CPOM Transport, Retention, and Measurement

CHAPTER 13

CPOM Transport, Retention, and Measurement Gary A. Lamberti∗ and Stanley V. Gregory† ∗ Department of Biological Sciences University of Notre Dame †

Department of Fisheries and Wildlife Oregon State University

I. INTRODUCTION Coarse particulate organic matter, or CPOM, in streams is defined as any organic particle larger than 1 mm in size (Cummins 1974). CPOM can be further divided into wood and nonwoody material (Cummins and Klug 1979), both of which are considered in this chapter. Wood includes all size classes from branches to entire trees that fall into stream channels. Wood can form impressive dams or accumulations across stream channels, which have important ecological functions (Bilby and Likens 1980). The nonwoody fraction includes allochthonous materials donated by riparian vegetation (e.g., leaves, needles, fruits, flowers, seeds, insect frass) and autochthonous materials produced within the stream (e.g., fragmented aquatic plants, dead aquatic animals). Smaller materials, including fine particulate organic matter (1 mm > FPOM > 045 m) and dissolved organic matter (DOM < 045 m), are discussed in Chapters 11 and 12. Allochthonous CPOM is a major energetic resource for stream ecosystems, providing a large proportion of the fixed carbon in small streams of both deciduous and coniferous forests and a significant input to larger streams and rivers (Vannote et al. 1980, Cummins et al. 1983). CPOM that enters streams is transported downstream by the unidirectional flow of lotic ecosystems, with very few mechanisms for upstream movement. Trapping of this material is therefore essential for the subsequent microbial colonization that normally precedes consumption by shredding macroinvertebrates (Cummins and Klug 1979). Methods in Stream Ecology

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The process of deposition and trapping, termed retention, provides the critical link between input and the long-term storage and processing of CPOM. The retentive capacity of streams for CPOM is a function of hydrologic, substraterelated, and riparian features (Speaker et al. 1984). High roughness of the channel (e.g., large substrate particle size, streambed heterogeneity, abundant wood), combined with certain hydraulic conditions (e.g., presence of backwaters, interstitial flow), tends to increase the CPOM trapping efficiency of stream reaches. Wood dams are particularly important retention structures (Bilby 1981, Smock et al. 1989). Young et al. (1978) noted that the probability that a particle in transport will be retained is a function of the “active” entrainment efficiency of that particle size by a channel obstacle (e.g., rock, log, root, etc.) and the density of those obstacles within the channel. Particles also will be retained “passively” when current velocity is less than the velocity required to keep the particle moving in the water column or along the streambed (Jones and Smock 1991) and thus the particle “settles”. Retention (R) can thus be expressed as a probability function:

PR = f E N V 

(13.1)

where E = entrainment efficiency by channel obstacles, N = obstacle density in the channel, and V = critical velocity required to transport a particle. If an organic particle is retained, it subsequently will either decompose, be consumed, or, if flow conditions change, be dislodged and transported further downstream (Speaker et al. 1984). Wood is a major roughness element in streams that influences channel morphology, decreases the average velocity within a reach, and physically traps material in transport (Lamberti and Berg 1995, Gregory et al. 2003a, Montgomery et al. 2003, Mutz 2003). The amount of wood (W ) in a stream channel is a function of the lateral input from the riparian forest (Fin ), transport into a reach from upstream (Tin ), biological decomposition (D), mechanical abrasion (A), and transport out of the reach to downstream areas (Tout ):

W = f Fin  Tin  D A Tout 

(13.2)

Causal factors for amounts of wood measured locally in a stream reach cannot be determined from simple inventories. Long-term measurements of input rates, sources, breakdown rates and transport can provide the information necessary to interpret local wood abundance, but such extensive studies are costly and time consuming. An alternative to measuring all physical and biological processes that affect storage of wood is simulation modeling. At least 14 models of wood dynamics have been developed for different regions (Gregory et al. 2003b). Some models address specific processes, whereas others provide quantitative representations of riparian forest growth and mortality, input processes, disturbance processes, and in-channel processes that modify wood storage. Studies of large wood and its influence on CPOM retention may require use of a regionally relevant model of stream wood dynamics (e.g., see example from the U.S. Pacific Northwest later

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in this chapter). Several models offer the ability to alter the critical parameters in the model so that the user can adapt the model to different tree species, flow regimes, and channel structure. In this chapter, we describe a quantitative field method to assess the CPOM retention efficiency of a specific stream reach. The method is most easily used in small streams (orders 1–4) but can be adapted for larger streams and rivers. The approach is intended not only to measure retention but to relate retention to hydraulics, streambed roughness, channel geomorphology, and riparian zone structure. Because large wood in the channel is central to CPOM retention, we also present two methods to quantify the abundance of large wood in stream reaches. Finally, we illustrate the application of a publicly available model to explore the dynamics of large wood under differing forest management scenarios. Our specific objectives are to (1) introduce the concept and importance of organic matter retention; (2) demonstrate how to measure retention, analyze data, and calculate indices of retention; (3) illustrate the utility of retention measurements for assessing stream channel condition; (4) describe the direct count and line-intersect methods for estimating large wood abundance in stream channels; and (5) demonstrate the use of a simulation model for wood input and dynamics. Note that this chapter focuses on short-term trapping of CPOM and does not consider its long-term storage or breakdown except in a modeling context (but see Chapters 30 and 31). Also, we do not describe benthic sampling of CPOM, sometimes referred to as coarse benthic organic matter (CBOM), because detailed methods are presented in Chapter 31. However, benthic sampling of CPOM can augment the exercises below because storage is the ultimate expression of transport and retention.

