A conceptual framework for understanding the biogeochemistry of dry riverbeds through the lens of soil science

Abstract

Intermittent rivers and ephemeral streams (IRES) encompass fluvial ecosystems that eventually stop flowing andrun dry at some point in space and time. During the dry phase, channels of IRES consist mainly of dry riverbeds(DRBs), prevalent yet widely unexplored ecotones between dry and wet phases that can strongly influence thebiogeochemistry of fluvial networks. DRBs are often overlooked because they do not strictly belong to eitherdomain of soil or freshwater science. Due to this dual character of DRBs, we suggest that concepts and knowledgefrom soil science can be used to expand the understanding of IRES biogeochemistry. Based on this idea, wepropose that DRBs can be conceptually understood as early stage soils exhibiting many similarities with soilsthrough two main forces: i) time since last sediment transport event, and ii) the development status of stabilizingstructures (e.g. soil crusts and/or vascular plants). Our analysis suggests that while DRBs and soils may differ inmaster physical attributes (e.g. soil horizons vs fluvial sedimentary facies), they become rapidly comparable interms of microbial communities and biogeochemical processes. We further propose that drivers of DRBs biogeochemistry are similar to those of soils and, hence, concepts and methods used in soil science are transferableto DRBs research. Finally, our paper presents future research directions to advance the knowledge of DRBs and tounderstand their role in the biogeochemistry of intermittent fluvial networks.