Time of Grazing and Cattle-Induced Damage to Stream banks 1

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1 This file was reated by sanning the printed publiation. Errors identified by the software have been orreted; however, some errors may remain. Time of Grazing and Cattle-ndued Damage to Stream banks 1 Clayton B. Marlow2 and Thomas M. Poganik3 Abstrat.--Cattle impat riparian ommuni ties through two proesses: grazing and trampling. Re-evaluation of management praties indiates that implementation of rest rotation grazing management and limiting attle use of riparian vegetation to 2% of the standing rop will redue impat. Rest rotation and light grazing may improve plant vigor but little information is available on how well either pratie ontrols bank damage from trampling. A three-year grazing study in southwestern Montana indiates that the level of attle use in the riparian zone has little bearing on streambank damage (r 2 =.6). Soil moisture ontent diretly affets (-2:.85) the streambanks suseptibility to trampling. Postponing or deferring grazing until streambanks have dried (<1% soil moisture) will further protet the riparian zone from damage. Degradation of western riparian zones has been largely attributed to attle grazing (Leopold 1974, Behnke and Zarn 1976, Behnke and Raleigh 1978, Oregon-Washington nterageny Wildlife Counil 1978, Platts 1979, and Davis 1982). Cattle ontribute to delines in riparian ommunity stability and water quality by removing protetive vegetation (grazing) and inreasing bank instability through trampling. Unstable banks then lead to aelerated erosion and elevated instream sediment loads (Winegar 1977 and Duff 1979) while the orresponding heavy use of vegetation inreases sediment prodution due to elevated surfae runoff (Rauzi and Hanson 1966). Redution in vegetative over may also lead to higher water temperatures (Johnson et al and Van Velson 1979) whih are ounterprodutive for aquati vertebrate and invertebrate populations. These impats have arisen due to past management or the lak thereor (Platts 1978). n many ases, riparian zones have been ignored in the planning proess beause their limited extent made them "sarifie areas" (Skovlin et al. 1977). Very often the "sarifie" ondition was reated by inorporation of sj:.reamside areas into large pastures and not identifying them as separate and distint management units (May and Davis 1982). As an outgrowth of this oversight problem, the Western Division Amerian Fisheries Soiety (1979) 1 Paper presented at the North Amerian Riparian Conferene. (The University of Arizona, Tuson, April 15-19, 1985). 2 1ayton B. Marlow is Assistant Professor, Animal & Range Sienes, Montana State University, Bozeman, Ml'. 3Thomas M. Poganik is Range Conservationist, USD Bureau of Land Management, Tonopah, NV. reommended inlusion of riparian onerns at all planning levels, and the rapid development of management praties that would redue riparian degradation. Platts (1979) expressed doubt that existing grazing management strategies were apable of orreting attle impats in riparian habitats, but several management alternatives have reently been re-examined. May and Davis (1982) reommended light grazing levels (2% forage removal) and hanges in pasture design to alleviate attle-indued problems. Rest rotation grazing systems appear to have promise for rehabilitating riparian areas without exluding attle for long periods (Kaufman and Krueger 1984), although some managers (Armour 1978, Storh 1979, and Platts 1982) question the effetiveness of rest rotation for long-term riparian improvements. The limited aeptane of rest rotation to protet riparian zones arises from a 1 ak of onsistent researh results (Kaufman and Krueger 1984). nonsistenies may be the result of inadequate information to develop site speifi riteria for protetion of the riparian resoure or from a variety of different experimental purposes and proedures all being lumped as "rest rotation". Any grazing system relies on the ontrol of the season and frequeny of grazing to be effetive. Consequently, managers must know how eah omponent of the eosystem (soils, vegetation, and animals) reats to grazing at different times of the year. Although May and Davis (1982) and Platts (1982) suggest that light grazing will produe improvements in the riparian zone, little information is available on how streambanks respond to trampling at different times during the year. Light grazing use may protet the vegetation, but we know little about 279

