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Excessive nitrogen input in natural ecosystems is a major threat to biodiversity. A coastal dune area near Amsterdam in the Netherlands suffers from high atmospheric nitrogen deposition affecting sensitive habitats such as fixed coastal dunes with herbaceous vegetation (‘grey dunes’). To mitigate its effect year round grazing was applied from 2007 until 2012. In winter, when natural food supply is low, the cattle received supplementary hay that caused additional inputs of nitrogen. Estimates based on nitrogen contents of hay, as well as of manure, showed the input through winter feeding (c. 3–14 kg N ha−1 .y−1 ) is in the same order of magnitude as both the actual deposition (c. 17 kg N ha −1 .y −1 ) and the critical load for a number of herbaceous habitat types (10–15 kg N ha−1 .y −1). Locally, the effect of winter feeding adds to the effect of nitrogen redistribution within the area caused by the cattle's terrain usage. We conclude that winter feeding may aggravate effects of atmospheric nitrogen deposition. [ABSTRACT FROM AUTHOR]

Question: Can the abiotic ranges of syntaxonomic units (associations) in terms of pH and nitrate concentration be estimated and then in principle be used to estimate critical loads for acid and nitrogen deposition? Location: Europe. Methods: Using splines, abiotic ranges of syntaxonomic units were estimated on the basis of measured soil pH and nitrate concentration and vegetation relevés. Owing to limited calibration data, this yielded responses for only a few syntaxa. In a second attempt, we used a 160 000-relevé training set; the syntaxon of each relevé was known but not their soil pH values and soil nitrate concentrations, so for each relevé, the soil pH and nitrate concentration were estimated by inference from species composition. We again estimated abiotic ranges using the spline method, including the 5th and 95th percentiles as a proxy for the ecological range. Results: The second (indirect) method yielded ranges for soil pH and for nitrate concentration for many of the associations. The means and percentiles were corrected for regression to the mean. Conclusions: It is not yet possible to directly estimate ranges for syntaxa for pH and nitrate on a large scale from the data available. However, indirectly estimated soil pH and nitrate concentrations are sufficiently available to derive ranges for many associations. The lower (5th) percentile of the indirectly estimated pH ranges for associations may be used as the starting point for the estimation of critical loads for acid deposition. The 95th percentile should still be regarded as a rather uncertain estimate of the maximum nitrate concentration. [ABSTRACT FROM AUTHOR]

Focuses on changes in large-scale patterns of plant biodiversity, predicted from environmental economic scenarios. Measures to preserve biodiversity by improving environmental quality; Impact of various European economic scenarios, on potential plant biodiversity in the Netherlands.

Plant species occurrence in Europe is affected by changes in nitrogen deposition and climate. Insight into potential future effects of those changes can be derived by a model approach based on field-based empirical evidence on a continental scale. In this paper, we present a newly developed empirical model PROPS, predicting the occurrence probabilities of plant species in response to a combination of climatic factors, nitrogen deposition and soil properties. Parameters included were temperature, precipitation, nitrogen deposition, soil pH and soil C/N ratio. The PROPS model was fitted to plant species occurrence data of about 800,000 European relevés with estimated values for pH and soil C/N ratio and interpolated climate and modelled N deposition data obtained from the Ensemble meteo data set and EMEP model results, respectively. The model was validated on an independent data set. The test of ten species against field data gave an average Pearson's r-value of 0.79. PROPS was applied to a grassland and a heathland site to evaluate the effect of scenarios for nitrogen deposition and climate change on the Habitat Suitability Index (HSI), being the average of the relative probabilities, compared to the maximum probability, of all target species in a habitat. Results for the period 1930–2050 showed that an initial increase and later decrease in nitrogen deposition led to a pronounced decrease in HSI, and with dropping nitrogen deposition to an increase of the HSI. The effect of climate change appeared to be limited, resulting in a slight increase in HSI. Image 1 • The probability of Plant species on an European scale can be simulated by new model named PROPS. • Increase of nitrogen deposition leads to a significant decrease of biodiversity. • The effect of climate change seems relatively small. • Climate change leads to a slight increase of biodiversity in the Netherlands. • The habitat suitability index calculation should be updated with unwanted species. [ABSTRACT FROM AUTHOR]

Forest understory plant communities in the eastern United States are often diverse and are potentially sensitive to changes in climate and atmospheric inputs of nitrogen caused by air pollution. In recent years, empirical and processed-based mathematical models have been developed to investigate such changes in plant communities. In the study reported here, a robust set of understory vegetation response functions (expressed as version 2 of the Probability of Occurrence of Plant Species model for the United States [US-PROPS v2]) was developed based on observations of forest understory and grassland plant species presence/absence and associated abiotic characteristics derived from spatial datasets. Improvements to the US-PROPS model, relative to version 1, were mostly focused on inclusion of additional input data, development of custom species-level input datasets, and implementation of methods to address uncertainty. We investigated the application of US-PROPS v2 to evaluate the potential impacts of atmospheric nitrogen (N) and sulfur (S) deposition, and climate change on forest ecosystems at three forested sites located in New Hampshire, Virginia, and Tennessee in the eastern United States. Species-level N and S critical loads (CLs) were determined under ambient deposition at all three modeled sites. The lowest species-level CLs of N deposition at each site were between 2 and 11 kg N/ha/yr. Similarly, the lowest CLs of S deposition, based on the predicted soil pH response, were less than 2 kg S/ha/yr among the three sites. Critical load exceedance was found at all three model sites. The New Hampshire site included the largest percentage of species in exceedance. Simulated warming air temperature typically resulted in lower maximum occurrence probability, which contributed to lower CLs of N and S deposition. The US-PROPS v2 model, together with the PROPS-CLF model to derive CL functions, can be used to develop site-specific CLs for understory plants within broad regions of the United States. This study demonstrates that species-level CLs of N and S deposition are spatially variable according to the climate, light availability, and soil characteristics at a given location. Although the species niche models generally performed well in predicting occurrence probability, there remains uncertainty with respect to the accuracy of reported CLs. As such, the specific CLs reported here should be considered as preliminary estimates. Image 1 • Niche models were developed for more than 1500 vascular plant species. • Critical loads of N and S deposition were less than 5 kg ha−1 yr−1 for certain species. • Critical load exceedance occurred at all model application sites. Critical loads of atmospheric nitrogen and sulfur deposition were determined for maintaining understory vegetation diversity. Critical load exceedance was found at all model application sites. [ABSTRACT FROM AUTHOR]