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To trust findings in computational science, scientists need workflows that trace the data provenance and support results explainability. As workflows become more complex, tracing data provenance and explaining results become harder to achieve. In this paper, we propose a computational environment that automatically creates a workflow execution's record trail and invisibly attaches it to the workflow's output, enabling data traceability and results explainability. Our solution transforms existing container technology, includes tools for automatically annotating provenance metadata, and allows effective movement of data and metadata across the workflow execution. We demonstrate the capabilities of our environment with the study of SOMOSPIE, an earth science workflow. Through a suite of machine learning modeling techniques, this workflow predicts soil moisture values from the 27 km resolution satellite data down to higher resolutions necessary for policy making and precision agriculture. By running the workflow in our environment, we can identify the causes of different accuracy measurements for predicted soil moisture values in different resolutions of the input data and link different results to different machine learning methods used during the soil moisture downscaling, all without requiring scientists to know aspects of workflow design and implementation.

Humid tropical forests play a dominant role in the functioning of Earth but are under increasing threat from changes in land use and climate. How forest vulnerability varies across space and time and what level of stress forests can tolerate before facing a tipping point are poorly understood. Here, we develop a tropical forest vulnerability index (TFVI) to detect and evaluate the vulnerability of global tropical forests to threats across space and time. We show that climate change together with land-use change have slowed the recovery rate of forest carbon cycling. Temporal autocorrelation, as an indicator of this slow recovery, increases substantially for above-ground biomass, gross primary production, and evapotranspiration when climate stress reaches a critical level. Forests in the Americas exhibit extensive vulnerability to these stressors, while in Africa, forests show relative resilience to climate, and in Asia reveal more vulnerability to land use and fragmentation. TFVI can systematically track the response of tropical forests to multiple stressors and provide early-warning signals for regions undergoing critical transitions.

Soil respiration (Rs), the soil‐to‐atmosphere flux of CO2, is a dominant but uncertain part of the carbon cycle, even after decades of study. This review focuses on progress in understanding Rs from laboratory incubations to global estimates. We survey key developments of in situ ecosystem‐scale Rs observations and manipulations, synthesize Rs meta‐analyses and global flux estimates, and discuss the most compelling challenges and opportunities for the future. Increasingly sophisticated lab experiments have yielded insights into the interaction among heterotrophic respiration, substrate supply, and enzymatic kinetics, and extended incubation‐based analyses across space and time. Observational and manipulative field‐based experiments have used improved measurement approaches to deepen our understanding of the integrated effects of environmental change and disturbance on Rs. Freely‐available observational databases have enabled meta‐analyses and studies probing the magnitude of, and constraints on, the global Rs flux. Key challenges for the field include expanding Rs measurements, experiments, and opportunities to under‐represented communities and ecosystems; reconciling independent estimates of global respiration fluxes and trends; testing and leveraging the power of machine learning and process‐based models, both independently and in conjunction with each other; and continuing the field's tradition of using novel experiments to explore diverse mechanisms and ecosystems. “Soil respiration” refers to the flow of carbon dioxide, mostly generated by plant roots and microbes, from the soil to the atmosphere. This flux is large and highly uncertain, and understanding it has significant implications for our ability to predict the effects of land use and climate change. This review summarizes advances, insights, and challenges in soil respiration science. It examines laboratory approaches and findings; documents changes in how researchers measure and understand soil respiration in the natural world; and describes efforts to estimate the global dynamics of soil respiration from openly‐available databases of observations. We conclude by discussing the most compelling challenges and opportunities for the future. Recent decades have seen large advances in measurement methods, experimental approaches, and data availability in soil respiration scienceLab and field‐based experiments have improved our understanding of the integrated effect of environmental change on soil respirationKey challenges include broadening access and continuing to explore diverse mechanisms and ecosystems using novel model‐experiment approaches Recent decades have seen large advances in measurement methods, experimental approaches, and data availability in soil respiration science Lab and field‐based experiments have improved our understanding of the integrated effect of environmental change on soil respiration Key challenges include broadening access and continuing to explore diverse mechanisms and ecosystems using novel model‐experiment approaches

Methane dynamics within salt marshes are complex because vegetation types, temperature, oscillating water levels, and changes in salinity and redox conditions influence CH4production, consumption, oxidation, and emissions. These non‐linear and complex interactions among variables affect the traditionally expected functional relationships and present challenges for interpreting and developing process‐based models. We employed empirical dynamic modeling (EDM) and convergent cross mapping (CCM) as a novel approach for characterizing seasonal/multiday and diurnal CH4dynamics by inferring causal variables, lags, and interconnections among multiple biophysical variables within a temperate salt marsh using 5 years of eddy covariance data. EDM/CCM is a nonparametric approach capable of quantifying the coupling between variables while determining time scales where variable interactions are the most relevant. We found that gross primary productivity, tidal creek dissolved oxygen, and temperature were important for seasonal/multiday dynamics (rho = 0.73–0.80), while water level was most important for diurnal dynamics during both the growing and dormancy phenoperiods (rho = 0.72 and 0.56, respectively). Lags for the top‐ranked variables (i.e., gross primary productivity, dissolved oxygen, temperature, water level) occurred between 1 and 5 weeks at the seasonal scale and 1–24 hr at the diurnal scale. The EDM had high prediction capabilities for intra‐/inter‐seasonal patterns and annual CH4sums but had limitations in representing large, infrequent fluxes. Results highlight the importance of non‐linearity, drivers, lag times, and interconnections among multiple biophysical variables that regulate CH4fluxes in tidal wetlands. This research introduces a novel approach to examining CH4fluxes, which will aid in evaluating current paradigms in wetlands and other ecosystems. The movement of methane gas in salt marshes is complex and influenced by various factors such as plant types, temperature, water level, and changes in water salinity and oxygen levels. These factors interact in complex ways, making predicting the outcome of methane production and movement difficult. We applied a new method of studying methane dynamics using Empirical Dynamic Modeling and Convergent Cross Mapping. After analyzing 5 years of ecosystem‐scale measurements of methane fluxes, we show that the amount of oxygen in the water, the temperature, and the amount of light received by plants are crucial for understanding regulating methane fluxes within days and across seasons. The interconnections among these variables are complex, and methane fluxes may have delayed responses (i.e., lag times), highlighting the importance of these interactions. This research improves our comprehension of how environmental factors interact to affect methane fluxes in wetlands. Methane dynamics in salt marshes are complex and influenced by multiple variablesEmpirical dynamic modeling and convergent cross mapping are novel approaches to characterizing CH4dynamicsResults highlight drivers, non‐linearities, lag times, and interconnections among multiple biophysical variables for CH4dynamics Methane dynamics in salt marshes are complex and influenced by multiple variables Empirical dynamic modeling and convergent cross mapping are novel approaches to characterizing CH4dynamics Results highlight drivers, non‐linearities, lag times, and interconnections among multiple biophysical variables for CH4dynamics