2 onurrent levels of bank damage. nformation on bank damage in relation to season of grazing ould be inorporated into the development of riparian grazing strategies and thereby improve the likelihood of suess. n 1981, a study was initiated in southwestern Montana to determine the relationship between the time of attle grazing and riparian degradation. Beause foothill ranges are traditionally used from June to Otober, attle grazed the study site from the third week of June until the first few days of Otober. Another ommon management pratie on these ranges is to base attle stoking rates on a 5S removal of the standing forage rop. This was also followed to make study results as appliable as possible to urrent grazing management strategies. STUDY STE DESCRPTON The riparian study was onduted on a small tributary of the Madison River in southwestern Montana (Fig. 1). Both the stream and its headwaters are loated on the Montana Agriultural Experiment Station's Red Bluff Researh Ranh. The Cottonwood Creek watershed (136 ha) is haraterized by moderate to steep slopes with elevations ranging from 2 m at the headwater spring to 14 m where it enters the Madison River. The stream is bordered on the south by slopes of 3-5 perent and on the north by rolling hills with 15 to 3 perent slopes. MONTANA Figure 1.--Loation of study site in southwestern Montana. The riparian ommunity is dominated by Kent~ky bluegrass {..f.qs pratensis L.), redtop (Agrostis stolonifera L.), timothy (Phleum pratense L.), smooth brome (~~ ~~ Leyss.), beaked sedge (~ rostrata Stokes), Sprengel's sedge (~ sprengelii Dewey), and white lover (Trifolium repens L.). Overstory inludes quaking aspen (Populus tremuloides Mihx.), willow (~ spp. L.), hokeherry (Prunus virginiana L.), and swamp gooseberry (..U...b. A laustre (Pers.) Poir.). The upland ommuni ties support Kentuky bluegrass, green needl egrass ~ yiridula Trin.), needleandthread (~ omata Trin. & Rupr.), bluebunh wheatgrass {Agropyron soiatum (Pursh.) Sri bn. & Smith), western wheatgrass (Agropyron smithii Ryd b.), daho fesue ( Festua idahoensis Elmer), and heatgrass brome (Bromus tetorum L.). Sea ttered dense stands of mountain big sagebrush (Artemisia tridentata ss~ yaseyana ( Rydb.) Beetle) interspersed with Wood's rose (~ woodsii (Lind) L.) and Roky Mountain juniper (Juniperus sopulorum Sarg.) our throughout. Cottonwood Creek is small (average flow.16 m3s-1) with hannel substrate omposed of angular gravel, silt, and fine lay. Banks have less than 2S of their total volume omposed of rok or gravel. Mean daily air temperatures range from 2 C in July and August to -11 C in Deember. The 4 to 5 mm of total annual preipitation ours primarily as snowfall during Otober through Marh and rainfall during May and June. Preipitation from thunderstorms in July, August, and September ontribute less than 2S of the annual total. METHODS A 5.5 ha setion of Cottonwood Creek was fened in the spring of Nine.6 ha paddoks, eah ontaining equivalent amounts of upland and riparian ommunities were reated by ross fening the original enlosure (Fig. 2). One paddok served as an ungrazed ontrol, the other eight were grazed sequentially, as follows: beginning with the paddok furthest downstream, four head of yearling attle were grazed in eah paddok for 14 days. Paddoks were grazed in order to prevent upstream use from onfounding time of year effets. One the paddok was grazed, it was not grazed again until the next year, when it was grazed at the same time. Streamflow was measured ontinuously with Parshal Type Flumes equipped with stage level reorders at the downstream edge of eah paddok. Moisture ontent of streambanks was measured at two points in eah paddok every time the attle were moved. This provided nine sample dates from early June until early Otober. Perent moisture ontent of the soil olumn was determined at 15 em, 3 em and 45 em depths by the neutron sattering tehnique (MHenry 1963). Channel damage was monitored by establishing five permanent hannel ross setion transets in eah paddok. The vertial distane from the level transet line to the hannel bed was measured at 1 em horizontal intervals (Fig. 3) prior to attle grazing and immediately afterward. The post-grazing ross-setional area was then ompared to the pre-grazing area to determine the magnitude of hange during the grazing period. Differenes were tested for signifiane at the.5 level with a standard paired t test (Gomez and Gomez 1984). Cattle use patterns were based on two, 24 hour observation periods eah week in 1982 and This produed 32 observations from early June until early Otober eah year. The ativity (feeding or resting) and ommunity (riparian or 28

