Fungal community composition and metabolism under elevated CO 2 and O 3

Atmospheric CO 2 and O 3 concentrations are increasing due to human activity and both trace gases have the potential to alter C cycling in forest ecosystems. Because soil microorganisms depend on plant litter as a source of energy for metabolism, changes in the amount or the biochemistry of plant litter produced under elevated CO 2 and O 3 could alter microbial community function and composition. Previously, we have observed that elevated CO 2 increased the microbial metabolism of cellulose and chitin, whereas elevated O 3 dampened this response. We hypothesized that this change in metabolism under CO 2 and O 3 enrichment would be accompanied by a concomitant change in fungal community composition. We tested our hypothesis at the free-air CO 2 and O 3 enrichment (FACE) experiment at Rhinelander, Wisconsin, in which Populus tremuloides , Betula papyrifera , and Acer saccharum were grown under factorial CO 2 and O 3 treatments. We employed extracellular enzyme analysis to assay microbial metabolism, phospholipid fatty acid (PLFA) analysis to determine changes in microbial community composition, and polymerase chain reaction–denaturing gradient gel electrophoresis (PCR–DGGE) to analyze the fungal community composition. The activities of 1,4-β-glucosidase (+37%) and 1,4,-β- N -acetylglucosaminidase (+84%) were significantly increased under elevated CO 2 , whereas 1,4-β-glucosidase activity (−25%) was significantly suppressed by elevated O 3 . There was no significant main effect of elevated CO 2 or O 3 on fungal relative abundance, as measured by PLFA. We identified 39 fungal taxonomic units from soil using DGGE, and found that O 3 enrichment significantly altered fungal community composition. We conclude that fungal metabolism is altered under elevated CO 2 and O 3 , and that there was a concomitant change in fungal community composition under elevated O 3 . Thus, changes in plant inputs to soil under elevated CO 2 and O 3 can propagate through the microbial food web to alter the cycling of C in soil.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47711/1/442_2005_Article_249.pd

Microbiota: the living foundation

Mudflats are highly productive regions that are important to local, regional and global aspects of ecology and biogeochemistry. They sequester organic carbon, recycle nutrient elements such as nitrogen and phosphorus, release climate-active gases to the atmosphere, and provide sustenance to countless resident and migrant animals. Microorganisms that remain hidden from sight underpin all of these, and many other, crucial ecosystem functions and services. This chapter explores the roles of microorganisms in mudflat sediments, their interactions with the other residents, and some of the contemporary techniques used to study and quantify the ways in which they influence biogeochemical cycles

Key Biochemical Attributes to Assess Soil Ecosystem Sustainability

Soil is not a renewable resource, at least within the human timescale. In general, any anthropic exploitation of soils tends to disturb or divert them from a more “natural” development which, by definition, represents the best comparison term for measuring the relative shift from soil sustainability. The continuous degradation of soil health and quality due to abuse of land potentiality or intensive management occurs since decades. Soil microbiota, being ‘the biological engine of the Earth’, provides pivotal services in the soil ecosystem functioning. Hence, management practices protecting soil microbial diversity and resilience, should be pursued. Besides, any abnormal change in rate of innumerable soil biochemical processes, as mediated by microbial communities, may constitute early and sensitive warning of soil homeostasis alteration and, therefore, diagnoses a possible risk for soil sustainability. Among the vastness of soil biochemical processes and related attributes (bioindicators) potentially able to assess the sustainable use of soils, those related to mineralisation-immobilisation of major nutrients (C and N), including enzyme activity (functioning) and composition (community diversity) of microbial biomass, have paramount importance due to their centrality in soil metabolism. In this chapter we have compared, under various pedoclimates, the impact of different agricultural factors (fertilisation, tillage, etc.) under either intensive and sustainable managements on soil microbial community diversity and functioning by both classical and molecular soil quality indicators, in order to outline the most reliable soil biochemical attributes for assessing risky shifts from soil sustainability