Application of the best available science to improve quantification of greenhouse gas (GHG) emissions at regional and national scales is key to climate action. Here, we present a two‐decade (2000–2019) GHG (CO2, CH4, and N2O) budget for Mexico derived from multiple products. Data from the National GHG Inventory, global observations, and the scientific literature were compared to identify knowledge gaps on GHG flux dynamics and discrepancies among estimates. Total mean annual GHG emissions were estimated at 695–910 TgCO2‐eqyear−1over these two decades, with 70% of the emissions attributable to CO2, 23% to CH4, and 5% to N2O (2% to other gases). When divided by sectors, we found agreement across emission estimates from various sources for fossil fuels, cattle, agriculture, and waste for all GHGs. However, considerable discrepancies were identified in the fluxes from terrestrial ecosystems. The disagreement was particularly large for the land CO2sink, where net biome production estimations from the national inventory were double those from any other observational product. Extensive knowledge gaps exist, mainly related to aquatic systems (e.g., outgassing in rivers) and the lateral fluxes (e.g., wood trade). In addition, limited information is available on CH4emissions from wetlands and soil CH4consumption. We expect these results to guide future research to reduce estimation uncertainties and fill the information gaps across Mexico. Mexico represents the 13th global emitter of greenhouse gases (GHGs) and the second among Latin American countries, releasing roughly 485 million tons of CO2, six million tons of CH4(equivalent to 160 million tons of CO2), and 0.1 million tons of N2O (equivalent to 35 million tons of CO2). However, large uncertainties prevail in the estimation of several components of each flux; thus, the application of the best available science to account for and improve these estimations is essential for sound mitigation policies. Here, we used multiple available products (national inventories, satellites, flux towers, dynamic global vegetation models, inversion models, and other data sources) to advance our understanding of the GHG budget of Mexico over the last 20 years. We found that fluxes from fossil fuel combustion (including energy production, transportation, industry, etc.), agriculture, livestock, and waste management agree remarkably well across products. In contrast, we documented large differences among products for land‐based fluxes (e.g., CO2capture) and scant available information on aquatic ecosystems (e.g., CH4emission from wetlands) and on lateral fluxes (e.g., emissions from trade). We expect these results to help in guiding future measuring efforts and policies to mitigate GHG emissions from Mexico. A greenhouse gas (GHG) budget for Mexico was calculated based on multiple products. We estimated fluxes for CO2, CH4, and N2O over the 2000–2019 periodTotal GHG emissions were 695 TgCO2‐eqyear−1in the national inventory and as much as a mean 910 TgCO2‐eqyear−1across productsGHG fluxes agreed well across products for emissions, but large discrepancies exist for the land CO2and CH4sinks A greenhouse gas (GHG) budget for Mexico was calculated based on multiple products. We estimated fluxes for CO2, CH4, and N2O over the 2000–2019 period Total GHG emissions were 695 TgCO2‐eqyear−1in the national inventory and as much as a mean 910 TgCO2‐eqyear−1across products GHG fluxes agreed well across products for emissions, but large discrepancies exist for the land CO2and CH4sinks

There is a need to optimize resources for large‐scale environmental monitoring efforts, especially in developing countries. We tested a flexible framework to optimize the design (i.e., selection of study sites) of an environmental observatory network (EON) using publicly available data for Mexico. This country represents a challenge for designing EONs because of its megadiversity and large climate and ecological heterogeneity. We address three pervasive challenges for designing EONs: (1) How to characterize and delineate ecologically similar areas, (2) how to set geographic priorities to establish new representative study sites, and (3) how to assess the representativeness of current and potential new study sites. We used unsupervised cluster analysis to spatially delineate ecologically similar sampling domains. We identified the most representative sites within each domain using a conditioned Latin Hypercube‐sampling strategy. Finally, we demonstrated the applicability of this approach by assessing the spatial representativeness of the eddy covariance network in Mexico (i.e., MexFlux). At least 84 distributed sampling sites are needed to represent >45% of the spatial heterogeneity of gross primary productivity (GPP) dynamics (i.e., GPP_mean and GPP_cv) and evapotranspiration (ET) dynamics (i.e., ET_mean and ET_cv) at the national level. The current array of MexFlux only represents 3% of GPP and 5% of ET dynamics spatial variability at the national‐level, while the same number of sites organized under an optimal framework nearly doubled these estimates. Our framework is based on a data‐driven approach and publicly available sources of information, so it could be applied anywhere in the world. Existe la necesidad de optimizar recursos para realizar esfuerzos de monitoreo ambiental a gran escala, especialmente en los países en vías de desarrollo. Probamos un protocolo flexible para optimizar el diseño (i.e., la selección de sitios de estudio) de una red de observatorios ambientales (ROA) utilizando datos disponibles públicamente para México. Este país representa un reto para el diseño de ROAs debido a su megadiversidad y gran heterogeneidad climática y ecológica. Abordamos tres retos generalizados para diseñar ROAs: 1) Cómo caracterizar y delinear áreas ecológicamente similares; 2) Cómo establecer prioridades geográficas para establecer nuevos sitios de estudio representativos; y 3) Cómo evaluar la representatividad de sitios de estudio actuales y nuevos sitios potenciales. Utilizamos métodos de clasificación de grupos para delimitar espacialmente dominios de muestreo ecológicamente similares. Identificamos los sitios más representativos dentro de cada dominio mediante una estrategia de muestreo usando Hipercubo Latino condicionado. Finalmente, demostramos la aplicabilidad de este enfoque al evaluar la representatividad espacial de la red de covarianza de vórtices en México (i.e., MexFlux). Se necesitan al menos 84 sitios de muestreo distribuidos para representar >45% de la heterogeneidad espacial de la dinámica de la productividad primaria bruta (GPP; i.e., GPP_meany GPP_cv) y la dinámica de evapotranspiración (ET; i.e., ET_meany ET_cv) a nivel nacional. La distribución actual de MexFlux sólo representa el 3% de GPPy el 5% de la variabilidad espacial de la dinámica ETa nivel nacional, mientras que la misma cantidad de sitios organizados bajo un marco óptimo casi duplicó estas estimaciones. Nuestro protocolo se basa en un enfoque basado en datos y en fuentes de información disponibles públicamente, por lo que podría aplicarse en cualquier parte del mundo. A novel approach was developed to inform selection of study sites across environmental observatory networksThis framework provides insights about network representativeness and is applicable across the worldThis study identified spatial information gaps across the eddy covariance network of Mexico (MexFlux)

Process‐based land surface models are important tools for estimating global wetland methane (CH4) emissions and projecting their behavior across space and time. So far there are no performance assessments of model responses to drivers at multiple time scales. In this study, we apply wavelet analysis to identify the dominant time scales contributing to model uncertainty in the frequency domain. We evaluate seven wetland models at 23 eddy covariance tower sites. Our study first characterizes site‐level patterns of freshwater wetland CH4fluxes (FCH4) at different time scales. A Monte Carlo approach was developed to incorporate flux observation error to avoid misidentification of the time scales that dominate model error. Our results suggest that (a) significant model‐observation disagreements are mainly at multi‐day time scales (<15 days); (b) most of the models can capture the CH4variability at monthly and seasonal time scales (>32 days) for the boreal and Arctic tundra wetland sites but have significant bias in variability at seasonal time scales for temperate and tropical/subtropical sites; (c) model errors exhibit increasing power spectrum as time scale increases, indicating that biases at time scales <5 days could contribute to persistent systematic biases on longer time scales; and (d) differences in error pattern are related to model structure (e.g., proxy of CH4production). Our evaluation suggests the need to accurately replicate FCH4variability, especially at short time scales, in future wetland CH4model developments. Land surface models are useful tools to estimate and predict wetland methane (CH4) flux but there is no evaluation of modeled CH4flux error at different time scales. Here we use a statistical approach and observations from eddy covariance sites to evaluate the performance of seven wetland models for different wetland types. The results suggest models have captured CH4flux variability at monthly or seasonal time scales for boreal and Arctic tundra wetlands but failed to capture the observed seasonal variability for temperate and tropical/subtropical wetlands. The analysis suggests that improving modeled flux at short time scale is important for future model development. Significant model‐observation disagreements were found at multi‐day and weekly time scales (<15 days)Models captured variability at monthly and seasonal time (42–142 days) scales for boreal and Arctic tundra sites but not for temperate and tropical sitesThe model errors show that biases at multi‐day time scales may contribute to persistent systematic biases on longer time scales Significant model‐observation disagreements were found at multi‐day and weekly time scales (<15 days) Models captured variability at monthly and seasonal time (42–142 days) scales for boreal and Arctic tundra sites but not for temperate and tropical sites The model errors show that biases at multi‐day time scales may contribute to persistent systematic biases on longer time scales

