BUSCADOR RECOLECTA

Fairy ring fungi are considered keystone species in grasslands due to their strong impact on soil physicochemical properties, but their effect on the associated bacterial community is poorly understood. Here, we analyze shifts in soil bacterial diversity and community composition across fairy rings using Illumina metabarcoding. A total of 254,135 MiSeq reads and between 405 and 1444 operational taxonomic units (OTUs) per soil sample were observed in a montane grassland in the Eastern Pyrenees. We found a strong reduction in all bacterial diversity indices inside the ring-affected zones compared to the outside grassland, especially in the stimulation (current ring) zone. The exception were Firmicutes, the dominant taxa in the grassland, which increased their relative abundance further in fairy ring-affected zones. The recovery of bacterial populations after the fungal front passage highlights the strong resilience of the bacterial communities to this biotic disturbance., This study was developed within the projects BIOGEI (CGL 201349142-C2-1-R) and CAPAS (CGL2010-22378-C03-01), funded by the Spanish Science Foundation (FECYT) together with the FPU program (FPU12/05849), run by the Spanish Ministry of Education. Funding from the project IMAGINE (CGL 2017-85490-R) together with the IF program (PRE2018-086312) allowed the completion of this work.

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.

Root turnover is an important carbon flux component in grassland ecosystems because it
replenishes substantial parts of carbon lost from soil via heterotrophic respiration and leaching.
Among the various methods to estimate root turnover, the root’s radiocarbon signature
has rarely been applied to grassland soils previously, although the value of this approach is
known from studies in forest soils. In this paper, we utilize the root’s radiocarbon signatures,
at 25 plots, in mountain grasslands of the montane to alpine zone of Europe.We place the
results in context of a global data base on root turnover and discuss driving factors. Root
turnover rates were similar to those of a subsample of the global data, comprising a similar
temperature range, but measured with different approaches, indicating that the radiocarbon
method gives reliable, plausible and comparable results. Root turnover rates (0.06–1.0 y-1)
scaled significantly and exponentially with mean annual temperatures. Root turnover rates
indicated no trend with soil depth. The temperature sensitivity was significantly higher in
mountain grassland, compared to the global data set, suggesting additional factors influencing
root turnover. Information on management intensity from the 25 plots reveals that root
turnover may be accelerated under intensive and moderate management compared to low
intensity or semi-natural conditions. Because management intensity, in the studied ecosystems,
co-varied with temperature, estimates on root turnover, based on mean annual temperature
alone, may be biased. A greater recognition of management as a driver for root
dynamics is warranted when effects of climatic change on belowground carbon dynamics
are studied in mountain grasslands., KB received support from the Swiss National Science Foundation, project 200021-115891 (www.snf.ch). SM received support from the Swiss State Secretariat for Education and Research, project C07.0031 (www.sbfi.admin.ch). MTS received support from the Spanish Ministry of Science and Innovation, (project CAPAS, CGL2010-22378-C03- 01) (www.idi.mineco.gob.es).

Global change modifies vegetation composition in grasslands with shifts in plant functional types (PFT). Although changes in plant community composition imply changes in soil function, this relationship is not well understood. We investigated the relative importance of environmental (climatic, management and soil) variables and plant functional diversity (PFT composition and interactions) on soil activity and fertility along a climatic gradient. We collected samples of soil and PFT biomass (grasses, legumes, and non-legume forbs) in six extensively managed grasslands along a climatic gradient in the Northern Iberian Peninsula. Variation Partitioning Analysis showed that abiotic and management variables explained most of the global variability (96.5%) in soil activity and fertility; soil moisture and grazer type being the best predictors. PFT diversity accounted for 27% of the total variability, mostly in interaction with environmental factors. Diversity-Interaction models applied on each response variable revealed that PFT-evenness and pairwise interactions affected particularly the nitrogen cycle, enhancing microbial biomass nitrogen, dissolved organic nitrogen, total nitrogen, urease, phosphatase, and nitrification potential. Thus, soil activity and fertility were not only regulated by environmental variables, but also enhanced by PFT diversity. We underline that climate change-induced shifts in vegetation composition can alter greenhouse gas—related soil processes and eventually the feedback of the soil to the atmosphere., This work was funded by the Spanish Science Foundation (FECYT) through the projects CAPAS (CGL2010-22378-C03-01), BIOGEI (CGL2013-49142-C2-1-R) and IMAGINE (CGL2017-85490-R). H. Debouk was supported by a FPI fellowship from the Spanish Ministry of Economy and Competitiveness (BES-2011-047009). L. San Emeterio was funded by a Talent Recruitment grant from Obra Social La Caixa—Fundación CAN.

