Download - ROOT BIOMASS IN RELATION TO CHANNEL MORPHOLOGY OF HEADWATER STREAMS

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATIONVOL. 37, NO. 6 AMERICAN WATER RESOURCES ASSOCIATION DECEMBER 2001

ROOT BIOMASS IN RELATION TO CHANNELMORPHOLOGY OF HEAD WATER STREAMS'

Zachary 0. Toledo and J. Boone Kauffman2

ABSTRACT: Intact riparian zones are the product of an incrediblycomplex multitude of linkages between the geomorphic, hydrologic,and biotiè features of the ecosystem. Land-use activities that severor alter these linkages result in ecosystem degradation. We exam-ined the relationship between riparian vegetation and channel mor-phology by sampling species composition and herbaceous rootbiomass in incised (down-cut and widened) versus unincised(intact) sections of unconstrained reaches in three headwaterstreams in northeastern Oregon. Incision resulted in a composition-al shift from wetland-obligate plant species to those adapted todrier environments. Root biomass was approximately two timesgreater in unincised sections than incised sections and decreasedwith depth more rapidly in incised sections than in unincised sec-tions. Thtal root biomass ranged from 2,153 g m2 to 4,759 g m2 inunincised sections and from 1,107 g m-2 to 2,215 g m-2 in incisedsections. In unincised sections less than 50 percent of the total rootbiomass was found in the top 10 cm, with approximately 20 percentin successive 10-cm depth increments. In contrast, incised sectionshad greater than 60 percent of the total root biomass in the top 10cm, approximately 15 percent in the 10 to 20 cm depth, less than 15percent in the 20 to 30 cm depth, and less than 10 percent in the 30to 40 cm depth. This distribution of root biomass suggests a positivefeedback between vegetation and channel incision: as incision pro-gresses, there is a loss of hydrologic connectivity, which causes ashift to a drier vegetation assemblage and decreased root structure,resulting in a reduced erosive resistance capacity in the lower zoneof the streambank, thereby allowing further incision and widening.(KEY TERMS: riparian ecosystems; erosion sedimentation; rootbiomass; root distribution; channel morphology; incision.)

INTRODUCTION

Riparian areas are zones of direct interactionbetween terrestrial and aquatic ecosystems (Gregoryet al., 1991). While riparian areas comprise only 1 to 2percent of the land area in arid systems (Kauffman

and Krueger, 1984), they are disproportionately sig-nificant in terms of biological production and diversity(Gregory et al., 1991; Naiman and Descamps, 1997;Patten 1998, Kauffman et al., 2001). Riparian areasare valuable to society through their multitude ofecosystem functions and processes, such as floodabatement, habitat for migratory birds and aquaticspecies (Naiman et al., 1993), maintenance of regionalbiodiversity (Naiman and Descamps, 1997), andwater quality control and nutrient cycling (Green andKauffman, 1989). Riparian areas have received con-siderable attention by scientists and managers (John-son et al., 1985; Abell, 1989; Clary et al., 1992;Tellman et al., 1993; Feller, 1998; Koehler andThomas, 2000; Wigington and Beschta, 2000) becauseof concerns centering on their widespread degradation[National Resource Council (NRC), 1992; Beschta,19971.

Riparian areas throughout the western UnitedStates have been altered or degraded through land-use activities including hydrologic alterations(Dominick and O'Neill, 1998), beaver removal(Naiman et al., 1988), and livestock grazing (Fleischn-er, 1994; Dwire et al., 1999; Kauffman and Pyke,2001). Like many western landscapes, eastern Oregonriparian areas have been affected by additional land-use activities, including mining, logging, splash dams,and road building (McIntosh et al., 1994).

Riparian-stream degradation occurs when hydro-logic, geomorphic, or biotic processes are disruptedsuch that interactions or linkages between these fea-tures are disrupted (Figure 1). For example, channelincision can sever linkages between floodplains andstreams, which then alters the biotic communities

'Paper No. 01046 of the Journal of the American Water Resources Association. Discussions are open until August 1, 2002.-

'Respectively, Fisheries Biologist, Mason, Bruce and Girard, Inc., 707 SW. Washington Street, Suite 1300, Portland, Oregon 97205; andProfessor, Department of Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, Oregon 97331 (E-MaillToledo: [email protected]).

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION 1653 JAWRA

Toledo and Kauffman

(Junk et al., 1989; Robertson et al., 2001). Incisionmay be expected when there is an imbalance betweenerosive and resistive forces acting on the bank andbed material (Schumm, 1999). Shifts in the forces act-ing on the bank can be caused by a change in thehydrology, geomorphology, or vegetation, which influ-ence each other in a positive feedback response (Fig-ure 1; Kauffman et al., 1997). The positive feedbackresponse can be described as follows: channel mor-phology influences the water availability to the ripari-an area (floodplain) (Leopold and Maddock, 1953),water availability affects plant species compositionthat comprises the riparian communities (Hupp andOsterkamp, 1996; Otting, 1998; Chapin et al., 2000),and both aboveground and belowground vegetationcomponents affect the channel morphology by influ-encing both erosive and resistive forces (Hickin, 1984;Thorne, 1990; Hupp, 1999).

