Microbial community structure and global trace gases

Abstract

Global change can affect soil processes by either altering the functioning of existing organisms or by restructuring the community, modifying the fundamental physiologies that drive biogeochemical processes. Thus, not only might process rates change, but the controls over them might also change. Moreover, previously insignificant processes could become important. These possibilities raise the question ‘Will changes in climate and land use restructure microbial communities in a way that will alter trace gas fluxes from an ecosystem?’ Process studies indicate that microbial community structure can influence trace gas dynamics at a large scale. For example, soil respiration and CH4 production both show ranges of temperature response among ecosystems, indicating differences in the microbial communities responsible. There are three patterns of NH4+ inhibition of CH4 oxidation at the ecosystem scale: no inhibition, immediate inhibition, and delayed inhibition; these are associated with different CH4 oxidizer communities. Thus, it is possible that changes in climate, land‐use, and disturbance regimes could alter microbial communities in ways that would substantially alter trace gas fluxes; we discuss the data supporting this conclusion. We also discuss approaches to developing research linking microbial community structure and activity to the structure and functioning of the whole ecosystem. Modern techniques allow us to identify active organisms even if they have not been cultivated; in combination with traditional experimental approaches we should be able to identify the linkages between these active populations and the processes they carry out at the ecosystem level. Finally, we describe scenarios of how global change could alter trace gas fluxes by altering microbial communities and how understanding the microbial community dynamics could improve our ability to predict future trace gas fluxes.

Microbial community modeling using reliability theory

“…However, in the same study, general functions such as decomposition had the opposite response; they increased as diversity decreased. These results are consistent with the idea that the reliability of narrowly distributed functions will be most sensitive to changes in microbial community composition (Schimel and Gulledge, 1998). In contrast, reduced diversity did not reduce the rate of the specialized functions of denitrification or ammonia oxidation in soil microcosms, where the inocula had been diluted to vary the diversity, provided the inoculum was sufficient to allow regrowth to the original abundance of the functional group (Wertz et al, 2006).…”

Microbial composition affects the functioning of estuarine sediments

“…For instance, a key to predicting the response of ecosystems to environmental change is to disentangle the importance of shifts in microbial composition versus the physiological plasticity of that community (Schimel et al, 2007;Singh et al, 2010;Comte and del Giorgio, 2011). Generally, ecosystem models assume that process rates-even when directly carried out by microorganisms-are determined by environmental conditions (Schimel and Gulledge, 1998), implicitly assuming that microbial communities are so physiological plastic that any differences in their composition are unimportant. Future transplant experiments might also consider more detailed temporal dynamics of microbial composition and functioning over time (for example, Berga et al, 2012).…”

Contribution of litter layer to soil greenhouse gas emissions in a temperate beech forest

“…Soil microbial communities strongly influence soil GHG fluxes (Conrad 1996;Schimel and Gulledge 1998), and are typically adapted to the type of plant litter in a certain environment (Ayres et al 2009;Madritch and Lindroth 2011). Although plant litter contributes the largest input of C and nutrients to forest soils (FAO 2010), there is a lack of knowledge on the explicit impact of the litter layer on forest soil GHG fluxes.…”