Removal of Woody Riparian Vegetation Substantially Altered a Stream Ecosystem in an Otherwise Undisturbed Grassland Watershed
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Riparian zones are key interfaces between stream and terrestrial ecosystems. Yet, we know of no whole-watershed experiments that cut only woody vegetation in the riparian zone in an otherwise intact watershed to isolate the role of riparian zones on stream ecology. We removed all of the woody riparian vegetation (from 10- and 30-m-wide buffers in headwaters and main channels, respectively) for 5 km of stream in a single watershed while leaving the remainder of the grassland watershed un-impacted. We assessed water chemistry changes 3 years before and 3 years after riparian wood removal and in two neighboring control watersheds with a before–after, control-impact design and analysis. Riparian woody removal caused 10–100-fold increases in mean stream water nitrate concentrations and pulses of high nitrate for 3 years thereafter. Other nutrients and total suspended solids increased 2–25 times for the 3 years of post-removal. In-stream rates of gross primary production, ecosystem respiration, and net ecosystem production had large treatment effect sizes but also high variance among samples. Past studies of whole-watershed deforestations showed similar water quality responses to our riparian deforestation. Riparian zones of grassland streams are sensitive to disturbance and likely impart relatively greater influence on stream structure and function than the upslope of the watershed. Our results further emphasize the role of riparian zones in biogeochemically linking aquatic and terrestrial habitats.
Keywordsdisturbance prairie restoration prairie stream riparian buffer water chemistry whole-stream metabolism woody encroachment woody removal
We thank the National Science Foundation (DEB-0218210, DEB-0823341) and Kansas State University for funding. We are very grateful for the numerous staff and volunteers that assisted with the back-breaking woody removal. Thanks to A. Kuhl and students who collected water samples and R. Ramundo for running analyses. This is publication no. 18-396-J from the Kansas Agricultural Station.
- Ameel J, Axler R, Owen C. 1993. Persulfate digestion for determination of total nitrogen and phosphorus in low-nutrient waters. Am Environ Lab 10:1–11.Google Scholar
- APHA. 1995. Standard methods for the examination of water and wastewater. 2nd edn. New York: American Public Health Association.Google Scholar
- Cohen J. 1977. Statistical power analysis for the behavioral sciences. revised edn. Orlando, FL: Academic Press.Google Scholar
- Hamilton L, King P. 1983. Tropical forested watersheds: hydrologic and soils response to major uses or conversions. Boulder: West View Press.Google Scholar
- Knight C, Briggs J, Nellis M. 1994. Expansion of gallery forest on Konza Prairie research natural area, Kansas, USA. Landsc Ecol 9:117–25.Google Scholar
- Rowe P. 1963. Streamflow increases after removing woodland-riparian vegetation from a southern California watershed. J For 61:365–70.Google Scholar
- Webster J, Tank J, Wallace J, Meyer J, Eggert S, Ehrman T, Ward B, Bennett B, Wagner P, McTammany M. 2000. Effects of litter exclusion and wood removal on phosphorus and nitrogen retention in a forest stream. Verhandlungen des Int Verein Limnol 27:1337–40.Google Scholar
- Zimnierman RJ, Goodlett GC. 1967. The influence of vegetation on channel form of small streams. In: Symposium on River Morphology. pp 255–75.Google Scholar