ARS | Publication request: Defoliation Impacts on Above and Below-ground Production in a Riparian Sedge Community

Submitted to: Extension Reports
Publication Type: Experiment Station
Publication Acceptance Date: May 1, 2008
Publication Date: June 1, 2008
Citation: Boyd, C.S., Svejcar, A.J. 2008. Defoliation Impacts on Above and Below-ground Production in a Riparian Sedge Community. Extension Reports. Range Field Day 2008 Progress Report. Oregon State University Agricultural Experiment Station, Special Report 1085. Burns, OR. pp. 3-819-23.

Interpretive Summary: In spite of the interest in grazing impacts on riparian systems, there is limited information on root response of riparian sedges to grazing. We evaluated both above-ground and below-ground productivity during 2004 – 2005 in plots clipped in either June or July to a 10.2 cm stubble height in a sedge-dominated riparian community. Clipping treatments slightly reduced season-long above-ground production and root production was reduced in 1 of the 4 treatment combinations (year x month of defoliation). Our results indicate that root production is resilient to moderate levels of defoliation during the growing season and suggest that grazing to a 10.2 cm stubble height will not substantially reduce below ground production.

Technical Abstract: In spite of the interest in grazing impacts on riparian systems, there is limited information on root response of riparian sedges to grazing. We evaluated both above-ground and below-ground productivity in plots clipped in either June or July to a 4 inch stubble height. The study was designed as a randomized block with 4 replications and conducted during 2004 and 2005. Root ingrowth cores were used to harvest annual root growth, and plots were clipped to estimate above-ground end-of-season standing crop. Water tables were higher in 2005 for most of the growing season. Clipping treatments reduced end-of-season above-ground standing crop, but season-long production (clipped mass + end-of-season mass) was less impacted by clipping treatment. Root mass was only reduced by the July 2005 clipping treatment, and root length density was not significantly impacted by any treatment. In our study, root abundance was very high and resilient to clipping treatments.