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Presentation was presented at the Arctic Science Summit Week 2023 (ASSW2023)that took place in Vienna, Austria on February 17-24, 2023 (February 21th, 2023). The presentation includes a synthesis of the published work ofMagnaniet Al.,2022,"Microscale drivers of summer CO2fluxes in the Svalbard High Arctic tundra" (Sci Rep) and subsequent analysis performed onto the 2021-2022 datasets.&nbsp

Presentation waspresented at the IASC workshop "ACZON" (Arctic Critical Zone Observatories) that took place in Pisa, Italy on January 11-12, 2023. The presentation includes a synthesis of the activities ofthe CZ Collective of theInstitute of Geosciences and Earth Resources (CNR, Pisa, Italy). &nbsp

The forthcoming project "WinterCZ" has been presented at the IASC workshop "ACZON" (Arctic Critical Zone Observatories) that took place in Pisa, Italy on January 11-12, 2023. It describes the major actions and challenges to be taken in the project, that will take place in 2023-2025 at the Ny Ålesund research base in Svalbard. The project is aimedto integrate the existing field instrumentation of the projects CZO@Bayelva and TMPT@CNR_NYA in Ny Ålesund (NO) to fill the knowledge gap on the properties and drivers of winter CO2 fluxes in the High Arctic. IGG-CNR shall install new fixed devices for winter monitoring of soil, snow, CO2 fluxes and microbiological activity in the Bayelva basin, developing data services and data-driven and process-based models. The consortium includes five partners: Institute of Geoscience and Earth Resources of CNR (CNR- IGG); Department of Biology of the University of Naples “Federico II” (UNINA-DB); Alfred- Wegener-Institut (AWI); Queen Mary University of London (QMUL); and University of Cologne (UoC).

Presentation made on 11/01/2023 within the workshop Towards an Arctic Critical Zone Observation Network (ACZON)

Continuous long-term eddy covariance (EC) measurements of CO2 fluxes (NEE) in a variety of terrestrial ecosystems are critical for investigating the impacts of climate change on ecosystem carbon cycling. However, due to a number of issues, approximately 30–60% of annual flux data obtained at EC flux sites around the world are reported as gaps. Given that the annual total NEE is mostly determined by variations in the NEE data with time scales longer than one day, we propose a novel framework to perform gap filling in NEE data based on machine learning (ML) and time series decomposition (TSD). The novel framework combines the advantages of ML models in predicting NEE with meteorological and environmental inputs and TSD methods in extracting the dominant varying trends in NEE time series. Using the NEE data from 25 AmeriFlux sites, the performance of the proposed framework is evaluated under four different artificial scenarios with gap lengths ranging in length from one hour to two months. The combined approach incorporating random forest and moving average (MA-RF) is observed to exhibit better performance than other approaches at filling NEE gaps in scenarios with different gap lengths. For the scenario with a gap length of seven days, the MA-RF improves the R2 by 34% and reduces the root mean square error (RMSE) by 55%, respectively, compared to a traditional RF-based model. The improved performance of MA-RF is most likely due to the reduction in data variability and complexity of the variations in the extracted low-frequency NEE data. Our results indicate that the proposed MA-RF framework can provide improved gap filling for NEE time series. Such improved continuous NEE data can enhance the accuracy of estimations regarding the ecosystem carbon budget.

Desert ecosystem CO2 exchange may play an important role in global carbon cycling. However, it is still not clear how the CO2 fluxes of shrub-dominated desert ecosystems respond to precipitation changes. We performed a 10-year long-term rain addition experiment in a Nitraria tangutorum desert ecosystem in northwestern China. In the growing seasons of 2016 and 2017, with three rain addition treatments (natural precipitation +0%, +50%, and +100% of annual average precipitation), gross ecosystem photosynthesis (GEP), ecosystem respiration (ER), and net ecosystem CO2 exchange (NEE) were measured. The GEP responded nonlinearly and the ER linearly to rain addition. The NEE presented a nonlinear response along the rain addition gradient, with a saturation threshold by rain addition between +50% and +100%. The growing season mean NEE ranged from −2.25 to −5.38 μmol CO2 m−2 s−1, showing net CO2 uptake effect, with significant enhancement (more negative) under the rain addition treatments. Although natural rainfall fluctuated greatly in the growing seasons of 2016 and 2017, reaching 134.8% and 44.0% of the historical average, the NEE values remained stable. Our findings highlight that growing season CO2 sequestration in desert ecosystems will increase against the background of increasing precipitation levels. The different responses of GEP and ER of desert ecosystems under changing precipitation regimes should be considered in global change models.

The transfer of CO2 from lakes to the atmosphere is a component of the global carbon equilibrium, while the quantification of the CO2 partial pressure (pCO2) is critical for exploring the contribution of freshwater CO2 emissions in the regional/global carbon budget. To investigate the daily variability of pCO2 and CO2 fluxes (fCO2), we conducted in situ biweekly pCO2 detection at 7:00, 10:00, 14:00, and 17:00 China Standard Time (CST) from Jan. to Sept. 2020 in the subtropical urbanizing Qinglonghu Lake in Chengdu, Sichuan, China. The pCO2 during the daytime varied greatly from 8.3 to 1,061.3 μatm, with an average of 137.7 μatm, while the average pCO2 (n = 11) clearly gradually decreased from 7:00 CST (204.9 ± 295.7 μatm) to 17:00 CST (93.5 ± 105.5 μatm). Similarly, the average fCO2 values were −19.3 (±27.5), −24.8 (±20.7), −29.2 (±9.1) and −30.4 (±10.7) mmol m2 h−1 at 7:00–17:00 CST, respectively. Further, we observed a negative correlation between pCO2 and water temperature and dissolved oxygen, but a positive correlation between pCO2 and total organic carbon and chlorophyll a. By a systematic overview of previously published data, we also discussed the differences and uncertainties in pCO2 and fCO2 estimates at regional and global scales. We therefore speculate that uncertainties may exist in the contributions of CO2 balance on lake surface in regional/global carbon budgets due to this daily pCO2 variation.

The full understanding of variation and temporal changes in carbon dioxide (CO2) fluxes in cropland may contribute to a reduction in CO2 emissions from agriculture. The aim of this study was to determine the CO2 exchange intensity in the three most popular crops in Poland. The CO2 fluxes in summer maize, winter oilseed rape and winter wheat fields were measured using the eddy covariance system. The seasonal dynamics of CO2 fluxes for all studied crops varied from each other due to individual dynamics in atmospheric CO2 assimilation of each species through the growing season. The weighted average values of CO2 fluxes calculated for the entire vegetation period were −22.22 µmol CO2 m−2 s−1, −14.27 µmol CO2 m−2 s−1 and −11.95 µmol CO2 m−2 s−1 for maize, oilseed rape and wheat, respectively. All the studied agro-ecosystems were carbon sinks during the growing season. The highest negative values of CO2 fluxes (−36.31 µmol CO2 m−2 s−1 and −33.56 µmol CO2 m−2 s−1) were observed in the maize field due to the high production of biomass. However, the maize field was also the most significant carbon source due to slow growth of plants at the beginning of the growing season, and due to leaving the field fallow after harvest until the next sowing. In these two periods, the CO2 fluxes ranged from 0.59 µmol CO2 m−2 s−1 to 3.72 µmol CO2 m−2 s−1. CO2 exchange over wheat and oilseed rape fields was less intense, but more even throughout the growing season. In the wheat field, the CO2 fluxes ranged from −1.70 µmol CO2 m−2 s−1 to −23.49 µmol CO2 m−2 s−1 and in the oilseed rape field they ranged from −1.40 µmol CO2 m−2 s−1 to −22.08 µmol CO2 m−2 s−1. In addition, the catch crop in the oilseed rape field contributed to the intensive absorption of CO2 after harvesting the main crop.

