A comparison of patterns of microbial C : N : P stoichiometry between topsoil and subsoil along an aridity gradient
2020
Abstract. Microbial stoichiometry and its potential driving factors play crucial roles
in understanding the balance of chemical elements in ecological interactions
and nutrient limitations along the aridity gradient. However, little is known
about the variation in these features along the aridity gradient due to the lack
of comprehensive field investigations. Additionally, previous studies
focused on the topsoil (0–10 or 0–20 cm); however, the minimum sampling
depth for topsoil could impact the results of the vertical distribution of
microbial stoichiometry. In the present study, we measured the variation in
microbial stoichiometry, examined the major influential factors (climatic,
edaphic, and biotic factors) along an aridity gradient, and determined whether
the sampling depth affected microbial C : N : P stoichiometry. From the topsoil
to the subsoil, the microbial C : N, C : P, and N : P ratios varied from 6.59 to
6.83, from 60.2 to 60.5, and from 9.29 to 8.91, respectively. Only the
microbial C : N ratio significantly increased with soil depth. The microbial
C : N ratio significantly increased with increasing aridity in both topsoil
and subsoil, while the microbial N : P ratio decreased along the aridity
gradient only for the topsoil. This result implied that drought-stimulated
microbes tend to be more N conservative, especially those in topsoil. Among
all the factors, the soil organic carbon (SOC) content and the fungi-to-bacteria ratio exerted the largest influence on the microbial C : N, C : P, and
N : P ratios at both soil depths, implying that the substrate supply and
microbial structure together controlled the microbial stoichiometry. The
results also revealed that the aridity index (AI) and plant aboveground
biomass (AGB) exerted negative impacts on the microbial C : N ratio at both
soil depths, and the effects of AI decreased in the subsoil. The results of
this study suggested that the flexibility of the microbial N : P ratio should
be considered when establishing the sampling depth for microbial
stoichiometry study.
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