STATION PAPER NO. 7 APRIL 1952

School of ForestryUniuersity of Minnesota

Uniuersity Farm, St. Paul, Minn.

THE MANITOUEXPERIMENTALFOREST... Its work and aims

ESTABLISHED 1936

U.S. Department of AgricultureForest Service

ROCKY MOUNTAIN FOREST AND RANGE EXPERIMENT STATION, FORT COLLINS, COLORADO

====̂ - w. G. McGINNIES, DIRECTOR —==5===

LOCATION

The Manitou Experimental Forest lies 28 milesnorthwest of Colorado Springs. The experimentalarea totals 25 square miles, and represents theland of the Front Range. Its general features

are shown in the map below.

MANITOU

EXPERIMENTAL FOREST

TO WOODLAND PARK

1

r PURPOSES

The Manitou Experimental Forest was established in 1936 to study problemsof land use as they relate to the management of all the resources of theFront Range. Of economic importance are water supply, recreation, live-stock grazing, farming, and timber production. The objective of researchwork on the Forest is to develop better methods of management to perpetu-ate or restore the natural resources for long-time productivity. Studiesare divided into (l) Range Management, (2) Artificial Revegetation, and(3) Watershed Management.

IMPORTANCE OF PROBLEMS STUDIED

Water supply is the most important subject of research at the Experi-mental Forest. Water yield from the forested watersheds amounts to10 to 20 percent of the annual precipitation, or about 1/4 acre-footper acre. Water is most usable if it is clear, thus the yield ofsediment must be considered along with water.

Livestock grazing is another important land use. The partsof the Forest that are suitable for grazing produce foragefor beef. Heavy grazing reduces the vegetation cover andbares the soil for accelerated runoff and erosion, which inturn clogs stream channels and reservoirs with sediment.

Recreation, timber production, and farming are lessimportant on the Forest. Elsewhere in the FrontRange these uses of land furnish a living for manylocal residents.

Trout Creek with Pikes Peak in backgroundManitou Experimental Forest

RESEARCH WORK

Because various kinds of land use are studied on theExperimental Forest, coordination of effort is im-portant. Under the direction of the Rocky MountainForest and Range Experiment Station at Fort Collins,Colorado, resident technicians undertake researchwork in range and watershed management. Several col-lege students in forestry are selected each year assummer assistants. Nearby residents are cooperatorsin many of the research studies. Every other year afield day is held as an "Open House," with a specialopportunity for public discussion of the researchprogram.

CLIMATE

The climate is mild, with an average yearly temperature ofabout 45 degrees. The mean monthly temperature for Januaryis 27 degrees; for July, 60 degrees. On the average thereare 113 days in the growing season, the frost-free periodextending from May 28 to September 18. Annual precipitationaverages about 17 inches; of this, 58 percent occurs duringthe growing season. Yearly precipitation has varied from8 inches to 26 inches.

JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC.

MONTHLY PRECIPITATION

BY 10 MINUTE PERIODS

CLOUDBURST

60 0 BY 10 MINUTE PERIODS

SHOWER

60 0 BY IO MINUTE PERIODS

LIGHT RAIN

60

TYPES OF SUMMER STORMS(Records averoged)

1

r TOPOGRAPHY AND SOILS

The Experimental Forest includes broad, gently rollingvalleys and plateaus, and rugged mountains with narrow,steep-walled canyons. The elevation ranges from 7,500to 9,500 feet. Granitic soils of low fertility and highcredibility occur in the rough eastern part. Alluvialsoils formed by stream outwash are of medium fertilityand occupy the level portions. Limestone soils, whichare the most productive, and sandstone soils also arefound in small areas of the Forest.

Examples of geologic and accelerated erosion are foundthroughout the Forest. The general distribution of thesoils is shown below.

I mile

NATIVE VEGETATION

The native vegetation is typical of ponderosa pineforests in the southern Rocky Mountains, Ponderosapine, Douglas fir, lodgepole pine, and aspen are theimportant tree species. Bunchgrasses make up mostof the grass vegetation. The most common are Arizonafescue and mountain muhly* Shrubs may be seen occa-sionally throughout the timbered areas.

The Experimental Forest has been grazed by livestockand logged* Below is a map showing the general dis-tribution of the native vegetation.