Compared with other forest systems, research interest in the potential for a stronger ecosystem carbon sequestration of evergreen forests throughout subtropical China has greatly increased. The eddy covariance technique is widely employed to determine accurate forest-atmosphere carbon dioxide (CO2) flux, which is subsequently used to determine forest ecosystem carbon exchange characteristics. The Dinghushan Biosphere Reserve, a subtropical monsoon evergreen broad-leaved forest, is a suitable study area due to its warm and humid climate (compared with other regions within the same latitude), consequently playing a role in the carbon cycle in the region. For this study, we hypothesized that the forest land in this region generally acts as a carbon sink, and that its carbon sequestration capacity increases over time despite the influence of climatic factors. Here, we compared net CO2 flux data derived from the eddy covariance technique over an 8-year study window. Additionally, we ascertained the effects of various environmental factors on net CO2 flux, while also using the Michaelis–Menten model and a physiologically based process model to track and report on ecosystem carbon exchange characteristics. We observed seasonal trends in daily ecosystem flux, indicative of sensitivity to climatic factors, such as air temperature, precipitation, and sunlight. The carbon sequestration capacity of the region exhibited seasonal variability, increasing from October to March (−264 g C m−2 year−1, i.e., 48.4%) while weakening from April to September (−150 g C m−2 year−1, i.e., 40.4%) on average. The net ecosystem exchange (NEE) rate varied from −518 to −211 g C m−2 year−1; ecosystem respiration (Re) varied from 1,142 to 899 g C m−2 year−1; and gross primary production (GPP) varied from 1,552 to 1,254 g C m−2 year−1. This study found that even though the Dinghushan Biosphere Reserve generally acts as a carbon sink, its carbon sequestration capacity did not increase significantly throughout the study period. The techniques (models) used in this study are suitable for application in other ecosystems globally, which can aid in their management and conservation. Finally, the Dinghushan Biosphere Reserve is both an exemplary and a model forest system useful in exploring CO2 absorption and sequestration from the atmosphere.

Globally, croplands represent a significant contributor to climate change, through both greenhouse gas emissions and land use changes associated with cropland expansion. They also represent locations with significant potential to contribute to mitigating climate change through alternative land use management practices that lead to increased soil carbon sequestration. In spite of their global importance, there is a relative paucity of tools available to support field- or farm-level crop land decision making that could inform more effective climate mitigation practices. In recognition of this shortcoming, the Simple Algorithm for Yield Estimate (SAFY) model was developed to estimate crop growth, biomass, and yield at a range of scales from field to region. While the original SAFY model was developed and evaluated for winter wheat in Morocco, a key advantage to utilizing SAFY is that it presents a modular architecture which can be readily adapted. This has led to numerous modifications and alterations of specific modules which enable the model to be refined for new crops and locations. Here, we adapted the SAFY model for use with spring barley, winter wheat and winter oilseed rape at selected sites in Ireland. These crops were chosen as they represent the dominant crop types grown in Ireland. We modified the soil–water balance and carbon modules in SAFY to simulate components of water and carbon budgets in addition to crop growth and production. Results from the modified model were evaluated against available in situ data collected from previous studies. Spring barley biomass was estimated with high accuracy (R2 = 0.97, RMSE = 95.8 g·m−2, RRMSE = 11.7%) in comparison to GAI (R2 = 0.73, RMSE = 0.44 m2·m−2, RRMSE = 10.6%), across the three years for which the in situ data was available (2011–2013). The winter wheat module was evaluated against measured biomass and yield data obtained for the period 2013–2015 and from three sites located across Ireland. While the model was found to be capable of simulating winter wheat biomass (R2 = 0.71, RMSE = 1.81 t·ha−1, RRMSE = 8.0%), the model was found to be less capable of reproducing the associated yields (R2 = 0.09, RMSE = 2.3 t·ha−1, RRMSE = 18.6%). In spite of the low R2 obtained for yield, the simulated crop growth stage 61 (GS61) closely matched those observed in field data. Finally, winter oilseed rape (WOSR) was evaluated against a single growing season for which in situ data was available. WOSR biomass was also simulated with high accuracy (R2 = 0.99 and RMSE = 0.52 t·ha−1) in comparison to GAI (R2 = 0.3 and RMSE = 0.98 m2·m−2). In terms of the carbon fluxes, the model was found to be capable of estimating heterotrophic respiration (R2 = 0.52 and RMSE = 0.28 g·C·m−2·day−1), but less so the ecosystem respiration (R2 = 0.18 and RMSE = 1.01 g·C·m−2·day−1). Overall, the results indicate that the modified model can simulate GAI and biomass, for the chosen crops for which data were available, and yield, for winter wheat. However, the simulations of the carbon budgets and water budgets need to be further evaluated—a key limitation here was the lack of available in situ data. Another challenge is how to address the issue of parameter specification; in spite of the fact that the model has only six variable crop-related parameters, these need to be calibrated prior to application (e.g., date of emergence, effective light use efficiency etc.). While existing published values can be readily employed in the model, the availability of regionally derived values would likely lead to model improvements. This limitation could be overcome through the integration of available remote sensing data using a data assimilation procedure within the model to update the initial parameter values and adjust model estimates during the simulation.

Extreme rainfall and drought events attributed to climate change are anticipated to occur in the current century, resulting in frequent drying and rewetting cycles (DWCs) in soils, which will, in turn, influence soil properties and microorganisms. Sample plots of Sophora japonica, Pinus tabulaeformis, and Ginkgo biloba were selected, and undisturbed soil columns were collected. CK was the constant drying treatment; the precipitation intensities of R80, R40, and R20 were 80 mm, 40 mm, and 20 mm, respectively, and the total precipitation for the four treatments was 160 mm. Significant differences were observed in the cumulative CO2 emissions among the various DWC frequencies for the same woodland soils. A significant correlation was observed between the Birch effect and the DWC frequencies of the three woodland soils. A Pearson’s correlation analysis revealed that background nutrient contents were the key factors influencing alpha diversity. In conclusion, DWCs generally increased CO2 fluxes, cumulative CO2 emissions, and the Birch effect in addition to decreasing the alpha diversity of soil microorganisms when compared to those in the constant drying treatment.

