A before-and-after assessment of patch-burn grazing and riparian fencing along headwater streams

Published source details Larson D.M., Dodds W.K., Whiles M.R., Fulgoni J.N. & Thompson T.R. (2016) A before-and-after assessment of patch-burn grazing and riparian fencing along headwater streams. Journal of Applied Ecology, 53, 1543-1553.
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Summary

Action: Use barriers to keep livestock out of ungrazed rivers/lakes

A replicated, randomized, controlled, before-and-after study in 2009–2013 of six stream reaches in Missouri, USA (Larson et al. 2016) found that fencing the riparian zone to exclude cattle moderated, but did not completely eliminate, increases in the abundance of algae growing on rocks. The study compared three different treatments: fenced (grazing in catchment but 20-m-wide riparian zones fenced to exclude cattle); unfenced (grazing in catchment with unfenced riparian zones) and ungrazed (no grazing in catchment). Grazing near to streams had a significant effect on algal abundance: it increased more over time in unfenced streams (before: 3–10; after: 5–18 µg chl a/cm²) than in ungrazed streams (before: 8–13; after: 5–16 µg chl a/cm²). Fencing somewhat mitigated this effect: changes in algal abundance in fenced streams (before: 2–7; after: 2–14 µg chl a/cm²) were statistically similar to the ungrazed streams. However, changes in algal abundance in the fenced streams also did not significantly differ from the unfenced streams. Methods: The study used six stream reaches, each within a separate prairie-dominated catchment (not burned or grazed since 2006). From April 2011, two random catchments received each fencing/grazing treatment (see above). Grazing involved approximately 0.8 calves/ha, between May and July. All catchments were also burned each April. Rocks were collected monthly to sample algae: before intervention (September 2009–March 2011) and after intervention (April 2011–July 2013). Algal abundance was determined from chlorophyll a.