Global soils store at least twice as much carbon as Earth’s atmosphere1,2. The global soil-to-atmosphere (or total soil respiration, RS) carbon dioxide (CO2) flux is increasing3,4, but the degree to which climate change will stimulate carbon losses from soils as a result of heterotrophic respiration (RH) remains highly uncertain5–8. Here we use an updated global soil respiration database9to show that the observed soil surface RH:RSratio increased significantly, from 0.54 to 0.63, between 1990 and 2014 (P= 0.009). Three additional lines of evidence provide support for this finding. By analysing two separate global gross primary production datasets10,11, we find that the ratios of both RHand RSto gross primary production have increased over time. Similarly, significant increases in RHare observed against the longest available solar-induced chlorophyll fluorescence global dataset, as well as gross primary production computed by an ensemble of global land models. We also show that the ratio of night-time net ecosystem exchange to gross primary production is rising across the FLUXNET201512dataset. All trends are robust to sampling variability in ecosystem type, disturbance, methodology, CO2fertilization effects and mean climate. Taken together, our findings provide observational evidence that global RHis rising, probably in response to environmental changes, consistent with meta-analyses13–16and long-term experiments17. This suggests that climate-driven losses of soil carbon are currently occurring across many ecosystems, with a detectable and sustained trend emerging at the global scale. Global soil respiration is rising, probably in response to environmental changes, suggesting that climate-driven losses of soil carbon are occurring worldwide.

Duodeno-jejunal bypass (DJB) operation improves glucose homeostasis in morbid obesity, independently of weight loss or reductions in adiposity, through mechanisms not yet fully elucidated. Herein, we evaluated the effects of DJB upon glucose homeostasis, endocrine pancreatic morphology, and β-cell responsiveness to potentiating agents of cholinergic and cAMP pathways, in western diet (WD) obese rats, at 2 months after operation. From 8 to 18 weeks of age male Wistarrats fed on a WD. After this period, a sham (WD Sham group) or DJB (WD DJB) operations were performed. At 2 months after operation glucose homeostasis was verified. Body weight was similar between WD DJB and WD Sham rats, but WD DJB rats showed a decrease in Lee index, retroperitoneal and perigonadal fat pads. Also, WD DJB rats displayed reduced fasting glycemia and insulinemia, and increased insulin-induced Akt activation in the gastrocnemius. Islets from WD DJB rats secreted less amounts of insulin, in response to activators of the cholinergic (carbachol and phorbol 12-myristate 13-acetate) and cAMP (forskolin and 3-isobutyl-1-methyl-xantine) pathways. Islets of WD DJB rats had higher sintaxin-1 protein content than WD Sham, but without modification in muscarinic-3 receptor, protein kinase (PK)-Cα, and (PK)-Aα protein amounts. In addition, islets of WD DJB animals showed reduction in islets and β-cell masses. DJB surgery improves fasting glycemia and insulin action in skeletal muscle. Better endocrine pancreatic morphofunction was associated, at least in part, with the regulation of the cholinergic and cAMP pathways, and improvements in syntaxin-1 islet protein content induced by DJB.

Large storm events possess significant erosive energy capable of mobilizing large amounts of sediment and particulate organic matter (POM) into fluvial systems. This study investigated how stream POM composition varied as a function of the watershed POM source, particle size, storm event magnitude, and seasonal timing. POM composition was characterized for multiple watershed sources and for stream POM following storms in a second‐order forested stream. Carbon (C) and nitrogen (N) amount, C:N ratio and isotopic content (13C and 15N) were determined for solid phase POM, whereas dissolved organic C, total N concentrations, and fluorescence characteristics were determined for solution/extracted POM. Key findings from this study were the following: (1) Composition of POM varied greatly with watershed sources with forest floor litter being C and N rich and labile, while stream banks and bed were C and N poor and recalcitrant. (2) Summer storms mobilized more carbon and nitrogen‐rich labile sources, while winter events mobilized more carbon‐ and nitrogen‐poor refractory material from near‐stream sources. (3) POM composition varied by size class, with the coarse POM showing more C and N rich and labile properties, while the fine POM displayed more degraded and refractory properties. If climate variability increases the magnitude and intensity of large storm events, our observations suggest that this will not only increase the inputs of POM to aquatic systems but also result in the delivery of coarser, C and N rich, and more bioavailable POM to the stream drainage network. Large storms can alter POM composition in streamsPOM composition varied with sources, particle class, and storm eventsChanges in POM could impact fluvial and aquatic ecosystems

Coastal margins could be hotspots for acidification due to terrestrial‐influenced CO2sources. Currently there are no long‐term (>20 years) records from biologically important coastal environments that could demonstrate sea surface CO2fugacity (fCO2) and pH trends. Here, multidecadal fCO2trends are calculated from underway and moored time series observations along the United States southeast coastal margin, also referred to as the South Atlantic Bight (SAB). fCO2trends across the SAB, derived from ∼26 years of cruises and ∼9.5 years from a moored time series, range from 3.0 to 4.5 µatm yr−1, and are greater than the open ocean increases. The pH decline related to the fCO2increases could be as much as −0.004 yr−1; a rate greater than that expected from atmospheric‐influenced pH alone. We provide evidence that fCO2increases and pH decreases on an ocean margin can be faster than those predicted for the open ocean from atmospheric influence alone. We conclude that a substantial fCO2increase across the marginal SAB is due to both increasing temperature on the middle and outer shelves, but to lateral land‐ocean interactions in the coastal zone and on inner shelf. Long‐term fCO2in coastal South Atlantic Bight is increasing at a rate greater than open oceanThe fCO2increase is likely a combination of increases from terrestrial sources, with little to no influence from temperatureThe related pH decrease on this coastal margin is likely greater than that of the open ocean

