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Mediterranean wood pastures are seminatural savannahlike agroecosystems that result from traditional silvopastoral practices, which shaped these systems into a mosaic of trees and open grassland. However, traditional silvo-pastoral uses are declining with the implications that this may have on the herbaceous layer, which is a very diverse and valuable resource. Here, we aim at assessing the influence of the tree – open grassland mosaic on the structure, diversity, and composition of the herbaceous layer. Specifically, assessing the canopy effect (a) under representative Iberian canopy types, considering traditional Quercus species stands and Pinus pinea plantations at different locations; and (b) along seasonality. For that purpose, we carried out vegetation surveys in Mediterranean wood pastures of the south SouthWest of the Iberian Peninsula. Our results show that the different components of the herbaceous layer performed differential responses to the presence/absence of tree canopies, as for instance shows the dominance of grasses under the canopy, while legumes and forbs were favoured in the open grassland. Also, the study plots differed in their composition of species and species richness, with a certain a reduction in the species richness in the plot dominated by P. pinea compared to plots dominated by Quercus species. The canopy effect was more pronounced at the more environmentally constrained location. Such canopy effects were generally more pronounced in spring than in autumn. In conclusion, it is highly advisable preserve the tree – open grassland mosaic and traditional Quercus species stands to maximize and preserve plant specific and functional diversity and ecosystem functionality.

Purpose: Mediterranean wood pastures are the largest agroforestry system in Europe. Traditional silvo-pastoral uses shaped these systems into a mosaic of trees and open grassland. However, little is known about how this structure may influence ecosystem carbon (C) and nitrogen (N) dynamics, considering different canopy types and interactions with the herbaceous layer.Aims: To unravel the canopy effect on C and N dynamics (1) under representative canopy types, including traditional Quercus stands and Pinus pinea L. plantations; and (2) in interaction with the herbaceous plant functional types (PFT).Methods: We analysed C and N content and the isotopic natural abundance on soil and plant materials at the open grassland and under the different tree canopies.Results: Under the canopy, soil C and N content, and N availability for the herbaceous layer increased. The canopy effect performed differences between Quercus and P. pinea plots, as detected on the belowground biomass C content. Also, the canopy effect was more pronounced with increasing environmental constraints, highlighting the relevance of trees in more restrictive environments. PFT ecophysiological characteristics interacted with tree canopies, as reflected the enhanced efficiency taking-up N, and/or exploiting symbiotic N of grasses, which was probably one of the causes of their dominancy under the canopy, at higher N availability.Conclusion: Changes in the tree coverage and tree species will significantly change ecosystem C and N storage and cycling. Therefore, it is highly advisable to preserve a balance between trees and open grassland, and traditional Quercus stands, to keep ecosystem services provisioning.

Mediterranean mountain grasslands, including the Pyrenees, are highly vulnerable to climate change, due to the increasing temperatures and heat weaves frequency, among other factors. However, the effects of the increased temperatures on CO2 fluxes in those ecosystems have been barley explored. To address this gap of knowledge, we established the FLUXPYR-ECOFUN micrometeorological flux network, which included three eddy covariance flux stations in grasslands along a management and a climatic gradient (montane to subalpine) at the Pyrenees; we aimed at assessing interactions among environmental and phenological drivers on CO2 fluxes, with special attention at the role of temperature as CO2 flux driver under the different climatic and management conditions across the studied gradient. Our results showed that temperature drove CO2 dynamics along the studied gradient in different ways. At the subalpine grassland net CO2 uptake was linearly enhanced by temperature and CO2 fluxes had not reached a temperature shifting point yet (according to the segmented linear models) at which the net uptake would become CO2 emissions. This suggests that in the short term, and under the incoming enhanced temperatures, sub-alpine grasslands in the Pyrenees might increase their net CO2 uptake, although the mid long-term uptake may be compromised. On the contrary, the montane grasslands already presented CO2 emissions at the highest temperatures, most likely driven by a decrease in the greenness and photosynthesis, which suggests that montane grasslands are expected to reduce their CO2 sink capacity under the increasing temperatures. Overall, mountain grasslands in the mid- to long-term in the Pyrenees may experience a reduction in their net CO2 uptake capacity under the current climate change scenario.

Background: Mediterranean holm oak meadows are semi‑natural savannah‑like agroecosystems that result from traditional silvo‑pastoral practices, which shaped these systems into a mosaic of trees and open grassland. However, traditional silvo-pastoral uses are declining with the implications that this may have on the herbaceous layer, a very biodiverse and valuable resource of these systems. Here, we aim at assessing the influence of the tree – open grassland mosaic on the structure, diversity, and composition of the herbaceous layer. Specifically, assessing the canopy effect (a) under representative Iberian canopy types, considering traditional Quercus species stands and Pinus pinea plantations at different locations; and (b) along seasonality. Results: The different components of the herbaceous layer performed differential responses to the presence/absence of tree canopies, as for instance shows the dominance of grasses under the canopy, while legumes and forbs were favoured in the open grassland. Also, there was a certain a reduction in the species richness in P. pinea dominated plots compared to plots dominated by Quercus species. There was a reduction of the aboveground biomass under the canopy at the more environmentally constrained location. Such canopy effects were generally more pronounced in spring that in autumn.Conclusion: It is highly advisable preserve the tree – open grassland mosaic and traditional Quercus species stands to maximize and preserve plant specific and functional diversity. The the optimum tree coverage might be dependent, not only on the primary ecosystem service (i. e. forage provision), but also on local conditions.

Biochar applications have been proposed for mitigating some soil greenhouse gas (GHG) emissions. However, results can range from mitigation to no effects. To explain these differences, mechanisms have been proposed but their reliability depends on biochar type, soil and climatic conditions. Furthermore, it is found that the mitigation capacity is dependent on how the biochar is aging under field conditions. The effects on N2O, CH4 and CO2 emission rates of a gasification pine biochar (applied as 0, 5, and 30 t ha−1) were studied between 8 and 21 months of the application in an alkaline soil cropped to barley under Mediterranean climate. Together with GHG, soil chemical and biological properties were assessed, namely, changes in labile organic matter content and nutrient status, and pH, as well as microbial abundance, activity, and functional composition. During the 2 years of the application, significant changes were observed at the highest rate of biochar application such as higher contents of water, K+, Mg2+, SO42−, higher basal respiration, and with non-significant changes in microbial community, though with some temporal effects. Regarding GHG, N2O decreases coupled with CH4 increases in the summer sampling were measured, although only for the highest application rate scenario. Such effects were unrelated to pH, bioavailable nitrogen status, or bulk soil microbial community shifts. We hypothesized that the key is the porous structure of our wood biochar, which is able to provide more and diversified microbial microhabitats in comparison to bulk soil. At higher temperatures in summer, biologically-induced anoxic conditions in biochar pores acting as microsites may be promoted, where total denitrification to N2 occurs which leads to N2O uptake, while CH4 production is promoted.