Figure 1. Linkages Between Geomorphology; Hydrology,and the Biota. Altering one of these features will result

in a positive feedback response to the others(modified from Kauffman et al., 1997).

Vegetation has been shown to strongly influencechannel morphology (Gregory and Gurnell 1988).Hickin and Nanson (1984) found that unvegetatedchannels could exhibit double the lateral channelmigration rates of vegetated channels. Smith (1976)found that bank sediment with a 5 cm root mat and aroot volume of 16 to 18 percent had 20,000 times theresistance of equivalent bank sediment without vege-tation or roots. Clifton (1989) reported that whenWickiup Creek (in central Oregon) was allowed to re-vegetate following livestock exclusion, the channelgained 60 cm of sediment within ten years and the

channel cross-sectional area had decreased by 94 per-cent after 50 years.

We hypothesized that there are four potentialresponses of root biomass to a decrease in water avail-ability associated with channel incision (Figure 2).There can be: (a) a lower total root biomass but with asimilar distribution within the soil horizons; (b) alower total root biomass and an increased rate of losswith depth; (c) no change in total root biomass or dis-tribution; or (d) an increased level of total rootbiomass. The second response, (b), would have thegreatest potential to affect channel morphology anderosion potential because there would be an overalldecrease in root biomass, particularly at greaterdepths. The objective of this study was to examine therelationships between riparian vegetation, rootbiomass, and channel morphology in incised andunincised stream channels.

STUDY SITES

The study reaches are located in the Blue Moun-tains of northeastern Oregon. During preliminaryreconnaissance, we examined 21 streams and selectedthree that met our criteria: an unconstrained alluvialchannel; a low level of recent human impact (i.e.,enhancement structures, livestock grazing, etc.); andthe presence of a hydrologic knickpoint (i.e., an areawhere an abrupt change of elevation and slope gradi-ent occurs (Brooks et al., 1997) that separates anupstream, unincised section from a downstream,incised section. Starting points of the sections werechosen with regards to tributary junctions, location ofknickpoints, and changes in valley form. Incised sec-tions were determined using previously collectedwater table data and/or physical parameters such asbank height and active channel width. Incised andunincised sections were similar in floodplain geomor-phology. The causes of channel incision likely includedroads, mining, and grazing.

Crane Creek (44°5308"N, 118°23'SO'W; elevation1,680 m) is a third-order tributary to the North ForkJohn Day River. The knickpoint was a road culvert;however, it was not determined whether the culvertinitiated or halted the headcut (knickpoint). Theunincised section was approximately 100 m upstreamfrom the incised section.

Little Fly Creek (45°03'45"N, 118'30'15'W; eleva-tion 1,460 m) is a third-order tributary to the GrandeRonde River. The knickpoint was also a culvert, whichhas halted the upstream migration of the headcut(Figure 3). The incised section was approximately200 m downstream of the unincised section.

JAWRA 1 654 JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION

Root Biomass in Relation to Channel Morphology of Headwater Streams

Root Biomass

/'______(a

Root Biomass

.b

Root Biomass

—7. /-(

c

Root Biomass

—D 7?

( d

Figure 2. Four Hypothesized Responses of Root Biomass to Channel Incision: (a) Less Overall Root Biomass ThanUnincised Stream, Same Rate of Loss With Depth; (b) Less Overall Root Biomass Than Unincised Stream, and anIncreased Rate of Loss With Depth; (c) No Change From an Unincised Stream; and (d) Increased Level of Biomass.

1977

Little Fly Creek

1999

Figure 3. The Incised Section of Little Fly Creek in 1977 (left) and 1999 (right). The man (circled) was standingat the headcut in 1977. The tree (circled) to the left of both photos provides reference and scale.Note the change in channel width and bank height - an obvious disconnect from the floodplain.


Thiedo and Kauffman

Squaw Creek (45°07'44N, 118°3223"W; elevation1,370 m) is a second-order tributary to the GrandeRonde River and has been the subject of a previousvegetative and hydrologic study, which described thepresence of the hydrologic knickpoint using watertable elevation (Otting, 1998). The end of the unin-cised section is approximately 10 m upstream fromthe beginning of the incised section.

METHODS

The length of each sampled section was at least 20-times the average active channel width, with a mini-mum length of 40 m. Average valley bottom width andaverage geomorphic floodplain width were measuredat high flow conditions from ten equally spaced tran-sects located perpendicular to the valley sides. Thegeomorphic floodplain was defined as the near hori-zontal surface formed by fluvial deposition (lateraland vertical accretion) from the channel, which is fre-quently flooded under present conditions (i.e., activelybeing formed; Knighton, 1998). The entrenchmentratio (floodplain width to active channel width) wasdetermined for each section.