Shellfish are increasingly been looked at as sustainable food sources that provide additional ecosystem services. However, their role as CO2 sinks or sources is still debated. To quantify it, shell accretion dynamics should be accounted for. However, the shell component is usually calculated with allometric scaling, in most bivalve models. With this study, shell accretion was added to a bioenergetic model of the Manilla clam (Ruditapes philippinarum), and a parameter linking assimilated energy towards shell growth (KSH) was calibrated for four sites, where clams from the same cohort were monitored during a transplant experiment. The model was then used to calculate CO2 fluxes resulting from respiration and shell calcification, taking into account CaCO3 stocked in the shell and CO2 emission. The findings show that KSH varied slightly among sites and that clams played a role as a moderate sink of CO2 over a whole year. CO2 fluxes were characterized by a seasonal variability: clams were net sources in wintertime and sinks in summer time, suggesting the need of accounting for seasonality and growth should shellfish farming be included in carbon markets.

Few works have been carried out on the coupled impacts of different management practices and tractor traffic on soil properties and degradation in vineyards, grape productivity and must quality. The influence of different tillage practices (conventional tillage – CT ; grass coverage in a given year – INV‐GC ; tillage in a given year – INV‐T) and continuous grass coverage (CGC) on soil compaction (BD), soil water content (SWC), CO2 emissions, grape yield and must quality have been investigated in a vineyard in Zagreb, Croatia. During 2017, soil properties were analysed in the 0‐10 cm and 10‐ 20 cm layers after three, six and eleven tractor traffic passes. The results showed that tractor traffic increased the BD in the CGC, INV‐GC and INV‐T treatments. The BD at the 0–10 cm and 10– 20 cm depths was significantly higher in CGC than in CT. During the wet year of 2017, CT and INV‐T had significantly higher SWCs than did CGC and INV‐ GC. The CO2 emissions under different management practices were INV‐T (120.3 CO2 ha‐1 year‐1) > CGC (111.4 CO2 ha‐1 year‐1) > INV‐GC (71.7 CO2 ha‐1 year‐1) > CT (51.5 kg CO2 ha‐1 year‐1). The effects of soil management on must quality and grape composition measurements were also detected. Grape yield was as follows: CT (5.37 kg vine‐1) > INV‐GC (4.43 kg vine‐1) > CGC (4.06 kg vine‐1) > INV‐T (3.87 kg vine‐1). Treatments had a significant impact only on pruning weight, pH value and free amino nitrogen (FAN), while no significant differences were found in the cluster number per vine, mean cluster weight, sugar content and titratable acids.

Atividades humanas vêm liberando grandes quantidades de dióxido de carbono (CO2) na atmosfera desde a Revolução Industrial. Parte desse excesso de CO2 é capturado pelos oceanos (carbono antropogênico, Cant) e vêm causando perturbações e alterações no ciclo do sistema carbonato. Essas alterações no sistema carbonato alteram o estado de acidificação dos oceanos. No oceano Atlântico Sul observa-se os vórtices das Agulhas, que estão entre as maiores estruturas de mesoescala dos oceanos. Por serem estruturas anticiclônicas, estes vórtices estão associados às regiões em que o oceano perde calor para a atmosfera, porém seu papel em relação ao sistema carbonato ainda é pouco estudado. Dessa forma, o objetivo principal dessa pesquisa de doutorado foi investigar a relação dos vórtices das Agulhas com a captura e transporte de CO2/Cant ao longo de suas vidas e qual o papel dessas estruturas no estado de acidificação no oceano Atlântico Sul. Como conclusão principal dessa tese, pudemos demonstrar que os vórtices das Agulhas são capazes não só de capturar mais CO2 do que as águas ao seu redor, como também de transferir para o interior da coluna d’água, podendo carregar mais Cant ao longo de suas trajetórias. Como estudos mostram que 30% dessas estruturas liberadas no vazamento das Agulhas atingem a costa Oeste do Oceano Atlântico Sul e chegam a interagir com a Corrente do Brasil, podemos indicá-los como um dos gatilhos que podem estar intensificando a acidificação observada para as camadas centrais dessa região. Human activities have been releasing large amounts of carbon dioxide (CO2) into the atmosphere since the Industrial Revolution. Part of this excess CO2 is captured by the oceans (anthropogenic carbon, Cant) and has been causing perturbations and changes in the carbonate system cycle. These changes in the carbonate system are now known to alter the acidification state of the oceans. In the South Atlantic Ocean are observed the Agulhas eddies, which are among the largest mesoscale structures in the oceans. Because they are anticyclonic structures, these eddies are associated with regions where the ocean loses heat to the atmosphere, but its role in relation to the carbonate system is still poorly studied. Thus, the main objective of this doctoral research was to investigate the relationship between the Agulhas eddies and CO2/ Cant uptake and transport throughout their lives and which role these structures play in the acidification state in the South Atlantic Ocean. As a main conclusion of this thesis, we have been able to demonstrate that the Agulhas eddies are able not only to capture more CO2 than the surrounding waters, but also to transfer into the water column and can carry more Cant along their trajectories. As studies show that 30% of these structures released in the Agulhas leakage reach the west coast of the South Atlantic Ocean and even interact with the Brazilian Current, we can indicate them as one of the triggers that may be intensifying the acidification observed for the central layers of this region

Many inland waters exhibit complete or partial desiccation, or have vanished due to global change, exposing sediments to the atmosphere. Yet, data on carbon dioxide (CO2) emissions from these sediments are too scarce to upscale emissions for global estimates or to understand their fundamental drivers. Here, we present the results of a global survey covering 196 dry inland waters across diverse ecosystem types and climate zones. We show that their CO2 emissions share fundamental drivers and constitute a substantial fraction of the carbon cycled by inland waters. CO2 emissions were consistent across ecosystem types and climate zones, with local characteristics explaining much of the variability. Accounting for such emissions increases global estimates of carbon emissions from inland waters by 6% (~0.12 Pg C y−1). Our results indicate that emissions from dry inland waters represent a significant and likely increasing component of the inland waters carbon cycle., Many inland waters seasonally or permanently dry up, thus exposing sediments to the atmosphere. Here the authors show that a substantial amount of CO2 is emitted from these dry sediments, increasing current inland water carbon flux estimates by 6%.

