Imbalanced atmospheric nitrogen and phosphorus depositions in China: Implications for nutrient limitation

Atmospheric wet nitrogen (N) and phosphorus (P) depositions are important sources of bioavailable N and P, and the input of N and P and their ratios significantly influences nutrient availability and balance in terrestrial as well as aquatic ecosystems. Here we monitored atmospheric P depositions by measuring monthly dissolved P concentration in rainfall at 41 field stations in China. Average deposition fluxes of N and P were 13.69 ± 8.69 kg N ha⁻¹ a⁻¹ (our previous study) and 0.21 ± 0.17 kg P ha⁻¹ a⁻¹, respectively. Central and southern China had higher N and P deposition rates than northwest China, northeast China, Inner Mongolia, or Qinghai-Tibet. Atmospheric N and P depositions showed strong seasonal patterns and were dependent upon seasonal precipitation. Fertilizer and energy consumption were significantly correlated with N deposition but less correlated with P deposition. The N:P ratios of atmospheric wet deposition (with the average of 77 ± 40, by mass) were negatively correlated with current soil N:P ratios in different ecological regions, suggesting that the imbalanced atmospheric N and P deposition will alter nutrient availability and strengthen P limitation, which may further influence the structure and function of terrestrial ecosystems. The findings provide the assessments of both wet N and P deposition and their N:P ratio across China and indicate potential for strong impacts of atmospheric deposition on broad range of terrestrial ecosystems.