Spatial variation of modelled total, dry and wet nitrogen deposition to forests at global scale. (December 2018)

• Record Type: Journal Article
• Authors: Schwede, Donna B.; Simpson, David; Tan, Jiani; Fu, Joshua S.; Dentener, Frank; Du, Enzai; deVries, Wim
• Is Part Of: Environmental pollution. Volume 243(2018)Part B
• Page Start: 1287
• Page End: 1301
• Publication Date: 2018-12
• Subjects: Nitrogen deposition -- Dry deposition -- Wet deposition -- Forest biomes -- Modelling approach; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2018.09.084
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Forests are an important biome that covers about one third of the global land surface and provides important ecosystem services. Since atmospheric deposition of nitrogen (N) can have both beneficial and deleterious effects, it is important to quantify the amount of N deposition to forest ecosystems. Measurements of N deposition to the numerous forest biomes across the globe are scarce, so chemical transport models are often used to provide estimates of atmospheric N inputs to these ecosystems. We provide an overview of approaches used to calculate N deposition in commonly used chemical transport models. The Task Force on Hemispheric Transport of Air Pollution (HTAP2) study intercompared N deposition values from a number of global chemical transport models. Using a multi-model mean calculated from the HTAP2 deposition values, we map N deposition to global forests to examine spatial variations in total, dry and wet deposition. Highest total N deposition occurs in eastern and southern China, Japan, Eastern U.S. and Europe while the highest dry deposition occurs in tropical forests. The European Monitoring and Evaluation Program (EMEP) model predicts grid-average deposition, but also produces deposition by land use type allowing us to compare deposition specifically to forests with the grid-average value. We found that, for this study, differences between the grid-average and forest specific could be as much as a factor of two and up to more than a factor of five in extreme cases. This suggests that consideration should be given to using forest-specific deposition for input to ecosystem assessments such as critical loads determinations. Graphical abstract: Image 1 Highlights: Deposition to forest biomes is estimated with global chemical transport models. Grid-average total nitrogen deposition to global forests is about 19 Tg N yr −1 . Global forest-specific deposition is 12% higher than the grid-average value. Regionally, forest-specific deposition is up to 2 times higher than grid-average values. Forest-specific deposition are important to evaluate critical load exceedances. Abstract : Estimates of nitrogen deposition to global forests by global models may be a factor of 2 or more higher if the forest-specific deposition is used, compared to the grid cell average value and is on average 12% higher for all global forests.