Channel measurements were taken at cross-chan-nel transects spaced at one meter during low flow con-ditions (Robison, 1988; Robison and Beschta, 1989).These measurements included active channel width,wetted width, thalweg depth, bank height, overhang-ing bank presence, and depth of overhang. Activechannel width was determined using visual cluessuch as scour, vertical accretion of fine sediment, andmorphology (Harrelson et al., 1994). Thalweg depth isthe point of greatest scour, or the maximum depthalong the cross-channel transect. Bank height wasdefined as the height from the water surface to thefirst dominant topographic plane of the streambank(floodplain).

Vegetation composition was collected within a 25-cm x 25-cm plot at one-meter intervals for 40 m alongthe green line of both banks for each section. Thegreen line is defined as the first perennial vegetationabove the stable low water line (Bauer and Burton,1993). All plants found in the plot were identified tospecies (Hitchcock and Cronquist, 1973; Walters andKeil, 1996) and their cover was recorded. Each specieswas assigned into a "wetland indicator category"ranging from wetland-obligate to upland-obligate(Table 1) based upon classifications in Reed (1986).Wetland indicator categories provide insight into thehydric environment occupied by each species, andthus provide some indication of hydrologic connectivi-ty at the immediate streambank.

TABLE 1. Wetland Indicator Categories (from FederalInteragency Committee for Wetland Delineation, 1989).

Probability ofOccurrence inin Wetlands

Wetland Indicator Category (:percent)

Obligate Wetland > 99

Facultative Wetland 67-99

Facultative 34-66

Facultative Upland 1-33

Obligate Upland <1

Herbaceous, below ground biomass (roots) wasdetermined from collections of a 67-mm. diameter soilcore to a depth of 40 cm (Otting, 1998). Sixteen coresper section (eight per bank) were samp'ed at equidis-tant points along the streambank. The samples weredivided in the field into 10-cm depth increments (0 to10 cm, 10 to 20 cm, 20 to 30 cm, and 30 to 40 cm) andplaced in plastic bags. Roots were separated fromsoils using a Hydropneumatic Elutriation System(Gillison's Variety Fabrication, Inc., Benzonia, Michi-gan) and 0.5-mm mesh screens to remove soil, rocks,and other debris. The washed samples were placed indrying ovens at 60°C for at least 24 hours. The sam-ples were then sorted to remove any remaining non-herbaceous material (wood, seeds, etc.) and dried toconstant dry weight. Weighed subsamples of the rootsfrom each depth increment and site were combustedin a muffle furnace at 500°C for 24 hours to determinebiomass on an ash-free basis (Bohm, 1979). The ash-free dry weight estimate is reported here becausetotal removal of soil particles is difficult and this bestreflects root mass.

Student's t-tests (Ramsey and Shafer, 1996) wereused to test for differences in the channel morphologyparameters. The nonparametric Wilcoxon rank sumtest and Kruskal-Wallis rank test were used to testfor differences in the non-normally distributed rootbiomass data.

Channel Morphology

RESULTS

Incised sections were characterized as wide chan-nels with shallow water depths at low flow, narrowfloodplains, high banks (deep channel), and low per-centages of overhanging banks (Table 2). Relative to

JAWRA 1656 JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION


the incised sections, the unincised sections were char-acterized as narrow channels with deep water depthsat low flow, wide floodplains, low banks, and high per-centages of overhanging banks (Figure 4). Averageactive channel width was less than 200 cm in theunincised sections while greater than 350 cm in theincised sections. Average wetted width was less than160 cm in the unincised sections (Table 2) and greaterthan 180 cm in the incised sections. Average thalwegdepth was significantly greater in unincised sectionscompared to incised sections.

Floodplain width was less than 10 m in all incisedsections while ranging from 15 to 34 m in the unin-cised sections (Table 2). Entrenchment ratios were 6.5to 18 times greater in the unincised sections than inthe incised sections. Even with the broad valley bot-toms, all of the incised sections had entrenchmentratios at or below two, with the floodplain less thantwo times as wide as the active channel. Thus only anarrow corridor of floodplain remained for aquatic-terrestrial interactions during overbank flows.

Unincised sections had mean bank heights lessthan 42 cm while the incised sections had mean bankheights of 43 to 150 cm. For example, the mean bankheight at Little Fly Creek was 41 cm and 150 cm inthe unincised and incised sections, respectively. Over59 percent of the sampled streambank length in theunincised sections had overhanging banks (59 percentat Squaw Creek to 100 percent in Crane Creek) whilethe frequency of overhanging banks along the sam-pled streambank length in the incised sections wasalways less than 50 percent (i.e., 31 percent at SquawCreek and 43 percent at Crane Creek). The averagedepth of overhanging banks was approximately 1.5 tothree times greater in the unincised sections than theincised sections.

