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Veröffentlichung Relevance of canopy drip for the accumulation of nitrogen in moss used as biomonitors for atmospheric nitrogen deposition in Europe(2015)High atmospheric deposition of nitrogen (N) impacts functions and structures of N limited ecosystems. Due to filtering and related canopy drip effects forests are particularly exposed to N deposition. Up to now, this was proved by many studies using technical deposition samplers but there are only some few studies analysing the canopy drip effect on the accumulation of N in moss and related small scale atmospheric deposition patterns. Therefore, we investigated N deposition and related accumulation of N in forests and in (neighbouring) open fields by use of moss sampled across seven European countries. Sampling and chemical analyses were conducted according to the experimental protocol of the European Moss Survey. The ratios between the measured N content in moss sampled inside and outside of forests were computed and used to calculate estimates for non-sampled sites. Potentially influencing environmental factors were integrated in order to detect their relationships to the N content in moss. The overall average N content measured in moss was 20.0 mg g- 1 inside and 11.9 mg g- 1 outside of forests with highest N values in Germany inside of forests. Explaining more than 70% of the variance, the multivariate analyses confirmed that the sampling site category (site with/without canopy drip) showed the strongest correlation with the N content in moss. Spatial variances due to enhanced dry deposition in vegetation stands should be considered in future monitoring and modelling of atmospheric N deposition.
Quelle: http://www.sciencedirect.com/Veröffentlichung Data from the Arizona FACE (Free-Air CO2 Enrichment) Experiments on Wheat at Ample and Limiting Levels of Water and Nitrogen(2017) Kimball, Bruce Arnold; Pinter Jr., Paul J.; LaMorte, Robert L.; Wechsung, GabrieleFour free-air CO2 enrichment (FACE) experiments were conducted on wheat (Triticum aestivum L. cv. Yecora Rojo) at Maricopa, Arizona, U.S.A. from December, 1992 through May, 1997. The first two were conducted at ample and limited (50% of ample) supplies of water, and second two at ample (350 kg N ha-1) and limited (70 and 15 kg N ha-1) supplies of fertilizer nitrogen. More than 50 scientists participated, and they collected a large and varied set of data on plant, soil, and microclimatic responses to the elevated CO2 and its interactions with the water and N treatments. The dataset has been popular with wheat growth modelers who have utilized the growth, yield, and other data to validate their models, which get used to predict likely future wheat productivity with projected global change. The dataset assembled herein contains many of these data, including management, soils, weather, physiology, phenology, biomass growth, leaf area, yield, quality, canopy temperatures, energy balance, soil moisture, nitrogen assimilation, and other data. Quelle: VerlagsinformationVeröffentlichung Nutrient criteria for surface waters under the European Water Framework Directive: Current state-of-the-art, challenges and future outlook(2019) Poikane, Sandra; Claussen, Ulrich; Kelly, Martyn G.; Salas Herrero, Fuensanta; Leujak, WeraThe aim of European water policy is to achieve good ecological status in all rivers, lakes, coastal and transitional waters by 2027. Currently, more than half of water bodies are in a degraded condition and nutrient enrichment is one of the main culprits. Therefore, there is a pressing need to establish reliable and comparable nutrient criteria that are consistent with good ecological status. This paper highlights the wide range of nutrient criteria currently in use by Member States of the European Union to support good ecological status and goes on to suggest that inappropriate criteria may be hindering the achievement of good status. Along with a comprehensive overview of nutrient criteria, we provide a critical analysis of the threshold concentrations and approaches by which these are set. We identify four essential issues: (1) Different nutrients (nitrogen and/or phosphorus) are used for different water categories in different countries. (2) The use of different nutrient fractions (total, dissolved inorganic) and statistical summary metrics (e.g., mean, percentiles, seasonal, annual) currently hampers comparability between countries, particularly for rivers, transitional and coastal waters. (3) Wide ranges in nutrient threshold values within shared water body types, in some cases showing more than a 10-fold difference in concentrations. (4) Different approaches used to set threshold nutrient concentrations to define the boundary between "good" and "moderate" ecological status. Expert judgement-based methods resulted in significantly higher (less stringent) good-moderate threshold values compared with data-driven approaches, highlighting the importance of consistent and rigorous approaches to criteria setting. We suggest that further development of nutrient criteria should be based on relationships between ecological status and nutrient concentrations, taking into account the need for comparability between different water categories, water body types within these categories, and countries. © 2019 The Authors. Published by Elsevier B.V.Veröffentlichung Comparison of methods for the estimation of total inorganic nitrogen deposition to forests in Germany(2020) Ahrends, Bernd; Schmitz, Andreas; Geupel, Markus; Prescher, Anne-KatrinA reliable quantification of total inorganic nitrogen (TIN) deposition to forests is required for the evaluation of ecological effects of TIN inputs to forests and to monitor the success of clean-air policy. As direct measurements are scarce, different modeling approaches have been developed to estimate TIN deposition to forests. Three common methods are the (i) "canopy budget model," (ii) "inferential method," and (iii) "emission based estimates" using a chemical transport model. Previous studies have reported considerable and site-specific differences between these methods, complicating the interpretation of results. We use data from more than 100 German intensive forest monitoring sites over a period of 16 years for a cross-comparison of these approaches. Non-linear mixed-effect models were applied to evaluate how factors like meteorology, terrain and stand characteristics affect discrepancies between the model approaches. Taking into account the uncertainties in deposition estimates, there is a good agreement between the canopy budget and the inferential method when using semi-empirical correction factors for deposition velocity. Wet deposition estimates of the emission based approach were in good agreement with wet-only corrected bulk open field deposition measurements used by the other two approaches. High precipitation amounts partly explained remaining differences in wet deposition. Larger discrepancies were observed when dry deposition estimates are compared between the emissions based approach and the other two approaches, which appear to be related to a combination of meteorological conditions and tree species effects. © 2020 Ahrends, Schmitz, Prescher, Wehberg, Geupel, Andreae and MeesenburgVeröffentlichung A national nitrogen target for Germany(2021) Geupel, Markus; Heldstab, Jürg; Schäppi, BettinaThe anthropogenic nitrogen cycle is characterized by a high complexity. Different reactive nitrogen species (NH3, NH4+, NO, NO2, NO3-, and N2O) are set free by a large variety of anthropogenic activities and cause numerous negative impacts on the environment. The complex nature of the nitrogen cycle hampers public awareness of the nitrogen problem. To overcome this issue and to enhance the sensitivity for policy action, we developed a new, impact-based integrated national target for nitrogen (INTN) for Germany. It is based on six impact indicators, for which we derived the maximum amount of nitrogen losses allowed in each environmental sector to reach related state indicators on a spatial average for Germany. The resulting target sets a limit of nitrogen emissions in Germany of 1053 Gg N yr-1. It could serve as a similar means on the national level as the planetary boundary for reactive nitrogen or the 1.5 ˚C target of the climate community on the global level. Taking related uncertainties into account, the resulting integrated nitrogen target of 1053 Gg N yr-1 suggests a comprehensible INTN of 1000 Gg N yr-1 for Germany. Compared to the current situation, the overall annual loss of reactive nitrogen in Germany would have to be reduced by approximately one-third. © 2021 by the authors