Imbalanced phosphorus and nitrogen deposition in China's forests
- 1State Key Laboratory of Earth Surface Processes and Resource Ecology, and College of Resources Science & Technology, Beijing Normal University, 100875 Beijing, China
- 2Environmental Systems Analysis Group, Wageningen University, P.O. Box 47, 6700 AA Wageningen, the Netherlands
- 3Alterra, Wageningen University and Research Center, P.O. Box 47, 6700 AA Wageningen, the Netherlands
- 4College of Resources and Environmental Sciences, China Agricultural University, 100193 Beijing, China
- 5Department of Ecology, and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, 100871 Beijing, China
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.