7

Herbaceous Stubble Height as a

Warning of Impending Cattle

Grazing Damage to Riparian Areas

Frederick C. Hall, and Larry Bryant

United States

Department of

Agriculture

Forest Service

Pacific Northwest

Research Station

General

Technical Report

PNW-GTR-362

September 1995
Authors FREDERICK C. HALL is a senior plant ecologist, Pacific Northwest Region,

RO, Box 3623, Portland, OR 97208; and LARRY BRYANT is a research

wildlife biologist, USDA Forest Service, Range Management, 201 14th Street

SW, Washington DC, 20250.
 9

Hall, Frederick C.; Bryant, Larry. 1995. Herbaceous stubble

height as a warning of impending cattle grazing damage to riparian areas. Gen. Tech. Rep. PNW-GTR-362. Portland, OR:

U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 9 p.

Prevention of damage to riparian areas from cattle grazing is essential for sound watershed management. Various stubble heights

of the most palatable species are used to predict when unacceptable impacts-heavy use or trampling, or both-are about to occur.

Managers can observe stubble height and usage and recommend

moving the cattle if undesirable effects from continued livestock

grazing are anticipated. Three guides for determining when to

move cattle are presented: (1) stubble height approaches 3

inches; (2) stubble height changes from 3 inches to 3/4 of an inch;

and (3) the most palatable vegetation starts drying regardless of

stubble height.

Keywords: Stubble height, riparian, damage, cattle, drying.

Abstract
Contents 1 Introduction

1 Riparian Ecosystems

1 Livestock Grazing

1 Concepts

2 Warning Signs

2 Application

2 Desired Future Condition

3 Establish Key Areas

3 Monitor

6 Conclusions

7 Literature Cited
 11

Introduction

Riparian Ecosystems

Livestock Grazing

Concepts

Riparian ecosystems are generally defined as a body of water with its adjacent soil and

vegetation. Cattle graze riparian areas throughout the inland Pacific Northwest. This

grazing may affect the vegetation and soils in undesirable ways. Methods are needed

to help predict when continued livestock grazing will begin to cause undesirable impacts on the riparian vegetation and soils. We have adequate criteria for documenting

damage after it occurs (General Accounting Office 1988); needed are methods to warn

of impending unwanted impacts. This paper presents some methods to predict when

cattle grazing may begin to adversely impact riparian ecosystems.

Riparian ecosystems have two important areas of concern: (1) woody vegetation for

shade, cover, and streambank protection; and (2) streambanks themselves, often

called "the green line," with their protective herbaceous vegetation. Cattle can affect

each of these in different ways. Direct browsing of shrubs reduces the cover and shade

they provide over the stream and could prevent their regeneration. Heavy use of

streambanks by cattle may cause direct physical damage through the breakdown of the

bank and the overuse of the herbaceous vegetation. Overuse may change the vegetation from protective sedges to open, nonprotective forbs. This fosters streambank erosion and reduces the filtering action of dense sedges, which tends to reduce sediment

loading (Clary and Medin 1985, Clary and Webster 1989, Elmore 1992, Platts 1989).

Livestock grazing allotments are an integral part of the USDA Forest Service's land

management activity. When livestock grazing is closely managed and monitored by

professional land managers, assumptions are made that some degree of cattle use is

compatible with riparian ecosystem management and that trends toward a desired future condition can be achieved while cattle graze the area (Bryant 1985, Clary and

Webster 1989, Elmore 1992, Elmore and Beschta 1987, Hanson 1993, Johnson 1992,

Platts 1989, Ratcliff and others 1987, Skoviin 1984). In short, riparian management objectives must be defined and criteria established by which these objectives can be appraised. If site-specific monitoring proves conditions are not improving and moving toward the desired state, then livestock grazing should not occur or grazing management

should be changed.

The following concepts were used to develop methods for predicting impending impacts:

• Cattle generally prefer grasses and forbs to woody vegetation, at least when the

herbaceous vegetation is green (Gillen and others 1985, Holechek and Vavra

1983, Kovalchik and Elmore 1992, Vavra and others 1980).

