Articles | Volume 14, issue 12
Biogeosciences, 14, 3097–3109, 2017
Biogeosciences, 14, 3097–3109, 2017

Research article 23 Jun 2017

Research article | 23 Jun 2017

Phosphorus addition mitigates N2O and CH4 emissions in N-saturated subtropical forest, SW China

Longfei Yu1, Yihao Wang2,3, Xiaoshan Zhang3, Peter Dörsch1, and Jan Mulder1 Longfei Yu et al.
  • 1Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Aas, Norway
  • 2Chongqing Academy of Forestry, 400036 Chongqing, China
  • 3Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 100085 Beijing, China

Abstract. Chronically elevated nitrogen (N) deposition has led to severe nutrient imbalance in forest soils. Particularly in tropical and subtropical forest ecosystems, increasing N loading has aggravated phosphorus (P) limitation of biomass production, and has resulted in elevated emissions of nitrous oxide (N2O) and reduced uptake of methane (CH4), both of which are important greenhouse gases. Yet, the interactions of N and P and their effects on greenhouse gas emissions remain elusive. Here, we report N2O and CH4 emissions together with soil N and P data for a period of 18 months following a single P addition (79 kg P ha−1, as NaH2PO4 powder) to an N-saturated, Masson pine-dominated forest soil at TieShanPing (TSP), Chongqing, south-western (SW) China. We observed a significant decline in both nitrate (NO3) concentrations in soil water (5 and 20 cm depths) and in soil N2O emissions, following P application. We hypothesise that enhanced N uptake by plants in response to P addition, resulted in less available NO3 for denitrification. By contrast to most other forest ecosystems, TSP is a net source of CH4. P addition significantly decreased CH4 emissions and turned the soil from a net source into a net sink. Based on our observation and previous studies in South America and China, we believe that P addition relieves N inhibition of CH4 oxidation. Within the 1.5 years after P addition, no significant increase of forest growth was observed and P stimulation of forest N uptake by understorey vegetation remains to be confirmed. Our study indicates that P fertilisation of N-saturated, subtropical forest soils may mitigate N2O and CH4 emissions, in addition to alleviating nutrient imbalances and reducing losses of N through NO3 leaching.

Short summary
In this study, we applied phosphorus (P) to a nitrogen (N)-saturated forest in the Chinese subtropics and observed significant decreases in both N2O and CH4 emission from soil within 1.5 years. This was associated with a strong decrease of mineral N in soil water, likely due to stimulated N uptake. Our findings suggest that P limitation could be one important reason for large greenhouse gas emissions reported in the subtropical forests receiving excessive N input.
Final-revised paper