3 6 N Ungrazed Sept ear y Sept Aug ear y Aug J u y ear y J u y June ear y June Figure 2.--Experimental grazing periods. pasture design and respetive 1 Uplilnd \ \ '',',,,\ : "' ~ 4 \... -J 2 Figure 3.--Measuring hannel area along a permanent transet line. upland) oupied by eah heifer was reorded hourly during eah observation period. The number of observations for eah ativity ategory and loation was totaled for eah grazing perio~ Differenes in the number of observations for feeding and resting in upland and riparian ommuni ties during eah period were tested for signifiane at the.5 level with a standard paired t test (Gomez and Gomez 1984). RESULTS Cattle use of riparian and upland ommuni ties exhibited a definite seasonal pattern (Fig. 4). n general, upland use delined from June to August while riparian use inreased. During the last half of the grazing season, use in both ommunity types remained fairly onstant exept during early September when snows fored attle into the uplands. Changes in stream hannel area also showed a seasonal trend (Fig 5) but were the JU 15 JU3 Jl15 JL3 AU 15 AU3 SE 15 SE3 Grazing period Figure 4.--Seasonal attle use of riparian and upland zones (average of 1982 and 1983 observation totals). reverse of attle use patterns (Fig. 6). nreased use of ripari~n ommunities by attle explained very little (r =.6) or the hange in hannel area during eah grazing period. Examination of streambank moisture ontent provided a possible explanation for the apparent lak of affet from trampling. Moisture levels delined until early September when snowfall began to reharge the soil profile (Fig. 7). Streambank hange was signifiantly orred (P<.5) with soil moisture ontent (Fig. 8). As bank moisture ontent inreased, so did the amount of hange in hannel area. Although hanges inreased in early September with snowfall indued reharge, frozen banks limited trampling damage. Changes in hannel area during August and September were not signifiantly different (P<.5) from hanges 281

4 E (..) 3 CT f) o Q).._ <X: Q) 2 Cll..r:. (). 1.,,. ' ', ' ' ' ', ' _, ',, :'1... J u 1 5 JU3 J L 1 5 J L3 AU 1 5 AU3 SE15 SE3 Grazing Period Figure 5.--Seasonal hanges in hannel area for "' OJ ro 1,,,,... ;;... _; ;,,, ; ; ; (/) : -~ ;; > ~. 2 ' \ ' ' ' ' ',,.,.,.....,....,, " \ '-. '., ', ', : ',, 6 (/) : 9 1 ' ~o ro ~ ~~U-15---JUT3----,J_1_5---Jrl3----ATU-15---A~U~3---~S~E1~5~SE~3 Grazing period or---~-----r----~--~----,-----r---~ JU 15 JU3 JL15 JL3 AU 15 AU3 SE 1 5 SE 3 Grazing period Figure 6.--Comparison of hanges in hannel area and orresponding attle use of adjaent riparian ommuni ties. whih ourred in the ungrazed paddok. Streambank moisture ontent explained 71% - 85% of the bank suseptibility to hange during all three years of the study. The greater level of hange whih ourred in 1983 may have been aused by dry spring onditions whih aused attle &o spend more time in the riparian ommuni ties during June. CONCLUSONS Cattle indued impats on streambank stability are not red to the level of riparian use. The greatest amount of bank alteration ours when soil moisture exeeds approximately 1%. n the arid and semi-arid regions of the 282

5 ~ ~.2 r.n ' , "'' \. \ \. \. \ \. \. \ \ \, \, ' V." ', / '-' _:;....,... "... /. " :.."/.", (j) Hl83 ~------r r r-----~~----~------~~----~-- JU15 JU3 JL 15 JL3 AU15 AU3 SE15 SE3 Grazing periods Figure 7.--Seasonal soil moisture ontent of stream banks (average of top 45 em) D,." 1982 E (,) ' (/) 4 o Cll Q).._ 3 <( - Q) Cll 2 ~ (.) 1 D ~ a a 6 a a ~--~----~------~------~------~------~------~ Soil Moisture (%) Figure B.