It has become clear that anthropogenic carbon invasion into the surface ocean drives changes in the seasonal cycles of carbon dioxide partial pressure (pCO(2)) and pH. However, it is not yet known whether the resulting sea-air CO2 fluxes are symmetric in their seasonal expression. Here we consider a novel application of observational constraints and modeling inferences to test the hypothesis that changes in the ocean's Revelle factor facilitate a seasonally asymmetric response in pCO(2) and the sea-air CO2 flux. We use an analytical framework that builds on observed sea surface pCO(2) variability for the modern era and incorporates transient dissolved inorganic carbon concentrations from an Earth system model. Our findings reveal asymmetric amplification of pCO(2) and pH seasonal cycles by a factor of two (or more) above preindustrial levels under Representative Concentration Pathway 8.5. These changes are significantly larger than observed modes of interannual variability and are relevant to climate feedbacks associated with Revelle factor perturbations. Notably, this response occurs in the absence of changes to the seasonal cycle amplitudes of dissolved inorganic carbon, total alkalinity, salinity, and temperature, indicating that significant alteration of surface pCO(2) can occur without modifying the physical or biological ocean state. This result challenges the historical paradigm that if the same amount of carbon and nutrients is entrained and subsequently exported, there is no impact on anthropogenic carbon uptake. Anticipation of seasonal asymmetries in the sea surface pCO(2) and CO2 flux response to ocean carbon uptake over the 21st century may have important implications for carbon cycle feedbacks. Plain Language Summary The ocean uptake of human released carbon dioxide (CO2) is causing the natural seasonal swings in seawater CO2 to grow over time. Using observations and numerical models, we conduct a theoretical experiment to see how the surface ocean may respond to continued carbon additions under business-as-usual future atmospheric CO2 concentrations. We find that between 1861 and 2100, the chemical properties of CO2 in seawater cause the seasonal CO2 maximum to grow by more than the seasonal CO2 minimum. As a result, the rate of summer surface ocean CO2 growth is different than winter, requiring year-round observations to accurately measure the overall annual ocean carbon absorption. Additionally, these seasonal CO2 changes affect how much carbon is lost from the ocean during high-CO2 periods relative to how much carbon is gained from the atmosphere during low-CO2 periods, creating a trend in the average ocean carbon absorption over years to decades that must be considered in the interpretation of marine carbon cycle observations and numerical models. These findings are important as they have implications for future rates of climate change and ocean acidification.

© 2018 Elsevier B.V. There is significant spatial and temporal variability associated with greenhouse gas (GHG) fluxes in high-latitude Arctic tundra environments. The objectives of this study are to investigate temporal variability in CO2 and CH4 fluxes at Barrow, AK and to determine the factors causing this variability using a novel entropy-based classification scheme. In particular, we analyzed which geomorphic, soil, vegetation and climatic properties most explained the variability in GHG fluxes (opaque chamber measurements) during the growing season over three successive years. Results indicate that multi-year variability in CO2 fluxes was primarily associated with soil temperature variability as well as vegetation dynamics during the early and late growing season. Temporal variability in CH4 fluxes was primarily associated with changes in vegetation during the growing season and its interactions with primary controls like seasonal thaw. Polygonal ground features, which are common to Arctic regions, also demonstrated significant multi-year variability in GHG fluxes. Our results can be used to prioritize field sampling strategies, with an emphasis on measurements collected at locations and times that explain the most variability in GHG fluxes. For example, we found that sampling primary environmental controls at the centers of high centered polygons in the month of September (when freeze-back period begins) can provide significant constraints on GHG flux variability – a requirement for accurately predicting future changes to GHG fluxes. Overall, entropy results document the impact of changing environmental conditions (e.g., warming, growing season length) on GHG fluxes, thus providing clues concerning the manner in which ecosystem properties may be shifted regionally in a future climate.

Sixteen years of surface water CO2 data from autonomous systems on cruise ships sailing in the Caribbean Sea and Western North Atlantic show marked changes on interannual timescales. The measured changes in fugacity (≈partial pressure) of CO2 in surface water, fCO2w, are based on over a million observations. Seasonally the patterns are similar to other oligotrophic subtropical regions with an amplitude of fCO2w of ≈40 μatm with low wintertime values, causing the area to be a sink, and high summertime values making it a source of CO2 to the atmosphere. On annual scales there was negligible increase of fCO2w from 2002 to 2010 and a rapid increase from 2010 to 2018. Correspondingly, the trend of air‐sea CO2 flux from 2002 to 2010 was strongly negative (increasing uptake or sink) at −0.05 ± 0.01 (mol m−2 year−1) year−1 and positive (decreasing uptake) at 0.02 ± 0.02 (mol m−2 year−1) year−1 from 2010‐2018. For the whole period from 2002 to 2018, the fCO2w lagged the atmospheric CO2 increase by 24 %, causing an increase in CO2 uptake. The average flux into the ocean for the 16 years is −0.20 ± 0.16 mol m−2 year−1 with the uncertainty reflecting the standard deviation in annual means. The change in multiannual trend in fCO2w is modulated by several factors, notably changes in sea surface temperature and ocean mixed layer depth that, in turn, affected the physical and biological processes controlling fCO2w DOC | NOAA | Climate Program Office (CPO). Grant Number: 100007298 Global Ocean Monitoring and Observations. Grant Number: 100007298 SI

CO 2 fluxes were measured during 18 months in a forest and a savannah in northern Benin. Higher values of carbon fluxes were found during the wet season at each site. A strong dependency of carbon fluxes on water relations was found in two contrasting sites. The forest sequestered 640 ± 50 and the savannah 190 ± 40 g C m −2 year −1 . In West Africa, the main mechanisms or factors governing the dynamics of ecosystems, especially the dynamics of the carbon fluxes and productivity, still remain less known. This study reports the carbon fluxes over two contrasting ecosystems, notably a protected forest (lat 9.79°N, long 1.72°E, alt 414 m) and a cultivated savannah (lat 9.74°N, long 1.60°E, alt 449 m) in northern Benin. The two sites were among those equipped by the AMMA-CATCH observatory and Oueme 2025 project. Flux data were analyzed at the daily and seasonal scales in order to understand their controlling variables. We discussed the patterns of CO2 fluxes and the characteristics of the two ecosystems. The study also focused on the different water usage strategies developed by the two ecosystems since the alternation between dry and wet seasons highly influenced the seasonal dynamics. Finally, the annual carbon sequestration was estimated together with its uncertainty. The carbon fluxes were measured during 18 months (July 2008–December 2009) by an eddy-covariance system over two contrasting sites in northern Benin. Fluxes data were computed following the standard procedure. The responses of CO2 fluxes to the principal climatic and edaphic factors, and the canopy conductance were studied. A clear CO2 fluxes response to main environmental factors was observed, however with difference according to the seasons and vegetation types. The ecosystem respiration showed the highest values during the wet season and a progressive decrease from wet to dry periods. Also, the carbon uptake values were high during the wet period, but low during the dry period. However, the CO2 fluxes for the protected forest were always higher than that for the cultivated savannah within each defined period. This was due to the seasonal changes not only in phenology and physiology but also to the acclimation to environmental conditions, especially to the soil water availability. The water use efficiency was influenced by VPD during the day conditions for two ecosystems. However, the VPD response curve of water usage was relatively constant for the protected forest during the transitional and wet seasons. In contrary, for the cultivated savannah the VPD response decreased about 46 % from transitional dry-wet to wet seasons and remained relatively constant until transitional wet-dry season. The close relationships between the net CO2 assimilation and the canopy conductance were found for the two ecosystems. This suggests a regulation of the stomata by a partial stomatal closure besides the radiation control. Finally, the forest sequestered at the annual scale 640 ± 50 and the savannah 190 ± 40 g C m−2 year−1. We conclude with a strong relation between the carbon fluxes and water in the two investigated ecosystems. Apart from the radiation control, the stomata also play an important role in the regulation of the CO2 assimilation in the two ecosystems.

