You are here:
Watershed Land Use and Seasonal Variation Constrain the Influence of Riparian Canopy Cover on Stream Ecosystem Metabolism
Citation:
Alberts, J., J. Beaulieu, AND I. Buffam. Watershed Land Use and Seasonal Variation Constrain the Influence of Riparian Canopy Cover on Stream Ecosystem Metabolism. ECOSYSTEMS. Springer, New York, NY, 20(3):553-567, (2017).
Impact/Purpose:
Little is known about how watershed and local scale controls interact to determine stream metabolic rates, or how the controls vary across seasons. The purpose of this study was to measure ecosystem metabolism in four urban and four reference streams during all four seasons of the year. This study is important because it reinforces the idea that the preservation and restoration of trees near rivers and streams may be an important tool in managing urbanized watersheds. This research would be relevant to other researchers and planners involved in watershed management.
Description:
While watershed and local scale controls on stream metabolism have been independently investigated, little is known about how controls exerted at these different scales interact to determine stream metabolic rates, or how these interactions vary across seasons. To address this knowledge gap, we measured ecosystem metabolism in four urban and four reference streams in northern Kentucky, USA, with paired closed and open riparian canopies, during each of the four seasons of the year. Gross primary production (GPP), ecosystem respiration (ER), and net ecosystem production (NEP) were all best predicted by models with season as a main effect, but interactions between season, canopy and watershed varied for each response. Urban streams exhibited higher GPP during most seasons, likely due to elevated nutrient loads. Open canopy reaches in both urban and forested streams supported higher rates of GPP than the closed canopy reaches during the summer and fall when the overhead vegetation shaded the closed reaches. Surprisingly, the effect of canopy cover on GPP was similar among urban and forested streams. The combination of watershed and local-scale controls resulted in urban streams that alternated between net heterotrophy (NEP 0) between seasons with and without dense canopy cover. This finding has management relevance because net production can lead to accumulation of algal biomass and associated issues like dissolved oxygen sags at night. Our study reinforces the idea that the preservation and restoration of canopied riparian zones may provide an important management tool in urbanized watersheds.