II. GENERAL DESIGN In practice, lotic retention can be viewed as the difference between the number of particles in transport at a given point in the stream and the number still in transport at some known distance downstream (Speaker et al. 1984). Retention is most easily measured by releasing known numbers of readily distinguishable particles into the channel. To compare different stream reaches within a study, the experimental approach must be standardized for type and number of particles released, length of experimental reach, and duration of the retention measurement. Many types of CPOM have been released into streams, including leaves (Speaker et al. 1984, Ehrman and Lamberti 1992), paper shapes (Webster et al. 1994), plastic strips (Bilby and Likens 1980, Speaker et al. 1988), wood dowels (Ehrman and Lamberti 1992), and even fish carcasses (Cederholm et al. 1989). In general, we believe that it is preferable to release natural (decomposable) materials into streams because particle retrieval is almost always less than 100% and because analogs (e.g., plastic items) may not behave the same as natural materials. In this chapter, we will demonstrate retention of leaves and small wood, but other materials significant to the specific stream can be substituted. For example, fruits are significant CPOM inputs in many tropical streams. We will also describe methods for quantifying the abundance of large wood, which provides important sites for CPOM retention, and modeling wood dynamics with simulation approaches.

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A. Site Selection The selection of a study stream in which to conduct this exercise may be influenced by logistical considerations. In general, wadeable third- to fourth-order streams are ideal. Very small streams at low flow have low transport, and the method described in this chapter is difficult (and can be dangerous) to conduct in large rivers. In general, however, this method can be scaled to a wide variety of stream sizes. Within the study stream, at least two reaches with contrasting channel features should be selected by the research coordinator. Ideally, one reach would have a relatively simple channel (straight, low roughness, limited hydraulic diversity, sparse wood) whereas the other reach should have a complex channel (sinuous, high roughness, diverse hydraulic conditions, abundant wood). Length of the experimental reach should be scaled to stream size, with length increasing with stream order. As a rule of thumb, start with a stream length that is ∼10 times the wetted channel width. For example, 50 m may be an appropriate length for a second-order stream, 100 m for a third-order stream, and 200 m for a fourth-order stream. Streams of the same size in different settings will have specific retention characteristics. If possible, use a pilot study to adjust reach length such that retention is not less than 10% nor greater than 90% of released particles.

B. Basic Method Leaves are the major form of nonwoody CPOM input to most streams and their retention is an important ecological process (Webster et al. 1999). In retention experiments, released leaves must be distinguishable from leaves found naturally in the channel and should be easy to obtain and manipulate. We have found that, for North American streams, abscised leaves of the exotic Asian ginkgo tree (Ginkgo biloba) meet these requirements. The leaves are tough even when wet, their size approximates that of many leaf-types of riparian vegetation, and the bright yellow leaves are easily spotted in the channel. Ginkgo trees have been planted worldwide as ornamentals (and very often on college campuses), which usually are male trees because female trees drop unpleasantly pungent fruits in the autumn. Other species of leaves can be substituted depending on their availability and the composition of local riparian vegetation. Released wood similarly must be easy to manipulate, distinguishable from natural wood in the channel, and of a realistic size. We have found that these requirements are met by wood dowels, which can be obtained at hardware stores in a range of diameters and lengths. Dowels, however, have a simpler shape than tree branches and will be a conservative estimator of wood retention. Alternatively, fallen branches can be collected from the site and marked with fluorescent paint to distinguish them from existing wood in the channel. Keep in mind that it is more difficult to standardize branches among releases than dowels. Physical data from the stream channel should be analyzed according to the level of measurements taken (see Chapters 2–4). At a minimum, the following parameters should be measured for each study reach: discharge, slope, sinuosity, cross-sectional area, planar wetted area, and volume of large wood (using direct counts or the line-intersect method). Retention data for leaves and small wood (using batch releases) should be fit to a negative exponential decay model, from which various indices of retention (e.g., the retention coefficient -k; average particle travel distance 1/k) can be calculated. Metrics for individual particle releases can be generated using simple statistics. If desired, CPOM releases can be conducted over longer periods of time, or at different seasons and discharges, to develop relationships between retention and stream temporal dynamics (e.g., Jones and Smock 1991, Webster et al. 1999).