Species and Community Composition

Calculation of streambank plant species composi-tion based upon wetland indicator categories providesa good indication of the degree of hydrologic connec-tivity between the channel and terrestrial zones (Fig-ure 5). Obligate-wetland and facultative-wetlandspecies dominated the unincised sections while facul-tative-upland species largely dominated the incisedsections. For example, obligate-wetland and faculta-tive-wetland categories composed 80 percent of thespecies in the unincised section of Crane Creek and86 percent of the species in the unincised section ofSquaw Creek. Whereas obligate-wetland and faculta-tive-wetland categories composed only 41 percent ofthe species in the unincised section of Crane Creekand 53 percent of the species in the unincised sectionof Squaw Creek. Incision clearly resulted in a compo-sitional shift to species adapted to drier environ-ments.

Herbaceous Root Biomass

There were dramatic differences in the rootbiomass of streambanks at incised and unincised sec-tions (Table 3). Total mean root biomass was approxi-mately two times greater in the unincised sectionsthan in the incised sections. For example, at CraneCreek mean root biomass (to 40 cm depth) was 3,263g rn-2 in the unincised section and 1,558 g rn-2 in theincised section. Similarly, at Squaw Creek mean rootbiomass (to 40 cm depth) was 4,759 g rn-2 in the unin-cised section and 2,215 g rn-2 in the incised section.

The distribution of root biomass with depth wasvastly different between the unincised and incised

TABLE 2. Channel Morphology (mean ± standarderror) Data for Three Meadow Streams in Northeast Oregon.Comparisons of characteristics between sections are all significantly different (p < 0.05).

Channel Measurement

StreamCrane Creek Little Fly Creek SquawCreek

Unincised IncisedUnincised Incised Unincised Incised

Entrenchment Ratio 31 ± 3.5 1.7 ±0.2 12 ± 0.8 1.4 ± 0.1 13 ± 0.8 2 ± 0.3

Floodplain Width (m) 34 ± 1.4 8 ± 0.4 25 ± 0.7 9 ± 1.0 15 ± 0.5 6 ± 1.0

Valley Width (m) +300 +300 63 ± 0.9 79 ± 0.8 37 ± 0.9 43 ± 2.9

Bank Height (cm) 31 ± 0.8 56 ± 2.2 41 ± 1.2 150 ± 5.8 30 ± 1.1 43 ± 2.3

Wetted Width (cm) 128 ± 8.0 323 ± 15.9 158 ± 4.9 200 ± 8.4 117 ± 6.2 185 ± 7.8

Active Channel Width (cm) 172 ± 8.4 529 ± 18.6 194 ± 7.8 853 ± 39.3 171 ± 7.1 357 ± 13.2

Thaiweg Depth (cm) 43 ± 1.6 35 ± 1.6 16 ± 1.0 14 ±0.9 27 ± 2.3 19 ± 1.1

Overhanging Bank Frequency 100% 43% 89% 44% 59% 31%


Soil Horizons

AlSilt loamA2Silt loam

ACFine sandyloamCGravelly sandyloamGravels

Coarse gravelsCobbles

Soil Horizons

AlSilt loamA2Silt loam

ACFine sandyloamCGravelly sandyloamGravels

Coarse gravelsCobbles

Figure4. Conceptual Cross Sections of an Intact (unincised) and Degraded (incised) Stream Channel in Unconstrained, Meadow-Dominated,Headwater Reaches in Northeastern Oregon. These representations are based upon results of this study and data presented in

Dwire (2001) and Otting (1998). In the intact reach, high flows inundate wet meadows. Water tables during base flow arewithin the rooting zones of the streamside vegetation and the dense root mass surrounds the channel. In contrast, high

flows do not interact with floodplain vegetation in incised reaches. The root mass is diminished such that thereis little connection with summer base flows and stream channel are marginally affected by root mass.


Toledo and Kauffman

cm0

40

80

120


Crane CreekUnincised Section

FACU13%

Little Fly Creek-Unincised Section

11%

OBL40%

Squaw Creek-Unincised Section

FACW11%

FACU2%

UPL3%

OBL75%

Crane Creek-Incised Section

Little Fly Creek-Incised Section

UPL5% OBL

Squaw Creek-Incised Section

UPL7%

OBL42%

Figure 5. Wetland Indicatory Category Cover ( percent) for the Unincised and Incised Sections of Crane Creek,Little Fly Creek, and Squaw Creek. OBL = wetland obligate, FACW =facultative wetland,

FAC = facultative, FACU = facultative upland, UPL = upland obligate.


UPL0%

UPL2% OBL

26%

15%

FAC13%

FACW

FACW4%

FAC

Toledo and Kauffman

TABLE 3. Mean Root Biomass (g rn-2) Along Streambanks of Three Meadow Streams in Northeast Oregon.