• Some degree of moderate use of palatable herbs (primarily grasses and sedges)

can occur without undesirable browsing of riparian shrubs and without streambank

damage (Clary and Webster 1989, Kauffman and Krueger 1984, Kauffman and

others 1983b, Kovalchik and Elmore 1992, Platts and Nelson 1989).

∗ The eating technique of cattle is used to fashion warning indicators. A premise is

that cow preference for forage species will shift as stubble heights drop below 3

inches (Cook and others 1967, Cook and Harris 1968).

Cattle prefer to reach their tongue out of the side of their mouth and draw in the

vegetation, tasting it as they do (fig. 1, p. 4). Thus they limit themselves to those
Warning Signs

Application

Desired Future Condition

species that taste best. But this preference begins to change as stubble heights

are lowered to 3 inches because the vegetation is too short to be pulled in by the

tongue. At this time, cattle must begin eating in bites (like a horse), which takes

up to twice the effort and time. Yet their rumen continues to say, "Fill me up." The

result is a shift to more quickly eaten and less palatable forage (Van Soest 1982).

Finally, cattle are limited by the thickness of their lower lip to stubble heights of

about 3/4 of an inch. At this stubble height, their preferences have changed dramatically and they must search for something to fill their rumen (Van Soest 1982).

• Cattle preference will change as herbaceous vegetation dries (Clary and Webster 1989, Gillen and others 1985, Hanson 1993, Kauffman and others 1983a).

Even at stubble heights above 3 inches, their preference may shift to shrubs.

The above concepts have been used to develop a set of three warning signs:

1.The stubble height of the most palatable species approaches 3 inches.

2.The stubble height on the most palatable species changes from 3 inches to 3/4 of

an inch.

3.Greenness (that is, crude protein, quality of forage) of the most palatable species

diminishes and the species shows signs of drying, thereby indicating a change in forage quality and a consequent change in palatability.

These stubble height and greenness factors are critical elements in palatability and

cause shifts in cattle forage preference, such as changing from grasses and sedges

to shrubs or from moist-site grasses and sedges to wet-site course sedges (Clary and

Webster 1989, Gillen and others 1985, Hanson 1993, Kauffman and others 1983a).

A two-pasture deferred rotation grazing system may be used as an illustration: Cattle

are assigned to graze for 2 months in each pasture during a 4-month season. In one

case, 3/4-inch stubble is reached by the end of the second week, which forces cattle

out onto less desirable rangeland. In this case, the 3/4-inch stubble is maintained

over the remaining 6 weeks while the cattle are held in the pasture. In the second

case, the pasture could be stocked such that the 3/4-inch stubble height occurs at the

end of the second month. Impacts on the riparian ecosystem of these two grazing

programs probably would be quite different: 6 weeks of grazing on 3/4-inch stubble

compared to a day or two on 3/4-inch stubble (Clary and Webster 1989, Johnson

1992). The concept of deferred-rotation grazing to "force use on the side hills" may

not adequately protect or enhance the riparian ecosystem (Clary and Webster 1989,

Elmore 1992, Johnson 1992, Myers 1989).

First and most important in reaching a desired future condition is to define what is

achievable (Clary and Webster 1989, Elmore 1992, Elmore and Beschta 1987,

Hansen 1993, Kovalchik and Elmore 1992, Myers 1989). Achievable means that the

site can grow the desired vegetation. Not all riparian ecosystems will support dense

shrubs or trees along the water's edge; for example, most riparian shrubs require a

certain degree of root aeration or a minimum percentage of dissolved oxygen in the
 13

water (Kovalchik 1992). These conditions often are provided by a gravel layer under

the soil through which water can move. A soil resting directly on a clay layer usually

does not have sufficient aeration to support dense shrubs (Bohn and Buckhouse

1985). Likewise, a raised water table, as might occur with beaver impoundments, may

reduce aeration to the point of discouraging woody vegetation (Stevens and Waring

1988).