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C. Advanced Methods Several advanced exercises involving additional sophistication, time, and facilities are also presented in this chapter. These are “research-level” approaches suitable for incorporation into published papers. First, an inventory of leaf and dowel entrapment in the channel can be performed after the release to better describe the pattern of retention and to quantify entrapment by specific benthic features. Second, we describe how basic hydraulic features of the channel can be described with slug releases of conservative solutes into the stream. Third, the dynamics of large wood will be modeled with simulations using a publicly available computer model. If desired, different levels of physical measurement of the channel can be performed (see Chapters 2–4), although these are not presented in this chapter. CPOM retention often is correlated with hydraulic retention (i.e., the retention of water within a reach). Hydraulic retention and discharge can be estimated by releasing a tracer, such as fluorescent dye, as a “slug” into the channel and measuring water movement and dilution through the reach. Discharge calculated from tracer releases and more conventional approaches can be compared (see Chapter 3). The use of tracers that are more conservative than dyes (e.g., chloride) is described in Chapters 8 and 10, along with more sophisticated continuous injections than are presented here. If dye slug releases are conducted, various hydraulic parameters (e.g., discharge, nominal transport time) can be calculated from a plot of dye concentration over time at a downstream sampling site.

III. SPECIFIC METHODS A. Basic Method: CPOM Transport and Retention Laboratory Preparation 1.

In the autumn, collect several thousand abscised leaves of an exotic tree, such as Ginkgo biloba, or other readily identifiable species. Air-dry the leaves by spreading them over screens, netting (seines work well), or even on the floor. Leaves can be stored dry in black garbage bags for a considerable length of time. Alternatively, you can use fresh-fallen leaves if the releases will be performed soon after collection (within days). 2. Count out two batches of 1000 leaves, used to conduct two releases in a third-order stream. Smaller or larger streams may require fewer or more leaves, respectively. The actual number of leaves is less important than knowing exactly how many are released. 3. The day before the release, soak leaves overnight in buckets of water to impart neutral buoyancy during transport. A soil sieve placed gently over the leaves will help to keep them submersed. Drain most of the water before departing into the field. 4. Obtain 60 wood dowels, each approximately 1.5 cm in diameter and 1 m in length; 50 dowels will be used in a single release, and recycled in subsequent releases. (Note: Other dowel sizes, or wood chips, can be used to test retention of variously sized CPOM.) Alternatively, natural sticks can be collected on site from the riparian zone before the release. These sticks can be marked with a spot of fast-drying spray paint to distinguish them from other wood.

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Field Physical Measurements 1.

Measure and flag an appropriate length (e.g., 100 m for a third-order stream) of at least two stream reaches differing in channel complexity, large wood abundance, or some other relevant feature. Stretch a meter tape along the bank over the length of the reach, with 0 m at the downstream end. 2. Measure major channel features at a level of intensity appropriate to the research objectives. We recommend working in a research team of three people (two making measurements and one recording data). Minimally, measurements should include slope, channel cross section, average width, depth, sinuosity, and substrate composition. Determine discharge using the cross-sectional approach (see Chapter 3). Repeat for each reach. 3. Measure the length (L) and average diameter (D) of all wood contacting the channel and larger than a minimum size (e.g., 1 m L × 10 cm D; Figure 13.1). Note if the wood is part of a dam (i.e., wood accumulation blocking some portion of stream flow). Option 2 to the Basic Method (below) describes an alternate estimation approach if wood is extremely abundant.

Direct Count Method

Large wood volume: m3/m2 = Σ(πLr2)/A

Line Intersect Method

Large wood volume: m3/m2 = π2Σd2/8L

FIGURE 13.1 Methods for measuring large wood in stream channels: Top: direct count method with formula for volume estimation; Bottom: line-intersect method with formula for volume estimation. (Illustrations by J. Miesbauer.)

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If this method is being used for a class demonstration, prior to the releases briefly discuss channel and riparian features. Have students predict retention for each reach (e.g., percentage of leaves that will be retained).

CPOM Releases 1.

Position several researchers at the downstream end of the study reach. Release the leaf batch (e.g., 1000 leaves) at the upstream end of the reach (e.g., 100 m mark) by dispersing leaves over the entire width of the stream channel over a span of about one minute (Figure 13.2A). 2. Collect nonretained leaves at the downstream end of the reach (0 m). Either of two approaches can be used to collect leaves. A beach seine can be stretched across the width of the channel (Figure 13.2D), with the bottom lead-line anchored, without gaps, to the streambed with rocks (in sand-bottom streams, tent stakes can be substituted for rocks). The top of the seine should be held out of the water by attaching it to a taut rope tied to trees on both banks. In strong flows, it may be further necessary to support the top and rear of the seine with wood pieces driven into the substrate. Alternatively, researchers can line up across the channel and collect leaves in transport with handheld dip nets (e.g., D-frame or delta nets). The seine method is more efficient, especially if the number of researchers is low. The

A

B

C

D

FIGURE 13.2 Photographs of (A) Ginkgo biloba leaf release into an Oregon stream, (B) wood dowel collection following release in a Michigan stream at high flow, (C) fluorescein dye release into an Indiana stream, and (D) beach seine stretched across the channel of a northern Alaska stream (anchored to the bottom with rocks) for capturing unretained leaves. (Photos by G. Lamberti.)