© 2021 The Authors., Aims: Understanding fine-grain diversity patterns across large spatial extents is fundamental for macroecological research and biodiversity conservation. Using the GrassPlot database, we provide benchmarks of fine-grain richness values of Palaearctic open habitats for vascular plants, bryophytes, lichens and complete vegetation (i.e., the sum of the former three groups). Location: Palaearctic biogeographic realm. Methods: We used 126,524 plots of eight standard grain sizes from the GrassPlot database: 0.0001, 0.001, 0.01, 0.1, 1, 10, 100 and 1,000 m and calculated the mean richness and standard deviations, as well as maximum, minimum, median, and first and third quartiles for each combination of grain size, taxonomic group, biome, region, vegetation type and phytosociological class. Results: Patterns of plant diversity in vegetation types and biomes differ across grain sizes and taxonomic groups. Overall, secondary (mostly semi-natural) grasslands and natural grasslands are the richest vegetation type. The open-access file ”GrassPlot Diversity Benchmarks” and the web tool “GrassPlot Diversity Explorer” are now available online (https://edgg.org/databases/GrasslandDiversityExplorer) and provide more insights into species richness patterns in the Palaearctic open habitats. Conclusions: The GrassPlot Diversity Benchmarks provide high-quality data on species richness in open habitat types across the Palaearctic. These benchmark data can be used in vegetation ecology, macroecology, biodiversity conservation and data quality checking. While the amount of data in the underlying GrassPlot database and their spatial coverage are smaller than in other extensive vegetation-plot databases, species recordings in GrassPlot are on average more complete, making it a valuable complementary data source in macroecology., GrassPlot development has been supported by the Bavarian Research Alliance (BayIntAn_UBT_2017_58), the Eurasian Dry Grassland Group (EDGG) and the International Association for Vegetation Science (IAVS); IB, CorM, JAC, IGM, DGM, MHe, DL and MTo were supported by the Basque Government (IT936‐16); CorM, IAx, MCh, JDa, PD, MHá, ZL, ZPr, EŠ and LT were supported by the Czech Science Foundation (19‐28491X); TR was supported by the Estonian Research Council (PUT1173); RJP was funded by the Strategic Research Programme of the Scottish Government’s Rural and Environmental Science and Analytical Services Division”; SBa was supported by the GINOP‐2.3.2‐15‐2016‐00019 project; GFi was partially supported by the MIUR initiative “Department of excellence” (Law 232/2016)"; BJA was funded by the Spanish Research Agency (grant AEI/ 10.13039/501100011033); AK, VB, IM, DS, IV and DV were supported by the National Research Foundation of Ukraine (2020.01/0140); MP and AH were supported by the Estonian Research Council (PRG874, PRG609), and the European Regional Development Fund (Centre of Excellence EcolChange); Data collection of HCP was funded by FORMAS (Swedish Research Council for Environment, Agricultural Science and Spatial Planning) and The Swedish Institute; JR was supported by the Czech Science Foundation (grant No. 20‐09895S) and the long‐term developmental project of the Czech Academy of Sciences (RVO 67985939); ATRA was funded by the Grant of Excellence Departments, MIUR‐Italy (ARTICOLO 1, COMMI 314 – 337 LEGGE 232/2016); JMA was supported by Carl Tryggers stiftelse för vetenskaplig forskning and Qatar Petroleum; AAli was supported by the Jiangsu Science and Technology Special Project (Grant No. BX2019084), and Metasequoia Faculty Research Startup Funding at Nanjing Forestry University (Grant No. 163010230), and he is currently supported by Hebei University through Faculty Research Startup Funding Program; ZB was supported by the NKFI K 124796 grant; The GLORIA‐ Aragón project of JLBA was funded by the Dirección General de Cambio Climático del Gobierno de Aragón (Spain); MCs and LDem were supported by DG Environment through the European Forum on Nature Conservation and Pastoralism and Barbara Knowles Fund, in collaboration with Pogány‐havas Association, Romania; JDa was partially supported by long‐term research development project no. RVO 67985939 of the Czech Academy of Sciences; BD and OV were supported by the NKFI KH 126476, NKFI KH 130338, NKFI FK 124404 and NKFI FK 135329 grants; BD, OV and AKe were supported by the Bolyai János Scholarship of the Hungarian Academy of Sciences; BE was funded by the Environmental Department of the Tyrolean Federal State Government, the MAB Programme of the Austrian Academy of Science, the Mountain Agriculture Research Unit and the Alpine Research Centre Obergurgl of Innsbruck University. The GLORIA projects of BE were funded by the EU project no. EVK2‐CT‐2000‐00056, the Earth System Sciences Program of the Austrian Academy of Sciences (project MEDIALPS), the Amt für Naturparke, Autonome Provinz Bozen‐Südtirol, the Südtiroler Wissenschaftsfonds and the Tiroler Wissenschaftsfonds; RGG was supported by the Spanish Ministry of Research to sample GLORIA sites in central Spain (CGL 2008‐00901/BOS) and present works by the Autonomous Region of Madrid (REMEDINAL TE‐CM, S2018/EMT‐4338); MJ was supporteLatviaed by Latvia Grant No. 194051; NP and SŠ were partly supported by the Slovenian Research Agency, core fundings P1‐0403 and J7‐1822.

Iberian holm oak meadows are savannah-like ecosystems that result from traditional silvo-pastoral practices. However, such traditional uses are declining, driving changes in the typical tree&mdash, open grassland structure of these systems. Yet, there are no studies integrating the whole ecosystem&mdash, including the arboreal and the herbaceous layer&mdash, as drivers of greenhouse gas (GHG: CO2, CH4 and N2O) dynamics. Here, we aimed at integrating the influence of tree canopies and interactions among plant functional types (PFT: grasses, forbs, and legumes) of the herbaceous layer as GHG exchange drivers. For that purpose, we performed chamber-based GHG surveys in plots dominated by representative canopy types of Iberian holm oak meadows, including Quercus species and Pinus pinea stands, the last a common tree plantation replacing traditional stands, and unraveled GHG drivers through a diversity-interaction model approach. Our results show the tree&ndash, open grassland structure, especially drove CO2 and N2O fluxes, with higher emissions under the canopy than in the open grassland. Emissions under P. pinea canopies are higher than those under Quercus species. In addition, the inclusion of diversity and compositional terms of the herbaceous layer improve the explained variability, with legumes enhancing CO2 uptake and N2O emissions. Changes in the tree cover and tree species composition, in combination with changes in the structure and composition of the herbaceous layer, will imply deep changes in the GHG exchange of Iberian holm oak meadows. These results may provide some guidelines to perform better management strategies of this vast but vulnerable ecosystem.