This study investigates the potential of the Sentinel-2 satellite for monitoring the seasonal changes in grassland total canopy chlorophyll content (CCC), fraction of photosynthetically active radiation absorbed by the vegetation canopy (FAPAR), and fraction of photosynthetically active radiation absorbed only by its photosynthesizing components (GFAPAR). Reflectance observations were collected on a continuous basis during growing seasons by means of a newly developed ASD-WhiteRef system. Two models using Sentinel-2 simulated data (linear regression-vegetation indices (VIs) approach and multiple regression (MR) reflectance approach) were tested to estimate vegetation biophysical parameters. To assess whether the use of full solar spectrum reflectance data is able to provide an added value in CCC and GFAPAR estimation accuracy, a third model based on partial least squares regression (PLSR) and the ASD-WhiteRef reflectance data was tested. The results showed that FAPAR remained quite stable during the reproduction and senescence stages, and no significant relationships between FAPAR and VIs were found. On the other hand, GFAPAR showed clearer seasonal trends. The comparison of the three models revealed no significant differences in the accuracies of CCC and GFAPAR predictions and demonstrated a strong contribution of SWIR bands to the explained variability of investigated parameters. The promising results highlight the potential of the Sentinel-2 satellite for retrieving biophysical parameters from space.

Climate change may turn Arctic biomes from carbon sinks into sources and vice versa, depending on the balance between gross ecosystem photosynthesis, ecosystem respiration (ER) and the resulting net ecosystem exchange (NEE). Photosynthetic capacity is species specific, and thus, it is important to quantify the contribution of different target plant species to NEE and ER. At Ny Alesund (Svalbard archipelago, Norway), we selected different Arctic tundra plant species and measured CO2 fluxes at plot scale and photosynthetic capacity at leaf scale. We aimed to analyze trends in CO2 fluxes during the transition seasons (beginning vs. end of the growing season) and assess which abiotic (soil temperature, soil moisture, PAR) and biotic (plot type, phenology, LAI, photosynthetic capacity) factors influenced CO2 emissions. NEE and ER differed between vegetation communities. All communities acted as CO2 sources, with higher source strength at the beginning than at the end of the growing season. The key factors affecting NEE were soil temperature, LAI and species-specific photosynthetic capacities, coupled with phenology. ER was always influenced by soil temperature. Measurements of photosynthetic capacity indicated different responses among species to light intensity, as well as suggesting possible gains in response to future increases in atmospheric CO2 concentrations. Species-specific adaptation to low temperatures could trigger significant feedbacks in a climate change context. Our data highlight the need to quantify the role of dominant species in the C cycle (sinks or sources), as changes of vegetation composition or species phenology in response to climate change may have great impact on the regional CO2 balance.

International audience; Nine surface water surveys were performed in the Formoso estuary (Brazil) during 2012-2013 mainly in summer and winter periods and during spring tide. Temporal variations of temperature, salinity, phosphate, silicate, total alkalinity, dissolved inorganic carbon, partial pressure of CO2 (pCO2) and water-air CO2 fluxes were analyzed. Low rates of water-air CO2 fluxes (4.7 ± 8.0 mmol C m-2 d-1) were estimated despite the different climate conditions. pCO2 values ranged from 190 to 988 matm. These values are lower than those observed in other tropical estuaries. CO2 fluxes presented in this study contribute to the characterization of humid tropical estuarine systems, thus filling an important geographical information gap.

Author(s): Rejmankova, E; Sullivan, BW; Ortiz Aldana, JR; Snyder, JM; Castle, ST; Reyes Morales, F | Abstract: Different functional groups of macrophytes vary in their impact on aquatic ecosystem structure and processes. The introduction of new species with different growth form, combined with a stochastic event, may have serious and irreversible consequences on lake functioning. Our goals were to document and explain physical, chemical, metabolic and biotic changes in the littoral zones of a volcanic lake before and following two coinciding events: invasion by a submersed macrophyte, Hydrilla verticillata (Hydrocharitaceae), followed by a rapid increase in the lake water level (g2.5nm). We recorded plant biomass, plant tissue C:N:P stoichiometry, macroinvertebrates, water characteristics data along transects through littoral zones, and measured gas emission in controlled mesocosms and in the lake. The native emergent species, Schoenoplectus californicus (Cyperaceae), was generally not able to survive such a rapid water level increase, and Hydrilla spread and formed dense mats further preventing Schoenoplectus regeneration. The impact of another introduced species, the free-floating Eichhornia crassipes (Pontederiaceae), was more localised, despite its much longer presence at the lake. Although the three species had comparable standing biomass, the two invader species had lower C:N:P ratios than Schoenoplectus, resulting in faster decomposition rates and indicating potential shifts in nutrient cycling within the ecosystem. The oxygen profile of the water column was altered by the non-native species in a significantly different manner: in Eichhornia, the saturation concentrations dropped down to 30%–50% of dissolved oxygen, while oxygen supersaturation was recorded in Hydrilla. Both Schoenoplectus and Eichhornia patches exhibited comparable carbon dioxide (CO2) fluxes, sequestering 230 and 300nmgnCO2nm−2nhr−1, respectively, during the day and emitting 250 and 200nmgnCO2nm−2nhr−1, respectively, during the night. Contrary to these two species, Hydrilla patches sequestered CO2 during the day (34nmgnCO2nm−2nhr−1) and night (44nmgnCO2nm−2nhr−1). The invasive species maintained a richer community of macroinvertebrates compared to several native species (excluding Schoenoplectus), both in taxa diversity and in numbers of individuals. When the results are considered in the regional context, an increase in nutrient supply could lead to the dominance of free-floating plants. We discussed management options more broadly considering the negative impacts of introduced species balanced against their beneficial effects, in the context of environmental changes.

Kalimantan peatland spans ∼5.9million ha (∼11% of Kalimantan's total terrestrial land area) as a part ofIndonesian peatlands, covers∼21 million ha, contains∼57.8 Gtof terrestrial carbon. Land cover change of peatland forest results in significant sources CO2 emissions. Thus, we identified to estimate carbon emissions generated by crop land and ex burnt activities in Kalimantan's peatlands degraded forest.Soil CO2 respiration was measured under four of the most prominent land cover and annual agricultural crops on 4-5 year post fire (fern, corn, pineapple) and newly burnt areas in West Kalimantan peatlands. Measurements were obtained from Licor 8100 and gatheredby monthly assessments. Among the land cover types showed different meanmonthly CO2 fluxes.Soil CO2 respiration on newly burnt peatland, pineapple plantation and fern covered showed the highest and not significantly different among them. Cornsmall-scale plantation soil respired the lowest and significantly different from the other three land covers. Dry vs. rainy month comparisons show huge different (>50%) monthly CO2 fluxes rate. Each land cover type has distinctive peat environmental factors that significantly affect CO2 respiration. Theresult indicates that each crop/cover types generate different level site factors, which affect different level of peat CO2 rates. The regression models of site factors measured for each specific land cover can be applied to obtain better estimate CO2 respiration rates of degraded peatland and agricultural crop cover types. Moreover, it is able to be applied as a baseline for degraded peatland management and CO2 emission mitigation.

