Dissolved organic carbon affects soil microbial activity and nitrogen dynamics in a Mexican tropical deciduous forest |
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Authors: | Noé Manuel Montaño Felipe García-Oliva Víctor J. Jaramillo |
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Affiliation: | (1) Centro de Investigaciones en Ecosistemas, Universidad Nacional Autónoma de México, Apartado Postal 27-3 Sta. María de Guido, 58090 Morelia, Michoacan, Mexico |
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Abstract: | Seasonal variation of dissolved organic C (DOC) and its effects on microbial activity and N dynamics were studied during two consecutive years in soils with different organic C concentrations (hilltop and hillslope) in a tropical deciduous forest of Mexico. We found that DOC concentrations were higher at the hilltop than at the hillslope soils, and in both soils generally decreased from the dry to the rainy season during the two study years. Microbial biomass and potential C mineralization rates, as well as dissolved organic N (DON) and NH4+ concentrations and net N immobilization were higher in soils with higher DOC than in soils with lower DOC. In contrast, net N immobilization and NH4+ concentration were depleted in the soil with lowest DOC, whereas NO3− concentrations and net nitrification increased. Negative correlations between net nitrification and DOC concentration suggested that NH4+ was transformed to NO3− by nitrifiers when the C availability was depleted. Taken together, our results suggest that available C appears to control soil microbial activity and N dynamics, and that microbial N immobilization is facilitated by active heterotrophic microorganisms stimulated by high C availability. Soil autotrophic nitrification is magnified by decreases in C availability for heterotrophic microbial activity. This study provides an experimental data set that supports the conceptual model to show and highlight that microbial dynamics and N transformations could be functionally coupled with DOC availability in the tropical deciduous forest soils. Responsible Editor: Chris Neill |
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Keywords: | C and N availability Dissolved organic C Microbial biomass Mexico Nitrification Tropical dry forests |
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