Type 5 Streams and Small Wetlands Literature Review

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Riparian Ecosystem Management Study (REMS)


In 2001, the Washington State Department of Natural Resources (DNR) initiated a research project to experimentally test a range of forested buffer configurations on the ecological functions and wildlife habitat supported by small headwater streams in western Washington.

Small, non-fish bearing, often seasonal streams comprise an estimated 50% of the total length of streams on state lands in western Washington. Currently, the ability to evaluate the effectiveness of different approaches to forest management on the ecology of these streams and the possible downstream effects to fish-bearing streams is limited. This project examines the effects of different stream buffers in association with timber harvest on small headwater (1st order) streams in western Washington. The results are intended to provide a better understanding of what stream function(s) should be protected and the buffer configurations necessary to protect those functions.

Concurrent research studies examining the effects of different buffer configurations on the biotic and abiotic functions of these small streams are being conducted by the DNR; the USDA Forest Service, Pacific Northwest Research Station, Olympia Forestry Sciences Laboratory (OFSL); the Washington State Department of Ecology (ECY); and the University of Washington (UW). Response variables include:

  • litter fall input
  • aquatic invertebrates
  • instream fine particulate organic matter
  • riparian associated mollusks
  • stream-associated and terrestrial amphibians
  • small mammals
  • air and stream temperature
  • down woody debris
  • fish occurrence
  • stand composition
  • stream hydrology
  • water chemistry
  • nutrient export
  • soil processes

Nine study sites, including 34 streams, are being monitored on state lands in the Capitol State Forest and Pacific county. Pre-treatment sampling was conducted for 1 to 2 years and is now complete. Harvest treatments were applied over the course of several years from 2003 – 2005. Data collection is planned to occur at approximately year 1, year 3, year 5, and year 10 following harvest. Year 1 post-treatment data collection is complete; year 3 data collection is in progress.

DNR Type 5 Research Overview

To study the potential effects of different management approaches, several research and monitoring sites were selected in Western Washington on DNR-managed, state trust lands. The following key questions define the objectives of the project:

  • What specific Type 5 stream functions should be protected and how will these be measured?

  • How does timber harvesting affect Type 5 stream functions, i.e., sediment delivery, channel morphology, water chemistry, changes in plant communities, water levels and amphibian and invertebrate populations?

  • What are the options for protecting Type 5 stream functions within the scope of the DNR Habitat Conservation Plan riparian management strategy?

The study design imposed a range of management configurations on adjacent Type 5 streams. Three buffer configurations are being compared: continuous buffers, discontinuous buffers, and no buffers. An unmanaged basin will be used as a control (see Figure 1). The continuous buffer encompasses the entire length of the headwater stream. The discontinuous buffer encompasses “sensitive areas” such as seeps, springs, or small wetlands located along the stream or within the sub-basin. On a stream with no buffer, the entire Type 5 segment is harvested.

Riparian Buffer Treatments

Figure 1. Conceptual study design of riparian buffer treatments.

Major Study Elements

All data was collected before and after treatment, and is being compared within and among treatment sites.

Streamside Vegetation: Overstory and understory response, including changes in species abundance, diversity and stature, was measured using a set of permanent, randomly located plot arrays. Permanent, variable-radius overstory plots and fixed-area understory plots allowed comparisons through time. Permanent photo points were used to document ground conditions and quantify changes in canopy cover. Principle Investigator: Dr. Richard Bigley, DNR.

Down Woody Debris: Changes in the quantity and quality of woody debris, including volume per unit area, species, and decay class, were measured in and along the study streams using a set of permanent, randomly located line transects. This data also provided context for measurements of animal abundance and sediment storage in the stream channel. Principle Investigator: Dr. Richard Bigley, DNR.

Stream-dwelling amphibians: The abundance and diversity of stream-dwelling amphibians was measured in each stream reach. Target species included the tailed frog (Ascaphus truei), Cope’s giant salamander (Dicamptodon copei), Pacific giant salamander (Dicamptodon tenebrosus), Columbia torrent salamander (Ryacotriton kezeri), red-legged frog (Rana aurora), and Pacific tree frog (Pseudacris regilla). The primary sampling method was a low-impact spotlight survey. If variances are large, the rapid assessment method (Hayes et al 2001) may be added and visits to each stream will be conducted less frequently. Principle Investigator: Dr. Martin Raphael, Olympia Forestry Sciences Laboratory.