Depth(cm)

StreamCrane Creek Little Fly Creek Squaw Creek

Unincised IncisedUnincised IncisedUnincised Incised

0-10 1,523a,1 1,180a,1 910a,1 669a,1 1,610a,1 l,271a,1

10-20 627b 192b 576A,b,1 176b,2 1,001b,1 523b

20-30 447b 128c 435b,1 149b,2 l,116a,b,1 255b,C

30-40 668b,1 59C 233C,2 112b,2 1,032b,1 166C

TOTAL 3,263 1,558 2,153 1,107 4,759 2,215

Notes: Letters denote significant differences (P < 0.05) within a section.Numbers denote significant differences between sections.Upper case letters denote significant differences at P < 0.10.All totals are significantly different between sections. Means are not compared between streams.

sections, with unincised sections retaining greaterproportions of their root biomass at depth thanincised sections (Figure 6). For example, the unin-cised sections had 34 to 47 percent of the total rootbiomass within the top 10 cm and approximately 20percent of the remaining root biomass within eachsubsequent 10 cm depth increment. Whereas theincised sections had 57 to 76 percent of the total rootbiomass within the top 10 cm followed by a rapid lossof root biomass with depth: approximately 15 percentin the 10 to 20 cm depth, less than 15 percent in the20 to 30 cm depth, and less than 10 percent of thetotal root biomass in the 30 to 40 cm depth. Compar-isons of root biornass in the top (0 to 10 cm) depthbetween incised and unincised sections at any of thesites found differences at p-values of 0.13 at CraneCreek, 0.12 at Little Fly Creek, and 0.12 at SquawCreek. There was a high proportion of root biomass atdepth in intact (unincised) riparian systems, with arapid reduction in root biomass at depth in degradedriparian systems.

DISCUSSION

The relatively high level of root biomass in unin-cised sections has been reported for other studies insimilar communities. Bernard and Fiala (1986)reported root biomass levels for three Carex-dominat-ed communities to range from 2,237 g rn-2 for Carextrichocarpa to 4,988 g rn-2 for C. lasiocarpa. In thisstudy, we found dramatic changes in species composi-tion as well as declines in root biornass in relation toincision. This is likely related to the loss of the watertable (decreased availability of water) close to the soilsurface. Manning et al. (1989), Dwire (2001), and

Otting (1998) found strong relationships betweenwater availability and root biomass. Manning et al.(1989) reported that root biomass decreased along asoil moisture (water availability) gradient in a Neva-da riparian system (3,382 g m-2 in wet meadow versus555 g rn-2 in dry meadow communities). Dwire (2001)reported that root biomass in dry, moist, and wetmeadow communities along West Chicken Creek (innortheast Oregon) were 749 g m2, 1,525 g m-2, and3,502 g rn-2, respectively. In areas within a northeastOregon riparian zone where groundwater alwaysremained close to the soil surface root biornass was4,375 g rn-2 (Otting, 1998) compared with 1,237 g rn-2in areas of the same meadow where groundwaternever reached the surface.

We found that root distributions responded to thehypothesis described in Figure 2b: both biomass anddistribution declined with incision. This pattern ofdiminished root biomass with depth occurred in allthree incised sections (Figure 6). There was a rela-tively even distribution of root biomass (no significantdifference) at depths of 10 to 40 cm at the unincisedsections of Crane and Squaw Creeks. In contrast,there were significant differences (i.e., loss withdepth) in these lower depths at the incised sections.These results support the hypothesis that sites with alow water table during base flows tend to decrease inroot biornass with depth at a faster rate than siteswith high water tables during base flows.

Vegetation composition and structure is a strongindicator of floodplain connectivity. The dramatic dif-ferences in species composition along the streambankover short stream distances demonstrate the stronginfluence of channel form on hydrologic connectivityand hence species composition. Otting (1998) found astrong correlation between species composition andwater availability, with approximately 75 percent of



IIIIIIIIIIIH 1111111 IllIllIllIllI

•

iIIIIIIIIlIIIiIlilIIiII

lIIIiiIIIl

Figure 6. Total Root Biomass (g m2) at 10-cm Depth Increments forCrane Creek, Little Fly Creek, and Squaw Creek.


Crane Creek

tiomass (g m2)

0 200 400 600 800 1000 1200 1400 1600 1800

0-10cm III10—20cm IjIIjI1IIIIIIIHhIIIIIIIPIIIIIJl!IIIIIII

2c—3o ciii

30—40 ciiiIIHlIIIIIIIIIIIlIIIIIIIIILlIIIIIIIIIIIIIll

Ununcised lncised

Little Fly Creek

tiomass (g m2)

0 200 400 600 800 1000 1200 1400 1600 1800

0-10cm

10-20cm

20-30 cm

30-40cm

Unincised Incised

Squaw Creek

Iiomass (g 2)0 200 400 600 800 1000 1200 1400 1600 1800

0-10cm

10—20cm IjIjIjIjIJIJIJIjjJIJIjIJIJIJIIIIIIIIIIIIIIIIIIIIIIIIIIlI

20-30cm JJJ!J!J!J!JItIIIIlIIIIIIIIIIUIIIIIIIIIIIIlIIlIIIIfIIIIIIUII

30—'ll cm IJIjI1jjjIIIIII)IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIlIIIIIIiIII

DUnncsed &ncis

Thiedo and Kauffman

the variance in community structure explained by theaverage growing season groundwater levels. In thisstudy, even minor channel morphology differences(i.e., less than 13-cm difference in mean bank heightat Squaw Creek) were related to dramatic species,root biomass, and structural differences (Table 2, Fig-ure 5). These differences are even more dramaticwhen one considers that the data were all collected atthe immediate margins of the streambank. These dif-ferences in above-ground and below-ground structurewould likely have differential effects on channel mor-phology and hydrology. With a decline in rootbiomass, stream channels would likely be more sus-ceptible to bank erosion, further exacerbating the lossof connection between hydrologic and biotic compo-nents of riparian ecosystems. Many of the subtlechannel differences may be difficult to observe quicklyin the field, however, the vegetation shifts in composi-tion can provide easily observable indicators of theecological condition of a given site.

