Atmosphere Plant Soil Interactions

Zwitterionic, cationic, and anionic per- and polyfluoroalkyl substances (PFAS) are increasingly reported in terrestrial and aquatic environments, but their inputs to agricultural lands are not fully understood. Here, we characterized PFAS in 47 organic waste products (OWP) applied in agricultural fields of France, including historical and recent materials. Overall, 160 PFAS from 42 classes were detected from target screening and homologue-based nontarget screening. Target PFAS were low in agriculture-derived wastes such as pig slurry, poultry manure, or dairy cattle manure (median ∑46PFAS: 0.66 μg/kg dry matter). Higher PFAS levels were reported in urban and industrial wastes, paper mill sludge, sewage sludge, or residual household waste composts (median ∑46PFAS: 220 μg/kg). Historical municipal biosolids and composts (1976-1998) were dominated by perfluorooctanesulfonate (PFOS), N-ethyl perfluorooctanesulfonamido acetic acid (EtFOSAA), and cationic and zwitterionic electrochemical fluorination precursors to PFOS. Contemporaneous urban OWP (2009-2017) were rather dominated by zwitterionic fluorotelomers, which represented on average 55% of ∑160PFAS (max: 97%). The fluorotelomer sulfonamidopropyl betaines (X:2 FTSA-PrB, median: 110 μg/kg, max: 1300 μg/kg) were the emerging class with the highest occurrence and prevalence in contemporary urban OWP. They were also detected as early as 1985. The study informs for the first time that urban sludges and composts can be a significant repository of zwitterionic and cationic PFAS.

Severe drought events are known to cause important reductions of gross primary productivity (GPP) in forest ecosystems. However, it is still unclear whether this reduction originates from stomatal closure (Stomatal Origin Limitation) and/or non-stomatal limitations (Non-SOL). In this study, we investigated the impact of edaphic drought in 2018 on GPP and its origin (SOL, NSOL) using a dataset of 10 European forest ecosystem flux towers. In all stations where GPP reductions were observed during the drought, these were largely explained by declines in the maximum apparent canopy scale carboxylation rate VCMAX,APP (NSOL) when the soil relative extractable water content dropped below around 0.4. Concurrently, we found that the stomatal slope parameter (G1, related to SOL) of the Medlyn et al. unified optimization model linking vegetation conductance and GPP remained relatively constant. These results strengthen the increasing evidence that NSOL should be included in stomatal conductance/photosynthesis models to faithfully simulate both GPP and water fluxes in forest ecosystems during severe drought. This article is part of the theme issue 'Impacts of the 2018 severe drought and heatwave in Europe: from site to continental scale'.

Abstract Although cell-anatomical variables are promising proxies reflecting seasonal as well as annual climate changes, their interdependencies are not yet fully understood. In the present study we assessed the changes in tree-ring width and various wood anatomical traits, including wall thickness, lumen diameter and tracheid diameter in the radial direction in saplings ofPinus sylvestrisunder six climatic conditions: 5°C warmer alone (ET) or combined with drought in June (ETJ) and in August (ETA) and CO2enrichment alone (EC, 770 ppm) or combined with drought in June (ECJ) and in August (ECA). The experiments related to temperature conditions using 2-year saplings and CO2conditions using 3-year saplings were completed in 2009 and 2010 in a greenhouse, respectively. Results showed that tree-ring width and tracheid diameter were not affected by any of the conditions applied, but the lumen diameter was larger and the wall thickness was thinner than those under control conditions. These reactions were verified under ETJin the warming treatment and under all conditions under CO2enrichment conditions. Our results indicated that drought counteracted the effects of elevated CO2concentrations on wood anatomical properties, signifying complex interactions between the two major effects of climate change. Our comparison of wood parameters through experiments highlight the potential effect of climate change — increased drought stress due to higher temperatures and water shortage as well as elevated ambient CO2, on tracheid lumen diameter and wall thickness. Whereas the ring-width and tracheid diameter practically remained unaffected under the above-mentioned conditions.