Iberian holm oak meadows are savannah-like ecosystems that result from traditional silvo pastoral practices. However, such traditional uses are declining, driving changes in the typical tree – open grassland structure of these systems. Yet, there are no studies integrating the whole ecosystem — including the arboreal and the herbaceous layer — as drivers of greenhouse gas (GHG: CO2, CH4 and N2O) dynamics. Here we aim at integrating the influence of tree canopies and interactions among plant functional types (PFT: grasses, forbs, and legumes) of the herbaceous layer as GHG exchange drivers. For that purpose, we performed chamber based GHG surveys in plots dominated by representative canopy types of Iberian holm oak meadows, including Quercus species and Pinus pinea stands, the last a common tree plantation replacing traditional stands; and unravelled GHG drivers through a diversity interaction model approach. Our results show that the tree – open grassland structure especially drove CO2 and N2O fluxes, with higher emissions under the canopy than in the open grassland. Emissions under P. pinea canopies being higher than those under Quercus species. In addition, the inclusion of diversity and compositional terms of the herbaceous layer improve the explained variability, legumes enhancing CO2 uptake and N2O emissions. Changes in the tree cover and tree species composition, in combination with changes in the structure and composition of the herbaceous layer, will imply deep changes in the GHG exchange of Iberian holm oak meadows. These results may provide some guidelines to perform better management strategies of this vast but vulnerable ecosystem.

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&mdash, related soil processes and eventually the feedback of the soil to the atmosphere.

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.

Soil is the largest terrestrial carbon pool, making it crucial for climate change mitigation. To disentangle the relationships of plant guild diversity with soil organic carbon (SOC) storage at broad spatial scales, we applied diversity-interaction models to a regional grassland database. The questions were if: 1) positive effects of plant guild diversity on SOC at broad spatial scales are similar to experiments; 2) the enhancement of SOC by legumes is constant in natural grasslands; and 3) the effects of legumes on SOC depend on interactions with other guilds. SOC increased with legume proportion up to 15-20%, then decreased, across broad spatial scales. Additionally, legume effects were enhanced when grasses were dominant, which could be related to the strong capacity of grasses for capturing nitrogen; grass carbon exudates; the balance symbiotic/non-symbiotic nitrogen. Our findings can facilitate the elaboration of regional and local strategies to ameliorate the soil capacity to absorb carbon.

Prescribed burning is a management tool used in the last years to prevent the invasion of woody vegetation in pastureland, decreasing the risk of extensive wildfires in vulnerable areas. Nevertheless, the effect of this practice in the soil is not yet fully understood, and more information is needed to ameliorate management practices. In order to understand how prescribed fire affect soil fertility, and the carbon (C) and nitrogen (N) cycles in pastures invaded by shrubs in Mediterranean areas, we carried out an experiment in Montseny, an acidic pre-littoral mountain range northern Barcelona (NE Iberian Peninsula). This area has experienced a decrease in traditional sheep stocks and therefore pastures endure strong shrub encroachment. We wanted to know: 1) what are the effects of prescribed burning on soil fertility in acidic Mediterranean pastures? and 2) are there legacy effects of the previous vegetation patches on the soil C and N cycles after prescribed burning? To answer those questions, we sampled soils before and after prescribed burning of a pasture heavily invaded by shrubs. Soils were sampled under six canopy types: Erica scoparia-dominated patches, Calluna vulgaris-dominated patches, Cytisus scoparius-dominated patches, Pteridium aquilinum-dominated patches and Cladonia-dominated biological crusts. The exact soil sampling point was recorded by a highly precise GPS, and each point resampled few days and six months after burning. As expected, soil fertility parameters varied with burning, including losses in soil phosphorus and nitrogen. In addition, several soil C and N parameters responded to the previous vegetation patches, including shifts in soil C and N concentration.

Biogeochemical cycling of elements largely occurs in dissolved state, but many elements may also be bound to natural nanoparticles (NNP, 1-100 nm) and fine colloids (100-450 nm). We examined the hypothesis that the size and composition of stream water NNP and colloids vary systematically across Europe. To test this hypothesis, 96 stream water samples were simultaneously collected in 26 forested headwater catchments along two transects across Europe. Three size fractions (~1-20 nm, >20-60 nm, and >60 nm) of NNP and fine colloids were identified with Field Flow Fractionation coupled to inductively coupled plasma mass spectrometry and an organic carbon detector. The results showed that NNP and fine colloids constituted between 2 ± 5% (Si) and 53 ± 21% (Fe; mean ± SD) of total element concentrations, indicating a substantial contribution of particles to element transport in these European streams, especially for P and Fe. The particulate contents of Fe, Al, and organic C were correlated to their total element concentrations, but those of particulate Si, Mn, P, and Ca were not. The fine colloidal fractions >60 nm were dominated by clay minerals across all sites. The resulting element patterns of NNP

Publisher's version (útgefin grein), Grassland diversity can support sustainable intensification of grassland production through increased yields, reduced inputs and limited weed invasion. We report the effects of diversity on weed suppression from 3 years of a 31-site continental-scale field experiment. At each site, 15 grassland communities comprising four monocultures and 11 four-species mixtures based on a wide range of species' proportions were sown at two densities and managed by cutting. Forage species were selected according to two crossed functional traits, “method of nitrogen acquisition” and “pattern of temporal development”. Across sites, years and sown densities, annual weed biomass in mixtures and monocultures was 0.5 and 2.0 t DM ha−1 (7% and 33% of total biomass respectively). Over 95% of mixtures had weed biomass lower than the average of monocultures, and in two-thirds of cases, lower than in the most suppressive monoculture (transgressive suppression). Suppression was significantly transgressive for 58% of site-years. Transgressive suppression by mixtures was maintained across years, independent of site productivity. Based on models, average weed biomass in mixture over the whole experiment was 52% less (95% confidence interval: 30%–75%) than in the most suppressive monoculture. Transgressive suppression of weed biomass was significant at each year across all mixtures and for each mixture. Weed biomass was consistently low across all mixtures and years and was in some cases significantly but not largely different from that in the equiproportional mixture. The average variability (standard deviation) of annual weed biomass within a site was much lower for mixtures (0.42) than for monocultures (1.77). Synthesis and applications. Weed invasion can be diminished through a combination of forage species selected for complementarity and persistence traits in systems designed to reduce reliance on fertiliser nitrogen. In this study, effects of diversity on weed suppression were consistently strong across mixtures varying widely in species' proportions and over time. The level of weed biomass did not vary greatly across mixtures varying widely in proportions of sown species. These diversity benefits in intensively managed grasslands are relevant for the sustainable intensification of agriculture and, importantly, are achievable through practical farm-scale actions., We thank the many colleagues who have assisted this work. We thank M. Coll for her early contribution. Co-ordination of this project was supported by the EU Commission through COST Action 852 ‘Quality legume-based forage systems for contrasting environments’. M.T.S., R.L. and A.R. were supported by the Spanish Ministry of the Economy and Competitiveness through projects CARBOAGROPAS (CGL2006-13555- C03- 01/ BOS) and BIOGEI (CGL2013-49142- C2- 1- R) and the Ministry of the Environment through OPS (209/PC08/3-08.2). L.K. was supported by an award from Science Foundation Ireland (09/RFP/EOB2546). A.L., J.A.F., J.C. and M.S. were partly supported by the EU FP7 project ‘AnimalChange’ under grant agreement no. 266018.