We made a commitment to better include underrepresented members of our community in the publication pipeline of JGR: Biogeosciences. This commitment consists of regular updates on our policies and practices, and concrete actions we intend to implement over the next year. So far, our progress to tackle biases and ensure equitable research in the biogeosciences has focused on improving diversity of our associate editor and reviewer pools, increasing awareness of unconscious bias in peer‐review, and promoting inclusion in global collaborations. In this update, we explore manuscript submissions and manuscript decisions by gender, and we present a pilot that aims to promote ethical and equitable global collaborations in resource‐poor settings. We end our editorial by presenting our next set of actions that we plan on completing over the next year, which include a more thorough analysis of reviewer demographics. Here we report on our progress for equitable and inclusive peer‐review and publishing for JGR: BiogeosciencesIn the past year we prioritized a pilot program to ensure equitable global collaborationsOur next set of key priorities to expand and diversify our reviewer pool and publishing community are highlighted Here we report on our progress for equitable and inclusive peer‐review and publishing for JGR: Biogeosciences In the past year we prioritized a pilot program to ensure equitable global collaborations Our next set of key priorities to expand and diversify our reviewer pool and publishing community are highlighted

Tidal channels are biogeochemical hotspots that horizontally exchange carbon (C) with marsh platforms, but the physiochemical drivers controlling these dynamics are poorly understood. We hypothesized that C‐bearing iron (Fe) oxides precipitate and immobilize dissolved organic carbon (DOC) during ebb tide as the soils oxygenate, and dissolve into the porewater during flood tide, promoting transport to the channel. The hydraulic gradient physically controls how these solutes are horizontally exchanged across the marsh platform‐tidal channel interface; we hypothesized that this gradient alters the concentration and source of C being exchanged. We further hypothesized that trace soil gases (i.e., CO2, CH4, dimethyl sulfide) are pushed out of the channel bank as the groundwater rises. To test these hypotheses, we measured porewater, surface water, and soil trace gases over two 24‐hr monitoring campaigns (i.e., summer and spring) in a mesohaline tidal marsh. We found that Fe2+and DOC were positively related during flood tide but not during ebb tide in spring when soils were more oxidized. This finding shows evidence for the formation and dissolution of C‐bearing Fe oxides across a tidal cycle. In addition, the tidal channel contained significantly (p< 0.05) more terrestrial‐like DOC when the hydraulic gradient was driving flow toward the channel. In comparison, the channel water was saltier and contained significantly (p< 0.05) more marine‐like DOC when the hydraulic gradient reversed direction. Trace gas fluxes increased with rising groundwater levels, particularly dimethyl sulfide. These findings suggest multiple physiochemical mechanisms controlling the horizontal exchange of C at the marsh platform‐tidal channel interface. Tidal salt marshes store large amounts of carbon belowground in soils, but there is also a significant amount of carbon flowing into and out of these ecosystems via tidal channels. We investigated the carbon flowing between the channel bank and surface water in a salt marsh in Delaware. We found that soil minerals (i.e., iron oxides) control the mobility of carbon as iron oxides retain carbon during ebb tides and release carbon during flood tides as the minerals dissolve. The gradient between the groundwater and surface water elevation (i.e., hydraulic gradient) controls the flow direction for dissolved carbon, altering the concentration and source of carbon found in the tidal channel across tidal cycles. In addition, gases trapped in channel banks are pushed out of the soils as the tide rises. These findings will improve our understanding of carbon cycles in these critical carbon sinks. Physiochemical mechanisms control horizontal exchange of carbon across marsh‐tidal channel interfaces, affecting lateral carbon fluxDissolution and reprecipitation of carbon‐bearing Fe oxides during flood and ebb tides control the horizontal mobility of carbonHydraulic gradients control the carbon character in the tidal channel, and rising tides push greenhouse gases out of the channel bank Physiochemical mechanisms control horizontal exchange of carbon across marsh‐tidal channel interfaces, affecting lateral carbon flux Dissolution and reprecipitation of carbon‐bearing Fe oxides during flood and ebb tides control the horizontal mobility of carbon Hydraulic gradients control the carbon character in the tidal channel, and rising tides push greenhouse gases out of the channel bank

La investigación es uno de los procesos necesarios para la construcción de conocimiento, por esta razón, en la carrera de nutrición de la universidad Mariano Gálvez se ha implementado la investigación como un importante componente del curso de química analítica. Durante este proceso, se evalúa el impacto desde la perspectiva del involucramiento científico como parte de un curso regular, aprovechando recursos institucionales y desarrollando investigaciones producto de la curiosidad de los estudiantes.

Chile has a strong forest sector based on plantations of exotic species and an extensive area of temperate rainforests with unique ecological features and a wealth of biodiversity and endemism. We present an overview of the forest sector of Chile focused on forest resources, silviculture, economy, social and environmental aspects, and forestry education and research. The Chilean forest sector is internationally known for its success. Although this is one of the most important economic activities of Chile, management between exotic species plantations and natural forests is very asymmetric. Currently, highly intensive silviculture is applied to forest plantations of Pinus radiata(radiata pine) and Eucalyptus(Eucalyptus globulus, Eucalyptus nitens) but only limited operational silviculture is applied to natural forests, even though there is considerable research to support it. There are still unresolved issues related to: conversion from natural forests to other land uses; pulp mills, and new efforts are needed from the government and large forestry companies to account for social and environmental demands. There is a good amount of university-level forestry education; however, there is an oversupply of professional foresters.Management and Policy ImplicationsThis work provides insights about the Chilean forestry sector and guidance for understanding the ecological, economic, social, and silvicultural complexity of its current framework. This review indicates that most of the challenges affecting large forestry companies come from social and environmental concerns. Improving the management of planted and natural stands, plus the relationship between large companies and indigenous communities, should be the focus of policymakers. In Chile, current socioenvironmental conflicts associated with large monoculture plantations and large clearcuts and the increasing high grading of natural forests have called for a new approach in the forestry sector. This new approach should consider the following: changes in silviculture and landscape management of forest plantations, including recovery of native forest patches in regions with large and continuous areas of monocultures of exotic species; adequate subsidies for promoting the conservation and management of natural forests, therefore reversing the high grading process that is now occurring in these forests; and forestry education and research that must serve these purposes to train professionals prepared for the challenges of a discipline with major environmental, social, and economic implications on people and local communities. Chile, with its high diversity and endemism, plus the opportunities for growing highly productive forests either from plantations or native forests, could become a model for forest ecosystem management.