Land use alters riparian biotic composition, chan-nel morphology, and hydrologic connectivity of mead-ow-dominated headwater streams. Biotic, hydrologic,and geomorphic features are linked in a positive feed-back relationship such that effects to one componentof the ecosystem will illicit changes in the others. Forexample, overgrazing by domestic livestock can altervegetation composition, which may reduce both rootbiomass and infiltration rates leading to increasedpeak flows. This could then result in channel widen-ing and incision. The challenge to land managers liesin the development of restoration approaches thatwould reverse processes of degradation and reconnectlinkages between stream channels and riparianzones.

ACKNOWLEDGMENTS

This paper was funded by grants from the U.S. EnvironmentalProtection Agency and the Bonneville Power Administration. Wewish to thank S. V. Gregory and R. L. Beschta for comments andinsights; Amy Toledo, Dian Cummings, Michael Samuel, andDaniel Lipe for assistance in the field and the laboratory; DianCummings for the assistance with Figure 4; the La Grande RangerDistrict (Wallowa-Whitman National Forest) and the Ukiah RangerDistrict (Umatilla National Forest) for valuable information andassistance; and three anonymous reviewers for their helpful com-ments and suggestions.

LITERATURE CITED

Abell, D. L. (Technical Coordinator), 1989. Proceedings of the Cali-fornia Riparian Systems Conference: Protection, Management,and Restoration for the 1990s (September 22-24, 1988, Davis,California). General Technical Report PSW-110, Pacific South-west Forest and Range Experiment Station, Forest Service, U.S.Department of Agriculture, Berkeley, California, 554 pp.

Bauer, S. B. and T. A. Burton, 1993. Monitm-ing Protocols to Evalu-ate Water Quality Effects of Grazing Management on WesternRangeland Streams. U.S. Environmental Protection Agency,Washington, D.C.

Bernard, J. M., and K. Fiala, 1986. Distribution and Standing Cropof Living and Dead Roots in Three Wetland Carex Species. Bul-letin of the Torrey Botanical Club 113:1-5.

Beschta, R. L.,1997. Restoration of Riparian and Aquatic Systemsfor Improved Aquatic Habitats in the Upper Columbia RiverBasin. In: Pacific Salmon and Their Ecosystems: Status andFuture Options, D. J. Stouder, P. A. Bisson, and R. J. Naiman(Editors). Chapman and Hall of International Thomas Publish-ing, New York, New York, pp. 475-491.

Bohm, W., 1979. Methods of Studying Root Systems. In: EcologicalStudies, W. D. Billings, F. Golley, 0. L. Lange, and J. S. Olson(Editors). Springer-Verlag, Vol. 33, 188 pp.

Brooks, K. N., P. F. Ffolliott, H. M. Gregersen, and L. F. DeBano,1997. Hydrology and the Management of Watersheds (SecondEdition). Iowa State University Press, Ames, Iowa.

Chapin, D. M., R. L. Beschta, and H. W. Shen, 2000. Flood Frequen-cies Required to Sustain Riparian Plant Communities in theUpper Klamath Basin, Oregon. In: Riparian Ecology and Man-agement in Multi-Land Use Watersheds, P. J. Wigington andR. L. Beschta (Editors). American Water Resources Association,Middleburg, Virginia, TPS-00-2. pp. 17-22.

Clary, W. P., E. D. McArthur, D. Bedunah, and C. L. Wambolt (Com-pilers), 1992. Proceedings-Symposium on Ecology and Manage-ment of Riparian Shrub Communities (May 29-31, 1991, SunValley, Idaho). General Technical Report INT-289, U.S. Depart-ment of Agriculture, Forest Service, Intermountain ResearchStation, Ogden, Utah, 232 pp.

Clifton, C. A., 1989. Effects of Vegetation and Land Use on ChannelMorphology. In: Practical Approaches to Riparian ResourceManagement: An Educational Workshop, R. E. Gresswell, B. A.Barton, and J. L. Kershner (Editors). Printed by U.S. Bureau ofLand Management, Billings, Montana; U.S. Government Print-ing Office, Washington, D.C., pp. 121-129.

Dominick, D. S. and M. P. O'Neill, 1998. Effects of Flow Augmenta-tion on Stream Channel Morphology and Riparian Vegetation:Upper Arkansas River Basin, Colorado. Wetlands 18(4):591-607.