Thermal infrared remote sensing observations have been widely used to provide useful information on surface energy and water stress for estimating evapotranspiration (ET). However, the revisit time of current high spatial resolution (<100 m) thermal infrared remote sensing systems, sixteen days for Landsat for example, can be insufficient to reliably derive ET information for water resources management. We used in situ ET measurements from multiple Ameriflux sites to (1) evaluate different scaling methods that are commonly used to derive daytime ET estimates from time-of-day observations; and (2) quantify the impact of different revisit times on ET estimates at monthly and seasonal time scales. The scaling method based on a constant evaporative ratio between ET and the top-of-atmosphere solar radiation provided slightly better results than methods using the available energy, the surface solar radiation or the potential ET as scaling reference fluxes. On average, revisit time periods of 2, 4, 8 and 16 days resulted in ET uncertainties of 0.37, 0.55, 0.73 and 0.90 mm per day in summer, which represented 13%, 19%, 23% and 31% of the monthly average ET calculated using the one-day revisit dataset. The capability of a system to capture rapid changes in ET was significantly reduced for return periods higher than eight days. The impact of the revisit on ET depended mainly on the land cover type and seasonal climate, and was higher over areas with high ET. We did not observe significant and systematic differences between the impacts of the revisit on monthly ET estimates that are based on morning or afternoon observations. We found that four-day revisit scenarios provided a significant improvement in temporal sampling to monitor surface ET reducing by around 40% the uncertainty of ET products derived from a 16-day revisit system, such as Landsat for instance.

The primary function of stomata is to minimize plant water loss while maintaining CO2 assimilation. Stomatal water loss incurs an indirect cost to photosynthesis in the form of non-stomatal limitations (NSL) via reduced carboxylation capacity (CAP) and/or mesophyll conductance (MES). Two optimal formulations for stomatal conductance (gs) arise from the assumption of each type of NSL. In reality, both NSL could coexist, but one may prevail for a given leaf ontogenetic stage or plant functional type, depending on leaf morphology. We tested the suitability of two gs formulations (CAP versus MES) on species from six plant functional types (C4 crop, C3 grass, fern, conifer, evergreen, and deciduous angiosperm trees). MES and CAP parameters (the latter proportional to the marginal water cost to carbon gain) decreased with water availability only in deciduous angiosperm trees, while there were no clear differences between leaf ontogenetic stages. Both CAP and MES formulations fit our data in most cases, particularly under low water availability. For ferns, stomata appeared to operate optimally only when subjected to water stress. Overall, the CAP formulation provided a better fit across all species, suggesting that sub-daily stomatal responses minimize NSL by reducing carboxylation capacity predominantly, regardless of leaf morphology and ontogenetic stage.

In 2013, in France, the « Energie Méthanisation Autonomie Azote » plan was published, and the ‘French agricultural and collective biogas model” should become a lever of the energetic and ecological transition. The results presented in this paper were produced between 2013 and 2016 and planned to explore several dimensions of this methane production plan. These works aimed at produce knowledges about biogas plant resources management and about digestate. Such knowledges and tools should be used to support biogas plant managers and territory stakeholders in order to analyze their own model from an agronomic and environmental point of view. Based on field experience cases, brakes and levers of such projects development have been gathered in a methodology guide. Upstream and downstream biomass and fertilizers flux have equally been explored in order to establish an analysis frame of resources management per biogas plant. Additional works have been conducted about digestate. Several digestates features were studied. Nitrogen fertilizing value of 5 digestate types were determined, and evidenced a great variability of digestates quality regarding this topic. Ammonia remains the major part of total nitrogen (>70%). Phosphorus bioavailability is 100%, as revealed by isotopic tracing. Biochemical fractioning and Carbon and Nitrogen potential mineralization showed variability of amending digestates properties (ISMO 73±8%, n=19). Nevertheless, these works remain limited by the number of biogas plants under study (n=3) and argue for going further into such analyses.