EXPERIMENTALFOREST HDQRS

Dominant PlantsDouglas-firPonderosa pineGrass

Aspen

Lodgepole pine

I mile

r RANGE MANAGEMENT

PASTURE STUDIES

Since 1942 yearling Hereford heifers furnished by local ranchers havebeen grazed for a 5-month season, June 1 to October 31, on six pasturesof about 300 acres each. Three rates of stocking representing heavy.moderate, and light use of the vegetation have been studied. The stock-ing rates of the pastures are:

Heavy - 57 percent of annual herbage removedModerate - 33 percent of annual herbage removedLight - 14 percent of annual herbage removed

EXPERIMENTAL PASTURES

PASTURE 1 II

HEAVY //USE //

• • \| \L

il /<^= FOREST HDQRS.

PRIMARY OBJECTIVES

Good cattleGood rangeGood watersheds

Best economyfor all

in the long run

PASTURE STUDIES

Stocking rate basedon yi% herbage re-moved. Heavy graz-ing reduces annualforage production,depletes the grassstand, gives poorcattle gains, and agross return of

per section

Stocking rate based on33$ herbage removed.Moderate grazing main-tains annual forageproduction, improvesthe grass stand, givesgood cattle gains, anda gross return of$2,162 per section

Stocking rate basedon 14$ herbage re-moved. Light graz-ing improves annualforage production,increases the grassstand, gives highcattle gains and agross return of$1,612 per section

8

r0)o

N

0>o»o

JQt_

TJc3OQ.

oo

0>o>o

x>i.0>X

JO

"o

Ott><A

C_0>ex

Cc_34-0>cr

FORAGE YIELD

RETURNS PER SECTION

MODERATEGRAZINGUSE

MAINTAINSA HIGHr FORAGE

YIELDS

2000

GIVESGREATERRETURNSPER SECTION

1000

PLANT GROWTH

Heavy use , Moderate use Light use No use

Both root and top growth of little bluestem(Andropogon scoparius) are reduced by heavy grazing use

Blue grama

Not only is herbage yield reduced byheavy grazing, but also less desirableforage species invade heavily grazedareas. Here blue grama, a low-yieldinggrass in mountain areas, is replacingmountain muhly, a high-producing, pal-atable bunchgrass.

Mountain muhly

10

r ARTIFICIAL REVEGETATION

In addition to learning how to manage native pastures it is also neces-sary to learn how to heal thy scars of past abuse. Methods of artificialrevegetation of abandoned fam lands and depleted range lands are tested.The objectives are to (l) increase forage production, and (2) stabilizeeroding soil. The first step is to find out what plants will grow bestin the Front Range areas.

Row plots where 130 grasses, legumes, and shrubshave been tested for adaptability

The best species from thenursery trials are thentested in field plots atmany different locationsto determine which arebest suited for differentelevations and sites.

A 1-year-old stand of intermediate wheatgrassseeded on depleted range land in South Park.The seedbed was prepared with a raoldboard plow

followed by packing and drilling.

11

PASTURE STUDIES

Small pastures of crested and intermediate wheatgrasses, Russian wild-rye, andsmooth bromegrass are being grazed at heavy, moderate. and light intensities.

SMOOTH BROME

• - -;- —-i—-r*j;t

Reseeded grasses are not miracle grasses. They can be destroyed by too heavygrazing. Grazing smooth brome to a 2-inch stubble will weaken the plants'

vigor and cause lower production

Livestock gains, herbage yields, and beef" productionshow clearly the advantages of successful reseeding

Reseededpasture

Herbage : Heifer days : Gainyield : grazing ; per day

Totalgain

Lbs./acre Per acre Lbs. : Lbs./acre

Smooth brome

Crested wheatgrass

Intermediatewheatgrass

Mixture: crestedwheatgrass, smoothbrome, sweet clover

Russian wild-rye

1,399 (4 yrs.) 42 (3 yrs.) 1.5 (3 yrs.) 65 (3 yrs.)

1,959 (4 yrs.) 44 (3 yrs.) 1.6 (3 yrs.) 77 (3 yrs.)

1,668 (2 yrs.) 47 (1 yr.) 1.7 (1 yr.) 84 (l yr.)