The use of machinery in vineyards is increasing soil compaction and erosion. However, there is a lack of information about the impacts of different management practices on soil conditions of vineyards. Therefore, the aim of this study was to assess soil compaction in Croatian vineyards under four different management systems: no-tillage (NT) system, conventional tillage (CT), yearly inversed grass covered (INV-GC) and tillage managed (INV-T) treatments. Four key top-soil (0–20 cm) parameters were assessed in the different land uses: bulk density (BD), penetration resistance (PR), soil water content (SWC) and carbon dioxide (CO2) fluxes. Tractor traffic increased the BD and PR in all treatments, with exception of CT treatment, as consequence of tillage. SWC showed higher values in INV-GC treatment during the dry period; meanwhile, it was similar during the wet season in every management type. Lower CO2 fluxes were found in INV-GC and NT than in the CT and INV-T treatments.

Intelligent agricultural solutions require data on the environmental impacts of agriculture. In order for operationalize decision-making for sustainable agriculture, one needs to establish the corresponding datasets and protocols. Increasing anthropogenic CO2 emissions into the atmosphere force the choice of growing crops aimed at mitigating climate change. For this reason, investigations of seasonal carbon exchange were carried out in 2013&ndash, 2016 at the Training Farm of the Vytautas Magnus University (former Aleksandras Stulginskis University), Lithuania. This paper compares the carbon exchange rate for different crops, viz., maize, ley, winter wheat, spring rapeseed and barley under conventional farming. This study focuses on the carbon exchange rate. We measure the emitted and absorbed CO2 fluxes by applying the closed chamber method. The biomass measurement and leaf area index (LAI) calculations at different plant growth stages are used to evaluate carbon exchange in different agroecosystems. The differences in photosynthetically assimilated CO2 rates were significantly impacted by the leaf area index (p = 0.04) during the plant vegetation period. The significantly (p = 0.02&ndash, 0.05) strong correlation (r = 0.6&ndash, 0.7) exists between soil respiration and LAI. Soil respiration composed only 21% of the agroecosystem carbon exchange. Plant respiration ranged between 0.034 and 3.613 &micro, mol m&minus, 2 s&minus, 1 during the vegetation period composed of a negligible ratio (mean 16%) of carbon exchange. Generally, respiration emissions were obviously recovered by the gross primary production (GPP) of crops. Therefore, the ecosystems were acting as an atmospheric CO2 sink. Barley accumulated the lowest mean GPP 12.77 &micro, 1. The highest mean GPP was determined for ley (14.28 &micro, 1) and maize (15.68 &micro, 1) due to the biggest LAI and particular bio-characteristics. Due to the highest NEP, the ley (12.66 &micro, 1) and maize (12.76 &micro, 1) agroecosystems sank the highest C from the atmosphere and, thus, they might be considered the most sustainable items between crops. Consequently, the appropriate choice of crops and their area in crop rotations may reduce CO2 emissions and their impact on the environment and climate change.

The increasing demand for renewable energy may lead to the conversion of millions of hectares into bioenergy plantations with a possible substantial transitory carbon (C) loss. In this study we report on the greenhouse gas fluxes (CO2, CH4, and N2O) measured using eddy covariance of a short-rotation bioenergy poplar plantation converted from agricultural fields. During the first six months after the establishment of the plantation (June-December 2010) there were substantial CO2, CH4, and N2O emissions (a total of 5.36 +/- 0.52 MgCO2eq ha(-1) in terms of CO2 equivalents). Nitrous oxide loss mostly occurred during a week-long peak emission after an unusually large rainfall. This week-long N2O emission represented 52% of the entire N2O loss during one and an half years of measurements. As most of the N2O loss occurred in just this week-long period, accurately capturing these emission events are critical to accurate estimates of the GHG balance of bioenergy. While initial establishment (June-December 2010) of the plantation resulted in a net CO2 loss into the atmosphere (2.76 +/- 0.16 Mg CO2eq ha(-1)), in the second year (2011) there was substantial net CO2 uptake (-3.51 +/- 0.56 Mg CO2eq ha(-1)). During the entire measurement period, CH4 was a source to the atmosphere (0.63 +/- 0.05 Mg CO2eq ha(-1) in 2010, and 0.49 +/- 0.05 Mg CO2eq ha(-1) in 2011), and was controlled by water table depth. Importantly, over the entire measurement period, the sum of the CH4 and N2O losses was much higher (3.51 +/- 0.52 Mg CO2eq ha(-1)) than the net CO2 uptake (-0.76 +/- 0.58 Mg CO2eq ha(-1)). As water availability was an important control on the GHG emission of the plantation, expected climate change and altered rainfall pattern could increase the negative environmental impacts of bioenergy. (C) 2012 Elsevier B.V. All rights reserved.

CO (2) fluxes were measured during 18 months in a forest and a savannah in northern Benin. Higher values of carbon fluxes were found during the wet season at each site. A strong dependency of carbon fluxes on water relations was found in two contrasting sites. The forest sequestered 640 +/- 50 and the savannah 190 +/- 40 g C m (-2) year (-1) . In West Africa, the main mechanisms or factors governing the dynamics of ecosystems, especially the dynamics of the carbon fluxes and productivity, still remain less known. This study reports the carbon fluxes over two contrasting ecosystems, notably a protected forest (lat 9.79A degrees N, long 1.72A degrees E, alt 414 m) and a cultivated savannah (lat 9.74A degrees N, long 1.60A degrees E, alt 449 m) in northern Benin. The two sites were among those equipped by the AMMA-CATCH observatory and Ou,m, 2025 project. Flux data were analyzed at the daily and seasonal scales in order to understand their controlling variables. We discussed the patterns of CO2 fluxes and the characteristics of the two ecosystems. The study also focused on the different water usage strategies developed by the two ecosystems since the alternation between dry and wet seasons highly influenced the seasonal dynamics. Finally, the annual carbon sequestration was estimated together with its uncertainty. The carbon fluxes were measured during 18 months (July 2008-December 2009) by an eddy-covariance system over two contrasting sites in northern Benin. Fluxes data were computed following the standard procedure. The responses of CO2 fluxes to the principal climatic and edaphic factors, and the canopy conductance were studied. A clear CO2 fluxes response to main environmental factors was observed, however with difference according to the seasons and vegetation types. The ecosystem respiration showed the highest values during the wet season and a progressive decrease from wet to dry periods. Also, the carbon uptake values were high during the wet period, but low during the dry period. However, the CO2 fluxes for the protected forest were always higher than that for the cultivated savannah within each defined period. This was due to the seasonal changes not only in phenology and physiology but also to the acclimation to environmental conditions, especially to the soil water availability. The water use efficiency was influenced by VPD during the day conditions for two ecosystems. However, the VPD response curve of water usage was relatively constant for the protected forest during the transitional and wet seasons. In contrary, for the cultivated savannah the VPD response decreased about 46 % from transitional dry-wet to wet seasons and remained relatively constant until transitional wet-dry season. The close relationships between the net CO2 assimilation and the canopy conductance were found for the two ecosystems. This suggests a regulation of the stomata by a partial stomatal closure besides the radiation control. Finally, the forest sequestered at the annual scale 640 +/- 50 and the savannah 190 +/- 40 g C m(-2) year(-1). We conclude with a strong relation between the carbon fluxes and water in the two investigated ecosystems. Apart from the radiation control, the stomata also play an important role in the regulation of the CO2 assimilation in the two ecosystems.