Dwire, K. A., B. A. McIntosh, and J. B. Kauffman, 1999. EcologicalInfluences of the Introduction of Livestock on Pacific NorthwestEcosystems. In: Northwest Lands, Northwest Peoples: Readingsin Environmental History, D. D. Gobel and P. W. Hirt (Editors).University of Washington Press. Seattle, Washington, pp. 313-335.

Dwire, K. A., 2001. Relations Among Hydrology, Soils, and Vegeta-tion in Riparian Meadows: Influence on Organic Matter Distri-bution and Storage. Ph.D. Dissertation, Oregon StateUniversity, Corvallis, Oregon.

Federal Interagency Committee for Wetland Delineation, 1989.Federal Manual for Identifying and Delineating JurisdictionalWetlands. U.S. Army Corps of Engineers, U.S. EnvironmentalProtection Agency, U.S. Fish and Wildlife Service, and USDASoil Conservation Service, Cooperative Technical Publication,Washington, D.C.

Feller, J. M., 1998. Recent Developments in the Law Affecting Live-stock Grazing on Western Riparian Areas. Wetlands 18(4):646-657.

Fleischner, T. L., 1994. Ecological Costs of Livestock Grazing inWestern North America. Conservation Biology 8:629-644.

Green, D. M. and J. B. Kauffman, 1989. Nutrient Cycling at theLand-Water Interface: The Importance of the Riparian Zone.In. Practical Approaches to Riparian Resource Management:An Educational Workshop, R. E. Gresswell, B. A. Barton, andJ. L. Kershner (Editors). Printed by U.S. Bureau of Land

JAWRA 1662 JOURNAL OF TNE AMERICAN WATER RESOURCES ASSOCIATION


Management, Billings, Montana; U.S. Government PrintingOffice, Washington D.C., pp. 61-68.

Gregory, K. J., and A. M. Gurnell, 1988. Vegetation and RiverChannel Form and Process. In: Biogeomorphology, H. A. Viles,(Editor). Basil Blackwell Ltd, Oxford, United Kingdom, pp. 11-42.

Gregory S. V., F. J. Swanson, W. A. McKee, and K. W. Cummins,1991. An Ecosystem Perspective of Riparian Zones. BioScience41:540-55 1.

Harrelson, C. C., C. L. Rawlins, and J. P. Potyondy, 1994. StreamChannel Reference Sites: An Illustrated Guide to Field Tech-nique. USDA Forest Service, General Technical Report RM-245,61 pp.

Hickin, E. J., 1984. Vegetation and River Channel Dynamics. Cana-dian Geographer 28: 111-126.

Hickin, E. J. and G. C. Nanson, 1984. Lateral Migration Rates ofRiver Bends. Journal of Hydraulic Engineering 110: 1557-1567.

Hitchcock, C. L. and A. Cronquist, 1973. Flora of the Pacific North-west. University of Washington Press, Seattle, Washington, andLondon, United Kingdom, 730 pp.

Hupp, C. R., 1999. Relations Among Riparian Vegetation, ChannelIncision Processes and Forms, and Large Woody Debris. In:Incised River Channels, S. E. Darby and A. Simon (Editors).John Wiley and Sons, Chichester, United Kingdom, pp. 219-245.

Hupp, C. R. and W. R. Osterkamp, 1996. Riparian Vegetation andFluvial Geomorphic Processes. Geomorphology 14:277-295.

Johnson, R. R., C. D. Ziebell, D. R. Patton, P. F. Ffolliott, and R. H.Hamre (Technical Coordinators), 1985. Riparian Ecosystemsand Their Management: Reconciling Conflicting Issues. FirstNorth American Riparian Conference (April 16-18, 1985, Thc-son, Arizona). General Technical Report RM-120, U.S. Depart-ment of Agriculture, Forest Service, Rocky Mountain Forest andRange Experiment Station, Fort Collins, Colorado, 523 pp.

Junk, W. J., P. B. Bayley, and R. E. Sparks, 1989. The Flood PulseConcept in River-Floodplain Systems. In: Proceedings of theInternational Large River Symposium, D. P. Dodge (Editor).Canadian Special Publication Fisheries and Aquatic Science, pp.110-127.

Kauffman, J. B., R. L. Beschta, N. Otting, and D. Lytjen, 1997. AnEcological Perspective of Riparian and Stream Restoration inthe Western United States. Fisheries 22:12-24.

Kauffman, J. B., and W. C. Krueger, 1984. Livestock Impacts onRiparian Ecosystems and Streamside Management Implica-tions. Journal of Range Management 37:430-437.

Kauffman, J. B., M. Mahrt, L. A Mahrt, and W. D. Edge, 2001.Wildlife Communities and Habitats of Riparian Ecosystems. In:Wildlife Habitats and Species Associations Within Oregon andWashington: Building a Common Understanding for Manage-ment. Oregon State University Press, Corvallis, Oregon.

Kauffman, J. B. and D. A. Pyke, 2001. Range Ecology, Global Live-stock Influences. In: Encyclopedia of Biological Diversity, S. A.Levin (Editor). Academic Press, San Diego, California, Vol. 5,pp. 33-52.