2,471 (4 yrs.) 47 (3 yrs.) 1.7 (3 yrs.) 91 (3 yrs.)

409 (1 yr.) Grazed for first time in 1951

12 I

r ADAPTABLE GRASSES

SMOOTH BROME: Widely known,widely used. Good springand summer pasture. Not asproductive as other grasses.Prefers moist ground.

CRESTED WHEATGRASS; Alsowidely known and used. Ex-cellent spring pasture andhay crop. High production,more resistant to grazingthan smooth brome.

INTERMEDIATE WHEATGRASS; Anewer importation from theold world. Excellent springand summer pasture, goodhay crop, and high seedproduction.

13

.

RUSSIAN WILD-RYE: An-other newer importa-tion. Low producer,but excellent earlyspring pasture. Readyfor grazing 2 to 3weeks earlier thancrested wheatgrass.

BLUEBUNCH WHEATGRASS; Na-tive to United States.Slower and more difficultto establish than othergrasses, but makes excel-lent summer pasture.

BIG BLUEGRASS; Nativeto United States. Ex-cellent late - fall,early winter pasture.Has had 8 to 10 inchesgreen growth at theExperimental Forest inlate December.

14 1

r WATERSHED MANAGEMENT

STREAM FLOW

Since 1939 stream flow, precipitation, and groundwater records have been taken in the 4,800-acreMissouri Gulch watershed. These records provideknowledge of various storm patterns occurring onthe watershed and their influence on stream flowand erosion. The watershed is grazed by livestock.

PLANT COVER

Records of precipitation, runoff, and erosionhave been kept since 1939 on six small ponder-osa pine watersheds of 1 to 2 acres in size.Recently, two watersheds have been cut andburned to encourage the growth of aspen andtwo to develop a grass stand, while two wereleft unchanged. These watershed studies willgive clues as to which type of vegetative coveris superior in managing a watershed.

SEDIMENTATION

Gully erosion and bank sloughing yield the greatestamount of sediment to stream channels. A sedimenta-tion study has been made of Manitou Lake. Gully andsheet erosion studies have been made on the experi-mental pastures. Erosion and sediment-yield charac-teristics of the soils have been determined.

Sediment bars in the South Platte River movedownstream at the rate of 1̂ miles per yearand are erosion depositions from steep slopes,

gullies, and roads.15

STREAM FLOW

Missouri Gulchstream gageduring

high springflow

A MISSOURI GULCH STORM

High runoff from cloudburst storms is related to storm distribution, totalprecipitation, and stream flow at the time of the storm (antecedent flow).High antecedent flow indicates a low watershed capacity to store additionalrain water. Storage capacity is influenced by vegetation which promoteswater absorption.

AUGUST 20, 1945

O = RECORDINGRAIN GAGE

= TOTAL INCHES RAINFALL

EXPERIMENTAL WATERSHEDMISSOURI GULCH

4,800 ACRESNOTESWatershed areaTotal precipitationVolume water producedVolume runoff waterRunoffPeak flowDaily antecedent flow

4,800 acres2.03 inches

776 acre-feet216 acre-feet

28 percent107 c.f.s.

16 acre-feet16

r WATER ABSORPTION

Grazing changes the water-absorbing capacity of the soil. Tests by apply-ing artificial rainfall to small plots scattered in the six pastures haveestablished this fact. The rates of water absorption decrease as grazingbecomes heavier.

Rocky Mountain infiltrometerused to apply rain to smallplots to obtain indices ofwater absorption, runoff anderosion under different con-ditions of vegetation, soil,

and use.

c_z>o

^=t_vex.

I--

4.9"/hr.

3.2'Hr.

l.5Vhr.

No. Heavily RainGrazing Grazed Applied

Heavy grazing decreases waferabsorption,

17

Too heavy grazing reduced water absorption. Decreased absorption of rainfallincreases runoff and erosion. Since 1939 grazing effects on runoff and erosionhave been studied on six plots of 1/100 acre each. Two of these have been grazedheavily, two moderately, and two ungrazed. Runoff and erosion are measured fromthe individual plots after each natural storm.

THE AVERA6E STORM CAUSING EROSION ON ifc ACREBUNCH 6RASS PLOTS RESULTS IN.

