Articles | Volume 16, issue 13
Research article
14 Jul 2016
Research article |  | 14 Jul 2016

Imbalanced phosphorus and nitrogen deposition in China's forests

Enzai Du, Wim de Vries, Wenxuan Han, Xuejun Liu, Zhengbing Yan, and Yuan Jiang

Abstract. Acceleration of anthropogenic emissions in China has substantially increased nitrogen (N) deposition during the last 3 decades and may result in an imbalance of atmospheric N and phosphorus (P) inputs in terrestrial ecosystems. However, the status of P deposition in China is poorly understood. This study synthesized data on total P and total N concentrations in bulk precipitation and throughfall from published literature to assess the characteristics of P deposition, N deposition and N : P deposition ratio in China's forests. Our results show relatively high mean rates of bulk P deposition (0.38 kg P ha−1 yr−1) and total P deposition (0.69 kg P ha−1 yr−1), but they were accompanied by even more elevated N inputs via bulk deposition (16.5 kg N ha−1 yr−1) and total deposition (21.6 kg N ha−1 yr−1), resulting in high N : P ratios in bulk deposition (44.4) and total deposition (32.8). Based on the difference between total deposition and bulk deposition, canopy-captured dry P and N deposition was estimated to be 0.31 kg P ha−1 yr−1 and 5.1 kg N ha−1 yr−1, respectively. We found significantly higher P deposition and lower N : P ratios at sites nearby than those far from semiarid regions. The estimated bulk and total deposition of P and N both showed a significant power-law increase with decreasing distance to the nearest large cities either in the areas nearby or far from semiarid regions. Our results suggest an anthropogenic alternation of regional P and N cycling, which may shift large areas of China's forests towards human-induced P limitation especially in southern China.

Short summary
Accelerated N emissions in China may lead to an imbalance of atmospheric nutrient inputs in various ecosystems. Our assessment of P and N deposition in China's forests showed relatively high rates of P deposition, but they were accompanied by even much higher N deposition, resulting in high N : P deposition ratios. P and N deposition both showed a power-law increase with closer distance to the nearest large cities. Our results suggest an anthropogenic imbalance of regional N and P cycling.
Final-revised paper