Salt marsh ecosystems are underrepresented in process‐based models due to their unique location across the terrestrial–aquatic interface. Particularly, the role of leaf nutrients on canopy photosynthesis (FA) remains unclear, despite their relevance for regulating vegetation growth. We combined multiyear information of canopy‐level nutrients and eddy covariance measurements with canopy surface hyperspectral remote sensing (CSHRS) to quantify the spatial and temporal variability of FAin a temperate salt marsh. We found that FAshowed a positive relationship with canopy‐level N at the ecosystem scale and for areas dominated by Spartina cynosuroides, but not for areas dominated by short S. alterniflora. FAshowed a positive relationship with canopy‐level P, K, and Na, but a negative relationship with Fe, for areas associated with S. cynosuroides, S. alterniflora, and at the ecosystem scale. We used partial least squares regression (PLSR) with CSHRS and found statistically significant data–model agreements to predict canopy‐level nutrients and FA. The red‐edge electromagnetic region and ∼770 nm showed the highest contribution of variance in PLSR models for canopy‐level nutrients and FA, but we propose that underlying sediment biogeochemistry can complicate interpretation of reflectance measurements. Our findings highlight the relevance of spatial variability in salt marshes vegetation and the promising application of CSHRS for linking information of canopy‐level nutrients with FA. We call for further development of canopy surface hyperspectral methods and analyses across salt marshes to improve our understanding of how these ecosystems will respond to global environmental change. Canopy photosynthesis in salt marshes contributes to the carbon stored in these ecosystems; however, its relationship with canopy‐level nutrients has been underrepresented in models. Reflectance from near surface remote sensing could be a cost‐effective nondestructive tool to monitor canopy photosynthesis and associated nutrients in salt marshes. We combined canopy‐level nutrient information with hyperspectral canopy reflectance to represent the spatial and temporal variability of canopy photosynthesis in a salt marsh in the Mid‐Atlantic cost of the U.S. We found that local variability such as different salt marsh species have an influence on the relationship between canopy photosynthesis and associated nutrients, in consequence the most limiting nutrients for photosynthesis were phosphorus, potassium, and sodium. We propose that underlying sediment biogeochemistry can potentially obscure the expected relationships between plant nutrients and photosynthesis in remote sensing of coastal wetlands. These results open the possibility to use similar reflectance information from airborne or spaceborne platforms to explore these relationships at broader scales. Local environmental variability influences the relationship of canopy nutrients with canopy photosynthesis in a salt marsh ecosystemSediment biogeochemistry can obscure expected relationships between plant nutrients and photosynthesis in remote sensing of coastal wetlandsCanopy surface hyperspectral remote sensing is a promising technique for studying vegetation dynamics of salt marshes Local environmental variability influences the relationship of canopy nutrients with canopy photosynthesis in a salt marsh ecosystem Sediment biogeochemistry can obscure expected relationships between plant nutrients and photosynthesis in remote sensing of coastal wetlands Canopy surface hyperspectral remote sensing is a promising technique for studying vegetation dynamics of salt marshes

Continental North America has been found to be a carbon (C) sink over recent decades by multiple studies employing a variety of estimation approaches. However, several key questions and uncertainties remain with these assessments. Here we used results from an ensemble of 19 state‐of‐the‐art dynamic global vegetation models from the TRENDYv9 project to improve these estimates and study the drivers of its interannual variability. Our results show that North America has been a C sink with a magnitude of 0.37 ± 0.38 (mean and one standard deviation) PgC year−1for the period 2000–2019 (0.31 and 0.44 PgC year−1in each decade); split into 0.18 ± 0.12 PgC year−1in Canada (0.15 and 0.20), 0.16 ± 0.17 in the United States (0.14 and 0.17), 0.02 ± 0.05 PgC year−1in Mexico (0.02 and 0.02) and 0.01 ± 0.02 in Central America and the Caribbean (0.01 and 0.01). About 57% of the new C assimilated by terrestrial ecosystems is allocated into vegetation, 30% into soils, and 13% into litter. Losses of C due to fire account for 41% of the interannual variability of the mean net biome productivity for all North America in the model ensemble. Finally, we show that drought years (e.g., 2002) have the potential to shift the region to a small net C source in the simulations (−0.02 ± 0.46 PgC year−1). Our results highlight the importance of identifying the major drivers of the interannual variability of the continental‐scale land C cycle along with the spatial distribution of local sink‐source dynamics. In recent decades terrestrial ecosystems in North America have absorbed more carbon (C) from the atmosphere than they have released, thus acting as a net land C sink. Nonetheless, several gaps remain in our understanding of how the newly assimilated C is partitioned among the various components of the land ecosystem, and about the impact of recent fires and extreme climatic events on the C stored in vegetation and the soil. In this study, we employed 19 state‐of‐the‐art global dynamic vegetation models to advance our understanding of the land C dynamics over North America over the period 2000–2019. Our results suggest that 57% of the newly assimilated C over this period went into the vegetation, 30% to the soils, and the rest as litter. These new land C gains were found mostly over the temperate and boreal forest regions, which together accounted for 81% of the entire North American sink. Finally, we show that fire and drought are closely related to the year‐to‐year variability of the sink magnitude, and during extreme conditions (e.g., during 2002) they have the potential to reverse the land into a C source to the atmosphere. Land C sink dynamics for North America were evaluated using 19 state‐of‐the‐art Dynamic Global Vegetation Models during 2000–2019North America has been a net C sink with a magnitude of 0.37 ± 0.38 PgC year−1and an increasing trend over timeWe identify different spatial and temporal drivers of the variability in land C fluxes across the region, including fire and drought Land C sink dynamics for North America were evaluated using 19 state‐of‐the‐art Dynamic Global Vegetation Models during 2000–2019 North America has been a net C sink with a magnitude of 0.37 ± 0.38 PgC year−1and an increasing trend over time We identify different spatial and temporal drivers of the variability in land C fluxes across the region, including fire and drought

In March 2013, 40 leading experts from across the world gathered at a workshop, hosted by the European Commission, Directorate General Joint Research Centre, Italy, to discuss the multiple benefits of soil carbon as part of a Rapid Assessment Process (RAP) project commissioned by Scientific Committee on Problems of the Environment (SCOPE). This collaboration led to the publication of the SCOPE Series Volume 71 “Soil Carbon: Science, Management and Policy for Multiple Benefits”; which brings together the essential scientific evidence and policy opportunities regarding the global importance of soil carbon. This short communication summarises the key messages of the assessment including research and policy implications.

Tidal wetlands are comprised of complex interdependent pathways where measurements of carbon exchange are often scale dependent. Common data collection methods (i.e., chambers and eddy covariance) are inherently constrained to different spatial and temporal scales which could generate biased information for applications of carbon accounting, identifying functional relationships and predicting future responses to climate change. Consequently, it is needed to systematically evaluate measurements derived from multiple approaches to identify differences and how techniques complement each other to reconcile interpretations. To accomplish this, we tested ecosystem‐scale eddy covariance with plot‐scale chamber measurements within a temperate salt marsh. We found good agreement (R2= 0.71–0.95) when comparing measurements of CH4emissions and CO2exchange but this agreement was dependent upon canopy phenology with discrepancies mainly arising during senescence and dormancy phenophases. The environmental drivers for CH4and CO2fluxes were mostly preserved across different measurement techniques, but the number of drivers increases while their individual strength decreases at the ecosystem scale. Empirical upscaling models parameterized with chamber measurements overestimated annual net ecosystem exchange (NEE; 108%) and gross primary production (GPP; 12%) while underestimating ecosystem respiration (Reco; 14%) and CH4emissions (69%) compared to eddy covariance measurements. Our results suggest that the environmental complexity of CH4and CO2fluxes in salt marshes may be underestimated by chamber‐based measurements, and highlights how different techniques are complementary while considering limitations at each level of measurement. Tidal wetlands are important landscape features which play a significant role in regional carbon cycling between land, ocean and the atmosphere. These ecosystems are very productive, with high rates of photosynthesis during the growing season, but they also emit methane and carbon dioxide which can offset carbon gains. Therefore, it is important to accurately measure and understand what factors regulate carbon cycling processes to better characterize how these systems function, calculate carbon budgets and help predict possible reposes to climate change. We compare several common measurement techniques including chamber and eddy covariance which incorporate information across different scales to evaluate the level of agreement and how these techniques can be combined to increase our understanding of ecosystem functionality. We found that techniques agree well when comparing time‐matched measurement windows but different plant development stages across the ecosystem likely impacted agreement during autumn and early winter. We found that primary factors regulating fluxes were similar across techniques but when considering data collected over more hours of the day with eddy covariance, additional factors were identified indicating measurements from chambers which are limited in both coverage across space and time may present an oversimplified view within tidal wetlands. Plot‐level and eddy covariance measurements had good overall agreement, but the strength of agreement was dependent upon plant phenologyThe relevance and influence of environmental drivers varied for all fluxes across different techniquesModels parameterized with plot‐level data overestimated ecosystem‐scale net ecosystem exchange but underestimated CO2and CH4emissions Plot‐level and eddy covariance measurements had good overall agreement, but the strength of agreement was dependent upon plant phenology The relevance and influence of environmental drivers varied for all fluxes across different techniques Models parameterized with plot‐level data overestimated ecosystem‐scale net ecosystem exchange but underestimated CO2and CH4emissions