RUNOFF

MODERATE GRAZINGof herbage removed

HEAVY GRAZING/3 of herbage removed

/^^—i—~o>

SOIL LOSS

0.56 Ib. soil (air dry)(18 tons per s/j. mi)

0.60 Ib. soil (air dry)(19 tons per so., mi)

Contain!

Ibs. soil (air dry)tons per SQ. mi.)

18

r PLANT COVER

LOGGING AND BURNINGA

SMALL PONDEROSA PINE WATERSHED

CONVERTED TO ASPEN ORIGINAL CONDITION

RUNOFF and EROSION

Watershed A - t.5 acres

4Lo *i

IF**°</>-*»

If0

2938 fbs.

—2.2"

1//^ .05"

Rain Runoff Erosion

Total of four storms- 1949

is •Is"o

4.6'

974fbs

.16"V77A

Rain Runoff Erosion

Total of four storms- 1945

19

SEDIMENTATION

(roily erosionaccounts

for60 percent

ofsedimentin

stream channelsand

reservoirs

SEDIMENT REDUCES STORAGE CAPACITY

ORIGINAL CAPACITY

PRESENTCAPACITY

Manitou Lake Reservoir

20

r RECREATIONAL USE OF THE FOREST

Each year, from 400 to 500 people visit the Manitou ExperimentalForest. For many of these visitors, it means seeing field researchwork for the first time. They often learn about practices whichapply directly to their home conditions.

Many hundreds of campers spend from a day to several weeks at thepublic picnic and camp ground beside Manitou Lake. The State Gameand Fish Department stocks the lake annually with legal-size trout.Week-end summer visitors from nearby towns make the lake and itscamp ground their headquarters.

During the fall months, the Forest is used for deer hunting,and trails make the area reasonably accessible for hunters.

Roads

The eastern part of the Forest is bounded by the Rampart Range road.It provides a scenic motor trip. The many lookout points and picnicgrounds give a panoramic view of the plains and valleys to the east.

Manitou LakePikes Peak in background

21

NOTES REGARDING THE EXPERIMENTAL FOREST

1. Visitors are always welcome. To obtain more detailed publishedinformation about the experimental work, ask the resident tech-nicians, or a letter may be addressed to the Director, Rocky Moun-tain Forest and Range Experiment Station, Fort Collins, Colorado.

2. Research at the Manitou Experimental Forest is coordinated to pro-vide knowledge about the many interrelated uses of forest lands.This is necessary in order to serve the greatest number of peoplein the long run. Research deals with the effect of use on renew-able resources and therefore necessarily requires a long time toaccomplish.

3. The economy of the area surrounding the Forest is one of mountainagriculture. Through the occupancy, development, and use of theland by people, various problems of land use, water rights, landownership, and tenure leases arise. No problem is static wherefull use of the resources is yet to be realized. Sedimentation ofstream channels and reservoirs has now become critical. Studies ofthe conditions affecting sedimentation will receive more emphasisin the future. To what extent native vegetation can aid in itspractical control is an important question. Likewise, emphasiswill be placed on upstream flood control. Damaging flood flows instreams start with severe storms in the upstream areas.

4* Opportunities are unlimited for graduate students to undertakefundamental research in the conservation of natural resources.Arrangements may be made through colleges, universities, foun-dations, or other interested groups and the U. S. Forest Serviceon a cooperative basis.

5. The facilities of the Manitou Experimental Forest are used fromtime to time for training schools, for undergraduate field work,and for field meetings of agricultural and conservation societies.Excellent examples, nearby and on the Forest, serve as on-the-ground illustrations of both beneficial and harmful practices inmountain agriculture.

22

FARMS AND CITIES OF COLORADO DEPEND

ON

FRONT RANGE WATERSHEDS

From the forested watersheds comes the waterfor homes, cities, industries, and farms.Water is a first necessity of western lifeand lirelihood. To be fully useful, its flowshould be controlled naturally and it should

be mud free.

23

CONSERVATION THROUGH RESEARCH

The Manitou Experimental Forest is a research unitof the Rocky Mountain Forest and Range ExperimentStation, which is maintained in cooperation with theColorado A & M College at Fort Collins, Colorado

Prepared by: L. D. Love, Forester, andW. M. Johnson, Range Conservationist