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individual netting approach results in greater involvement of researchers in actual leaf collection, but some leaves may be missed. 3. Continue collecting leaves for a period of time specified by the coordinator, usually at least 15 minutes and up to 1 hr, or when leaf transport ceases. Release interval should be consistent for all reaches. Count all collected (i.e., nonretained) leaves. 4. Release 50 dowels or sticks into the stream channel and hand-collect nonretained wood at the downstream end of the reach (Figure 13.2B). Count nonretained wood pieces. Retrieve retained dowels from the channel at the end of the exercise. 5. Move upstream to the next reach and repeat the procedure.

Data Analysis 1.

Calculate reach physical parameters, such as slope, planar surface, cross-sectional area, mean depth, current velocity, hydraulic radius, sinuosity, and discharge (see Chapters 2–4). These fundamental physical parameters can be related empirically or theoretically to observed retention values. 2. Determine the density (pieces per reach) and total volume (in m3 ) of wood in each reach, assuming that a cylinder approximates the geometry of a log such that:

volume = Lr 2

(13.3)

where L is the length of the piece (m) and r is the radius (m), and then summing for all wood pieces in the reach. Alternatively, you can calculate the volume of wood (m3 ) per unit area (A, in m2 ) of stream channel:

volume per unit area = Lr 2 /A

3.

(13.4)

Fit the leaf and stick retention data to a negative exponential decay model of the form:

Pd = P0 e −kd

(13.5)

where P0 = number of particles released into the reach and Pd = number of particles still in transport at some downstream distance d from the release point. Calculate the slope −k (the instantaneous retention rate) and its reciprocal 1/k (the average distance traveled by a particle before it is retained). If particles are not inventoried after the release, then the model will be based on two data points, P0 and Pd . See Advanced Method 1 for data analysis if particles were re-inventoried in the channel.

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Option 1 to Basic Method: Single Particle Release Method 1.

As an alternative to batch releases of particles described above, the single-particle release method can be used (Webster et al. 1994). Single particles (e.g., leaves, sticks) or artificial analogs (e.g., “Rite-in-the-Rain” field paper, cut into consistent shapes) are released into the channel and individual travel distances are recorded. 2. Release a known number (e.g., 25–50) of visible particles one-by-one into the channel and record the distance traveled and retention structure for each particle. Repeat this procedure in as many stream reaches, or sub-reaches, as desired. Mean travel distances can be compared statistically among reaches using ANOVA, or relationships with stream characteristics such as discharge can be explored with regression (e.g., Webster et al. 1994, 1999). 3. This approach is especially useful in highly retentive streams where few or no particles may travel the entire stream reach, thereby invalidating the exponential decay model. However, this method requires relatively high water clarity and shallow depths to follow individual particles for their entire travel.

Option 2 to Basic Method: Line-Intersect Estimation of Large Wood 1.

The line-intersect method (LIM) can be used in place of direct counts of large wood in streams having high volumes of wood. For LIM, diameters are measured for all pieces of wood intersecting multiple line transects placed perpendicular to the longitudinal axis of flow (Figure 13.1). LIM was designed to estimate wood on the forest floor (DeVries 1974, Van Wagner 1968), but recently has been adapted for both small streams (Wallace et al. 2001) and large rivers (Wallace and Benke 1984, Benke and Wallace 1990). 2. In each study reach, use a tape measure to establish a transect every 5 or 10 m perpendicular to streamflow. Measure the diameter of all large wood pieces intersecting the transect line, using log calipers if available. 3. Compute the wood volume per unit area (m3/m2 ) for each transect using the following equation:

volume =  2



d 2 /8L

(13.6)

where d is the diameter of a wood piece (m) and L is the length of the transect line (m) across the stream (Van Wagner 1968). To estimate the average large wood volume (m3/m2 ) for a reach, sum wood volumes for each transect and then divide by the total number of transects. 4. In large rivers or in streams with large amounts of wood, LIM may reduce the effort required to estimate large wood volume. However, LIM may overestimate or underestimate the actual large wood volume, determined by direct counts, depending on stream characteristics and large wood distribution (Wallace et al. 2001, Miesbauer 2004).

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Option 3 to Basic Method: Long-term CPOM Retention and Transport 1.

Conduct CPOM release as in described above, but with one or more of the following modifications. 2. Release dowels over a time span of several weeks or months, depending on the stream and research objectives. 3. Inventory the location of dowels in the channel, but leave them in place and reinventory after varying periods of time. Different sizes of wood also can be released. Year-classes of wood can be marked differently, permitting year-to-year evaluation of transport. Additional releases of leaves and wood can be conducted in different seasons or at different discharges to describe more precisely the temporal dynamics of retention.

