Biotic drivers of river and floodplain geomorphology – New molecular methods for assessing present‐day and past biota

Abstract

Geomorphology has increasingly considered the role of biotic factors as controls upon geomorphic processes across a wide range of spatial and temporal scales. Where timescales are long (centennial and longer), it has been possible to quantify relationships between geomorphic processes and vegetation using, for example, the pollen record. However, where the biotic agents are fauna, longer term reconstruction of the impacts of biological activity upon geomorphic processes is more challenging. Here, we review the prospect of using environmental DNA as a molecular proxy to decipher the presence and nature of faunal influences on geomorphic processes in both present and ancient deposits. When used appropriately, this method has the potential to improve our understanding of biotic drivers of geomorphic processes, notably fauna, over long timescales and so to reconstruct how such drivers might explain the landscape as we see it today. Copyright © 2017 John Wiley & Sons, Ltd.

Zoogeomorphological behaviours in fish and the potential impact of benthic feeding on bed material mobility in fluvial landscapes

“…Why is this important? Because, despite seminal work (Darwin, 1881), growing theoretical understanding (Steiger and Corenblit, 2012), strong empirical evidence (Phillips, 2009;Rice et al, 2016), technological innovations (Larsen et al, 2017) and societal implications (Orlandini et al, 2015), geomorphologists have not fully assessed or incorporated the role of biological energy in models of geomorphological processes. The relative exclusion of biological processes from geomorphological thinking may have happened for a complex mixture of reasons, including historic accident, propinquity, key gatekeeper personalities, lack of conceptual frameworks and the inertia of conventional thought (Johnson, 2002).…”

“…In general, the results of small‐scale experiments and local observations have not been scaled up. New technologies, including eDNA, are making it easier to establish the distribution of zoogeomorphic agents, and thence their potential to have impacts, over large scales (Larsen et al, ). At present, in the absence of evidence demonstrating the impact of river organisms across larger spatial and temporal scales, a pervasive assumption remains that zoogeomorphic effects are inconsequential relative to geophysical forcing for fluvial sediment fluxes and landscape development.…”

Late Quaternary biotic and abiotic controls on long‐term sediment flux in a northern Australian tropical river system

“…The cyclicity of the system means that, instead of contrasting physical and biotic controls on geomorphology and sediment flux (e.g. Tal and Paola, ; Gurnell, ), we rather have to consider the control of vegetation as part of a longer‐term cycle, in which the dominance of biotic and abiotic processes not only switch, but depend on each other (Lane et al , ; Larsen et al , ). This adds a new and contrasting perspective to earlier studies on the longer‐term evolution along the middle reaches of Top End river systems that argued for a dominance of either climate or sea‐level control on shifts between aggradational and degradational episodes over Holocene timescales (Roberts, ; Nanson et al , ).…”

Biogeomorphology: Past, present and future

“…For example, Meitzen (2009) Monitoring in a wider sense encompasses longer term proxies of environmental change, such as the use of isotopes in soil profiles to investigate changing soil nutrient status by Chadwick et al (2007) in Hawaii and the use of 137 Cs surveys to investigate redistribution of organic carbon across a landscape (Ritchie et al, 2007). Environmental DNA has recently been proposed as novel potential proxy for long term monitoring of the changing role of fauna in fluvial biogeomorphology (Larsen et al, 2018). ungulates (Grudzinski et al, 2018), to experimental removal of vegetation from salt marshes to simulate disturbance (Temmerman et al, 2012).…”