Hall,J. and Wadsworth,R.(2010): Estimating the effect of abiotic factors on modifying the sensitivity of vegetation to nitrogen deposition: An application of endorsement theory. Water Air Soil Pollut., 212, 441-459.

『植物の窒素沈着に対する感受性を変えるような非生物的要因の影響を見積る:エンドースメント(“裏書”)理論(“反省的認証説”)の適用』


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 (e.g., ‘dry heaths’) and as a range of values (e.g., between 10 and 20 kg N ha-1 year-1). There may be considerable variation in vegetation communities within a broad habitat and there is a requirement (e.g., 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 (e.g., climate, management) that may influence the vegetation response to nitrogen deposition and hence, the critical loads. The endorsement theory approach is tested for 22 heathland community types in the UK (as described by the National Vegetation Classification of Rodwell, Cambridge University Press, vol. 3, 1991) to determine if the critical load for a community should be nearer the upper or lower limit of the published ranges. The results give a ‘confident’ endorsement for one heath community and a ‘likely’ endorsement for a further 13 communities for a critical load at the lower limit. The endorsements suggest that the critical load for most heaths should be at the lower end of the range meaning that current estimates of the exceeded area calculated using the mid-point of the range is an underestimate.

Keywords: Endorsement theory; Critical loads; Nitrogen; Eutrophication; Abiotic factors; national vegetation classification』

1. Introduction
2. Methods
 2.1. Compiling the abiotic data for the heathland communities
 2.2. Nitrogen critical loads and modifying factors
 2.3. Compiling the evidence for setting critical loads for heathland vegetation communities
  2.3.1. Toxic effects
  2.3.2. Productivity and competition
   Climatic conditions
   Nutrient conditions
   Base status
  2.3.3. Removal of excess nitrogen
   Leaching
   Denitrification
   Management
 2.4. Endorsing a decision for critical loads
 2.5. Developing an alternative weighting scheme
3. Discussion
 3.1. Comparison with Ashmore and Hicks
 3.2. Comparison with modelling studies
 3.3. Implications for policy of adopting an endorsement approach
4. Conclusions
Acknowledgements
References


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