B. Advanced Method 1: Importance of Different Retention Structures 1. 2.

Conduct CPOM release as in the Basic Method above. Inventory the location, number, and retention structure for retained leaves and wood. This is best accomplished by dividing the reach into longitudinal increments of 5 m using the bankside meter tape. 3. Researchers should move up the channel as a single line of observers, perpendicular to flow. 4. Leaves are located and counted within each increment, noting also the retention structure (e.g., rock, wood, bank, etc.; see Table 13.1). Released wood can be inventoried simultaneously and then removed for re-use. 5. The inventory data can be used to refine the exponential model and produce a more accurate estimate of -k, or to fit retention data to an alternate regression model (e.g., linear, power) more appropriate for the specific reach. The inventory most likely will not turn up all of the retained leaves; therefore, it is necessary to normalize inventory data to a percent of total leaves found. Graph the particle transport data for each release, using distance downstream from the release point as the x-axis and percent of particles still in transport as the y-axis (see Ehrman and Lamberti 1992 for examples). Using a bar diagram, plot the percentage of leaves or dowels retained by specific channel structures in each reach. Describe the longitudinal pattern of retention and identify important retention structures within the channel.

C. Advanced Method 2: Hydraulic Characterization Using Dye Releases 1.

Carefully and accurately weigh several batches of fluorescent dye (e.g., 1.0 g of fluorescein powder or rhodamine-WT liquid) into scintillation vials. Number a set of empty scintillation vials from 1 to 100. 2. Qualitatively estimate the amount of dye to be released (1.0 g is appropriate for about 025 m3/s discharge—about a third-order stream). Thoroughly dissolve the dye in a small volume of water (e.g., 1 L). Release the dye slurry at the upstream end of the reach into a constricted, turbulent zone, if available, to ensure rapid mixing

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TABLE 13.1 Sample Data Sheet for Inventory of Retained CPOM Particles. POM Type:

Stream:

Date: Team:

Location: Total Released:

Reach:

Notes:

Length: Total Captured:

Duration:

Total Retained: Location

Unit

Meter Mark

Riffle or Pool

Number of particles retained on structure Rocks

Roots

Backwater

Bank

Wood

Debris Dam

0–5 5–10 10–15 . . . 95–100

of the dye with the stream water (Figure 13.2C). In slower moving water, dispense the dye evenly across the stream channel. Position researchers at the downstream end of the reach with the numbered scintillation vials, a stopwatch, and a notebook. 3. At the downstream end of the reach, the dye concentration curve must be measured accurately by taking water samples as the plume passes through the reach. Commence sampling of water from the thalweg (main thread of flow) in the numbered scintillation vials immediately following the release. Sampling frequency and duration will depend on transport time related to stream size, reach length, and channel geomorphology. We recommend that water samples be drawn every 5 seconds as the dye plume passes through the downstream end of the reach. The interval between samples can be lengthened for the trailing edge of the plume. Continue sampling even after visible dye has passed from the reach and until the coordinator indicates to stop (e.g., 5–10 min in a third-order stream). Record elapsed time with each numbered water sample (see Table 13.2). 4. In the laboratory, calibrate a fluorometer with a standard concentration series of the released dye (within the expected dilution range, such as 0.1, 1, 10, and 100 g/L. Measure and record dye concentration in each water sample using the fluorometer. Dilute samples if dye concentration exceeds your calibration curve.

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TABLE 13.2 Sample Data Sheet for Conducting Hydraulic Retention Study. Stream:

Dye:

Date:

Location:

Concentration:

Team:

Reach:

Volume:

Notes:

Length: Elapsed Time (min:sec)

5.

Vial Number

0:0

1

0:5

2

0:10

3

.

.

.

.

.

.

5:00

n

Dye can be used to calculate several hydraulic parameters, of which we will discuss discharge and transport time. Discharge (Q, in L/s) can be calculated from dye dilution using the equation:  Q = VCu / Cd −Cb dt

(13.7)

where V = volume of dye released in L, Cu = concentration of released dye in g/L, Cd = instream dye concentration at time t in g/L, and Cb = background fluorescence in g/L. In general, Cb effectively will be zero and V will equal 1.0 or a very small number compared to stream discharge, and thus can be ignored. The denominator can be calculated by first plotting the measured dye concentration (in g/L) on the y-axis against time (in seconds) on the x-axis (see Ehrman and Lamberti 1992); then, integrate the area under the dye concentration curve using computer digitation, numerical, or graphical methods (Gordon et al. 1992). Divide Q by 1000 to convert to m3/s. Nominal transport time (NTT; Triska et al. 1989) is an appropriate measure of hydraulic retention as indicated by a dye slug release. NTT is calculated as the time interval required for 50% of the dye to pass out of the reach. Integration of the concentration curve, starting at the origin and proceeding

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until 50% of the total area is found, will yield the NTT. NTT generally increases with reach complexity and the presence of certain channel features, such as large pools or significant interstitial flow.

