| Environmental variation and nitrogen addition impacts on the methane (CH4) cycle of non-wetland terrestrial soil were examined at multiple scales. The investigation used literature review and meta-analysis, modeling, field observations of gas fluxes, soil properties and microbial communities. The literature review revealed a consensus that a great variation exists in forest methane flux. A meta-analysis of this database revealed a significant trend of greater N addition increasing CH4 release in agricultural systems than in non-agricultural ones. Gas flux and microbiological measurements were made in the NJ Pinelands at 36 plots across two sites, separated by 40-50 m, which differed in water table height but shared overstory vegetation types, and showed greater CH4 consumption in the well-drained site than the poorly-drained site. Nitrogen addition caused CH4 release from the poorly-drained site but not from the well-drained site. The total magnitude of CH4 consumption in all well-drained plots was -5.38 kg CH 4 ha-1 yr-1, which is similar to a recently published global average for forest CH4 consumption, -5.70 kg CH 4 ha-1 yr-1, based on 92 measurements around the globe. These findings were extrapolated using a NASA global climate model, and the total soil sink for methane was 60 Tg yr-1.;Analysis of the microbial composition of the Pinelands sites was performed using quantitative polymerase chain reaction (qPCR) and Phylochip 16S DNA microarrays. QPCR was used in order to enumerate copies of two functional genes involved in CH4 oxidation and production. The average concentration of methanogen genes in the poorly-drained site was 63,434.2 gene copies g-1 wet soil, which was significantly different from 1.5 copies g -1 wet soil in the well-drained site. The concentration of methanotroph genes was also greater in the poorly-drained site, with an average of 4,662,626 copies g-1 wet soil, than in the well-drained site, which averaged 578,613 copies g-1 wet soil. The lower site had a more variable community structure than the upper site, while the upper site had greater richness of operational taxonomic units (OTUs). The upper site had greater OTU richness of methanotrophs and nitrifiers. |