--Relationship between streambank moisture ontent and level of hannel area hange (straight lines were fitted with use of a linear regression equation. a western United States, soil moisture usually falls below this level in July or early August. Autumn reharge of the soil profile does not appear to intensify impat beause banks freeze and are less suseptible to tramplin~ Beause of the grazing suseptibility of moist streambanks, redution in attle numbers will produe little riparian improvement. Fewer attle will simply restrit bank damage to loalized spots in the pasture. These damaged areas, although infrequent, will ontinue to ontribute to further riparian degradation. This an be avoided by deferring attle use until after banks have dried suffiiently to limit trampling damage. The length of the grazing period an then be based on the reommended level of forage utilization within the riparian zone (Platts 1982, May and Davis 1982). The additional ross-fening neessary to gain this level of grazing ontrol 283

6 will also improve grazing management in the adjaent uplands. Early season attle use an be alternated among pastures so eah pasture is only grazed during June and July one every four or fiv~ years. ntegration of this type of grazing management into the overall resoure management program should enhane the potential for riparian improvement and protetion. LTERATURE CTED Armour, Carl Livestok management approahes and the fisheries resoure. p. 39. ln Pro., Forum - Grazing and Riparian/Stream Eosystems. Trout Unlimited, n. Behnke and Zarn Biology and management of threatenea and endangered western trout. USDA For. Ser. Gen. Teh. Rep. Rm-28, 45 pp. Roky Mountain For. and Range Exp. Sta., Fort Collins, CO. Behnke and Raleigh Grazing and the riparian zone: mpat and management perspetives. pp ~ Strategies for Protetion and Management of Floodplain Wetlands and Other Riparian Eosystems. USDA For. Ser. GTR- W- 12. Davis, J. W Livestok vs. riparian habitat management - there are solutions. pp l.n Wildlife - Livestok Relationships Symposium: Pro. 1. Univ. daho, For., Wildl. and Range Exp. Sta., Mosow, D. Duff, D. A Riparian habitat reovery on Big Creek, Rik County, Utah. p. 91. l.n Pro. Forum - Grazing and Riparian/Stream Eosystems. Trout Unlimited, n. Johnson, R.R., L.T. Haight and J.M. Simpson Endangered speies vs. endangered habitats: a onept. pp ljl mportane, Preservation and Management of Riparian Habitat. USDA For. Ser. Gen. Teh. Rep. RM- 43. pp Kaufman, J.B. and W.C. Krueger Livestok impats on riparian eosystems and streamside management impliations a review. J. Range Manage. 37( 5): Leopold, A.S Eosystem deterioration under multiple use. Pro. Wild Trout Management Symposium. pp USD Fish and Wildl. Se~ and Trout Unlimited, Denver, CO. MHenry, J. R Theory and appliation of neutron sattering in the measurement of soil moisture. Soil Si. 95: Oregon-Washington nterageny Wildlife Counil Managing riparian zones for fish and wildlife in eastern Oregon and eastern Washington. Unpub. Platts, W.S Livestok interations with fish and their environments: Tran. 43rd North Amer. Wildl. and Natural Res. Conf W ildl. Manage. nst. Washington, D.C. Platts, w.s Livestok grazing and riparian/stream eosys~ems. pp JA Pro., Forum-Grazing and Riparian/Stream Eosystems. Trout Unlimited, n. Platts, w.s Sheep and attle grazing strategies on riparian-stream environments. pp l.n Wildlife-Livestok Relationships Symposium: Pro. 1. Uni v. daho For., Wil dl. and Range Exp. Sta., Mosow, D. Rauzi, F. and C.L. Hanson Water intake and runoff as affeted by intensity of grazing. J. Range Manage. 19: Skovlin, J.M., W.R. Meehan, J.C. Bukhouse and M. Vavra A method of study for determining the influene of grazing on riparian and aquati habitats in the Blue Mountains of Oregon. ln Pro. Symp. Livestok nterations with Wildlife, Fisheries and Their Environments. USDA For. Ser. Pa. Southwest For. and Range Exp. Sta., Berkeley, CA. Storh, R Livestok/streamside management programs in eastern Oregon. pp ~ Pro., Forum - Grazing and Riparian/ Stream Eosystems. Trout Unlimited, n. Van Velson, R Effets of livestok grazing upon rainbow trout in Otter Creek. pp ln Pro., Forum - Grazing and Riparian/Stream Eosystems. Trout Unlimited, n. Western Division Amerian Fisheries Soiety Management and Protetion of Western Riparian Stream Exosystems. Tualatin, OR. 24 pp. Winegar, H. H Camp Creek hannel fening - plant, wildlife and soil and water response. Rangema~s J. 4:1-12. May, B. and B. D a vi s P r a t i e s for livestok grazing and aquati habitat protetion on western rangelands. pp ln Wildlife-Livestok Relationships Symposium: Pro. 1. Univ. daho, For., Wildl and Range Exp. Sta., Mosow, D. 284