|Testa, Sam - Sam|
|Shields Jr, Fletcher|
|COOPER, CHARLES - Retired ARS Employee|
Submitted to: Ecohydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/27/2010
Publication Date: 8/25/2010
Citation: Testa III, S., Shields Jr., F.D., Cooper, C.M. 2011. Macroinvertebrate response to stream restoration by large wood addition. Ecohydrology. 4:631-643. DOI:10.1002/eco.146.
Interpretive Summary: Small streams that have cut down 15 feet or more below their original depth are generally non-productive. Current federal regulations require that streams and lakes should be “healthy” enough to support appropriate forms of life. Knowing how to improve degraded streams requires projects that test methods which bring about stream restoration. The aquatic animals, especially insects, found in streams provide a good indicator of stream conditions that support life and how these conditions change as we attempt to improve flowing water. We found that watershed improvement is essential to improving downstream water. Streams must be stable and not subject to natural events such as major flooding before improvements like addition of large woody debris (a major component necessary for many animals) will work. Results from this research will assist farmers, watershed managers, water district personnel, and state agencies who are responsible for recommending stream improvements to meet regulatory requirements, and federal action agencies, including the USDA-NRCS, USDA-Forest Service, and US-EPA.
Technical Abstract: Channel incision processes resulting primarily from channel straightening/dredging and watershed deforestation have been among the most profound degradations in our streams. Physical changes to streams affected by channel incision processes have included significant increases in streambed degradation by deepening, channel widening and a resulting unstable, migrating substrate. We examined the aquatic macroinvertebrate community in a severely degraded, incised small stream in the hill lands of north central Mississippi as it responded to the placement of introduced wood and associated construction stresses. Seventy-four large woody debris structures composed of >1,100 trees were constructed to stabilize the channel and stimulate distinct changes in habitat. Community response to construction and insertion of wood was super-imposed on harsh extremes associated with incised streams. While the number of invertebrates collected before and after construction changed very little, there was a large shift in taxa composition with only moderate similarity between communities before and after placement of large woody debris. Before and after construction comparisons of abundance revealed increases in filtering and gathering collectors and decreases in predators, scrapers and shredders when Chironomidae were excluded. Probable cause was linked to absence of debris dams, leaf packs, and total organic carbon after completion of large woody debris structures. Improvements from addition of wood were temporary. Without creation of suitable stable habitat and lack of available sources for drift or immigration, recovery was limited. Extremes in discharge as shown by frequent "reset" kept the stream from reaching equilibrium. Study results showed that restoration efforts must reach a habitat improvement threshold which includes watershed and upstream improvements before significant long-term improvement can occur.