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Agriculture has an important potential role in mitigating greenhouse gas emissions (GHG). However, practices that reduce C[O.sub.2] emissions from soils and increase the soil organic C level may stimulate [N.sub.2]O emissions. This is particularly critical in Quebec where heavy soils and a humid climate may limit the adoption of agricultural practices designed to mitigate GHG. The objective of this work was to study the effects of two tillage and N fertilization regimes on C[O.sub.2] and [N.sub.2]O fluxes and the seasonal variability in emissions of these gases, associated with corn (Zea mays L.) grown in southwestern Quebec. Different seasonal emission patterns of C[O.sub.2] and [N.sub.2]O were observed. Higher [N.sub.2]O fluxes occurred during the spring and were associated with precipitation events, while higher C[O.sub.2] flues occurred in mid-season and were related to temperature. Conventional tillage (CT) had greater peaks of C[O.sub.2] emissions than no-till (NT) only after disking in the spring. Once corn was established, differences between tillage systems were small. Peaks of [N.sub.2]O emission occurred in both systems (NT and CT) following N application. Plots receiving 180 kg N [ha.sup.-1] in both tillage systems had large peak of [N.sub.2]O emission rates during the wettest parts of the season. The CT and NT systems generally had similar cumulative C[O.sub.2] emissions but NT had higher cumulative [N.sub.2]O emissions than CT. Our findings suggests that changing from CT to NT under the heavy soil conditions of Quebec may increase GHG, mainly as result of the increase in [N.sub.2]O emission. This negative effect of NT could be reduced by avoiding fertilizing when precipitation is more intense. Abbreviations: CT, conventional tillage; GHG, greenhouse gas emissions; NT, no-till; WFPS, water-filled pore space.

This study identified microbial functional groups like total culturable bacteria, potential N2-fixing free living bacteria, N2-fixing hydrocarbonoclastic bacteria, N-assimilating hydrocarbonoclastic bacteria, total fungi, actinobacteria, P-solubilizers, lipolytic microorganisms, and starch, cellulose, pectin and protein degrading microorganisms, isolated from the rhizosphere of four species of mangroves (Red, Black, White, and Button) from the natural protected area at the Terminos Lagoon, Campeche, México. Overall, microbial populations showed significant differences (P < 0.05) among the four mangrove species. The rhizosphere of White mangrove showed better chemical and textural soil properties, and harbored the highest microbial populations when compared to the remaining mangrove species. The principal component analysis indicated that two components accounted the 85.3% of the total variation. The most significant textural and chemical soil properties were the major components, CP1 (organic matter and total organic carbon) and CP2 (sand and clay). Microbial populations correlated (P < 0.05, Pearson coefficient) with sand and clay particles, and with some soil chemical properties such as organic matter. The total nitrogen and organic carbon significantly correlated with cellulose degraders, while phosphorus with N2-fixing bacteria, total fungi, and with pectin and starch degraders. [ABSTRACT FROM AUTHOR]