Are rate changes in biotic processes altering subsurface hydrologic partitioning in the Anthropocene?
The degree to which subsurface architecture – pores space and connectivity—fluctuates and/or evolves is largely ignored in predictions of how Earth’s critical zone can respond to changes in biotic processes (direct and indirect) in the Anthropocene. Specifically, changes in microbial carbon decomposition rates and root growth can influence the generation of macropores, whose porosity accounts for only ~2% of the subsurface but accounts for ~70% of water transmitted to depth. We argue that the community needs to consider that changes in the subsurface structure throttles the partitioning of water, and thus the fluxes of carbon, nutrients, and weathering products. Using empirical data and modeling we explore this connectivity between biotic processes (e.g., root growth, carbon turn over) and subsurface pore structure from the pedon to the continental scale, quantifying the impact of this interaction on stocks and fluxes of water and nutrients. We then examine how over longer time periods, this change in hydrologic partitioning can influence the depth to which reaction fronts propagate into the subsurface and the role in which these changes could influence the trajectory of landscape evolution.