In addition to vegetation, other riparian objectives should be considered. One is to reduce or eliminate bank breakage by livestock trampling (Kauffman and others 1983b,

Platts and Nelson 1989). Another is to leave enough stubble height on streambank

sedges to reduce soil surface erosion and filter out sediment (Clary and Webster

1989, Stevens and Waring 1988).

After defining the desired future condition, determine if cattle grazing is compatible

with attaining these conditions. If it is, then establish key areas where livestock use

can be monitored. These key areas should be the most palatable locations within

the riparian ecosystem; often, they are patches within apparently homogeneous areas

(fig. 2, following page). They will be the ones evaluated for stubble height and drying

of the vegetation (fig. 3, p. 5). Site-specific objectives and conditions may dictate taller

stubble heights or other standards.

When residual vegetation is needed during high flow periods to trap and retain silt and

buffer banks, stubble heights below 3 inches may be acceptable when enough spring

soil moisture remains after livestock removal to allow regrowth to 3 inches or more.

Monitor key areas as follows:

1. As stubble height approaches 3 inches for the most palatable species, such as

Kentucky bluegrass, assume that cattle preference will change and unacceptable

grazing use will begin.

Monitor shifts in preference to assure that unacceptable impacts are not occurring

on desired vegetation. If they are, move the livestock; if they are not, continue the

grazing and continue the monitoring.

2. As the grazing season advances, monitor drying soil and vegetation curing in the

key areas. Cattle preference will shift as species palatable in spring and early

summer become dry, particularly Kentucky bluegrass and other introduced species.

3. If livestock continue to graze, stubble height of the most palatable species (that is,

Kentucky bluegrass) will decrease from 3 inches toward 3/4 of an inch. Assume

that cattle preference has changed to the degree that unacceptable grazing is

about to occur or is occurring (fig. 3). Prepare to move the livestock to avoid damage (fig. 4, p. 5).

Monitor frequently enough, at least once per week, to detect changes in cattle preference that will adversely impact the established grazing management objectives.

Establish Key Areas

Monitor
Figure 1—The preferred method of

eating by cattle is to reach their

tongue out and draw forage into their

mouth, tasting it as they do. This feeding method works only when the forage is tall enough to be drawn in and

bitten off. At a stubble height of about

3 inches, the animal must change its

biting method because forage is too

short to be drawn into the mouth.

Change in eating method is associated with change in preference for

forage species. (Photo by Ben

Roché.)

Figure 2—Pattern of cattle use in a meadow of Kentucky bluegrass and sedges. Kentucky bluegrass

is grazed to 1-1/2-inch stubble while the less palatable sedges are essentially ungrazed. At this level

of use, when bluegrass is still green, no damage has been done to the shrubs or stream edge (line of

low shrubs near bottom of hill).
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Figure 3—Change from 3-inch stubble of Kentucky bluegrass to 3/4-inch stubble. Cattle were removed before the 3/4-inch level was reached thus preventing damage to the riparian area.

Figure 4—Kentucky bluegrass after 2 weeks at a 3/4-inch stubble level. Less palatable sedges have been grazed to

4 inches and willows have been heavily browsed. Two weeks of use at 3/4-inch stubble was too long and resulted in

the unwanted browsing of the willows.
4. If grazing impacts are acceptable as stubble height approaches 3/4 of an inch,

monitor the situation at least twice per week and move the animals at the first

hint of unacceptable use or soil damage (fig. 4, p. 5). More frequent monitoring is

desirable.

At stubble heights below 3 inches, and particularly at 3/4 of an inch, livestock can

quickly cause damage to the riparian ecosystem, often within a few days. Intensively managed pastures that can be monitored frequently and where livestock

can be moved effectively may be appropriate for this intensity of use. Extensively

managed pastures, not monitored to this standard or where livestock removal may

be tenuous, are probably not appropriately grazed to less than 3 inches in stubble

height.

