An experimental test of the hypothesis of non‐homeostatic consumer stoichiometry in a plant litter–microbe system

Abstract

Stoichiometric homeostasis of heterotrophs is a common, but not always well-examined premise in ecological stoichiometry. We experimentally evaluated the relationship between substrate (plant litter) and consumer (microorganisms) stoichiometry for a tropical terrestrial decomposer system. Variation in microbial C : P and N : P ratios tracked that of the soluble litter fraction, but not that of bulk leaf litter material. Microbial N and P were not isometrically related, suggesting higher rates of P than N sequestration in microbial biomass. Shifts in microbial stoichiometry were related to changes in microbial community structure. Our results indicate that P in dissolved form is a major driver of terrestrial microbial stoichiometry, similar to aquatic environments. The demonstrated relative plasticity in microbial C : P and N : P and the critical role of P have important implications for theoretical modelling and contribute to a process-based understanding of stoichiometric relationships and the flow of elements across trophic levels in decomposer systems.

C, N and P fertilization in an Amazonian rainforest supports stoichiometric dissimilarity as a driver of litter diversity effects on decomposition

“…This is in line with the theory of ecological stoichiometry stating that the ratios of elements, and particularly that of the key elements C, N and P controls growth and activity of decomposers to an important degree [11][12][13]. C : N : P stoichiometry of microbial decomposer communities is much narrower than that of their plant litter substrates [14], and the combined use of different elements provided by different litter types in mixtures should stimulate decomposer growth and would lead to faster decomposition of litter mixtures. Consequently, the divergence in litter stoichiometry of component species should be a strong predictor of diversity effects on litter mixture decomposition [15].…”

Microbial respiration per unit microbial biomass depends on litter layer carbon-to-nitrogen ratio

“…One further way in which microorganisms can react to imbalanced substrate stoichiometry is to gradually adjust the microbial biomass stoichiometry to the substrate as recently shown for microorganisms in tropical litter (Fanin et al, 2013). However, in this study, I did not find a significant relation between the litter C : N ratio and the microbial C : N ratio, indicating that the microbial community did not adapt its biomass composition to the litter layer stoichiometry.…”

Aquatic heterotrophic bacteria have highly flexible phosphorus content and biomass stoichiometry

“…Furthermore, the bacterial assemblage (of multiple strains) exhibited greater stoichiometric plasticity than has been documented in any other species or assemblage, including terrestrial and aquatic primary producers (Sterner and Elser, 2002;Persson et al, 2010). These experiments demonstrate that previous assumptions of low and invariant C:P biomass (Tanaka et al, 2009;Fanin et al, 2013) and high relative P content for bacteria (Wolfe-Simon et al, 2010) do not represent the physiological flexibility of bacteria in natural assemblages. Although mean cellular P content decreased under P limitation, much of the flexibility in C:P biomass was due to a substantial increase in cellular C content ( Supplementary Figure 1), likely owing to the accumulation of C-rich storage molecules (Thingstad et al, 2005).…”