Estimating the effect of abiotic factors on modifying the sensitivity of vegetation to nitrogen deposition: an application of endorsement theory

Abstract: Many natural and semi-natural vegetation communities are sensitive to eutrophication; most eutrophication is caused by human activities. Critical loads have been developed in Europe to provide an effects-based approach to pollutant abatement including nitrogen deposition. Critical loads to protect ecosystems from eutrophication from excess nitrogen are only specified for very broad habitat types (eg "dry heaths") and as a range of values (eg between 10 and 20 kg N ha-1 yr-1). There may be considerable variation in vegetation communities within a broad habitat and there is a requirement (eg. from conservation agencies etc.) for more precise critical loads for more clearly specified receptors (habitats, vegetation communities). This paper demonstrates the use of Endorsement Theory to rationalise incomplete, qualitative and conflicting information on abiotic parameters (eg, climate, management) that may influence the vegetation response to nitrogen deposition and hence the critical loads. The results are shown for 22 heaths described in the National Vegetation Classification, identifying whether the critical load should be nearer the upper or lower limit of the published ranges. The policy implications for critical loads exceedance for European Dry Heaths are also discussed

Response of epiphytic bryophytes to simulated N deposition in a subtropical montane cloud forest in southwestern China

A field manipulation experiment was conducted in a subtropical montane cloud forest in southwestern China to determine the possible responses of epiphytic bryophytes to increasing nitrogen (N) deposition from community to physiology level, and to find sensitive epiphytic bryophytes that may be used as indicators for assessing the degree of N pollution. N addition had significantly negative effects on species richness and cover of the epiphytic bryophyte community. Harmful effects of high N loads were recorded for chlorophyll, growth, and vitality of the species tested. The decline of some epiphytic bryophytes may result from detrimental effects on degradation to photosynthetic pigments. Bazzania himalayana (Mitt.) Schiffn., Bazzania ovistipula (Steph.) Mizut., and Homaliodendron flabellatum (Sm.) Fleisch. are candidates in atmospheric nitrogen monitoring. Epiphytic bryophytes in the montane cloud forest are very sensitive to increasing N deposition and often difficult to recover once they have been destroyed, providing early detection of enhanced N pollution for trees or even the whole forest ecosystem. The inference that increasing N pollution may lead to loss of biodiversity is a concern to the developing economy in western China, and should alert the government to the adverse impacts caused by increased industrial pollution during the process of China’s West Development

Intracellular and extracellular ammonium (NH4(+)) uptake and its toxic effects on the aquatic biomonitor Fontinalis antipyretica

ACESSO via B-on: http://dx.doi.org/ 10.1007/s10646-009-0374-6The objective of this work is to validate the use of the aquatic moss Fontinalis antipyretica as biomonitor of NH4 + aquatic pollution. In order to achieve this objective we needed to understand the pattern of uptake of NH4 + by the moss and evaluate the impact of high concentrations on its physiological performance. The cellular location of NH4 + in the moss is crucial for understanding its monitoring capacity. We were able to show that a sequential elution technique, based on the use of NiCl2 as an efficient displacing agent, allowed the quantification of the cellular location of NH4 +. This was done along a concentration gradient and time of exposure. The extracellular and intracellular NH4 + concentrations that caused significant physiological impact in membrane permeability of F. antipyretica were the same that caused significant decreasing in the photosynthetic capacity of the same moss. The former NH4 + concentration thresholds were shown to decrease with increasing exposure time. These results are important since under natural conditions lower concentration of NH4 + are present in waters but for very long periods of time. The importance of applying this knowledge in biomonitoring studies to fulfil the requirements of the Water Framework Directive is discussed