D. Advanced Method 3a: Modeling Wood Accumulation It is possible to model the input, retention, breakdown, and movement of large wood using simulation models (see review of 14 models in Gregory et al. 2003b). To illustrate the application of simulation modeling for evaluating ecological and physical processes that influence the storage of wood, we will use a publicly available version of OSU Streamwood (Meleason et al. 2003), an integrated model of riparian stand dynamics and wood dynamics in streams of the U.S. Pacific Northwest developed by Mark Meleason. 1.

2. 3.

4.

5. 6.

7. 8.

9.

Download OSU Streamwood from the H.J. Andrews LTER website (http://www.fsl.orst.edu/lter/data/tools/models/streamwood.cfm) as a compressed file. Also download the User’s Guide to assist in running the model for future applications. Create a folder on your computer’s directory named OSU_Streamwood. Unzip the model and place the files in your OSU_Streamwood folder. Double left-click (PC users) to open the StreamWood application file (StreamWood.exe or “StreamWood MFC Application”). Mac users will need to “select” files in all instances. Double left-click on “Environment” under streamwood.bsn in the left window. In this window you can specify the wood dimensions, key wood processes, operation of the riparian stand model, and flow regime. Click the box next to “Use Forest Model” and then click OK. Double left-click on “Sections.” OSU Streamwood allows the user to set up a network of stream sections with different riparian conditions or different geomorphic characteristics. The default version has three sections composed of four reaches. For example, S1R1 is “Section 1 Reach 1” and is the downstream reach of the network. S2R1 is immediately above S1R1. S2 indicates that it is the second section and R1 indicates that it flows into section 1. S2R2 is still in section 2 and flows into S2R1 (i.e., longitudinal series of reaches). S3R1 is the third section that flows into section 1. That means that it is a tributary to the mainstem with its confluence at the boundary between sections 1 and 2 of the mainstem (S1R1 and S2R1). Double left-click on each of the reaches. An “environment” tab will appear for each of the four reaches. Double left-click on the “Environment” tab for S1R1. The reach characteristics are described and can be modified. Click on “Same Forest Model Conditions for Both Riparian Zones.” Click box next to “Grow a Riparian Forest from 76–100 m from Stream Bank.” Note that riparian forest automatically grows from 0–75 m, but this can be modified (unselect) for different forest management regimes. Then click on “Define Riparian Forest Management Regime.” This allows you to define the management of both the riparian management zone and the upslope forest. For this phase of the exercise, use the default values and click OK. Note that this will mean that there is no forest harvest in this model run. Repeat this step for the other three reaches.

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12. 13.

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Left click on the “Results” tab on the upper toolbar and then click on “Set Results.” This allows the user to set the interval at which the model records the results. The default is a 10-yr interval. Click OK. Left click on the “Run” tab on the upper toolbar and then click on “Model.” Type in the name of the simulation. This window allows you to change the time extent for the model run. Change the time from 400 yr to 600 yr. The model is a probabilistic model and the Monte Carlo simulation can be used to explore the variance in model output. For this exercise, do not click “use Monte Carlo” and we will generate a single run of the model. Click “Run.” When the hourglass disappears, the model run is complete. You can display the outcomes for each reach. If you click on the down arrow to the right of “Source,” you can select the reach to be displayed. If you click on “Variables,” you can select the variable to be displayed. The choices include “NuChLog”—number of logs in the active channel, “NuToLog”—number of logs in the active channel, floodplain, and hillslope that touch the channel, “ChanVol”—volume of logs in the active channel, and “Tot_Vol”—volume of logs in the active channel, floodplain, and hillslope that touch the channel. Multiple graphs can be displayed simultaneously by clicking on “Multiline.” Click on S2R2. Then click on “ChanVol.” Then click on “Multiline.” Then click on S2R1 (the downstream reach). The click on S1R1 (the most downstream reach). Note that the wood storage in the channel tends to reach an inflection at approximately 300 yr and the downstream reach continues to accumulate wood because of transport from upstream. You can obtain the numerical values for this model run in the files for Forest and Stream under the Results folder in the OSU_Streamwood folder that you initially created prior to running the model.

E. Advanced Method 3b: Modeling Effects of Timber Harvest on Wood Accumulation This modification of the previous exercise illustrates the effects of timber harvest on the accumulation of wood in stream channels. 1. 2.

