and N2O fluxes and pmoA and nosZ gene abundance. Tree cover had no effect on methane fluxes; conversely, whereas the UC plots were net emitters of nitrous oxide, the loss of tree cover resulted in a shift in the emission pattern such that the OA plots were a net sink for nitrous oxide. In a seasonal time scale, the UC had higher gene abundance of Type I methanotrophs. Methane flux correlated negatively with abundance of Type I methanotrophs in the UC plots. Nitrous oxide flux correlated negatively with nosZ gene abundance at the OA plots in contrast to that at the UC plots. In the UC soil, soil organic matter had a positive effect on soil extracellular enzyme activities, which correlated positively with the N2O flux. Our results demonstrated that tree cover affects soil properties, key enzyme activities and abundance of microorganisms and, consequently net CH4 and N2O exchange.
authors.affiliation: Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa Oeiras, Portugal.
authors.forename: Alla
authors.initials: A
authors.lastname: Shvaleva
authors.affiliation: Department of Environmental Science, University of Eastern Finland Kuopio, Finland.
authors.forename: Henri M P
authors.initials: HM
authors.lastname: Siljanen
authors.affiliation: Centro de Estudos Florestais, Instituto Superior de Agronomia, Universidade de Lisboa Lisboa, Portugal.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Correia
authors.affiliation: Centro de Estudos Florestais, Instituto Superior de Agronomia, Universidade de Lisboa Lisboa, Portugal.
authors.forename: Filipe
authors.initials: F
authors.lastname: Costa E Silva
authors.affiliation: Department of Environmental Science, University of Eastern Finland Kuopio, Finland.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Lamprecht
authors.affiliation: Centro de Estudos Florestais, Instituto Superior de Agronomia, Universidade de Lisboa Lisboa, Portugal.
authors.forename: Raquel
authors.initials: R
authors.lastname: Lobo-do-Vale
authors.affiliation: Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa Oeiras, Portugal.
authors.forename: Catarina
authors.initials: C
authors.lastname: Bicho
authors.affiliation: Landscape, Environment, Agriculture and Food, Instituto Superior de Agronomia, Universidade de Lisboa Lisboa, Portugal.
authors.forename: David
authors.initials: D
authors.lastname: Fangueiro
authors.affiliation: Centre for Ecology and Hydrology Penicuik, UK.
authors.forename: Margaret
authors.initials: M
authors.lastname: Anderson
authors.affiliation: Centro de Estudos Florestais, Instituto Superior de Agronomia, Universidade de Lisboa Lisboa, Portugal.
authors.forename: João S
authors.initials: JS
authors.lastname: Pereira
authors.affiliation: Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa Oeiras, Portugal.
authors.forename: Maria M
authors.initials: MM
authors.lastname: Chaves
authors.affiliation: Centre for Ecology Evolution and Environmental Changes, Faculdade de Ciências, Universidade de Lisboa Lisboa, Portugal.
authors.forename: Cristina
authors.initials: C
authors.lastname: Cruz
authors.affiliation: Department of Environmental Science, University of Eastern Finland Kuopio, Finland.
authors.forename: Pertti J
authors.initials: PJ
authors.lastname: Martikainen
keywords: Mediterranean; enzymes; methane; nitrous oxide; nosZ; oak woodland; pmoA