The study of air‐sea CO2fluxes (FCO2) in the coastal region is needed to better understand the processes that influence the direction and magnitude of FCO2and to constrain the global carbon budget. We implemented a 1 year (January through December 2009) paired study to measure FCO2in the intertidal zone (the coastline to 1.6 km offshore) and the near‐shore (∼3 km offshore) off the north‐western coast of Baja California (Mexico); a region influenced by year‐round upwelling. FCO2was determined in the intertidal zone via eddy covariance; while in the near‐shore using mooring buoy sensors then calculated with the bulk method. The near‐shore region was a weak annual net source of CO2to the atmosphere (0.043 mol CO2m−2y−1); where 91% of the outgassed FCO2was contributed during the upwelling season. Sea surface temperature (SST) and ΔpCO2(from upwelling) showed the strongest relationship with FCO2in the near‐shore, suggesting the importance of meso‐scale processes (upwelling). FCO2in the intertidal zone were up to four orders of magnitude higher than FCO2in the near‐shore. Wind speed showed the strongest relationship with FCO2in the intertidal zone, suggesting the relevance of micro‐scale processes. Results show that there are substantial spatial and temporal differences in FCO2between the near‐shore and intertidal zone; likely a result of heterogeneity. We suggest that detailed spatial and temporal measurements are needed across the coastal oceans and continental margins to better understand the mechanisms which control FCO2, as well as reduce uncertainties and constrain regional and global ocean carbon balances. Spatial variation influences CO2 flux estimates in coastal regionsDifferent processes control ocean CO2 flux during different seasons/locations

Here we are presenting a statement of Diversity, Equity and Inclusion (DEI) for JGR: Biogeosciences. This statement includes current policies and practices, and details concrete actions that we intend to implement over the next year to better include underrepresented groups in the publication process. The impact of our journal is enhanced when a representative pool of contributors participates in the process of scientific publicationIncreasing reviewer and editor diversity is the best opportunity we have to remove bias from the peer review processKey priorities to expand and diversify our editorial, reviewing, and publishing community are highlighted The impact of our journal is enhanced when a representative pool of contributors participates in the process of scientific publication Increasing reviewer and editor diversity is the best opportunity we have to remove bias from the peer review process Key priorities to expand and diversify our editorial, reviewing, and publishing community are highlighted

Acetylene reduction assay (ARA) was applied to determine the rate of nitrogen fixation by cyanoprokaryotes in a wetland in El Edén Ecological Reserve. The data obtained throughout a hydrological cycle showed both an increase of fixed nitrogen during wet periods and an important amount of nitrogen rate produced by non-heterocytic filamentous and colonial blue-green algae. The results support the importance of the contribution of algae to nutrient balance in the wetland ecosystem. Se realizó la prueba de reducción de acetileno para determinar la tasa de fijación de nitrógeno por cianoprokariotes en un humedal tropical de la Reserva Ecológica El Edén. Los datos obtenidos durante un ciclo hidrológico muestran tanto un incremento en el nitrógeno fijado durante el periodo de lluvias como una importante cantidad en la tasa de fijación de nitrógeno producida por algas verdeazules filamentosas no heterocitosas y coloniales. Los resultados respaldan la importancia de la contribución de las algas en el balance de nutrimentos en el humedal.

Measurements of atmospheric ammonia (NH3) concentrations and fluxes are limited in coastal regions in the eastern U.S. In this study, continuous and high temporal resolution measurements (5s) of atmospheric NH3concentrations were recorded using a cavity ring‐down spectrometer in a temperate tidal salt marsh at the St Jones Reserve (Dover, DE). Micrometeorological variables were measured using an eddy covariance system which is part of the AmeriFlux network (US‐StJ). Soil, plant, and water chemistry were also analyzed to characterize the sources and sinks of atmospheric NH3. A new analytical methodology was used to estimate the average ecosystem‐scale diurnal cycle of NH3fluxes by replicating the characteristics of a chamber experiment. This virtual chamber approach estimates positive surface fluxes in continuing strongly stable conditions when mixing with the air above is minimal. Our findings show that tidal water level may have a significant impact on NH3emissions from the marsh. The largest fluxes were observed at low tide when more soil was exposed. While it is expected that NH3fluxes will peak when the air temperature maximizes, high tide occurred concurrently with midday peaks in solar irradiance led to a decrease in NH3fluxes. Furthermore, soil, plant, and water chemistry measurements underpinning the NH3concentrations and fluxes lead us to conclude that this coastal wetland ecosystem can act as either a sink or a source of NH3. Such measurements provide novel data on which we can base reliable parameterizations to simulate NH3emissions from coastal salt marsh ecosystems using surface‐atmosphere transfer models. Coastal wetlands such as salt marshes, mangroves, and seagrasses provide a natural environment for the sequestration and long‐term storage of carbon dioxide (CO2) from the atmosphere. As a fertilizer, nitrogen (N) increases the vegetative growth and thus more CO2may be fixed in plants as biomass representing the short‐term storage pool of carbon, therefore reducing its atmospheric level. Salt marshes, in particular, have been identified as being highly effective at carbon sequestration as well as adsorbing and transforming N. However, there are limited atmospheric measurements of ammonia (NH3) concentrations and exchanges in coastal areas of the Eastern and Mid‐Atlantic U.S. This pilot study represents one of the few atmospheric measurements of NH3over temperate tidal salt marshes in the Mid‐Atlantic U.S. The high temporal resolution measurements of NH3concentrations indicated that local sources, such as agriculture and industry, may have a considerable impact on the local atmospheric NH3concentrations. The results also show that tidal water levels in salt marshes may have a significant effect on NH3emissions. Continuous and high temporal resolution of ammonia (NH3) concentrations were measured using cavity ring‐down spectroscopy over a salt marshAverage diurnal cycles of NH3fluxes were estimated in a coastal ecosystem using a new analytical methodologyTidal water level was identified as a key parameter influencing NH3emissions in wetlands Continuous and high temporal resolution of ammonia (NH3) concentrations were measured using cavity ring‐down spectroscopy over a salt marsh Average diurnal cycles of NH3fluxes were estimated in a coastal ecosystem using a new analytical methodology Tidal water level was identified as a key parameter influencing NH3emissions in wetlands