Follow steps 1–7 in Advanced Method 3a above. Under the “Environment” tab for S1R1, click on “Same Forest Model Conditions for Both Riparian Zones.” Click box next to “Grow a Riparian Forest from 76–100 m from Stream Bank.” Then click on “Define Riparian Forest Management Regime.” Under the Riparian Management Area box on the left side of the window, set “Years Between Cut” to 50. In this box, “Total RMA Width,” “No-Cut Width,” “Min Basal Area for Cut,” “Min Num of Leave Trees for Cut,” and “Min DBH of Leave Trees” should be automatically set at zero. Under the Riparian Forest Outside of RMA box on the right side of the window, set “Years Between Cut” to 50. Then click OK. This simulates a 50-yr harvest rotation with no riparian buffer or management area. Repeat this step for the other three reaches. 3. Left click on the “Run” tab on the upper toolbar and then click on “Model.” Type in the name of the simulation. This window allows you to change the time extent for the model run. Change the time from 400 yr to 600 yr. Again, for this exercise, do not click “use Monte Carlo” and we will generate a single run of the model. 4. Click “Run.”

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When the hourglass disappears the model run is complete. In the “Source” box, click on S2R2. Then click on “ChanVol.” Then click on “Multiline.” Then click on S2R1 (the downstream reach). Then click on S1R1 (the most downstream reach). Note that the wood storage in the channel tends to reach an inflection at approximately 200 yr instead of 300 yr as in the previous nonharvest exercise. Also note the sequence of peaks and declines that reflect the impact of harvest on recruitment of wood to the channel. Lastly, the storage of wood in the channel under a 50-yr harvest cycle was less than 10% of the volume that would accumulate without harvest (or other forms of forest disturbance).

IV. QUESTIONS 1.

2. 3. 4.

5.

6. 7.

8.

9.

To what features do you attribute any differences in retention of leaves and wood between the two study reaches? What were the most important retention structures in the two reaches? Were they the same for leaves and wood? Were more leaves retained in pools or in riffles? Why? What are the mechanisms responsible for retention in these two types of bedforms? Did the exponential model adequately describe the POM retention patterns? What exactly do the parameters of this model describe? Are there more appropriate models? What physical features influenced hydraulic retention? Did the measurement of discharge with dye correspond to that determined from the area-velocity technique? What are the limitations of the dye slug release approach? How do you think stream size (order) would affect retention of POM and water? Speculate about retention efficiency in smaller or larger streams than the one you studied. How might discharge and season affect retention in the same stream? Compare the wood volumes estimated by direct counts and line-intersect methods. Did they correspond or deviate? Why do you think that is so? In light of your findings, discuss the implications of stream and riparian management practices that tend to reduce the amount of wood loading to streams, to simplify stream channels, or to modify the hydrograph. How would you expect the decay rates of wood (e.g., different tree species, different temperature) to influence the accumulation of wood in a stream reach? How could you use the model to explore this question? How would stream discharge influence the storage of wood in stream reaches? How could you use the model to examine the potential consequences of altered hydrologic patterns on wood dynamics?

V. MATERIALS AND SUPPLIES Materials for CPOM Releases Dried or fresh-fallen leaves (e.g., 3000 abscised Ginkgo biloba leaves). Garbage bags (to store leaf batches until released) Buckets [two 20-L (5-gallon), to soak leaves] Wood dowels (60 dowels ca. 1 m L × 1.5 cm D) Fluorescent dye (fluorescein powder or rhodamine-WT liquid) Current velocity meter (optional)

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Dip (D-frame) nets (1 per investigator) Field notebook with data sheets Flagging tape Log calipers (if available) Meter sticks Metric tapes (100 m, 50 m, 10 m) Scintillation vials (100 plastic; numbered) Seine with lead line (at least as long as the channel width) Stadia rod and clinometer or hand level (for measuring slope) Stopwatch Scintillation vials (to hold dye samples) Laboratory Equipment for Optional Dye Release Electronic balance (±001 g) Fluorometer with filters for specific fluorescent dye Computer with digitizing software

