An increasing trend of inorganic nitrogen deposition across montane regions of China

Abstract

China has experienced a dramatic increase in the total inorganic nitrogen (TIN) deposition rate over the past three decades and has become one of the hotspots of N deposition worldwide. However, the status and trends of TIN deposition across Chinese mountain regions, which occupy over 60% of the land area of China, are still unclear. Here, we established a time series dataset of TIN deposition across Chinese mountains by data collection to evaluate the status and tendency of TIN deposition in mountain regions. The average TIN deposition flux in the mountains was approximately 9.62 kg N/ha/yr, with a maximum value of 23.49 kg N/ha/yr found in northern montane regions. There was a significant increasing trend of TIN deposition during the last two decades across China's montane regions (p < 0.05), different from the decreasing temporal trend from cropland/city sites. The temporal pattern of TIN deposition in montane areas was spatial and elevation dependent, showing an obvious increasing trend in both Southwest and Northeast Chinese montane areas and in the montane areas with lower (<1000 m. asl) and middle (1000–3000 m. asl) elevations. Our results highlighted the different temporal trends of TIN deposition in China's mountain regions from cropland/city areas, which should be considered in earth system models and environmental policy-making.