The impact of atmospheric reactive nitrogen (Nr) deposition on carbon (C) sequestration in soils and biomass of unfertilised, natural, semi-natural and forest ecosystems has been much debated. Many previous results of this dC / dN response were based on changes in carbon stocks from periodical soil and ecosystem inventories, associated with estimates of Nr deposition obtained from large-scale chemical transport models. This study and a companion paper (Flechard et al., 2019) strive to reduce uncertainties of N effects on C sequestration by linking multi-annual gross and net ecosystem productivity estimates from 40 eddy covariance flux towers across Europe to local measurement-based estimates of dry and wet Nr deposition from a dedicated collocated monitoring network. To identify possible ecological drivers and processes affecting the interplay between C and Nr inputs and losses, these data were also combined with in situ flux measurements of NO, N2O and CH4 fluxes, soil NO3− leaching sampling, as well as results of soil incubation experiments for N and greenhouse gas (GHG) emissions, surveys of available data from online databases and from the literature, together with forest ecosystem (BASFOR) modelling. Multi-year averages of net ecosystem productivity (NEP) in forests ranged from −70 to 826 g (C) m−2 yr−1 at total wet + dry inorganic Nr deposition rates (Ndep) of 0.3 to 4.3 g (N) m−2 yr−1; and from −4 to 361 g (C) m−2 yr−1 at Ndep rates of 0.1 to 3.1 g (N) m−2 yr−1 in short semi-natural vegetation (moorlands, wetlands and unfertilised extensively managed grasslands). The GHG budgets of the forests were strongly dominated by CO2 exchange, while CH4 and N2O exchange comprised a larger proportion of the GHG balance in short semi-natural vegetation. Nitrogen losses in the form of NO, N2O and especially NO3− were of the order of 10–20 % of Ndep at sites with Ndep 3 g (N) m−2 yr−1, indicating that perhaps one third of the sites were in a state of early to advanced N saturation. Net ecosystem productivity increased with Nr deposition up to 2–2.5 g (N) m−2 yr−1, with large scatter associated with a wide range in carbon sequestration efficiency (CSE, defined as the NEP / GPP ratio). At elevated Ndep levels (> 2.5 g (N) m−2 yr−1), where inorganic Nr losses were also increasingly large, NEP levelled off and then decreased. The apparent increase in NEP at low to intermediate Ndep levels was partly the result of geographical cross-correlations between Ndep and climate, indicating that the actual mean dC / dN response at individual sites was significantly lower than would be suggested by a simple, straightforward regression of NEP vs. Ndep.

Soils store about four times as much carbon as plant biomass1, and soil microbial respiration releases about 60 petagrams of carbon per year to the atmosphere as carbon dioxide2. Short-term experiments have shown that soil microbial respiration increases exponentially with temperature3. This information has been incorporated into soil carbon and Earth-system models, which suggest that warming-induced increases in carbon dioxide release from soils represent an important positive feedback loop that could influence twenty-first-century climate change4. The magnitude of this feedback remains uncertain, however, not least because the response of soil microbial communities to changing temperatures has the potential to either decrease5,6,7 or increase8,9 warming-induced carbon losses substantially. Here we collect soils from different ecosystems along a climate gradient from the Arctic to the Amazon and investigate how microbial community-level responses control the temperature sensitivity of soil respiration. We find that the microbial community-level response more often enhances than reduces the mid- to long-term (90 days) temperature sensitivity of respiration. Furthermore, the strongest enhancing responses were observed in soils with high carbon-to-nitrogen ratios and in soils from cold climatic regions. After 90 days, microbial community responses increased the temperature sensitivity of respiration in high-latitude soils by a factor of 1.4 compared to the instantaneous temperature response. This suggests that the substantial carbon stores in Arctic and boreal soils could be more vulnerable to climate warming than currently predicted. This work was carried out with Natural Environment Research Council (NERC) funding (grant number NE/H022333/1). K.K. was supported by an Academy of Finland post-doctoral research grant while finalizing this manuscript. P.M. was supported by ARC FT110100457 and NERC NE/G018278/1, and B.K.S by the Grain Research and Development Corporation and ARC DP130104841.

Question: Many functional diversity indices require the calculation of functional trait dissimilarities between species. However, very little is known about how the dissimilarity measure used might affect conclusions about ecological processes drawn from functional diversity. Methods: We simulated real applications of functional diversity, to illustrate the key properties of the two most common families of dissimilarity measures: (1) ‘Gower’ distance, using only ‘mean trait’ value per species and then standardizing each trait, e.g. relative to its range; (2) ‘trait overlap’ between species, which takes into account within-species trait variability.We then examine how these approaches could affect conclusions about ecological processes commonly assessed with functional diversity. We also propose a new R function (‘trova’, i.e. TRait OVerlAp) which performs computations to estimate species trait dissimilaritywith different types of data. Results: The trait overlap approach generally produces a less context-dependentmeasure of functional dissimilarity. For example, the results are less dependent on the transformation of trait data (often required in empirical datasets) and on the particular pool of species considered (i.e. trait range, regularity and presence of outliers). The results therefore could bemore easily compared across studies and biomes. Further, trait overlap more reliably reproduces patterns expected when niche differentiation structures communities. The Gower approach, on the contrary,more reliably detects environmental filtering effects. Conclusion: The two approaches imply different conceptions of how species dissimilarities relate to niche differentiation. Trait overlap is suitable for testing the effect of species interactions on functional diversity within local communities, especiallywhen relatively small differences in species traits are linked to different resource acquisition. Gower is better suited to detecting changes in functional diversity along environmental gradients, as greater differences in trait values reflect increased niche differentiation. Combining trait overlap and Gower approachesmay provide a novel way to assess the joint effects of environmental filtering and niche complementarity on community assembly. We suggest that attention should be given not only to the index of functional diversity considered but also whether the dissimilarity used is appropriate for the study context.