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).

Forage systems are the major land use, and provide essential resources for animal feeding. Assessing the influence of forage species on net ecosystem CO2 exchange (NEE) is key to develop management strategies that can help to mitigate climate change, while optimizing productivity of these systems. However, little is known about the effect of forage species on CO2 exchange fluxes and net biome production (NBP), considering: species ecophysiological responses; growth and fallow periods separately; and the management associated with the particular sown species. Our study assesses the influence of cereal monocultures vs. cereal legume mixtures on (1) ecosystem scale CO2 fluxes, for the whole crop season and separately for the two periods of growth and fallow; (2) potential sensitivities of CO2 exchange related to short-term variations in light, temperature and soil water content; and (3) NBP during the growth period; this being the first long term (seven years) ecosystem scale CO2 fluxes dataset of an intensively managed forage system in the Pyrenees region. Our results provide strong evidence that cereal-legume mixtures lead to higher net CO2 uptake than cereal monocultures, as a result of higher gross CO2 uptake, while respiratory fluxes did not significantly increase. Also, management associated with cereal legume mixtures favoured vegetation voluntary regrowth during the fallow period, which was decisive for the cumulative net CO2 uptake of the entire crop season. All cereal legume mixtures and some cereal monocultures had a negative NBP (net gain of C) during the growth period, indicating C input to the system, besides the yield. Overall, cereal legume mixtures enhanced net CO2 sink capacity of the forage system, while ensuring productivity and forage quality., We would like to thank F. Gouriveau, E. Ceschia and J. Elbers for their critical contribution to the installation of the eddy covariance tower and to data analysis, and D. Estany and H. Sarri for field assistance. The flux tower was installed during the FLUXPYR project (EFA34/08, INTERREG IV-A POCTEFA, financed by EU-ERDF, Generalitat de Catalunya and Conseil Régional Midi-Pyrénées). The following additional projects also contributed with funding to this work: CAPACITI (FP7/2007-2013 grant agreement n° 275855), AGEC 2012 (Generalitat de Catalunya), CAPAS (Spanish Science Foundation, CGL2010-22378-C03-01), BIOGEI (Spanish Science Foundation, CGL2013-49142-C2-1-R, supported by a FPI fellowship for Mercedes Ibañez, BES-2014-069243) and IMAGINE (Spanish Science Foundation, CGL2017-85490-R). We would like to acknowledge the Forest Science and Technology Centre of Catalonia (CTFC) for support with study site maintenance.

Plant functional traits underlie vegetation responses to environmental changes such as global warming, and consequently influence ecosystem processes. While most of the existing studies focus on the effect of warming only on species diversity and productivity, we further investigated (i) how the structure of community plant functional traits in temperate grasslands respond to experimental warming, and (ii) whether species and functional diversity contribute to a greater stability of grasslands, in terms of vegetation composition and productivity. Intact vegetation turves were extracted from temperate subalpine grassland (highland) in the Eastern Pyrenees and transplanted into a warm continental, experimental site in Lleida, in Western Catalonia (lowland). The impacts of simulated warming on plant production and diversity, functional trait structure, and vegetation compositional stability were assessed. We observed an increase in biomass and a reduction in species and functional diversity under short-term warming. The functional structure of the grassland communities changed significantly, in terms of functional diversity and community-weighted means (CWM) for several traits. Acquisitive and fast-growing species with higher SLA, early flowering, erect growth habit, and rhizomatous strategy became dominant in the lowland. Productivity was significantly positively related to species, and to a lower extent, functional diversity, but productivity and stability after warming were more dependent on trait composition (CWM) than on diversity. The turves with more acquisitive species before warming changed less in composition after warming. Results suggest that (i) the short-term warming can lead to the dominance of acquisitive fast growing species over conservative species, thus reducing species richness, and (ii) the functional traits structure in grassland communities had a greater influence on the productivity and stability of the community under short-term warming, compared to diversity effects. In summary, short-term climate warming can greatly alter vegetation functional structure and its relation to productivity., Spanish Science Foundation funded the
project CAPAS (CGL2010-22378-C03-01), http://
www.fecyt.es/: MTS. Spanish Science Foundation funded the project BIOGEI (CGL2013-49142-C2-1-
R), http://www.fecyt.es/: MTS. Spanish Ministry of
Economy and Competitiveness funded the FPI shortterm visit to the Czech Academy of Sciences (BES-2011-047009): HD.

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.

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.