Dataset Information

Microbial mechanisms mediating increased soil C storage under elevated atmospheric N deposition.

ABSTRACT: Future rates of anthropogenic N deposition can slow the cycling and enhance the storage of C in forest ecosystems. In a northern hardwood forest ecosystem, experimental N deposition has decreased the extent of forest floor decay, leading to increased soil C storage. To better understand the microbial mechanisms mediating this response, we examined the functional genes derived from communities of actinobacteria and fungi present in the forest floor using GeoChip 4.0, a high-throughput functional-gene microarray. The compositions of functional genes derived from actinobacterial and fungal communities was significantly altered by experimental nitrogen deposition, with more heterogeneity detected in both groups. Experimental N deposition significantly decreased the richness and diversity of genes involved in the depolymerization of starch (?12%), hemicellulose (?16%), cellulose (?16%), chitin (?15%), and lignin (?16%). The decrease in richness occurred across all taxonomic groupings detected by the microarray. The compositions of genes encoding oxidoreductases, which plausibly mediate lignin decay, were responsible for much of the observed dissimilarity between actinobacterial communities under ambient and experimental N deposition. This shift in composition and decrease in richness and diversity of genes encoding enzymes that mediate the decay process has occurred in parallel with a reduction in the extent of decay and accumulation of soil organic matter. Our observations indicate that compositional changes in actinobacterial and fungal communities elicited by experimental N deposition have functional implications for the cycling and storage of carbon in forest ecosystems.

SUBMITTER: Eisenlord SD

PROVIDER: S-EPMC3568582 | biostudies-literature | 2013 Feb

REPOSITORIES: biostudies-literature

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Microbial mechanisms mediating increased soil C storage under elevated atmospheric N deposition.

Eisenlord Sarah D SD Freedman Zachary Z Zak Donald R DR Xue Kai K He Zhili Z Zhou Jizhong J

Applied and environmental microbiology 20121207 4

Future rates of anthropogenic N deposition can slow the cycling and enhance the storage of C in forest ecosystems. In a northern hardwood forest ecosystem, experimental N deposition has decreased the extent of forest floor decay, leading to increased soil C storage. To better understand the microbial mechanisms mediating this response, we examined the functional genes derived from communities of actinobacteria and fungi present in the forest floor using GeoChip 4.0, a high-throughput functional- ...[more]

PMID: 23220961

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Project description:Most experimental studies measuring the effects of climate change on terrestrial C cycling have focused on processes that occur at relatively short time scales (up to a few years). However, climate-soil C interactions are influenced over much longer time scales by bioturbation and soil weathering affecting soil fertility, ecosystem productivity, and C storage. Elevated CO2can increase belowground C inputs and stimulate soil biota, potentially affecting bioturbation, and can decrease soil pH which could accelerate soil weathering rates. To determine whether we could resolve any changes in bioturbation or C storage, we investigated soil profiles collected from ambient and elevated-CO2plots at the Free-Air Carbon-Dioxide Enrichment (FACE) forest site at Oak Ridge National Laboratory after 11 years of 13C-depleted CO2 release. Profiles of organic carbon concentration, ?13C values, and activities of 137Cs, 210Pb, and 226Ra were measured to ?30 cm depth in replicated soil cores to evaluate the effects of elevated CO2 on these parameters. Bioturbation models based on fitting advection-diffusion equations to 137Cs and 210Pb profiles showed that ambient and elevated-CO2 plots had indistinguishable ranges of apparent biodiffusion constants, advection rates, and soil mixing times, although apparent biodiffusion constants and advection rates were larger for 137Cs than for 210Pb as is generally observed in soils. Temporal changes in profiles of ?13C values of soil organic carbon (SOC) suggest that addition of new SOC at depth was occurring at a faster rate than that implied by the net advection term of the bioturbation model. Ratios of (210Pb/226Ra) may indicate apparent soil mixing cells that are consistent with biological mechanisms, possibly earthworms and root proliferation, driving C addition and the mixing of soil between ?4 cm and ?18 cm depth. Burial of SOC by soil mixing processes could substantially increase the net long-term storage of soil C and should be incorporated in soil-atmosphere interaction models.

Project description:Numerous studies have shown that the continuous increase of atmosphere CO2 concentrations may have profound effects on the forest ecosystem and its functions. However, little is known about the response of belowground soil microbial communities under elevated atmospheric CO2 (eCO2) at different soil depth profiles in forest ecosystems. Here, we examined soil microbial communities at two soil depths (0 to 5 cm and 5 to 15 cm) after a 10-year eCO2 exposure using a high-throughput functional gene microarray (GeoChip). The results showed that eCO2 significantly shifted the compositions, including phylogenetic and functional gene structures, of soil microbial communities at both soil depths. Key functional genes, including those involved in carbon degradation and fixation, methane metabolism, denitrification, ammonification, and nitrogen fixation, were stimulated under eCO2 at both soil depths, although the stimulation effect of eCO2 on these functional markers was greater at the soil depth of 0 to 5 cm than of 5 to 15 cm. Moreover, a canonical correspondence analysis suggested that NO3-N, total nitrogen (TN), total carbon (TC), and leaf litter were significantly correlated with the composition of the whole microbial community. This study revealed a positive feedback of eCO2 in forest soil microbial communities, which may provide new insight for a further understanding of forest ecosystem responses to global CO2 increases.IMPORTANCE The concentration of atmospheric carbon dioxide (CO2) has continuously been increasing since the industrial revolution. Understanding the response of soil microbial communities to elevated atmospheric CO2 (eCO2) is important for predicting the contribution of the forest ecosystem to global atmospheric change. This study analyzed the effect of eCO2 on microbial communities at two soil depths (0 to 5 cm and 5 to 15 cm) in a forest ecosystem. Our findings suggest that the compositional and functional structures of microbial communities shifted under eCO2 at both soil depths. More functional genes involved in carbon, nitrogen, and phosphorus cycling were stimulated under eCO2 at the soil depth of 0 to 5 cm than at the depth of 5 to 15 cm.

Dataset Information

Microbial mechanisms mediating increased soil C storage under elevated atmospheric N deposition.

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Microbial mechanisms mediating increased soil C storage under elevated atmospheric N deposition.

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