Continental-scale assessments of 21st century global impacts of climate change on biodiversity have forecasted range contractions for many species. These coarse resolution studies are, however, of limited relevance for projecting risks to biodiversity in mountain systems, where pronounced microclimatic variation could allow species to persist locally, and are ill-suited for assessment of species-specific threat in particular regions. Here, we assess the impacts of climate change on 2632 plant species across all major European mountain ranges, using high-resolution (ca. 100 m) species samples and data expressing four future climate scenarios. Projected habitat loss is greater for species distributed at higher elevations; depending on the climate scenario, we find 36-55% of alpine species, 31-51% of subalpine species and 19-46% of montane species lose more than 80% of their suitable habitat by 2070-2100. While our high-resolution analyses consistently indicate marked levels of threat to cold-adapted mountain florae across Europe, they also reveal unequal distribution of this threat across the various mountain ranges. Impacts on florae from regions projected to undergo increased warming accompanied by decreased precipitation, such as the Pyrenees and the Eastern Austrian Alps, will likely be greater than on florae in regions where the increase in temperature is less pronounced and rainfall increases concomitantly, such as in the Norwegian Scandes and the Scottish Highlands. This suggests that change in precipitation, not only warming, plays an important role in determining the potential impacts of climate change on vegetation.

In this study we examined ecosystem respiration (R-ECO) data from 104 sites belonging to FLUXNET, the global network of eddy covariance flux measurements. The goal was to identify the main factors involved in the variability of R-ECO: temporally and between sites as affected by climate, vegetation structure and plant functional type (PFT) (evergreen needleleaf, grasslands, etc.). We demonstrated that a model using only climate drivers as predictors of R-ECO failed to describe part of the temporal variability in the data and that the dependency on gross primary production (GPP) needed to be included as an additional driver of R-ECO. The maximum seasonal leaf area index (LAI(MAX)) had an additional effect that explained the spatial variability of reference respiration (the respiration at reference temperature T-ref=15 degrees C, without stimulation introduced by photosynthetic activity and without water limitations), with a statistically significant linear relationship (r2=0.52, P 70% of the variance for most vegetation types. Exceptions include tropical and Mediterranean broadleaf forests and deciduous broadleaf forests. Part of the variability in respiration that could not be described by our model may be attributed to a series of factors, including phenology in deciduous broadleaf forests and management practices in grasslands and croplands.

Terrestrial carbon resources are major drivers of development in West Africa. The distribution of these resources co-varies with ecosystem type and rainfall along a strong Northeast-Southwest climatic gradient. Soil organic carbon, a strong indicator of soil quality, has been severely depleted in some areas by human activities, which leads to issues of soil erosion and desertification, but this trend can be altered with appropriate management. There is significant potential to enhance existing soil carbon stores in West Africa, with benefits at the global and local scale, for atmospheric CO2 mitigation as well as supporting and provisioning ecosystem services. Three key factors impacting carbon stocks are addressed in this review: climate, biotic factors, and human activities. Climate risks must be considered in a framework of global change, especially in West Africa, where landscape managers have few resources available to adapt to climatic perturbations. Among biotic factors, biodiversity conservation paired with carbon conservation may provide a pathway to sustainable development, and biodiversity conservation is also a global priority with local benefits for ecosystem resilience, biomass productivity, and provisioning services such as foodstuffs. Finally, human management has largely been responsible for reduced carbon stocks, but this trend can be reversed through the implementation of appropriate carbon conservation strategies in the agricultural sector, as shown by multiple studies. Owing to the strong regional climatic gradient, country-level initiatives will need to consider carbon sequestration approaches for multiple ecosystem types. Given the diversity of environments, global policies must be adapted and strategies developed at the national or sub-national levels to improve carbon storage above and belowground. Initiatives of this sort must act locally at farmer scale, and focus on ecosystem services rather than on carbon sequestration solely.

Questions: Trait differentiation among species occurs at different spatial scales within a region. How does the partitioning of functional diversity help to identify different community assembly mechanisms? Location: Northeastern Spain. Methods: Functional diversity can be partitioned into within-community (α) and among-communities (β) components, in analogy to Whittaker's classical α and β species diversity concept. In light of ecological null models, we test and discuss two algorithms as a framework to measure α and β functional diversity (the Rao quadratic entropy index and the variance of trait values). Species and trait (specific leaf area) data from pastures under different climatic conditions in NE Spain are used as a case study. Results: The proposed indices show different mathematical properties but similarly account for the spatial components of functional diversity. For all vegetation types along the climatic gradient, the observed α functional diversity was lower than expected at random, an observation consistent with the hypothesis of trait convergence resulting from habitat filtering. On the other hand, our data exhibited a remarkably higher functional diversity within communities compared to among communities (α≫β). In contrast to the high species turnover, there was a limited functional diversity turnover among communities, and a large part of the trait divergence occurred among coexisting species. Conclusions: Partitioning functional diversity within and among communities revealed that both trait convergence and divergence occur in the formation of assemblages from the local species pool. A considerable trait convergence exists at the regional scale in spite of changes in species composition, suggesting the existence of ecological redundancy among communities.

The relationship of plant species and functional diversities to community-level δ 13 C, as a proxy for water carbon relations, was assessed in pastures from two climatic regions in NE Spain. Overall, community δ 13 C was negatively related to species diversity, but positively related to functional diversity. However, pronounced differences between climatic regions were found: smaller variations in δ 13 C and thus carbon–water relations were observed for communities under humid conditions, which had higher species diversity but were more functionally redundant than communities under arid conditions. Thus, if species and functional diversities affect plant carbon–water relations at the community and hence at the ecosystem level seems to depend strongly on functional redundancy, i.e., the overlap in plant traits among the species present.

A pan-European experiment carried out at 28 sites across Europe showed strong benefits of sward diversity in agricultural grasslands. We systematically varied the relative abundance of four agronomic plant species (sown species evenness), and found that 4-species mixtures yielded more forage than could be expected on the basis of the monoculture yields. Mixtures generally yielded more than even the best performing monoculture (transgressive overyielding). Mixtures strongly reduced the incidence of unsown species in the sward. These diversity effects were consistent over the wide range of environmental conditions and persisted over three harvest years and in highly fertilized conditions. These results indicate a strong potential for agronomic mixtures to contribute to more sustainable agricultural systems. Agronomic diversity can improve forage yield and reduce weed invasion in intensively managed grasslands, and may also enhance the provision of other ecosystem services.