If shrub use and bank breakage are to be avoided, critically evaluate cattle shift in

preference as stubble height approaches 3 inches. Assume that shrub use will occur

at stubble heights below 3 inches, or as the most palatable vegetation cures. If grazing is to continue, verify that unacceptable use is not occurring.

Unacceptable impacts from livestock grazing can be avoided in riparian areas by recognizing that a shift in cattle preference can occur as the 3-inch stubble height is approached. Assume undesirable impacts will occur at any time as stubble height

changes from 3 inches to 3/4 of an inch as a result of major shifts in livestock preference. Drying of herbaceous forage, particularly Kentucky bluegrass, also will cause a

shift in preference that may adversely impact riparian ecosystems.

Conclusions
 17

Bohn, C.C.; Buckhouse, J. 1985. Some responses of riparian soils to grazing management in northeastern Oregon. Journal of Range Management. 38(4): 378-381.

Bryant, L.D. 1985. Livestock management in the riparian ecosystem. In: Riparian

ecosystems and their management: reconciling conflicting uses: First North American riparian conference; 1985 April 16-18; Tucson, AZ. Gen. Tech. Rep. RM-120.

Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain

Forest and Range Experiment Station: 285-289.

Clary, W.P.; Medin, D.E. 1985. Differences in vegetation biomass and structure due to

cattle grazing in a northern Nevada riparian ecosystem. Res. Pap. INT-427. Ogden,

UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 8 p.

Clary, Warren P.; Webster, Bert F. 1989. Managing grazing of riparian areas in the

Intermountain Region. Gen. Tech. Rep. INT-263. Ogden, UT: U.S. Department of

Agriculture, Forest Service, Intermountain Research Station. 11 p.

Cook, C.W.; Harris, L.E. 1968. Nutritive value of seasonal ranges. Bull. 472. [Location

of publisher unknown]: Utah Agricultural Experiment Station.

Cook, C.W.; Harris, L.E.; Young, M.L. 1967. Botanical and nutritive content of diets in

cattle and sheep under single and common use on mountain ranges. Journal of Animal Science. 26:1169-1174.

Elmore, Wayne. 1992. Riparian responses to grazing practices. In: Watershed management: balancing sustainability and environmental change. New York:

Springer-Verlag: 442-457.

Elmore, W.; Beschta, R.L. 1987. Riparian areas: perceptions in management. Rangelands. 9: 260-265.

General Accounting Office. 1988. Public rangelands: some riparian areas restored

but widespread improvements will be slow. B-230548. Washington, DC: U.S. Accounting Office, Resources, Community and Economic Development Division. 85p.

Gillen, R.L.; Krueger, W.C.; Miller, R.F. 1985. Cattle use of riparian meadows in the

Blue Mountains of northeastern Oregon. Journal of Range Management. 38(3):

205-209.

Hanson, Paul. 1993. Developing a successful riparian wet land grazing management

plan for the upper Ruby River cattle and horse allotment in southwestern Montana.

In: Riparian management: common threads and shared interests: a western regional

conference on river management strategies; 1993 February 4-6; Albuquerque, NM.

Gen. Tech. Rep. RM-226. Fort Collins, CO: U.S. Department of Agriculture, Forest

Service, Rocky Mountain Forest and Range Experiment Station: 328-335.

Holechek, J.L.; Vavra, M. 1983. Drought effects on diet and weight gains of yearling

heifers in northeastern Oregon. Journal of Range Management. 36(2): 227-231.

Literature Cited
Johnson, Kendall L. 1992. Management for water quality on rangeland through best

management practices: the Idaho approach. In: Watershed management: balancing

sustainability and environmental change. New York: Springer-Verlag: 415-441.

Kauffman, J. B.; Krueger, W.C. 1984. Livestock impacts on riparian ecosystems and

streamside management implications—a review. Journal of Range Management.

37(5): 430-438.

Kauffman, J. B.; Krueger, W.C.; Vavra, M. 1983a. Effects of late season cattle grazing on riparian plant communities. Journal of Range Management. 36(6): 685-691.

