Pools and fluxes of osmolytes in moist soil and dry soil that has been re-wet

摘要

When dry soils are re-wet there is a pulse of soil respiration that could be partially fuelled by the osmolytes that had accumulated within microbial biomass during the preceding drying phase. We hypothesize that if the pulse of respiration in re-wet soil is because microbes respond to the hypo-osmotic shock of re-wetting by expelling osmolytes and then re-capture osmolytes for use as respiratory substrates: a) rewetting will lead to a massive flux of osmolytes from microbial biomass into the extracellular fraction of soil, and b) following rewetting there will be a decrease in the total pool of osmolytes (i.e. in microbial biomass + the extracellular fraction of soil) that is proportional to the extra C that is respired by rewet soil compared to permanently moist soil.