Nutrient Control of Microbial Carbon Cycling Along an Ombrotrophicminerotrophic Peatland Gradient

Future climate change and other anthropogenic activities are likely to increase nutrient availability in many peatlands, and it is important to understand how these additional nutrients will influence peatland carbon cycling. We investigated the effects of nitrogen and phosphorus on aerobic CH4 oxidation, anaerobic carbon mineralization (as CO2 and CH4 production), and anaerobic nutrient mineralization in a bog, an intermediate fen, and a rich fen in the Upper Peninsula of Michigan. We utilized a 5-week laboratory nutrient amendment experiment in conjunction with a 6-year field nutrient fertilization experiment to consider how the relative response to nitrogen and phosphorus differed among these wetlands over the short and long term. Field fertilizations generally increased nutrient availability in the upper 15 cm of peat and resulted in shifts in the vegetation community in each peatland. High nitrogen concentrations inhibited CH4 oxidation in bog peat during short-term incubations; however, long-term fertilization with lower concentrations of nitrogen stimulated rates of CH4 oxidation in bog peat. In contrast, no nitrogen effects on CH4 oxidation were observed in the intermediate or rich fen peat. Anaerobic carbon mineralization in bog peat was consistently inhibited by increased phosphorus availability, but similar phosphorus additions had few effects in the intermediate fen and stimulated CH4 production and nutrient mineralization in the rich fen. Our results demonstrate that nitrogen and phosphorus are important controls of peatland microbial carbon cycling; however, the role of these nutrients can differ over the short and long term and is strongly mediated by peatland type

Metagenomic analysis reveals a marked divergence in the structure of belowground microbial communities at elevated CO2

Abstract Understanding the responses of biological communities to elevated CO 2 (eCO 2 ) is a central issue in ecology, but little is known about the influence of eCO 2 on the structure and functioning (and consequent feedbacks to plant productivity) of the belowground microbial community. Here, using metagenomic technologies, we showed that 10 years of field exposure of a grassland ecosystem to eCO 2 dramatically altered the structure and functional potential of soil microbial communities. Total microbial and bacterial biomass were significantly increased at eCO 2 , but fungal biomass was unaffected. The structure of microbial communities was markedly different between ambient CO 2 (aCO 2 ) and eCO 2 as indicated by detrended correspondence analysis (DCA) of gene-based pyrosequencing data and functional gene array data. While the abundance of genes involved in decomposing recalcitrant C remained unchanged, those involved in labile C degradation and C and N fixation were significantly increased under eCO 2. Changes in microbial structure were significantly correlated with soil C and N contents and plant productivity. This study provides insights into potential activity of microbial community and associated feedback responses of terrestrial ecosystems to eCO 2

Appendix B. ANOVA tables of species and community responses to nutrient addition in the bog, the intermediate fen, and the rich fen.

ANOVA tables of species and community responses to nutrient addition in the bog, the intermediate fen, and the rich fen

Appendix E. Nitrogen use efficiency and Nitrogen response efficiency in leaves and wood of dominant shrub species in response to nutrient addition in the bog, the intermediate fen, and the rich fen.

Nitrogen use efficiency and Nitrogen response efficiency in leaves and wood of dominant shrub species in response to nutrient addition in the bog, the intermediate fen, and the rich fen

Appendix C. Detailed description of plant-level production and N efficiency responses of representative vascular species to nutrient addition in the bog, the intermediate fen, and the rich fen.

Detailed description of plant-level production and N efficiency responses of representative vascular species to nutrient addition in the bog, the intermediate fen, and the rich fen

Appendix A. List of dominant vascular species in the bog, the intermediate fen, and the rich fen.

List of dominant vascular species in the bog, the intermediate fen, and the rich fen

Appendix D. Biomass, production, and N uptake in leaves and wood of dominant shrub species in to response to nutrient addition in the bog, the intermediate fen, and the rich fen.

Biomass, production, and N uptake in leaves and wood of dominant shrub species in to response to nutrient addition in the bog, the intermediate fen, and the rich fen

Metagenomic analysis reveals a marked divergence in the structure of belowground microbial communities at elevated CO2

Understanding the responses of biological communities to elevated CO2 (eCO2) is a central issue in ecology, but little is known about the influence of eCO2 on the structure and functioning (and consequent feedbacks to plant productivity) of the belowground microbial community. Here, using metagenomic technologies, we showed that 10 years of field exposure of a grassland ecosystem to eCO2 dramatically altered the structure and functional potential of soil microbial communities. Total microbial and bacterial biomass were significantly increased at eCO2, but fungal biomass was unaffected. The structure of microbial communities was markedly different between ambient CO2 (aCO2) and eCO2 as indicated by detrended correspondence analysis (DCA) of gene-based pyrosequencing data and functional gene array data. While the abundance of genes involved in decomposing recalcitrant C remained unchanged, those involved in labile C degradation and C and N fixation were significantly increased under eCO2. Changes in microbial structure were significantly correlated with soil C and N contents and plant productivity. This study provides insights into potential activity of microbial community and associated feedback responses of terrestrial ecosystems to eCO2