Ecoenzymatic stoichiometry of microbial organic nutrient acquisition in soil and sediment

Abstract

Biota can be described in terms of elemental composition, expressed as an atomic ratio of carbon:nitrogen:phosphorus (refs 1-3). The elemental stoichiometry of microoorganisms is fundamental for understanding the production dynamics and biogeochemical cycles of ecosystems because microbial biomass is the trophic base of detrital food webs. Here we show that heterotrophic microbial communities of diverse composition from terrestrial soils and freshwater sediments share a common functional stoichiometry in relation to organic nutrient acquisition. The activities of four enzymes that catalyse the hydrolysis of assimilable products from the principal environmental sources of C, N and P show similar scaling relationships over several orders of magnitude, with a mean ratio for C:N:P activities near 1:1:1 in all habitats. We suggest that these ecoenzymatic ratios reflect the equilibria between the elemental composition of microbial biomass and detrital organic matter and the efficiencies of microbial nutrient assimilation and growth. Because ecoenzymatic activities intersect the stoichiometric and metabolic theories of ecology, they provide a functional measure of the threshold at which control of community metabolism shifts from nutrient to energy flow.

The decomposition of ectomycorrhizal fungal necromass

“…C, N, P) and the recalcitrance, or the resistance to decomposition, of the molecules comprising the litter. Decomposition is generally favored by relatively low litter C:N ratios (Cleveland and Liptzin, 2007), which presumably helps to maintain the low C:N ratio of microbial cells (Sinsabaugh et al, 2009;Manzoni et al, 2010), yet, there is increasing evidence that additional aspects of quality beyond basic stoichiometry also can play a role determining decomposition rates. Koide and Malcolm (2009) tested the role of C and N concentrations on the decomposition rate of EM fungal necromass in a litterbag study and found that initial N concentration was a good predictor of the decomposition rate of these tissues.…”

“…Relatively labile compounds can persist in SOM for long periods as a consequence of physical protection either through soil aggregation or sorption (Nelson et al, 1979;Six et al, 2006;Grandy and Robertson, 2007;Grandy and Neff, 2008). Fungal hyphae have intimate physical and chemical interactions with soil structures, which can lead to stabilization and protection of organic compounds in soils (Tisdall, 1994;Rillig et al, 2015).…”

The effect of temperature and substrate quality on the carbon use efficiency of saprotrophic decomposition

“…Microbial growth requires a stoichiometric balance between carbon and other elements (especially nitrogen and phosphorus; Frost et al 2006;Nordgren et al 1988;Sinsabaugh et al 2009). If the availability of other nutrients is below the stoichiometric requirements, there is a risk that excess carbon will be respired and converted into CO 2 (or excreted in the form of organic compounds) rather than being used for biosynthesis, leading to reduced CUE (Ågren and Bosatta 1987;Manzoni and Porporato 2009).…”

Effects of regenerating vegetation on soil enzyme activity and microbial structure in reclaimed soils on a surface coal mine site

“…Soil enzyme activities integrate information about microbial status and soil physicochemical conditions (Aon and Colaneri, 2001;Sinsabaugh et al, 2010), and are indicators of the functioning of soil ecosystems (Ciarkowska et al, 2014). They have been similarly used in studies on the effectiveness of reclaimed treatments on soil quality (Li et al, 2012;Schimann et al, 2012;Finkenbein et al, 2013;Ciarkowska et al, 2014).…”