BIOGEOCHEMICAL CONSEQUENCES OF RAPID MICROBIAL TURNOVER AND SEASONAL SUCCESSION IN SOIL

TLDR

Soil microbial communities can rapidly adapt to changing environmental conditions. The study combines biogeochemical and molecular methods to demonstrate rapid microbial biomass turnover and succession over a year, enabling a temporally explicit nitrogen cycle model that explains seasonal loss and retention of dissolved and inorganic nitrogen. The results show that microbial community turnover is the main source of dissolved and inorganic nitrogen for plant uptake during the growing season, and that this linkage between turnover, succession, and biogeochemical fluxes applies broadly across terrestrial ecosystems.

Abstract

Soil microbial communities have the metabolic and genetic capability to adapt to changing environmental conditions on very short time scales. In this paper we combine biogeochemical and molecular approaches to reveal this potential, showing that microbial biomass can turn over on time scales of days to months in soil, resulting in a succession of microbial communities over the course of a year. This new understanding of the year-round turnover and succession of microbial communities allows us for the first time to propose a temporally explicit N cycle that provides mechanistic hypotheses to explain both the loss and retention of dissolved organic N (DON) and inorganic N (DIN) throughout the year in terrestrial ecosystems. In addition, our results strongly support the hypothesis that turnover of the microbial community is the largest source of DON and DIN for plant uptake during the plant growing season. While this model of microbial biogeochemistry is derived from observed dynamics in the alpine, we present several examples from other ecosystems to indicate that the general ideas of biogeochemical fluxes being linked to turnover and succession of microbial communities are applicable to a wide range of terrestrial ecosystems.