Questions: Is plant diversity in mesic grassland ecosystems vulnerable in the short-term to extreme climate change events? How rapidly can responses in vegetation composition occur in perennial grasslands? Are the expected compositional changes related to rare species losses or to shifts in the relative abundance of the dominants? Location: Subalpine mesic grasslands on limestone in the Pyrenees. Methods: Transplanting turves from the upland, with cold-temperate climate, to a lowland location, with continental Mediterranean climate. Results: Transplanting led to decreased biodiversity and strong shifts in vegetation composition. Results from both permutation tests and traditional multivariate analysis suggested different trajectories of vegetation depending on the initial species pool. Vegetation showed a tendency to converge in composition in the lowland over time, independently of initial differences. Estimated changes in relative biomass of the five most abundant species between the upland and...

11 páginas, 4 figuras, 4 tablas., The prediction of soil C stocks across the landscape has been increasingly studied in many areas of the world. Soil organic C storage in mountain areas is highly heterogeneous, mainly as a result of local-scale variability in the soil environment (topography, stoniness, parent material) and microclimate. The aims of the present study are to estimate soil organic C stocks (SOCS) in mineral soils of high-altitude grasslands of the Pyrenees and determine whether climatic and topographic variables can be used as predictors of SOCS and organic C content in the surface soil horizons of these ecosystems. For that purpose we sampled 35 soil profiles in subalpine and alpine grasslands including a range of altitudes, slopes and aspects. We analysed the soils for stoniness, bulk density, total C, texture, and C-to-N ratio and determined topographical variables. We used georeferenced climatic information for climatic descriptions of the sites. SOCS were highly correlated with soil depth. However, we were not able to predict soil depth by using environmental and topographic variables. In spite of this fact, altitude and aspect explained 41.2% of the SOCS variability while summer temperature and precipitation combined with aspect explained 56.9% of the variability of the organic C content of the surface layer (OC). The SOCS were low at high altitudes, probably as a result of an overall temperature limitation of net primary productivity. Under these conditions, the effect of aspect was small. The highest SOCS occurred at the lowest altitudes for ENE or WNW aspects, showing sharper decreases towards the south than to the north. The harsh climatic conditions and low-plant productivity that occur at the northern slopes reduced SOCS at the highest altitudes. In contrast, southern aspects showed similar organic C content along the altitudinal gradient. The OC variability in the surface soils not explained by climatic or topographic variables was partially related to the characteristics of soil organic matter, which may depend on the plant communities., This work was funded in part by the European Commission under the EMERGE (EVK1-CT- 1999-00032) and CARBOMONT (EVK2-CT-2001-00125) projects, by the Spanish Ministry of Science and Technology under the CARBOPAS (REN2002-04300- C02-02) project and the Spanish Interministerial Committee on Science and Technology (grant REN2000- 0889/GLO).

Different components of biodiversity may vary independently of each other along environmental gradients giving insights into the mechanisms that regulate species coexistence. In particular, the functional diversity (FD) or the presence of rare or endemic species in natural assemblages do not necessarily increase with species diversity. We studied if different components of plant species diversity (species richness, Simpson diversity, evenness) varied similarly to FD (measured as a generalization of the Simpson index) and rarity along grazing intensity and climatic gradients. Plots under different sheep grazing regimes (high and low intensity, abandonment) were surveyed in five locations along a climatic gradient in north-eastern Spain, from semi-arid lowland to moist upland locations. Variation in species diversity, functional diversity and rarity followed different patterns. Species diversity was lowest in water-stressed environments (arid locations and southern aspects) and increased with grazing more makedly in humid locations. The FD was comparable between the most species-poor and species-rich locations and decreased with grazing in the moistest location, i.e. where species diversity markedly increased. The FD did not show a strong correlation with species richness nor with the Simpson index and less specious communities could show the highest functional diversity. The rarest species in the region were more frequently found in the abandoned areas, which held the lowest species diversity. Consequently, the mechanisms that enhance the diversity of species do not necessarily support a functional differentiation among those species or the maintenance of rare species in a region. We hypothesize that the degree of dependence of functional diversity on species diversity might be mostly related to the amplitude of the species' traits pool and on how species partition the niche space available.

1. The consequences of global warming and changes in resource availability were investigated in subalpine grasslands in the Pyrenees. These communities are considered to be especially vulnerable to climate change because of their position at the south-western edge of the semi-natural grassland biome in Europe. 2. Changes in patterns of above- and below-ground biomass were assessed for different plant guilds in two experiments, in which turves were transplanted from upland to lowland locations. The first experiment aimed to evaluate general responses to warming and drought, and the second to disentangle the effects of possible underlying mechanisms through resource manipulation by means of a nitrogen × phosphorus fertilization experiment. 3. The increased above-ground biomass in grassland turves transplanted to lowlands suggested that biomass production was more temperature-limited than water-limited. The enhancement effect found in the upland turves following phosphorus addition supported the hypothesis of a strong limitation arising from reduced nutrient availability, confirming the central role played by phosphorus in these grasslands and its potential importance in the response to global change. 4. Nitrogen addition did not stimulate total biomass but affected guild composition. Grasses dominated the uplands and at high resource levels, while forbs dominated the lowlands and when water and nutrients decreased. The counterintuitive effect of increased biomass with decreased water in the lowlands was related to shifts in dominance from grasses to forbs, probably enabled by decreased nutrient availability under drought conditions. 5. Synthesis and applications. Environmental factors interacted in complex ways, producing changes in biomass distribution and guild proportions in subalpine grassland. In addition, the results suggested that the capability of high-altitude grasslands to provide quality forage in summer time could be threatened in the northern Mediterranean region under climate change conditions because of: (i) a decrease in their reliability as a result of complex biomass interactions with temperature, water and nutrient dynamics; (ii) expected feedback mechanisms; and (iii) compositional shifts.

Summary We compared pristine and managed beech – fi r mixed forests in Bosnia to assess the impact of management on plant species diversity, vegetation structure and soil – vegetation interaction. Traditionally, management of Bosnian mixed forests has been by the opening of small gaps, similar to those occurring naturally. Species composition revealed three successional vegetation groups, two mainly in managed forests (regenerating and mature) and one mainly in pristine old growth forests. Managed sites showed a tendency to be more diverse in plant species than pristine sites, and were also more heterogeneous. Diversity was clearly explained by vegetation groups; mature managed stands showing the highest plant diversity and regenerating stands the lowest, both in terms of species richness and abundance distributions. Plant diversity decreased with canopy cover and increased with carbon concentration in the A h horizon, being accurately modelled by both factors. Although topographical conditions were homogeneous among sites, vegetation was very sensitive to small changes in environmental variables at the local scale. Vegetation refl ected a combination of past situations, represented by C in the A h horizon, and current conditions, represented by canopy cover and the C : N ratio in the LF organic layers, suggesting both sensitivity to present-day environmental conditions as well as the imprint of past events.