In this study, we compared coupled and uncoupled land surface model simulations of surface soil moisture (SM) with passive microwave remote sensing observations of SM over the contiguous US (CONUS). For this purpose, we used the following: (i) the European Space Agency's Soil Moisture and Ocean Salinity (SMOS) satellite retrieved L3 surface SM; (ii) the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) SM derived using LPRM; and (iii) the coupled and uncoupled ORCHIDEE land surface model. The comparison was achieved by computing the temporal mean difference between the normalized remotely-sensed and the model-SM datasets. It was found that both coupled and uncoupled models are drier than the remotely sensed data (particularly the SMOS data) over the principal aquifers of the CONUS. These aquifers are known as one of the places where irrigation is intensive. Therefore, the reason behind this model’ dryness could be the fact that the models do not take into account the irrigation activities, which can be monitored by the remotely-sensed observations. Time series of SM over irrigated pixels also showed that SMOS was wetter than the models mainly during the irrigation period.

Abstract. For the past decade, observations of carbonyl sulfide (OCS or COS) have been investigated as a proxy for carbon uptake by plants. OCS is destroyed by enzymes that interact with CO2 during photosynthesis, namely carbonic anhydrase (CA) and RuBisCO, where CA is the more important one. The majority of sources of OCS to the atmosphere are geographically separated from this large plant sink, whereas the sources and sinks of CO2 are co-located in ecosystems. The drawdown of OCS can therefore be related to the uptake of CO2 without the added complication of co-located emissions comparable in magnitude. Here we review the state of our understanding of the global OCS cycle and its applications to ecosystem carbon cycle science. OCS uptake is correlated well to plant carbon uptake, especially at the regional scale. OCS can be used in conjunction with other independent measures of ecosystem function, like solar-induced fluorescence and carbon and water isotope studies. More work needs to be done to generate global coverage for OCS observations and to link this powerful atmospheric tracer to systems where fundamental questions concerning the carbon and water cycle remain.

Abstract Phenology is a first‐order control on productivity and mediates the biophysical environment by altering albedo, surface roughness length and evapotranspiration. Accurate and transparent modelling of vegetation phenology is therefore key in understanding feedbacks between the biosphere and the climate system. Here, we present the phenor r package and modelling framework. The framework leverages measurements of vegetation phenology from four common phenology observation datasets, the PhenoCam network, the USA National Phenology Network (USA‐NPN), the Pan European Phenology Project (PEP725), MODIS phenology (MCD12Q2) combined with (global) retrospective and projected climate data. We show an example analysis, using the phenor modelling framework, which quickly and easily compares 20 included spring phenology models for three plant functional types. An analysis of model skill using the root mean squared (RMSE) error shows little or no difference regardless of model structure, corroborating previous studies. We argue that addressing this issue will require novel model development combined with easy data assimilation as facilitated by our framework. In conclusion, we hope the phenor phenology modelling framework in the r language and environment for statistical computing will facilitate reproducibility and community driven phenology model development, in order to increase their overall predictive power, and leverage an ever growing number of phenology data products.

The Ecology principle is at the core of organic farming. Regarding nutrient management, this principle implies that chemical fertiliser should be banned and be replaced by enhanced recycling (within and among farms) and biological nitrogen fixation by legumes. However, based on the survey of 63 organic farms in three French districts, we demonstrated that organic farming can be somehow, indirectly reliant on chemical fertiliser. Such reliance is due to two major factors. First, organic farms import a large share of their nutrients (23% of nitrogen and 73% of phosphorus entering organic farms, mostly as manure) from conventional farms. Second, organic farms can rely on nutrient accumulated in soils prior to the conversion: this legacy effect results in the 70% anthropogenic signature of the P in organic crop and animal products. These results suggest that organic farming development can conflict with the Ecology principle. However, this paper also demonstrates that some solutions exist to limit the indirect reliance on chemical fertilisers. In particular, the diversity of agricultural productions at the district scale is a strong leverage to increase nutrient recycling among organic farms.