Long-term coppicing leads to the development of massive root systems. A disproportionate carbon investment in root maintenance has been pointed as a cause of the widespread decline of abandoned coppices. We aimed at assessing how coppicing has influenced root and shoot development and related carbon loss ascribed to maintenance of woody tissues in Quercus pyrenaica. For this goal, results from published studies on root dynamics, woody biomass and respired CO2 fluxes in an abandoned Q. pyrenaica coppice were integrated and extended to quantify overall respiratory expenditures of above- and below-ground woody organs. Internal and external CO2 fluxes together with soil CO2 efflux were monitored in eight stems from one clone across a growing season. Stems and roots were later harvested to quantify the functional biomass and scale up root and stem respiration (RR and RS, respectively) to the clone and stand levels. Below- and above-ground biomass was roughly equal. However, the root-to-shoot ratio of respiration (RR/RS) was generally below one. Relatively higher RS suggests enhanced metabolic activity aboveground during the growing season, and highlights an unexpected but substantial contribution of RS to respiratory carbon losses. Moreover, soil and stem CO2 efflux to the atmosphere in Q. pyrenaica fell in the upper range of reported rates for various forest stands distributed worldwide. We conclude that both RS and RR represent an important carbon sink in this Q. pyrenaica abandoned coppice. Comparatively high energetic costs in maintaining multiple stems per tree and centennial root systems might constrain aboveground performance and contribute to coppice stagnation.

This paper estimates CO2 fluxes in a municipal site for final disposal of solid waste, located in Gualeguaychu, Argentina. Estimations were made using the accumulation chamber methods, which had been calibrated previously in laboratory. CO2 fluxes ranged from 31 to 331 g m−2 day−1. Three different populations were identified: background soil gases averaging 46 g m−2 day−1, intermediate anomalous values averaging 110 g m−2 day−1 and high anomalous values averaging 270 g m−2 day−1. Gas samples to a depth of 20 cm were also taken. Gas fractions, XCO2 < 0.1, XCH4 < 0.01, XN2 ~0.71 and XO2 ~0.21, δ13C of CO2 (−34 to −18‰), as well as age of waste emplacement, suggest that the study site may be at the final stage of aerobic biodegradation. In a first approach, and following the downstream direction of groundwater flow, alkalinity and δ13C of dissolved inorganic carbon (−15 to 4‰) were observed to increase when groundwater passed through the disposal site. This suggests that the CO2 generated by waste biodegradation dissolves or that dissolved organic matter appears as a result of leachate degradation. Fil: Sanci, Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; Argentina Fil: Panarello, Hector Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotopica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; Argentina Fil: Ostera, Hector Adolfo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Nine surface water surveys were performed in the Formoso estuary (Brazil) during 2012-2013 mainly in summer and winter periods and during spring tide. Temporal variations of temperature, salinity, phosphate, silicate, total alkalinity, dissolved inorganic carbon, partial pressure of CO2 (pCO(2)) and water-air CO2 fluxes were analyzed. Low rates of water-air CO2 fluxes (4.7 +/- 8.0 mmol C m(-2) d(-1)) were estimated despite the different climate conditions. pCO(2) values ranged from 190 to 988 mu atm. These values are lower than those observed in other tropical estuaries. CO2 fluxes presented in this study contribute to the characterization of humid tropical estuarine systems, thus filling an important geographical information gap.

Temporal scales of variability for the partial pressure of CO2 (pCO2) in the surface waters of two stratified Mediterranean reservoirs were examined through the temporal decomposition of 5 month time series with hourly sampling frequency. pCO2 time series included similar patterns of variability at daily,biweekly, and seasonal scales regardless of the difference in amplitude of the pCO2 variation in the two reservoirs studied. Daily variability was strongly related to the day-night cycles of metabolic activity, accounting for about one third of the total amplitude in pCO2 variation. At a biweekly scale, wind forcing led to higher rates of air-water CO2 exchange and subsequently temporary partial mixing events associated to relevant increase of CO2 concentration in surface waters. Seasonal variability accounted for one third of the amplitude of the pCO2 variability and was coupled to the seasonal dynamics of water temperature and thermal stratification of the water column. Our results provide evidence that CO2 emission from stratified water bodies shows significant variability at daily, biweekly, and seasonal scales; all of which should be taken into consideration in the analyses of the carbon fluxes. The wind-induced mixing events, operating at temporal scales between daily and seasonal cycles, may become a major factor controlling the pCO2 dynamics. Hence, some of the most common models for computing CO2 fluxes from pCO2 were not able to reproduce the biweekly response patterns of CO2 emissions to wind forcing.

Increases in respiration rates following management activities in croplands are considered a relevant anthropogenic source of CO(2). In this paper, we quantify the impact of management events on cropland respiration fluxes of CO(2) as they occur under current climate and management conditions. Our findings are based on all available CarboEurope IP eddy covariance flux measurements during a 4-year period (2004-2007). Detailed management information was available for 15 out of the 22 sites that contributed flux data, from which we compiled 30 types of management for European-scale comparison. This allowed us to address the question of how management activities influence ecosystem respiration. This was done by comparing respiration fluxes during 7,14, and 28 days after the management with those observed during the matching time period before management. Median increases in respiration ranged from +83% (early season tillage) to -50% (rice paddy flooding and burning of rice residues) on the 28 days time scale, when only management types with a minimum of 7 replications are considered. Most management types showed a large variation among events and between sites, indicating that additional factors other than management alone are also important at a given site. Temperature is the climatic factor that showed best correlation with site-specific respiration fluxes. Therefore, the effect of temperature changes between the time periods before and after management were taken into account for a subset of 13 management types with adequate statistical coverage of at least 5 events during the years 2004-2007. In this comparison, late-season moldboard ploughing (30-45 cm) led to highest median increase in respiration on the 7 days timescale (+43%), which was still +15% in the 28 days comparison. On average, however, management-induced increases in respiration losses from croplands were quite moderate (typically

