The Use of Plastic Strips to Measure Leaf Retention by Riparian Vegetation in a Coastal Oregon Stream

Abstract

The feasibility of using strips of plastic instead of leaves for estimating the rate of retention of coarse particulate organic matter (CPOM; >1 mm in diam) in streams was tested by simultaneously measuring retention of leaves and strips of plastic cut to approximately the same size as the leaves in six third-and fourth-order streams. There was no significant difference in the retention rates between the two methods when all six study reaches were considered together, nor was there a difference in the location of retention of leaves and strips of plastic within a reach. However, the retention rate of plastic strips was significantly higher than that of leaves in the two reaches with the highest flows. Plastic strips were used to assess the importance of shrubby riparian vegetation in retaining CPOM in a third-order stream. The density of streamside shrubs was reduced to approximately 60% and 0% of naturally occurring levels, and retention was measured by releasing known quantities of plastic strips into the stream. Retention was highest in the reaches where shrub densities were not reduced, intermediate in reaches that were thinned, and lowest in reaches where shrubs had been completely removed. Riparian vegetation was directly or indirectly responsible for 68% of the retention in the cleared reaches, 79% of the retention in the thinned sections and 84% of the retention in the control reaches.

Comparison of coarse particulate organic matter retention in meandering and straightened sections of a third-order New Zealand stream

“…Snags were the dominant retentive structures, supporting the findings of Speaker et al (1988) who found sticks, roots and stems (all considered as snags here) as the most important retention structures of plastic strips. While being the dominant retention structure in both section types, snags were responsible for trapping a greater proportion of CPOM in meanders.…”

“…In our study paper strips were good proxies of the Eucalyptus leaves as similar proportions were retained with similar drift distances. Speaker et al (1988) found the retention rates and properties of Ginkgo leaves and plastic strips were similar in small streams, but few other studies have compared the retention of artificial versus actual leaves. Of the two different dowel CPOM types, the 200 mm lengths were retained more than the 100 mm lengths.…”

Leaf transport and retention in a high gradient stream

“…Various techniques have been used to make the released leaves distinguishable from natural leaves, including marking the leaves with dye or paint (Jones and Smock, 1991;Chergui et al, 1993), using artificial replacements such as plastic strips or wooden dowels (Speaker et al, 1988;Webster et al, 1994), or using a leaf species absent from the study site (Ehrman and Lamberti, 1992). An alternative method is to release leaves individually and then to follow them until they are retained or reach the end of the study reach.…”

Forestry and the aquatic environment: studies in an Irish context

“…The overall effect is a significant enhancement of habitat heterogeneity in the stream system. The altered characteristics of stream channels with significant woody debris (especially complex arrays of different sizes) also has the potentially positive effects of increasing retention of allochthonous matter (Speaker et al, 1988;Gregory et al, 1991), and hence invertebrate production. Additionally fish populations may benefit from provision of low-velocity refuges, profitable feeding positions and visually isolated or sheltered cover from competitors and predators, hence positive relationships have been demonstrated between debris and salmonid density or productivity (Bisson et al, 1987;Inoue and Nakano, 1998;Lehane et al, 2002).…”