Fungal and bacterial pathways along a gradient of climate and productivity

A primary distinction among soil food webs is based on fungal versus bacterial pathways of decomposition; these are expected to differ between meadows and forests. To examine which climatic limitations imposed on net primary production (NPP) might relate to the properties of soil food webs, we selected six sites with paired forests and meadows. Our comparison of biomass of both active and total fungi and bacteria in meadows and forests throughout the year indicates that while forests and meadows show an apparent difference in dominance of total bacteria versus fungi, metabolically active microbial biomass is instead determined by season.   Biomass of active microbes varies strongly and similarly by season in both forests and meadows. Where photosynthesis is constrained by summer drought and high evaporative demand, fungal food webs are more prominent, which likely results in a commensurate reduction in carbon cycling. When water is not limiting as in springtime, bacterial food webs dominate in meadows and wet coastal forests, which is expected to correspond with an increase in activity that releases more nutrients.  If the patterns between seasonal parameters and food web properties increase in parallel, this model can serve as a basis for wider application.