Knighton, D., 1998. Fluvial Forms and Processes: A New Perspec-tive. Arnold, London, United Kingdom.

Koehler, D. A and A. E. Thomas (Compilers), 2000. Managing forEnhancement of Riparian and Wetland Areas of the WesternUnited States: An Annotated Bibliography. General TechnicalReport RMRS-GTR-54, U.S. Department of Agriculture, ForestService, Rocky Mountain Research Station, Ogden, Utah, 369pp.

Leopold, L. B. and T. Maddock, Jr., 1953. The Hydraulic Geometryof Stream Channels and Some Physiographic Implications. U.S.Geological Survey Professional Paper 252, U.S. GovernmentPrinting Office, Washington D.C.

Manning, M. E., S. R. Swanson, T. Svejcar, and J. Trent, 1989.Rooting Characteristics of Four Intermountain Meadow Com-munity Types. Journal of Range Management 42:309-312.

McIntosh, B. A., J. R. Sedell, J. E. Smith, R. C. Wissmar, S. E.Clarke, G. H. Reeves, and L. A. Brown, 1994. Management His-tory of Eastside Ecosystems: Changes in Fish Habitat Over 50Years, 1935 to 1992. General Technical Report PNW-GTR-321,U.S. Department of Agriculture, Forest Service, Pacific North-west Research Station, Portland, Oregon, 55 pp.

Naiman, R. L., and H. Decamps, 1997. The Ecology of Interfaces:Riparian Zones. Annual Review of Ecology and Systematics28:621-658.

Naiman, R. J., H. Decamps, and M. Pollock, 1993. The Role ofRiparian Corridors in Maintaining Regional Biodiversity. Eco-logical Applications 3:209-212.

Naiman, R. J., C. A. Johnson, and J. C. Kelley, 1988. Alteration ofNorth American Streams by Beaver. BioScience 38:753-762.

National Research Council (NRC), 1992. Restoration of AquaticEcosystems. National Academy of Sciences, Washington, D.C.

Otting, N. J., 1998. Ecological Characteristics of Montane Flood-plain Plant Communities in the Upper Grande Ronde RiverBasin, Oregon. M.S. Thesis. Oregon State University, Corvallis,Oregon.

Patten, D. T., 1998. Riparian Ecosystems of Semi-Arid North Amer-ica: Diversity and Human Impacts. Wetlands 18:498-5 12.

Ramsey, F. L. and D. W. Shafer, 1996. The Statistical Sleuth: ACourse in Methods of Data Analysis. Duxbury Press, Belmont,California.

Reed, P. B., 1996. Draft Revision of 1988 National List of PlantSpecies That Occur in Wetlands: Northwest (Region 9). U.S.Fish and Wildlife Service, Washington, D.C.

Robertson, A. I., P. Bacon, and G. Heagney, 2001. The Responses ofFloodplain Primary Production to Flood Frequency and Timing.Journal of Applied Ecology 38: 126-136.

Robison, E. G., 1988. Large Woody Debris and Channel Morphologyof Undisturbed Streams in Southeast Alaska. M.S. Thesis. Ore-gon State University, Corvallis, Oregon.

Robison, E. G. and R. L. Beschta, 1989. Estimating Stream Cross-Sectional Area from Wetted Width and Thalweg Depth. PhysicalGeography 10:190-198.

Schumm, S. A., 1999. Causes and Controls of Channel Incision. In:Incised River Channels, S. E. Darby and A. Simon (Editors).John Wiley and Sons, Chichester, United Kingdom, pp. 19-33.

Smith, D. G., 1976. Effect of Vegetation on Lateral Migration ofAnastomosed Channels of a Glacier Meltwater River. Bulletin ofthe Geological Society of America 87:857-60.

Tellman, B., H. J. Cortner, M. G. Wallace, L. F. DeBano, and R. H.Hamre (Technical Coordinators), 1993. Riparian Management:Common Threads and Shared Interests. A Western RegionalConference on River Management Strategies (February 4-6,1993, Albuquerque, New Mexico). General Technical Report RM-226, U.S. Department of Agriculture, Forest Service, RockyMountain Forest and Range Experiment Station, Fort Collins,Colorado, 419 pp.

Thorne, C. R., 1990. Effects of Vegetation on Riverbank Erosion andStability. In: Vegetation and Erosion: Processes and Environ-ments, J. B. Thornes (Editor). John Wiley and Sons, New York,New York, pp. 125-144.

Walters, D. R. and D. J. Keil, 1996. Vascular Plant Taxonomy.Kendall/Hunt Publishing Company, Dubuque, Iowa.

Wigington, P. J. and R. L. Beschta (Editors), 2000. Riparian Ecologyand Management in Multi-Land Use Watersheds. AmericanWater Resources Association, Middleburg, Virginia, TPS-00-2,616 pp.


Download - ROOT BIOMASS IN RELATION TO CHANNEL MORPHOLOGY OF HEADWATER STREAMS

Top Related