Globally, inland waters emit over 2 Pg of carbon per year as carbon dioxide, of which the majority originates from streams and rivers. Despite the global significance of fluvial carbon dioxide emissions, little is known about their diel dynamics. Here we present a large-scale assessment of day- and night-time carbon dioxide fluxes at the water-air interface across 34 European streams. We directly measured fluxes four times between October 2016 and July 2017 using drifting chambers. Median fluxes are 1.4 and 2.1\uffe2\uff80\uff89mmol\uffe2\uff80\uff89m\uffe2\uff88\uff922 h\uffe2\uff88\uff921 at midday and midnight, respectively, with night fluxes exceeding those during the day by 39%. We attribute diel carbon dioxide flux variability mainly to changes in the water partial pressure of carbon dioxide. However, no consistent drivers could be identified across sites. Our findings highlight widespread day-night changes in fluvial carbon dioxide fluxes and suggest that the time of day greatly influences measured carbon dioxide fluxes across European streams.The tropical rainforest mesocosm within the Biosphere 2 Laboratory, a model system of some 110 species developed over 12\uffe2\uff80\uff83years under controlled environmental conditions, has been subjected to a series of comparable drought experiments during 2000\uffe2\uff80\uff932002. In each study, the mesocosm was subjected to a 4\uffe2\uff80\uff936 week drought, with well\uffe2\uff80\uff90defined rainfall events before and after the treatment. Ecosystem CO2 uptake rate (Aeco) declined 32% in response to the drought, with changes occurring within days and being reversible within weeks, even though the deeper soil layers did not become significantly drier and leaf\uffe2\uff80\uff90level water status of most large trees was not greatly affected. The reduced Aeco during the drought reflected both morphological and physiological responses. It is estimated that the drought\uffe2\uff80\uff90induced 32% reduction of Aeco has three principal components: (1) leaf fall increased two\uffe2\uff80\uff90fold whereas leaf expansion growth of some canopy dominants declined to 60%, leading to a 10% decrease in foliage coverage of the canopy. This might be the main reason for the persistent reduction of Aeco after rewatering. (2) The maximum photosynthetic electron transport rate at high light intensities in remaining leaves was reduced to 71% for three of the four species measured, even though no chronic photo\uffe2\uff80\uff90inhibition occurred. (3) Stomata closed, leading to a reduced ecosystem water conductance to water vapour (33% of pre\uffe2\uff80\uff90drought values), which not only reduced ecosystem carbon uptake rate, but may also have implications for water and energy budgets of tropical ecosystems. Additionally, individual rainforest trees responded differently, expressing different levels of stress and stress avoiding mechanisms. This functional diversity renders the individual response heterogeneous and has fundamental implications to scale leaf level responses to ecosystem dynamics.
", "keywords": ["580", "0301 basic medicine", "leaf area", "net ecosystem CO(2) exchange", "photosynthesis", "CLIMATE-CHANGE", "chlorophyll fluorescence", "CANOPY TREE", "drought", "15. Life on land", "6. Clean water", "FRENCH-GUIANA", "03 medical and health sciences", "leaf fall", "tropical trees KeyWords Plus: ATMOSPHERIC CO2 CONCENTRATIONS", "PHOTOSYSTEM-II", "XANTHOPHYLL CYCLE", "WATER-VAPOR", "L LEAVES", "13. Climate action", "leaf growth", "tropical rainforest", "photosynthetic electron transport", "GAS-EXCHANGE"]}, "links": [{"href": "https://doi.org/10.1111/j.1365-3040.2004.01231.x"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Plant%2C%20Cell%20%26amp%3B%20Environment", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.1111/j.1365-3040.2004.01231.x", "name": "item", "description": "10.1111/j.1365-3040.2004.01231.x", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.1111/j.1365-3040.2004.01231.x"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2004-10-01T00:00:00Z"}}, {"id": "10.5194/bg-17-1033-2020", "type": "Feature", "geometry": null, "properties": {"updated": "2026-09-20T16:19:36Z", "type": "Journal Article", "created": "2020-02-26", "title": "\"Estimating causal networks in biosphere\u2013atmosphere interaction with the PCMCI approach\"", "description": "Abstract. The dynamics of biochemical processes in terrestrial ecosystems are tightly coupled