The relative importance of abiotic factors in community assembly is debated and thought to be dependent on the scale. I investigated the relative role of topography and soils as structuring agents at the landscape and the community scales in 126 subalpine calcareous grasslands in the Pyrenees, in terms of species composition and abundance. I wished to know: (1) the role of abiotic factors in the organization of plant communities across the landscape; (2) how much of the variation in community distribution was accounted for by abiotic factors; and (3) how well their role applied to the distribution of dominant species at the landscape and the community scales. The hypothesis was: abiotic factors play an important role in community distribution in the landscape, but species interactions are more important within communities. Multivariate methods generated four communities, organized in two contrasting groups along the main vegetation axis, which explained 13% of the variation: mesic grasslands ( Nardus stricta and Festuca nigrescens communities) and xeric grasslands ( Carex humilis and Festuca gautieri communities). Mesic communities were more acidic and fertile than xeric communities. Changes in the abiotic environment, accounting for up to 80% of the variation in the vegetation, were smooth, while the transition between xeric and mesic grasslands was sharp in terms of species composition. The distribution in the landscape of the first main species from each community was closely related to abiotic factors, which modeled poorly the abundance of the main species at smaller scales. At the within-community scale, the explanatory power of biotic relationships was community dependent, producing the most significant models for plants highly dominant within their communities, such as N. stricta and F. gautieri . Contrary to current hypothesis, there was a shift from mainly positive relationships among dominant species in fertile mesic communities to mainly negative in infertile xeric ones.

It is well accepted that intense anthropogenic activities threaten European heathland communities. The negative impact of high intensities of livestock grazing on heath survival has been demonstrated in many studies, however, it does not seem a straightforward consequence in some cases: in the southern Pyrenees, the existence of large heathland patches in intensively grazed areas suggests that other factors interact and affect heath success. In order to gain insight into the factors affecting heath success, this paper analyses the pattern of occurrence of ericaceous shrubs—particularly Erica vagans—and their effects on soils when compared to herbaceous vegetation, under a complex biotic disturbance regime. Survey plots were established in grassland and heathland communities disturbed by both livestock and by burrowing animals on soils with different levels of basic resources. Relative cover of the species on and off molehills was studied. In heathland plots, ericaceous shrubs were more common on old molehills than off them. This pattern was strongest in the poorest soils. Below established heath shrubs, independently of the initial properties of the soils, some basic resources were more available than in intershrub areas. In grazed ecosystems, where continuous trampling and removal of biomass occurs, the heath canopy provides a site for accumulation of litter and insects, which contribute to the build up of a resource-rich layer. We conclude that successful establishment on ubiquitous molehills and suitable, localised changes in the soil under shrubs are some of the factors that explain the success of ericaceous shrubs in complex biotically disturbed areas.

The preservation of the floristic diversity of natural ecosystems and the maintenance of extensive livestock grazing are two of the major priorities of European Union agricultural and environmental policies. Temperate natural and seminatural grasslands are among the most threatened ecosystems in Europe. In order to establish the most appropriate management practices that prevent degradation and maintain the richness of these ecosystems, detailed analyses of the mechanisms that regulate biodiversity of the communities are particularly necessary. In this study we make a comparative analysis of the species richness and the diversity of the main rangeland communities in a widespread, heterogeneous area located in the Western Spanish Pyrennees. The nature and the contribution of perennials and annuals to the diversity patterns encountered are studied and related to the mechanisms suggested to regulate diversity in each case. Higher diversity values were reported in more environmentally stressed, xeric and moist communities. High spatial and temporal heterogeneity and low rates of competitive displacement related to the scarcity of basic resources are among the factors suggested to regulate the diversity of these communities. In areas where environmental factors are more favorable, such as perennial-dominated mesic rangelands, the enhancement of the diversity seemed more dependent on biotic disturbances, such as herbivory, that decreased the cover of perennials and favored the recruitment of short-lived species. Dispersal processes related to traditional nomadic grazing allow a flow of species from one rangeland to another but also enhance the establishment of species coming from lowland habitats. Most of the annuals enhancing the diversity of the mesic community were ruderals. The consideration of ruderals as exotics or as species belonging to this grazing ecosystem poses an interesting, controversial topic related to the ecological quality of the diversity estimated for these communities.

Stable isotopes and their potential for detecting various and complex ecosystem processes are attracting an increasing number of scientists. Progress is challenging, particularly under global change scenarios, but some established views have been challenged. The IX meeting of the Spanish Association of Terrestrial Ecology (AAET, Úbeda, 18–22 October 2009) hosted a symposium on the ecology of stable isotopes where the linear mixing model approach of partitioning sinks and sources of carbon and water fluxes within an ecosystem was challenged, and new applications of stable isotopes for the study of plant interactions were evaluated. Discussion was also centred on the need for networks that monitor ecological processes using stable isotopes and key ideas for fostering future research with isotopes.

The development of models of the relationship between biodiversity and ecosystem function (BEF) has advanced rapidly over the last 20 years, incorporating insights gained through extensive experimental work. We propose Generalised Diversity‐Interactions models that include many of the features of existing models and have several novel features. Generalised Diversity‐Interactions models characterise the contribution of two species to ecosystem function as being proportional to the product of their relative abundances raised to the power of a coefficient θ. A value of θ < 1 corresponds to a stronger than expected contribution of species' pairs to ecosystem functioning, particularly at low relative abundance of species. Varying the value of θ has profound consequences for community‐level properties of BEF relationships, including: (i) saturation properties of the BEF relationship; (ii) the stability of ecosystem function across communities; (iii) the likelihood of transgressive overyielding. For low values of θ, loss of species can have a much greater impact on ecosystem functioning than loss of community evenness. Generalised Diversity‐Interactions models serve to unify the modelling of BEF relationships as they include several other current models as special cases. Generalised Diversity‐Interactions models were applied to seven data sets and three functions: total biomass (five grassland experiments), community respiration (one bacterial experiment) and nitrate leaching (one earthworm experiment). They described all the nonrandom structure in the data in six experiments, and most of it in the seventh experiment and so fit as well or better than competing BEF models for these data. They were significantly better than Diversity‐Interactions models in five experiments. Synthesis. We show that Generalized Diversity‐Interactions models quantitatively integrate several methods that separately address effects of species richness, evenness and composition on ecosystem function. They describe empirical data at least as well as alternative models and improve the ability to quantitatively test among several theoretical and practical hypotheses about the effects of biodiversity levels on ecosystem function. They improve our understanding of important aspects of the relationship between biodiversity (evenness and richness) and ecosystem function (BEF), which include saturation, effects of species loss, the stability of ecosystem function and the incidence of transgressive overyielding.

