Abstract
Soil ecological stoichiometry provides powerful theories to integrate
the complex interplay of element cycling and microbial communities into
biogeochemical models. One essential assumption is that microbes
maintain stable C:N:P (carbon:nitrogen:phosphorus) ratios independent of
resource supply, although such homeostatic regulations have rarely been
assessed in individual microorganisms. Here, we report an unexpected
high flexibility in C:N and C:P values of saprobic fungi along nutrient
supply gradients, overall ranging between 7-126 and 20-1488,
respectively, questioning microbial homeostasis. Fungal N:P varied
comparatively less due to simultaneous reductions in mycelial N and P
contents. As a mechanism, internal recycling processes during mycelial
growth and an overall reduced N and P uptake appear more relevant than
element storage. The relationships among fungal stoichiometry and growth
disappeared in more complex media. These findings affect our
interpretation of stoichiometric imbalances among microbes and soils and
are highly relevant for developing microbial soil organic carbon and
nitrogen models.