Stream-bank and terrestrial amphibians: The abundance and diversity of terrestrial amphibians was measured along each stream reach. Target species included the western red-backed salamander (Plethodon vehiculum), Ensatina (Ensatina escholtzii), Van Dyke’s salamander (P. vandykei), northwestern salamander (Abystoma gracile), and rough-skinned newt (Taricha granlulosa). These species were captured using pitfall arrays. An array consists of 18 traps spaced at 5-meter intervals and arranged in a zigzag pattern. One array was placed along each side of the stream within 2 meters of the primary stream channel, for a total of 36 traps per stream. Traps were set continuously from May to September each year. Principal Investigator: Dr. Martin Raphael, Olympia Forestry Sciences Laboratory.

Small mammals: The abundance and diversity of small mammals was measured along each stream reach. Target species included insectivorous, cricetine, and microtine mammals, such as shrews (Sorex spp.), moles (Scapanus spp.), deer mice (Peromuscus spp.), and voles (Clethryonomys spp. and Microtus spp.). Insectivores and some voles will be captured using pitfall arrays (as described above); voles and cricetines will be captured in live traps. Two live traps were placed within 2 meters of each pitfall; traps were set for 10 days during August each year. Principal Investigator: Dr. Martin Raphael, Olympia Forestry Sciences Laboratory.

Aquatic invertebrates and detritus: The abundance and diversity of aquatic invertebrates and the contribution of fine particulate organic matter to downstream fish-bearing waters was measured in each stream. Invertebrates and detritus were collected at 3 to 6 week intervals (depending on season) in drift nets installed at weirs located at the downstream end of each headwater channel. Organisms were identified to order, family, or genus. Detritus was dried and weighed. Results were expressed in units of weight per unit volume of water. Principal Investigator: Dr. Peter Bisson, Olympia Forestry Sciences Laboratory.

Litter input: The amount of forest litter deposited in the headwater streams or adjacent riparian zones was measured using an array of litter traps along each stream. Litter was collected every 30 days and sorted into its relative components (leaves, needles, twigs, etc.). Data was reported as litter biomass per square meter of stream or riparian zone. Principal Investigator: Dr. Peter Bisson, Olympia Forestry Sciences Laboratory.

Riparian mollusks: The abundance and diversity of mollusks (primarily snails and slugs) in riparian areas along each stream reach was measured using a combination of laminated cardboard “cover structures” and duff samples. Sample sites were arrayed in a grid along each headwater stream. Mollusk surveys took place in fall and spring. Principal Investigator: Dr. Joan Ziegltrum, Portland Forestry Sciences Laboratory.

Fishes: Fish abundance was measured in the downstream, fish-bearing segments into which the type 5 streams drain. Surveys looked for aggregations of fishes (primarily native trout and sculpins) near the mouths of the headwater streams, which would indicate that the streams contribute something of ecological importance (e.g., food organisms, cool water) to fishes in the receiving stream. The lowermost reaches of each stream were surveyed to determine if they were occupied seasonally, for example, during winter. All fish surveys were accomplished by backpack electrofishing. Principal Investigator: Dr. Peter Bisson, Olympia Forestry Sciences Laboratory.

Stream temperature: Stream temperature was measured at the downstream end of each headwater stream and in the receiving, fish-bearing stream to assess temperature affects resulting from discharge originating in small watersheds. Electronic temperature loggers (i-buttons) were placed above, at, and below the mouth of each small stream, and in the lowermost 50 meters of each Type 5 stream. Temperature monitoring was conducted from late spring to late fall to construct maps of temperature sensitivity and variation before and after treatments. Summer peak temperatures were evaluated to 303d thermal listing criteria for water quality impairment. Principal Investigator Dr. Peter Bisson, Olympia Forestry Sciences Laboratory.

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