Environmental observatory networks (EONs) provide information to understand and forecast the spatial and temporal dynamics of Earth's biophysical processes. Consequently, representativeness analyses are important to provide insights for improving EONs' management, design, and interpretation of their value‐added products. We assessed the representativeness of registered FLUXNET sites (n= 41, revised on September 2018) across Latin America (LA), a region of great importance for the global carbon and water cycles, which represents 13% of the world's land surface. Nearly 46% of registered FLUXNET sites are located in evergreen broad‐leaf forests followed by sites in woody savannas (∼20%). Representativeness analyses were performed using a 0.05° spatial grid for multiple environmental variables, gross primary productivity (GPP), and evapotranspiration (ET). Our results showed a potential representativeness of 34% of the surface area for climate properties, 36% for terrain parameters, 34% for soil resources, and 45% when all aforementioned environmental variables were summarized into a principal component analysis. Furthermore, there was a 48% potential representativeness for GPP and 34% for ET. Unfortunately, data from these 41 sites are not all readily available for the scientific community, limiting synthesis studies and model benchmarking/parametrization. The implication is that global/regional data‐driven products are forced to use information from FLUXNET sites outside LA to predict patterns in LA. Representativeness could increase to 86% (for GPP) and 80% (for ET) if 200 sites are optimally distributed. We discussed ongoing challenges, the need to enhance interoperability and data sharing, and promote monitoring efforts across LA to increase the accuracy of regional‐to‐global data‐driven products. Environmental observatory networks (EONs) provide information to better understand, model, and forecast the spatial and temporal dynamics of Earth's biophysical processes. Consequently, representativeness analyses of EON's are important to provide insights for improving EONs' management, design, and interpretation of their value‐added products (e.g., datasets, model predictions). We assessed the representativeness of registered FLUXNET sites (n= 41, revised on September 2018) across Latin America (LA), a region of great importance for the global carbon and water cycles, which represents nearly 13% of the world's land surface area. Representativeness analyses were performed using multiple environmental variables, gross primary productivity (GPP), and evapotranspiration (ET) across LA. Our results showed potential spatial representativeness of 34% of the surface area for climate properties, 36% for terrain parameters, 34% for soil resources, and 45% when all aforementioned environmental variables were summarized. Furthermore, there was a 48% potential representativeness for GPP and 34% for ET. Our results represent a best‐case scenario because data from these 41 sites is not all readily available for the scientific community. We discussed the need to enhance collaboration, promote the participation of active/inactive sites to share information with local, regional and international networks, and promote monitoring efforts across this region of the world. There is a need to promote data sharing and improve the representativeness of environmental networks across Latin AmericaCurrently, 48% of gross primary productivity and 34% of evapotranspiration patterns are represented by FLUXNET sitesData‐driven products are forced to use information outside Latin America to predict patterns within this region There is a need to promote data sharing and improve the representativeness of environmental networks across Latin America Currently, 48% of gross primary productivity and 34% of evapotranspiration patterns are represented by FLUXNET sites Data‐driven products are forced to use information outside Latin America to predict patterns within this region

Although drylands cover >40% of the land surface, models of ecosystem gross primary productivity (GPP) generally have been designed for mesic temperate ecosystems. Arguably, GPPmodels often lack a good representation of vegetation phenology, particularly not estimating the ecosystem effects of the prolonged foliage senescence which may be common in drylands. To estimate daily GPPfor a water‐limited Mediterranean shrubland, we propose a simple framework (GPPmod) using light use efficiency, a spectral vegetation index derived from digital cameras, and five meteorological variables, including an index of functional senescence of foliage (i.e., heat degree‐days). We tested the model with different combinations of meteorological variables but without senescence, using 1 year's data. The best formulation showed good agreement with GPPderived from eddy covariance (GPPEC; r2= 0.53, RMSE = 0.77). However, including the foliage senescence parameter significantly improved model performance (r2= 0.74, RMSE = 0.49), especially during the fall season. In the following year, we validated the parameters: The overall GPPmodand GPPECcomparison yielded an r2= 0.78. We postulate that models that mainly rely on meteorological variables or greenness indices could yield an overestimation of annual GPPbetween 24% and 90%, while models including the foliage senescence parameter reduced that bias by 10% to 34%. Our results highlight the importance of incorporating the phenology of foliage senescence in models regarding productivity in drylands or dry sclerophyll ecosystems. Los modelos para predecir la productividad primaria bruta (GPP) se han diseñado principalmente para ecosistemas templados mésicos, sin considerar que las zonas áridas y semiáridas cubren >40% de la superficie continental terrestre. Entonces, podría argumentarse que los modelos de GPPa menudo carecen de una buena representación de la fenología de la vegetación y, en particular, no incorporan los periodos de senescencia del follaje que son comunes en zonas áridas y semiáridas. Nosotros proponemos un modelo matemático simple para estimar a escala diaria la GPP(GPPmod) en un matorral mediterráneo utilizando la eficiencia de uso de luz, un índice de vegetación producto de cámaras digitales, y cinco variables meteorológicas que incluyen un índice de senescencia funcional del follaje (p. ej., suma de grados de calor). Probamos nuestro modelo utilizando un año de datos con diferentes combinaciones de variables meteorológicas y con y sin el índice de senescencia. La mejor formulación mostró una buena correspondencia de la GPPestimada con la técnica de correlación turbulenta (GPPEC; r2= 0.53, RMSE = 0.77). Sin embargo, el incluir el índice de senescencia mejoró significativamente el rendimiento del modelo (r2= 0.74, RMSE = 0.49), en especial durante la temporada de otoño. Para el siguiente año validamos los parámetros: en general la comparación de GPPmody GPPECobtuvo un r2= 0.78. Esto implica que los modelos basados en índices de verdor y variables meteorológicas podrían estar sobreestimando la GPPanual entre 24 y 92%, y ese sesgo podría ser reducido entre 10 y 34% al incorporar nuestro índice de senescencia del follaje. Nuestros resultados resaltan la importancia de incorporar la senescencia del follaje en modelos de productividad primaria para zonas áridas y semiáridas. We modeled GPPusing phenocam and meteorological dataGPPwas overestimated in autumn using a light use efficiency modelIncorporating foliage senescence improved GPPestimates

Plants have the capacity to store and reallocate stored non-structural C, but little is known about the age and ecological roles of these pools. It was thought that plants allocate recently assimilated C to produce new fine roots. However, there is recent evidence that plants can allocate old stored C for the production of fine roots following a large-infrequent disturbance (LID) providing a new dimension of the fate and the implied role of stored C in plants. Here, I explore other possible adaptations of plants to allocate stored C reserves, and provide a series of open questions on the fate of old stored C in plants. Specifically, I propose that another metabolic function of old stored C may be for supporting mycorrhizal fungi colonization after a large-infrequent disturbance, because the production of hyphae may be more economical in terms of C to the plant under stressful conditions. Finally, in order to better understand plant resilience to LIDs it is critical to understand the mechanisms that regulate the fate of old stored C in plants.

