Abstract
Previous studies have shown that biological structures such as plant roots can have large impacts on landscape morphodynamics, and that physical models that do not incorporate biology can generate qualitatively incorrect predictions of sediment transport. However, work to date has focused almost entirely on the impacts of single, usually dominant, species. Here we ask whether multiple, coexisting species of hydropsychid caddisfly larvae have different impacts on sediment mobility compared to single-species systems due to competitive interactions and niche differences. We manipulated the presence of two common species of net-spinning caddisfly (Ceratopsyche oslari, Arctopsyche californica) in laboratory mesocosms and measured how their silk filtration nets influence the critical shear stress required to initiate sediment grain motion when they were in monoculture versus polyculture. We found that critical shear stress increases non-additively in polycultures where species were allowed to interact. Critical shear stress was 26% higher in multi-species assemblages compared to the average single-species monoculture, and 21% greater than levels of stability achieved by the species having the largest impact on sediment motion in monoculture. Supplementary behavioral experiments suggest the non-additive increase in critical shear stress may have occurred as competition among species led to shifts in the spatial distribution of the two populations and complementary habitat use. To explore the implications of these results for field conditions, we used results from the laboratory study to parameterize a common model of sediment transport. We then used this model to estimate potential bed movement in a natural stream for which we had measurements of channel geometry, grain size, and daily discharge. Although this extrapolation is speculative, it illustrates that multi-species impacts could be sufficiently large to reduce bedload sediment flux over annual time scales in streams where multiple species of caddisfly are present.
Highlights
In most fields of natural science, the historical view has been that the abundance, distribution, and biological diversity of organisms are controlled by spatial and temporal variation in the abiotic environment [1,2]
A growing number of case studies have shown that biological structures must be incorporated into physical process models to predict the evolution of channel morphology and downstream movement of water, sediment, and nutrients [10,11,12]
We have demonstrated experimentally that silk nets from a multi-species assemblage of caddisfly larvae have the potential to generate non-additive increases in the critical shear stress required to initiate sediment transport during high flow events compared to single species monocultures
Summary
In most fields of natural science, the historical view has been that the abundance, distribution, and biological diversity of organisms are controlled by spatial and temporal variation in the abiotic environment [1,2]. A growing number of case studies have shown that biological structures (e.g., plant roots on riverbanks) must be incorporated into physical process models to predict the evolution of channel morphology and downstream movement of water, sediment, and nutrients [10,11,12]. A few studies have considered that natural habitats consist of a diverse assemblage of interacting species that must use their environment differently in space or time to coexist [14,15]. If coexisting species use their environment differently, and the biological structures created by these species impact processes that influence sediment motion, accounting for interactions among species will be essential to developing better predictive models of sediment transport
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
