Suchergebnisse

Measurements of greenhouse gas (GHG) fluxes, particularly methane (CH4) and nitrous oxide (N2O) in mountain ecosystems are scarce due to the complexity and unpredictable behavior of these gases, in addition to the remoteness of these ecosystems. In this context, we measured CO2, CH4, and N2O fluxes in four semi-natural pastures in the Pyrenees to investigate their magnitude and range of variability. Our interest was to study GHG phenomena at the patch-level, therefore we chose to measure the gas-exchange using a combination of a gas analyzer and manual chambers. The analyzer used is a photoacoustic field gas-monitor that allows multi-gas instantaneous measurements. After implementing quality control and corrections, data was of variable quality. We tackled this by categorizing data as to providing quantitative or only qualitative information: 50% and 59% of all CH4 and N2O data, respectively, provided quantitative information above the detection limit. We chose not to discard data providing only qualitative information, because they identify highest- and lowest-flux peak periods and indicate the variability of the fluxes, along different altitudes and under different climatic conditions. We chose not to give fluxes below detection limit a quantitative value but to acknowledge them as values identifying periods with low fluxes. ; We would like to thank Helena Sarri and Mercedes Ibañez, for their assistance during field work. We would also like to thank Mari Pihlatie from the University of Helsinki for fruitful discussions and suggestions. This work was funded by the Spanish Science Foundation (FECYT) through the projects CAPAS (CGL2010-22378-C03-01) and BIOGEI (CGL2013-49142-C2-1-R). The project was also developed within the project CAPACITI supported by a Marie Curie Intra European Fellowship within the 7th European Community Framework to NA (PIEF-GA-2010-275855), HD was supported by a FPI fellowship from the Spanish Ministry of Economy and Competitiveness (BES-2011-047009). Funding through the project "Potential for capture or emission of greenhouse gases in agro-pastoral systems" (2012-AGEC-00080) by the Catalan Government is also acknowledged. We are particularly grateful to two anonymous reviewers for improving the paper, through their useful comments and suggestions.

Incluye material complementario ; Grasslands are one of the major sinks of terrestrial soil organic carbon (SOC). Understanding how environmental and management factors drive SOC is challenging because they are scale-dependent, with large-scale drivers affecting SOC both directly and through drivers working at small scales. Here we addressed how regional, landscape and grazing management, soil properties and nutrients, and herbage quality factors affect 20 cm depth SOC stocks in mountain grasslands in the Pyrenees. Taking advantage of the high variety of environmental heterogeneity in the Pyrenees, we built a dataset (n = 128) that comprises a wide range of environmental and management conditions. This was used to understand the relationship between SOC stocks and their drivers considering multiple environments. We found that temperature seasonality (difference between mean summer temperature and mean annual temperature; TSIS) was the most important geophysical driver of SOC in our study, depending on topography and management. TSIS effects on SOC increased in exposed hillsides, slopy areas, and relatively intensively grazed grasslands. Increased TSIS probably favours plant biomass production, particularly at high altitudes, but landscape and grazing management factors regulate the accumulation of this biomass into SOC. Concerning biochemical SOC drivers, we found unexpected interactive effects between grazer type, soil nutrients and herbage quality. Soil N was a crucial SOC driver as expected but modulated by livestock species and neutral detergent fibre contenting plant biomass; herbage recalcitrance effects varied depending on grazer species. These results highlight the gaps in knowledge about SOC drivers in grasslands under different environmental and management conditions. They may also serve to generate testable hypotheses in later/future studies directed to climate change mitigation policies. ; Research in this paper is based on the PAS-TUS Database, which was compiled from different funding sources over time, the most relevant being the EU Interreg III-A Programme (I3A-4-147-E) and the POCTEFA Programme/Interreg IV-A (FLUXPYR, EFA 34/08); the Spanish Science Foundation FECYT-MICINN (CARBOPAS: REN2002-04300-C02-01; CAR-BOAGROPAS: CGL2006-13555-C03-03 and CAPAS: CGL2010-22378-C03-01); and the Foundation Catalunya-La Pedrera and the Spanish Institute of Agronomical Research INIA (CARBO-CLUS: SUM2006-00029-C02-0). Leticia San Emeterio was funded through a Talent Recruitment grant from Obra Social La Caixa- Fundación CAN. The ARAID Foundation provided support to Juan José Jiménez. This work was funded by the Spanish Science Foundation FECYT-MINECO (projects BIOGEI: GL2013-49142-C2-1-R and IMAGINE: CGL2017-85490-R) and the University of Lleida (PhD Fellowship to Antonio Rodríguez).

Grasslands are one of the major sinks of terrestrial soil organic carbon (SOC). Understanding how environmental and management factors drive SOC is challenging because they are scale-dependent, with large-scale drivers affecting SOC both directly and through drivers working at small scales. Here we addressed how regional, landscape and grazing management, soil properties and nutrients, and herbage quality factors affect 20 cm depth SOC stocks in mountain grasslands in the Pyrenees. Taking advantage of the high variety of environmental heterogeneity in the Pyrenees, we built a dataset (n=128) that comprises a wide range of environmental and management conditions. This was used to understand the relationship between SOC stocks and their drivers considering multiple environments. We found that temperature seasonality (difference between mean summer temperature and mean annual temperature; TSIS) was the most important geophysical driver of SOC in our study, depending on topography and management. TSIS effects on SOC increased in exposed hillsides, slopy areas, and relatively intensively grazed grasslands. Increased TSIS probably favours plant biomass production, particularly at high altitudes, but landscape and grazing management factors regulate the accumulation of this biomass into SOC. Concerning biochemical SOC drivers, we found unexpected interactive effects between grazer type, soil nutrients and herbage quality. Soil N was a crucial SOC driver as expected but modulated by livestock species and neutral detergent fibre contenting plant biomass; herbage recalcitrance effects varied depending on grazer species. These results highlight the gaps in knowledge about SOC drivers in grasslands under different environmental and management conditions. They may also serve to generate testable hypotheses in later/future studies directed to climate change mitigation policies. ; Research in this paper is based on the PASTUS Database, which was compiled from different funding sources over time, the most relevant being the EU Interreg III-A Programme (I3A-4-147-E) and the POCTEFA Programme/Interreg IV-A (FLUXPYR, EFA 34/08); the Spanish Science Foundation FECYT-MICINN (CARBOPAS: REN2002-04300-C02-01; CARBOAGROPAS: CGL2006-13555-C03-03 and CAPAS: CGL2010-22378-C03-01); and the Foundation Catalunya-La Pedrera and the Spanish Institute of Agronomical Research INIA (CARBOCLUS: SUM2006-00029-C02-0). Leticia San Emeterio was funded through a Talent Recruitment grant from Obra Social La Caixa – Fundación CAN. The ARAID Foundation provided support to Juan José Jiménez. This work was funded by the Spanish Science Foundation FECYT-MINECO (projects BIOGEI: GL2013-49142-C2-1-R and IMAGINE: CGL2017-85490-R) and the University of Lleida (PhD Fellowship to Antonio Rodríguez).