Given the importance of root dynamics for soil C storage, the aim of this study was to analyze first the seasonal dynamics of belowground productivity and then the short-term effects of grazing exclosure on root dynamics in mountain grasslands. Soil coring and root ingrowth cores were used to assess belowground biomass (BGB) and productivity in grazed and ungrazed (grazing exclosures) plots in two mountain grasslands. Annual belowground production ranged from 472 to 590 gm−2, representing from 14 to 22% of the maximum root biomass measured over the year. Spring was the most productive season, accounting for more than 50% of total annual production, indicating that factors besides temperature may affect seasonal root dynamics. Although belowground production was much higher in the top 5 cm compared to deeper, the relative productivity rate (production-to-BGB ratio) and renewal time was higher at the subsurface (5–15 cm) layer. The contribution of the subsurface layer to total belowground production increased in spring, possibly due to occasional freezing events at the uppermost layer in the early growing season. The stronger seasonality in subsurface relative productivity rates may reflect depth-dependent changes in root characteristics and lifespan. Excluding grazing increased belowground productivity in summer, but its effects on BGB showed great variability between sites. This study was funded by the Spanish Ministry of Science and Education (MEC) within the framework of the Carbopas (REN2002-04300-C02-02) project and by the European Comission under Carbomont project (EVK1- CT-2001-00125). This research was also supported by the Balangeis project (SUM2006-0030-CO2-02), Agroeco II (CGL2009-13497-CO2-02) and the Graccie project (Consolider Nº 22422) launched by the Spanish Ministry of Science and Technology.

Management affects ecosystem structure in many ways. Structural changes in ecosystems, including shifts in vegetation composition and species diversity, will affect the goods and services provided at ecosystem and regional scales. This is relevant for agricultural production and agro-biodiversity preservation in the context of management changes currently occurring in many regions. We sampled 39 sainfoin swards in the Eastern Pyrenees to assess changes in vegetation structure with sward management and evaluated how those changes might sustain agro-diversity regionally. Three sward managements coexist in the region: (a) mown plus sheep-grazed, (b) mown plus cattle-grazed and (c) only mown. Plant species composition and richness, and various biomass variables were estimated at peak biomass on swards with the three managements and different ages. We used a synchronic approach to study time effects, in which swards of different ages are sampled simultaneously, in a space by time substitution. Multivariate analysis and similarity indices revealed strong shifts in vegetation composition with management, enhanced with sward age, when the suppressive effect of sown on unsown plants relaxed. Generally, plant species richness increased with time. Old mown swards showed the highest number of species per plot (34 in 4 m2). Cattle-grazed swards showed the highest within- and between-treatment vegetation dissimilarity with time. Biomass variables responded mainly to time effects, but total aboveground biomass decreased with unsown species and increased with species richness depending on management. Thus, the diversity of managements modified the expected outcome in local and regional agro-diversity and sward structure. Our results are novel because they demonstrate strong effects of grazing by different animals on local and regional agro-diversity and herbage composition in those ephemeral legume-based forage systems. Farmers and managers should take into account those shifts in order to achieve agricultural goals, including agro-diversity conservation and sustainable forage production at ecosystem and regional scales. The CARBOPAS (REN2002-04300-C02-01 and 02) and the CARBOAGROPAS (CGL2006-13555-C03-01/BOS) projects from the Spanish Science Foundation (FECYT), the Dept. Agricultura (DAR) and the Dept. Treball of the Catalan Government, the Fundació Territori i Paisatge (FTiP) and the I3A-5-147-E project of the EU INTERREG III-A program contributed with funding.

We develop a modeling framework that estimates the effects of species identity and diversity on ecosystem function and permits prediction of the diversity–function relationship across different types of community composition. Rather than just measure an overall effect of diversity, we separately estimate the contributions of different species interactions. This is especially important when both positive and negative interactions occur or where there are patterns in the interactions. Based on different biological assumptions, we can test for different patterns of interaction that correspond to the roles of evenness, functional groups, and functional redundancy. These more parsimonious descriptions can be especially useful in identifying general diversity–function relationships in communities with large numbers of species. We provide an example of the application of the modeling framework. These models describe community-level performance and thus do not require separate measurement of the performance of individual species. This flexible modeling approach can be tailored to test many hypotheses in biodiversity research and can suggest the interaction mechanisms that may be acting.

This paper aims to analyse the present situation of silvopastoral systems in the Northeastern Iberian Peninsula and to foresee the role that silvopastoralism might play in the future. In the region, silvopasture form part of an extensive livestock farming system which integrates agriculture, livestock production and forestry, mostly in family-based farms. Forest grazing is the most important silvopastoral system in the study area where the mountainous topography and the dominant Mediterranean climate influence the grazing strategies. Despite the low contribution of silvopastoralism to the total Gross Domestic Product of the Catalan region, extensive livestock systems play an important social and economic role in the structure of rural areas. Moreover, this role is expected to increase in the future due to the implementation of new agrienvironment measures in the framework of the latest European financial program (2007–2013). The present paper discusses the role of silvopastoralism as an economically viable tool to prevent wildfires and conserve biodiversity in these systems.

8 páginas, 3 tablas, 4 figuras., Although a large amount of soilcarbon (C) is stored in subsurfacesoils, most studies on soil C dynamics focus on the upper layers. The aim of this study is to assess the factors that regulate C mineralization in mountaingrasslandsoils under standard laboratory conditions to compare regulation mechanisms at surface and subsurface horizons. For this purpose soil samples of surface and subsurface horizons from 35 locations were incubated under laboratory conditions, CO2 efflux rates were measured and microbial biomass C (MBC) and net N mineralization were determined. We also analysed the samples for pH, extractable C after fumigation (Cfe), potentially mineralizable N (PMN), reactive and non-reactive P, sum of exchangeable bases and clay content in order to assess the influence of soil characteristics on C mineralization. The influence of climate of each site on soil C mineralization under the same laboratory conditions was also explored for surface and subsurface horizons. C mineralization in surface horizons related positively with Cfe content, suggesting that microbial activity in this horizon was mainly regulated by the availability of C. By contrast, in subsurface horizons, C mineralization related with PMN and was independent of measured C fractions, suggesting that microbial activity in subsurface horizons was limited by the availability of N and that the available forms of C were more stable in these horizons. The effects of local climate on laboratory C mineralization were significant in both soil horizons, with lower rates of C mineralization being recorded in soils from wetter and warmer sites. This fact, suggested that the C stabilisation mechanisms in mountaingrasslandsoils may be affected by the climate in which soils develop., This study was partially funded by the European Commission (EMERGE and CarboEurope-IP projects), by the Spanish Ministry of Science and Education (CARBOPAS and Agroeco projects) and INIA (Balangeis project). CEAM is financially supported by Generalitat Valenciana and Bancaixa. This study is a result of the activities of the Pyrenean Limnological Observatory of Global Change, a joint initiative of the Center for Advanced Studies-CSIC and the Center for High Mountain Research, University of Barcelona.