to local meteorological conditions. Understanding these interactions is an essential prerequisite for predicting, e.g. the response of the terrestrial carbon cycle to climate change. However, many empirical studies in this field rely on correlative approaches and only very few studies apply causal discovery methods. Here we explore the potential for a recently proposed causal graph discovery algorithm to reconstruct the causal dependency structure underlying biosphere\uffe2\uff80\uff93atmosphere interactions. Using artificial time series with known dependencies that mimic real-world biosphere\uffe2\uff80\uff93atmosphere interactions we address the influence of non-stationarities, i.e. periodicity and heteroscedasticity, on the estimation of causal networks. We then investigate the interpretability of the method in two case studies. Firstly, we analyse three replicated eddy covariance datasets from a Mediterranean ecosystem. Secondly, we explore global Normalised Difference Vegetation Index time series (GIMMS\uffc2\uffa03g), along with gridded climate data to study large-scale climatic drivers of vegetation greenness. We compare the retrieved causal graphs to simple cross-correlation-based approaches to test whether causal graphs are considerably more informative. Overall, the results confirm the capacity of the causal discovery method to extract time-lagged linear dependencies under realistic settings. For example, we find a complete decoupling of the net ecosystem exchange from meteorological variability during summer in the Mediterranean ecosystem. However, cautious interpretations are needed, as the violation of the method's assumptions due to non-stationarities increases the likelihood to detect false links. Overall, estimating directed biosphere\uffe2\uff80\uff93atmosphere networks helps unravel complex multidirectional process interactions. Other than classical correlative approaches, our findings are constrained to a few meaningful sets of relations, which can be powerful insights for the evaluation of terrestrial ecosystem models.
", "keywords": ["Agriculture and Food Sciences", "PINE FOREST", "Evolution", "0207 environmental engineering", "02 engineering and technology", "01 natural sciences", "CO2 EXCHANGE", "Behavior and Systematics", "Life", "QH501-531", "BEECH FOREST", "QH540-549.5", "Earth-Surface Processes", "0105 earth and related environmental sciences", "QE1-996.5", "NET ECOSYSTEM EXCHANGE", "Ecology", "CARBON-DIOXIDE EXCHANGE", "SPRUCE FOREST", "Geology", "WATER-VAPOR FLUXES", "15. Life on land", "13. Climate action", "GRANGER-CAUSALITY", "INTERANNUAL VARIABILITY", "GAS-EXCHANGE"]}, "links": [{"href": "https://bg.copernicus.org/articles/17/1033/2020/bg-17-1033-2020.pdf"}, {"href": "https://doi.org/10.5194/bg-17-1033-2020"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Biogeosciences", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.5194/bg-17-1033-2020", "name": "item", "description": "10.5194/bg-17-1033-2020", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.5194/bg-17-1033-2020"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2020-02-26T00:00:00Z"}}, {"id": "11579/142540", "type": "Feature", "geometry": null, "properties": {"updated": "2026-09-20T16:21:57Z", "type": "Journal Article", "created": "2021-06-10", "title": "Carbon dioxide fluxes increase from day to night across European streams", "description": "AbstractGlobally, inland waters emit over 2 Pg of carbon per year as carbon dioxide, of which the majority originates from streams and rivers. Despite the global significance of fluvial carbon dioxide emissions, little is known about their diel dynamics. Here we present a large-scale assessment of day- and night-time carbon dioxide fluxes at the water-air interface across 34 European streams. We directly measured fluxes four times between October 2016 and July 2017 using drifting chambers. Median fluxes are 1.4 and 2.1\uffe2\uff80\uff89mmol\uffe2\uff80\uff89m\uffe2\uff88\uff922 h\uffe2\uff88\uff921 at midday and midnight, respectively, with night fluxes exceeding those during the day by 39%. We attribute diel carbon dioxide flux variability mainly to changes in the water partial pressure of carbon dioxide. However, no consistent drivers could be identified across sites. Our findings highlight widespread day-night changes in fluvial carbon dioxide fluxes and suggest that the time of day greatly influences measured carbon dioxide fluxes across European streams.