Coastal salt marshes store large amounts of carbon but the magnitude and patterns of greenhouse gas (GHG; i.e., carbon dioxide (CO2) and methane (CH4)) fluxes are unclear. Information about GHG fluxes from these ecosystems comes from studies of sediments or at the ecosystem‐scale (eddy covariance) but fluxes from tidal creeks are unknown. We measured GHG concentrations in water, water quality, meteorological parameters, sediment CO2efflux, ecosystem‐scale GHG fluxes, and plant phenology; all at half‐hour intervals over 1 year. Manual creek GHG flux measurements were used to calculate gas transfer velocity (k) and parameterize a model of water‐to‐atmosphere GHG fluxes. The creek was a source of GHGs to the atmosphere where tidal patterns controlled diel variability. Dissolved oxygen and wind speed were negatively correlated with creek CH4efflux. Despite lacking a seasonal pattern, creek CO2efflux was correlated with drivers such as turbidity across phenological phases. Overall, nighttime creek CO2efflux (3.6 ± 0.63 μmol/m2/s) was at least 2 times higher than nighttime marsh sediment CO2efflux (1.5 ± 1.23 μmol/m2/s). Creek CH4efflux (17.5 ± 6.9 nmol/m2/s) was 4 times lower than ecosystem‐scale CH4fluxes (68.1 ± 52.3 nmol/m2/s) across the year. These results suggest that tidal creeks are potential hotspots for CO2emissions and could contribute to lateral transport of CH4to the coastal ocean due to supersaturation of CH4(>6,000 μmol/mol) in water. This study provides insights for modeling GHG efflux from tidal creeks and suggests that changes in tide stage overshadow water temperature in determining magnitudes of fluxes. A tidal creek was a hotspot for CO2efflux compared to the surrounding wetlandChanges in tide stage, not water temperature variability, regulated diel creek CO2and CH4effluxThe relative influence of nontidal drivers of creek CO2and CH4efflux varied by plant phenological phases

Tropical dry forests (TDF) are one of the most widely distributed tropical land‐cover types in Mexico, but their regional‐to‐global contribution to the carbon and water cycles is still highly uncertain. We measured CO2and water vapor fluxes between the ecosystem and atmosphere using the eddy covariance technique from 2016 to 2018 in an old‐growth TDF in northwestern Mexico. First, we investigated the magnitude and seasonality of evapotranspiration (ET), net ecosystem production (NEP) and its contributing fluxes, gross ecosystem production (GEP), and ecosystem respiration (Reco). Second, we explored the main environmental factors controlling carbon and water fluxes as well as tested if this ecosystem acted as a net carbon source or sink. During the study period, all precipitation entering the ecosystem went back to the atmosphere through ET (738.9 ±58.26 mm y−1). Ecosystem respiration (2203.16 ±244.2 g C m−2y−1) was consistently larger than GEP (1975.32 ±295.52 g C m−2y−1), determining an annual NEP (−227.6 ±59.4 g C m−2y−1) that resulted in net annual carbon losses. This forest maintained its water use efficiency (WUE; GEP/ET) across years (2.53–3.24), but water availability constrained light use and maximum carbon assimilation rates. Our results render relevance to the feedback between soil water content and net radiation as the main environmental variables controlling ecosystem fluxes in this old‐growth TDF. El bosque tropical seco (BTS) es una de las coberturas terrestres más ampliamente distribuidas en México, pero su contribución regional y global a los ciclos del carbono y del agua es aún muy incierta. Medimos los flujos de CO2y vapor de agua entre el ecosistema y la atmósfera utilizando la técnica de covarianza de vórtices entre 2016 y 2018 en un BTS maduro en el noroeste de México. Primero, investigamos la magnitud y la estacionalidad de la evapotranspiración (ET), la producción neta del ecosistema (NEP) y sus flujos contribuyentes, la producción bruta del ecosistema (GEP) y la respiración del ecosistema (Reco). En segundo lugar, exploramos los principales factores ambientales que controlan los flujos de carbono y de agua, y probamos si este ecosistema actuó como fuente o sumidero neto de carbono. Durante el período de estudio, la precipitación que recibió el ecosistema regresó a la atmósfera a través de ET (738.9 ± 58.26 mm y−1). La respiración del ecosistema (2203.16 ± 244.2 g C m−2y−1) fue consistentemente mayor que la GEP (1,975.32 ± 295.52 g C m−2y‐1), determinando una NEP anual (−227.6 ± 59.4 g C m−2y−1) que resultó en pérdidas netas anuales de carbono. Este bosque mantuvo su eficiencia en el uso del agua (WUE; GEP / ET) a lo largo de los años (2.53–3.24), pero la disponibilidad de agua restringió el uso de la luz y las tasas máximas de asimilación de carbono. Nuestros resultados dan relevancia a la retroalimentación entre el contenido de agua del suelo y la radiación neta como las principales variables ambientales que controlan los flujos del ecosistema en este bosque tropical seco maduro. The contribution of tropical forests to the carbon and water cycles is still uncertain. This is especially true for tropical dry forests with high rainfall seasonality and light availability that may affect their carbon sequestration potential. In this study, we report the results of continuous measurements over a 3 year period of carbon and water fluxes between the atmosphere and a tropical dry forest ecosystem in northwestern Mexico using the eddy covariance technique. We found that the studied old‐growth forest was a net carbon source to the atmosphere across years. This result can be explained by ecosystem respiration (the sum of plant and microbial respiration) since it was constantly larger than the gross ecosystem production (or whole‐ecosystem photosynthesis). The main drivers of carbon and water fluxes were soil water content and net solar radiation, but the relative effect of net solar radiation was strongly dependent on soil moisture. In addition to demonstrating the importance of water and light for controlling whole‐ecosystem processes in seasonally dry tropical forests, our results suggest old‐growth tropical forests with little disturbance can act as carbon sources to the atmosphere. Therefore, further studies should investigate ecosystem fluxes in forests under different disturbance or successional stages. An old‐growth tropical dry forest was a net carbon source regardless of precipitation variabilityCarbon and water fluxes were highly seasonal and varied interannuallyMain drivers of carbon and water fluxes were soil water content and net solar radiation

Soil organic carbon (SOC) information is fundamental for improving global carbon cycle modeling efforts, but discrepancies exist from country‐to‐global scales. We predicted the spatial distribution of SOC stocks (topsoil; 0–30 cm) and quantified modeling uncertainty across Mexico and the conterminous United States (CONUS). We used a multisource SOC dataset (>10 000 pedons, between 1991 and 2010) coupled with a simulated annealing regression framework that accounts for variable selection. Our model explained ~50% of SOC spatial variability (across 250‐m grids). We analyzed model variance, and the residual variance of six conventional pedotransfer functions for estimating bulk density to calculate SOC stocks. Two independent datasets confirmed that the SOC stock for both countries represents between 46 and 47 Pg with a total modeling variance of ±12 Pg. We report a residual variance of 10.4 ±5.1 Pg of SOC stocks calculated from six pedotransfer functions for soil bulk density. When reducing training data to define decades with relatively higher density of observations (1991–2000 and 2001–2010, respectively), model variance for predicted SOC stocks ranged between 41 and 55 Pg. We found nearly 42% of SOC across Mexico in forests and 24% in croplands, whereas 31% was found in forests and 28% in croplands across CONUS. Grasslands and shrublands stored 29 and 35% of SOC across Mexico and CONUS, respectively. We predicted SOC stocks >30% below recent global estimates that do not account for uncertainty and are based on legacy data. Our results provide insights for interpretation of estimates based on SOC legacy data and benchmarks for improving regional‐to‐global monitoring efforts. Multisource topsoil organic carbon prediction and prediction variance in Mexico and the conterminous United StatesCalculated stocks of 46–47 Pg of SOC (0‐ to 30‐cm depth, years 1991–2010) using a simulated annealing regression frameworkPredicted stocks >30% below recent global estimates that are largely based on legacy data

Abstract 3611

No relevant conflicts of interest to declare.

No relevant conflicts of interest to declare.

Abstract 2749