Kauffman, J.B.; Krueger, W.C.; Vavra, M. 1983b. Impacts of cattle on streambanks in

northeastern Oregon. Journal of Range Management. 36(6): 683-684.

Kovalchik, Bernard L. 1992. Growth and yield of willows in central Oregon compared

to reports in world literature. In: Proceedings-Symposium on ecology and management of riparian shrub communities; 1991 May 29-31; Sun Valley, ID. Gen.

Tech. Rep. INT-289. Ogden, UT: U.S. Department of Agriculture, Forest Service,

Intermountain Research Station: 83-88.

Kovalchik, Bernard L.; Elmore, Wayne. 1992. Effects of cattle grazing systems on

willow-dominated plant associations in central Oregon. In: Proceedings Symposium

on ecology and management of riparian shrub communities; 1991 May 29-31; Sun

Valley, ID. Gen. Tech. Rep. INT-289. Ogden, UT: U.S. Department of Agriculture,

Forest Service, Intermountain Research Station: 111-119.

Myers, Lewis H. 1989. Grazing and riparian management in southwestern Montana. In:

Practical approaches to riparian resource management: an educational workshop;

1989 May 8-11; Billings MT Billings, MT: U.S. Department of the Interior, Bureau of

Land Management: 117-120.

Platts, William; Nelson, Rodger L. 1989. Characteristics of riparian plant communities

and streambanks with respect to grazing in northeastern Utah. In: Practical approaches to riparian resource management: an education workshop; 1989 May

8-11; Billings, MT Billings, MT: U.S. Department of the Interior, Bureau of Land Management: 73-81.

Platts, William S. 1989. Compatibility of livestock grazing strategies with fisheries. In:

Practical approaches to riparian resource management: an educational workshop;

1989 May 8-11; Billings, MT Billings, MT: U.S. Department of the Interior, Bureau of

Land Management: 103-110.

Ratliff, R.D.; George, M.R.; McDougaid, NX 1987. Managing livestock grazing on

meadows of California's Sierra Nevada: a manager-user guide. Coop. Exten. Leafl.

21421. [Location of publisher unknown]: University of California, Division of Agriculture and Natural Resources. 9 p.

Skoviin, Jon M. 1984. Impacts of grazing on wetlands and riparian habitat: a review of

our knowledge. In: Developing strategies for rangeland management: a report pre-
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pared by the committee on developing strategies for rangeland management. Boulder, CO: Westview Press: 1001-1103. In cooperation with: National Research Council; National Academy of Sciences.

Stevens, L.E.; Waring, G.L. 1988. The effects of prolonged flooding on the riparian

plant community in Grand Canyon. In: Riparian ecosystems and their management:

reconciling conflicting uses: 1st North American riparian conference; 1985 April 16-

18; Tucson, AZ. Gen. Tech. Rep. RM-1 20. Fort Collins, CO: U.S. Department of

Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station:

81-86.

Van Soest, P.J. 1982. Nutritional ecology of the ruminant. Corvallis, OR: O&B Books

Inc.

Vavra, M.; Krueger, W.C.; Wheeler, W.P. 1980. Cattle grazing potential on clearcuts.

Res. Rep. 586. Corvallis, OR: Oregon State University, Agricultural Experiment Station.
Hall, Frederick C.; Bryant, Larry. 1995. Herbaceous stubble height as a warning of

impending cattle grazing damage to riparian areas. Gen. Tech. Rep. PNW-GTR-362.

Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 9 p.

Prevention of damage to riparian areas from cattle grazing is essential for sound watershed management. Various stubble heights of the most palatable species are used to

predict when unacceptable impacts-heavy use or trampling, or both-are about to occur.

Managers can observe stubble height and usage and recommend moving the cattle if

undesirable effects from continued livestock grazing are anticipated. Three guides for

determining when to move cattle are presented: (1) stubble height approaches 3

inches; (2) stubble height changes from 3 inches to 3/4 of an inch; and (3) the most

palatable vegetation starts drying regardless of stubble height.

Keywords: Stubble height, riparian, damage, cattle, drying.

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