Exploring the importance of autocorrelation in flow-ecology management, Associate Editor, Angela Strecker discusses the recent article by Bruckerhoff et al., Flow–ecology relationships are spatially structured and differ among flow regimes.

In ecology, it is widely accepted that stream flow is a master variable for fishes. Human alterations to rivers have changed the flow regime significantly, often dampening the natural variability and changing the timing of peak flows, among other changes.  Scientists have sought to link the ecology of fish species with the different components of the flow regime in order to develop water management guidelines, called environmental flows, which ‘describe the quantity, timing, and quality of freshwater flows and levels necessary to sustain aquatic ecosystems which, in turn, support human cultures, economies, sustainable livelihoods, and wellbeing’.

Little Mulberry Creek - Dan Magoulick, Arkansas Cooperative Fish and Wildlife Research Unit
Little Mulberry Creek, Arkansas. Photo by Dan Magoulick, Arkansas Cooperative Fish and Wildlife Research Unit.

Inherent in both biological and hydrological data is the phenomenon of spatial autocorrelation, where nearby sites tend to be similar.  For instance, species may have clumped distribution, or streams that are in close proximity may have a similar flow regime.  Ecologists have embraced the use of species traits as a way of identifying flow-ecology relationships but, until now, there has been little consideration of the importance of spatial autocorrelation in these relationships.  Bruckerhoff et al. used stream network models with and without spatial features to assess the importance of autocorrelation in flow-ecology relationships.  Critically, they conducted analyses at the regional scale, which is most appropriate for management.

Bleeding Shiner - Dustin Lynch, Arkansas Natural Heritage Commission
Bleeding Shiner, an opportunistic life history strategist. Photo by Dustin Lynch, Arkansas Natural Heritage Commission.

Using species data from the Arkansas GAP Analysis at over 300 sites, the authors concluded that spatial structure comprised a large component of the variation in the relationship between fish traits and hydrology.  However, the degree of importance depended on the flow regime; with differences between runoff, intermittent and groundwater dominated streams, as well as the traits, being considered.  The authors suggest that scientists and managers consider these differences between flow regimes when planning data collection and developing flow-ecology relationships.

Read the full article, Flow–ecology relationships are spatially structured and differ among flow regimes in Journal of Applied Ecology.