Specific microbial gene abundances and soil parameters contribute to C, N, and greenhouse gas process rates after land use change in Southern Amazonian Soils

Author(s)

Lammel, Daniel R. ^{[1, 2]} ; Feigl, Brigitte J. ^[1] ; Cerri, Carlos C. ^[1] ; Nuesslein, Klaus ^[2]

Affiliation

^[1] Univ Sao Paulo, Ctr Energia Nucl Agr, Piracicaba - Brazil

^[2] Univ Massachusetts, Dept Microbiol, Amherst, MA 01003 - USA

• Document type: Journal article
• Source: FRONTIERS IN MICROBIOLOGY; v. 6, OCT 6 2015.
• Web of Science Citations: 25

Abstract

Ecological processes regulating soil carbon (C) and nitrogen (N) cycles are still poorly understood, especially in the world's largest agricultural frontier in Southern Amazonia. We analyzed soil parameters in samples from pristine rainforest and after land use change to pasture and crop fields, and correlated them with abundance of functional and phylogenetic marker genes (amoA, nirK, nirS, norB, nosZ, nifH, mcrA, pmoA, and 16S/18S rRNA). Additionally, we integrated these parameters using path analysis and multiple regressions. Following forest removal, concentrations of soil C and N declined, and pH and nutrient levels increased, which influenced microbial abundances and biogeochemical processes. A seasonal trend was observed, suggesting that abundances of microbial groups were restored to near native levels after the dry winter fallow. Integration of the marker gene abundances with soil parameters using path analysis and multiple regressions provided good predictions of biogeochemical processes, such as the fluxes of NO3, N20, CO2, and CH4. In the wet season, agricultural soil showed the highest abundance of nitrifiers (amoA) and Archaea, however, forest soils showed the highest abundances of denitrifiers (nirK, nosZ) and high N, which correlated with increased N20 emissions. Methanogens (mcrA) and methanotrophs (pmoA) were more abundant in forest soil, but methane flux was highest in pasture sites, which was related to soil compaction. Rather than analyzing direct correlations, the data integration using multivariate tools provided a better overview of biogeochemical processes. Overall, in the wet season, land use change from forest to agriculture reduced the abundance of different functional microbial groups related to the soil C and N cycles; integrating the gene abundance data and soil parameters provided a comprehensive overview of these interactions. Path analysis and multiple regressions addressed the need for more comprehensive approaches to improve our mechanistic understanding of biogeochemical cycles. (AU)

• FAPESP's process: 05/59012-1 - Environmental impact of the expansion of agriculture in the south-east of Amazonia
• Grantee: Carlos Clemente Cerri
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 07/07570-6 - Microbial soil structure in different land uses on agricultural expansion border in southeast Amazon and its relations with greenhouse gases emission
• Grantee: Daniel Renato Lammel
• Support Opportunities: Scholarships in Brazil - Doctorate