Increased phosphorus availability mitigates the inhibition of nitrogen deposition on CH₄ uptake in an old-growth tropical forest, southern China

• Main Authors: S. Dong, L. Liu, J. Mo, W. Zhu, T. Zhang
• Format: Article
• Language: English
• Published: Copernicus Publications 2011-09-01
• Series: Biogeosciences
• Online Access: http://www.biogeosciences.net/8/2805/2011/bg-8-2805-2011.pdf
• ISSN: 1726-4170; 1726-4189

It is well established that tropical forest ecosystems are often limited by phosphorus (P) availability, and elevated atmospheric nitrogen (N) deposition may further enhance such P limitation. However, it is uncertain whether P availability would affect soil fluxes of greenhouse gases, such as methane (CH₄) uptake, and how P interacts with N deposition. We examine the effects of N and P additions on soil CH₄ uptake in an N saturated old-growth tropical forest in southern China to test the following hypotheses: (1) P addition would increase CH₄ uptake; (2) N addition would decrease CH₄ uptake; and (3) P addition would mitigate the inhibitive effect of N addition on soil CH₄ uptake. Four treatments were conducted at the following levels from February 2007 to October 2009: control, N-addition (150 kg N ha⁻¹ yr^−1), P-addition (150 kg P ha⁻¹ yr^−1), and NP-addition (150 kg N ha⁻¹ yr⁻¹ plus 150 kg P ha⁻¹ yr⁻¹). Static chamber and gas chromatography techniques were used to quantify soil CH₄ uptake every month throughout the study period. Average CH₄ uptake rate was 31.2 ± 1.1 μg CH₄-C m⁻² h⁻¹ in the control plots. The mean CH₄ uptake rate in the N-addition plots was 23.6 ± 0.9 μg CH₄-C m⁻² h⁻¹, significantly lower than that in the controls. P-addition however, significantly increased CH₄ uptake by 24% (38.8 ± 1.3 μg CH₄-C m⁻² h⁻¹), whereas NP-addition (33.6 ± 1.0 μg CH₄-C m⁻² h⁻¹) was not statistically different from the control. Our results suggest that increased P availability may enhance soil mathanotrophic activity and root growth, resulting in potentially mitigating the inhibitive effect of N deposition on CH₄ uptake in tropical forests.