The ADVEX project involved conducting extensive advection measurements at three sites, each with a different topography. One goal of the project was to measure the [CO2] balance under night-time conditions, in an attempt to improve NEE estimates. Four towers were arranged in a square around a main tower, with the sides of the square about 100 m long. Equipped with 16 sonic anemometers and [CO2] sampling points, the towers were installed to measure vertical and horizontal advection of [CO2]. Vertical turbulent fluxes were measured by an eddy covariance system at the top of the main tower. The results showed that horizontal advection varied greatly from site to site and from one wind sector to another, the highest values being reached when there were large friction velocities and fairly unstable conditions. There was less variation in vertical advection, the highest values being reached when there were low friction velocities and stable conditions. The night-time NEE estimates deduced from the mass balance were found to be incompatible with biologically driven fluxes because (i) they varied strongly from one wind sector to another and this variation could not be explained in terms of a response of the biologic flux to climate, (ii) their order of magnitude was not realistic and (iii) they still showed a trend vs. friction velocity. From a critical analysis of the measurement and data treatment we concluded that the causes of the problem are related to the representativeness of the measurement (control volume size, sampling resolution) or the hypotheses underlying the derivation of the [CO2] mass balance (ignoring the horizontal turbulent flux divergence). This suggests that the improvement of eddy flux measurements by developing an advection completed [CO2] mass balance at night would be practically difficult. (C) 2010 Elsevier B.V. All rights reserved. (Less)

17th Conference on Hydrology, American Meteorological Society Annual General Meeting, February 9 - 13, 2003, Long Beach, California, available, unclassified, unlimited

We present 9 years of eddy covariance measurements made over an evergreen Mediterranean forest in southern France. The goal of this study was to quantify the different components of the carbon (C) cycle, gross primary production (GPP) and ecosystem respiration (R-eco), and to assess the effects of climatic variables on these fluxes and on the net ecosystem exchange of carbon dioxide. The Puechabon forest acted as a net C sink of -254 g C m(-2) yr(-1), with a GPP of 1275 g C m(-2) yr(-1) and a R-eco of 1021 g C m(-2) yr(-1). On average, 83% of the net annual C sink occurred between March and June. The effects of exceptional events such the insect-induced partial canopy defoliation that occurred in spring 2005, and the spring droughts of 2005 and 2006 are discussed. A high interannual variability of ecosystem C fluxes during summer and autumn was observed but the resulting effect on the annual net C budget was moderate. Increased severity and/or duration of summer drought under climate change do not appear to have the potential to negatively impact the average C budget of this ecosystem. On the contrary, factors affecting ecosystem functioning (drought and/or defoliation) during March-June period may reduce dramatically the annual C balance of evergreen Mediterranean forests.

11 páginas, 5 tablas, 4 figuras., [EN]: Conservation tillage has been promoted as a solution to counteract constraints caused by intensive agriculture. In this work the effects of two conservation tillage systems, reduced tillage (RT) and no-tillage (NT) were compared to the traditional tillage (TT) in a long- (15 years, RT) and short-term experiment (3 years, NT). Both experiments were carried out under semi-arid, rainfed agriculture of Mediterranean SW Spain. Tillage caused a sharp increase in soil CO2 emissions immediately after tillage implementation, with a maximum value of 6.24 g CO2 m-2 h-1 under long-term TT treatment. Along the year, losses of carbon through CO2 emission were higher (905 and 801 g C m-2 year-1 for the long- and shortterm TT treatments respectively), than those estimated for conservation systems (764 and 718 g C m-2 year-1 for RT and NT respectively). Conservation tillage systems accumulated more soil organic carbon (SOC) in surface than the corresponding TT treatments (1.24 and 1.17 times greater for RT and NT, respectively, at 0-10 cm depth). Despite SOC accumulation would be moderate other variables related to soil quality, such as dehydrogenase activity, can be consistently increased in soil surface in conservation tillage, as the stratification ratio values indicated. Crop yields in conservation tillage were similar to or even greater than those obtained in TT. The agricultural (soil quality) and environmental (less CO2 emission to the atmosphere) benefits derived from conservation tillage make this system recommendable for semi-arid Mediterranean rainfed agriculture., [ES]: El laboreo de conservación representa una solución para contrarrestar las limitaciones de la agricultura intensiva. En este trabajo se comparó el efecto de dos sistemas de laboreo de conservación, laboreo reducido (RT) y no-laboreo (NT), con laboreo tradicional (TT) en un experimento de larga duración (15 años, RT) y otro de corta duración (3 años, NT), bajo condiciones semi-áridas mediterráneas de secano (SE España). El laboreo aumentó las emisiones de CO2 en el momento de las labores, con un valor máximo de 6,24 g CO2 m-2 h-1 bajo el tratamiento TT del experimento de larga duración. A lo largo del año, las pérdidas de carbono CO2 fueron mayores (905 y 801 g C m-2 año-1 para los tratamientos TT de larga y corta duración, respectivamente) que las estimadas bajo laboreo de conservación (764 y 718 g C m-2 año-1 para RT y NT, respectivamente). Los sistemas de laboreo de conservación acumularon más carbono orgánico total (SOC) en superficie que sus correspondientes tratamientos TT (1,24 y 1,17 veces mayor para RT y NT, respectivamente, profundidad 0-10 cm). A pesar de la moderada acumulación de SOC, otras variables de calidad de suelo, como la actividad deshidrogenasa, pueden aumentar considerablemente en superficie bajo laboreo de conservación, así como valores de razón de estratificación. La producción del cultivo en laboreo de conservación fue similar o mayor que en TT. Los beneficios agrícolas del laboreo de conservación (calidad del suelo) y medioambientales (menores emisiones de CO2 a la atmósfera), hacen a este sistema recomendable para condiciones mediterráneas semi-áridas de secano., The CICYT Project AGL2005-02423 and the Andalusian Autonomous Government (AGR 151 Group) supported this work.

The alpine grassland of Gran Paradiso National Park (Italy) resulted from centuries of human activities that created high biodiversity semi-natural areas below the timberline. The progressive abandonment of management practices as well as climate change lead to variations in species diversity. In order to apply active management actions for maintaining such ecosystem a long-term monitoring programme started in 2016. We will present the first results of spatial and temporal variability of CO2 fluxes from grasslands in relation to meteo-climatic conditions, together with soil properties.

As part of the quality assurance and quality control activities within the CarboEurope-IP network, a comparison of eddy-covariance software was conducted. For four five-day datasets, CO2 flux estimates were calculated by seven commonly used software packages to assess the uncertainty of CO2 flux estimates due to differences in post-processing. The datasets originated from different sites representing different commonly applied instrumentation and different canopy structures to cover a wide range of realistic conditions. Data preparation, coordinate rotation and the implementation of the correction for high frequency spectral losses were identified as crucial processing steps leading to significant discrepancies in the CO2 flux results. The overall comparison indicated a good although not yet perfect agreement among the different software within 5–10% difference for 30-min CO2 flux values. Conceptually different ideas about the selection and application of processing steps were a main reason for the differences in the CO2 flux estimates observed. A balance should be aspired between scientific freedom on the one hand, in order to advance methodical issues, and standardisation of procedures on the other hand, in order to obtain comparable fluxes for multi-site synthesis studies., Biogeosciences, 5 (2), ISSN:1726-4170

The alpine grassland of Gran Paradiso National Park (Italy) resulted from centuries of human activities that created high biodiversity semi-natural areas below the timberline. The progressive abandonment of management practices as well as climate change lead to variations in species diversity. In order to apply active management actions for maintaining such ecosystem a long-term monitoring programme started in 2016. We will present the first results of spatial and temporal variability of CO2 fluxes from grasslands in relation to meteo-climatic conditions, together with soil properties.