VI. REFERENCES Benke, A. C., and J. B. Wallace. 1990. Woody dynamics in coastal plain blackwater streams. Canadian Journal of Fisheries and Aquatic Sciences 47:92–99. Bilby, R. E. 1981. Role of organic debris dams in regulating the export of dissolved and particulate matter from a forested watershed. Ecology 62:1234–1243. Bilby, R. E., and G. E. Likens. 1980. Importance of organic debris dams in the structure and function of stream ecosystems. Ecology 61:1107–1113. Cederholm, C. J., D. B. Houston, D. L. Cole, and W. J. Scarlett. 1989. Fate of coho salmon (Oncorhynchus kisutch) carcasses in spawning streams. Canadian Journal of Fisheries and Aquatic Sciences 46:1347–1355. Cummins, K. W. 1974. Structure and function of stream ecosystems. BioScience 24:631–641. Cummins, K. W., and M. J. Klug. 1979. Feeding ecology of stream invertebrates. Annual Review of Ecology and Systematics 10:147–172. Cummins, K. W., J. R. Sedell, F. J. Swanson, G. W. Minshall, S. G. Fisher, C. E. Cushing, R. C. Petersen, and R. L. Vannote. 1983. Organic matter budgets for stream ecosystems. Pages 299–353 in J. R. Barnes and G. W. Minshall (Eds.) Stream Ecology: Application and Testing of General Ecological Theory. Plenum Press, New York, NY. DeVries, D. G. 1974. Multi-stage line intersect sampling. Forest Science 20:129–133. Ehrman, T. P., and G. A. Lamberti. 1992. Hydraulic and particulate matter retention in a 3rd-order Indiana stream. Journal of the North American Benthological Society 11:341–349. Gordon, N. D., T. A. MacMahon, and B. L. Finlayson. 1992. Stream Hydrology. An Introduction for Ecologists. John Wiley and Sons, Chichester, UK. Gregory, S. V., K. L. Boyer, and A. M. Gurnell (Eds.). 2003a. The Ecology and Management of Wood in World Rivers. American Fisheries Society, Symposium 37, Bethesda, MD. Gregory, S. V., M. Meleason, and D. J. Sobota. 2003b. Modeling the dynamics of wood in streams and rivers. Pages 315–336 in S. V. Gregory, K. L. Boyer, and A. M. Gurnell (Eds.) The Ecology and Management of Wood in World Rivers. American Fisheries Society, Symposium 37, Bethesda, MD. Jones, J. B., and L. A. Smock. 1991. Transport and retention of particulate organic matter in two low-gradient headwater streams. Journal of the North American Benthological Society 10:115–126. Lamberti, G. A., and M. B. Berg. 1995. Invertebrates and other benthic features as indicators of environmental change in Juday Creek, Indiana. Natural Areas Journal 15:249–258. Meleason, M. A., S. V. Gregory, and J. Bolte. 2003. Implications of selected riparian management strategies on wood in Cascade Mountain streams of the Pacific Northwest. Ecological Applications 13:1212–1221. Miesbauer, J. M. 2004. An Assessment of Large Woody Debris, Fish Populations, and Organic Matter Retention in Upper Midwestern Streams. M.S. thesis, University of Notre Dame, Notre Dame, IN.

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Montgomery, D. R., B. D. Collins, J. M. Buffington, and T. B. Abbe. 2003. Geomorphic effects of wood in rivers. Pages 21–48 in S. V. Gregory, K. L. Boyer, and A. M. Gurnell (Eds.) The Ecology and Management of Wood in World Rivers. American Fisheries Society, Symposium 37, Bethesda, MD. Mutz, M. 2003. Hydraulic effects of wood in streams and rivers. Pages 93–108 in S. V. Gregory, K. L. Boyer, and A. M. Gurnell (Eds.) The Ecology and Management of Wood in World Rivers. American Fisheries Society, Symposium 37, Bethesda, MD. Smock, L. A., G. M. Metzler, and J. E. Gladden. 1989. Role of debris dams in the structure and function of low-gradient headwater streams. Ecology 70:764–775. Speaker, R. W., K. J. Luchessa, J. F. Franklin, and S. V. Gregory. 1988. The use of plastic strips to measure leaf retention by riparian vegetation in a coastal Oregon stream. American Midland Naturalist 120:22–31. Speaker, R. W., K. Moore, and S. V. Gregory. 1984. Analysis of the process of retention of organic matter in stream ecosystems. Verhandlungen der Internationalen Vereinigung für Theoretische und Angewandte Limnologie 22:1835–1841. Triska, F. J., V. C. Kennedy, R. J. Avanzino, G. W. Zellweger, and K. E. Bencala. 1989. Retention and transport of nutrients in a third-order stream: Channel processes. Ecology 70:1877–1892. Van Wagner, C. E. 1968. The line intersect method in forest fuel sampling. Forest Science 14:20–26. Vannote, R. L., G. W. Minshall, K. W. Cummins, J. R. Sedell, and C. E. Cushing. 1980. The river continuum concept. Canadian Journal of Fisheries and Aquatic Sciences 37:130–137. Wallace, J. B., and A. C. Benke. 1984. Quantification of woody habitat in subtropical coastal plain streams. Canadian Journal of Fisheries and Aquatic Sciences 41:1643–1652. Wallace, J. B., J. R. Webster, S. L. Eggert, J. L. Meyer, and E. R. Siler. 2001. Large woody debris in a headwater stream: Long-term legacies of forest disturbance. International Review of Hydrobiology 86:501–513. Webster, J. R., E. F. Benfield, T. P. Ehrman, M. A. Schaeffer, J. L.Tank, J. J. Hutchens, and D. J. D’Angelo. 1999. What happens to allochthonous material that falls into streams? Freshwater Biology 41:687–705. Webster, J. R., A. P. Covich, J. L.Tank, and T. V. Crockett. 1994. Retention of coarse organic particles in streams in the southern Appalachian Mountains. Journal of the North American Benthological Society 13:140–150. Young, S. A., W. P. Kovalak, and K. A. Del Signore. 1978. Distances travelled by autumn-shed leaves introduced into a woodland stream. American Midland Naturalist 100:217–222.