Phosphorus rather than nitrogen enhances CO 2 emissions in tropical forest soils: Evidence from a laboratory incubation study

• Published in: European journal of soil science Vol. 71; no. 3; pp. 495 - 510
• Main Authors: Hui, Dafeng, Porter, Wesley, Phillips, Jana R., Aidar, Marcos P.M., Lebreux, Steven J., Schadt, Christopher W., Mayes, Melanie A.
• Format: Journal Article
• Language: English
• Published: 01.05.2020
• ISSN: 1351-0754; 1365-2389
• DOI: 10.1111/ejss.12885

Abstract Ecosystem functional responses such as soil CO 2 emissions are constrained by microclimate, available carbon (C) substrates and their effects upon microbial activity. In tropical forests, phosphorus (P) is often considered as a limiting factor for plant growth, but it is still not clear whether P constrains microbial CO 2 emissions from soils. In this study, we incubated seven tropical forest soils from Brazil and Puerto Rico with different nutrient addition treatments (no addition, Control; C, nitrogen (N) or P addition only; and combined C, N and P addition (CNP)). Cumulative soil CO 2 emissions were fit with a Gompertz model to estimate potential maximum cumulative soil CO 2 emission ( C m ) and the rate of change of soil C decomposition ( k ). Quantitative polymerase chain reaction (qPCR) was conducted to quantify microbial biomass as bacteria and fungi. Results showed that P addition alone or in combination with C and N enhanced C m , whereas N addition usually reduced C m , and neither N nor P affected microbial biomass. Additions of CNP enhanced k , increased microbial abundances and altered fungal to bacterial ratios towards higher fungal abundance. Additions of CNP, however, tended to reduce C m for most soils when compared to C additions alone, suggesting that microbial growth associated with nutrient additions may have occurred at the expense of C decomposition. Overall, this study demonstrates that soil CO 2 emission is more limited by P than N in tropical forest soils and those effects were stronger in soils low in P. Highlights A laboratory incubation study was conducted with nitrogen, phosphorus or carbon addition to tropical forest soils. Soil CO 2 emission was fitted with a Gompertz model and soil microbial abundance was quantified using qPCR. Phosphorus addition increased model parameters C m and soil CO 2 emission, particularly in the Puerto Rico soils. Soil CO 2 emission was more limited by phosphorus than nitrogen in tropical forest soils.