Pinyon Pine and Juniper Tree Invasion into New Mexico’s

Grasslands:

Dr. M. Karl Wood, Director

Water Resources Research Institute

New Mexico State University

Some Hydro-Ecological Considerations

The Nature of New Mexico’s Watersheds

# 1Environmental Problem

in New Mexico?Tree and Shrub Increase and Invasion!

Such as: Salt Cedar, Russian Olive, Mesquite,Creosotebush,

andespecially Pinyon Pines and Junipers

1900

1960

Landscapes Containing Pinyon Pines and Junipers

Low lands Steep Hillsides Mesa Tops

Physiographic Positions

Seed dispersal by gravity, water, wind, animals, etc

Rocky and sparse vegetation,

incapable of carrying a fire

Roots from Pinyon Pines and Junipers

Extend about 2.5 times the radius of the crown,

in all directions, and just beneath surface of soil

Erosion After Dominance

Grassland Pinyon-Juniper Pinyon-Juniper Dominated Invasion Established

Amount of Erosion

Erosion After Dominance

Grassland Pinyon-Juniper Pinyon-Juniper Dominated Invasion Established

Amount of Erosion

Diversity(number of plant

& animalspecies)

Bare Early Intermediate Late Climax Rock

Seral Stage

Pinyon pine and Juniper• Climax on steep, rocky hillsides

• Invade lowlands & mesa tops by gravity, water, wind, animals, etc

• Controlled by fire in invaded areas until fire became scarce

• Compete with grass-forb-shrub understory which results in extremely high erosion rates

Kinds of Mismanagement!

• Cessation of wildfire by fire suppression

• Limiting use of shrub and tree control tools such as:

a. Fuelwood harvest b. Mechanical removal c. Herbicide applications

Kinds of Mismanagement!

• Overgrazing?

Solutions!

• The Clean Water Act amendments of 1972 require the application of Best Management Practices to control non-point source pollution

• Best Management Practices were determined for all New Mexico lands by the State of New Mexico and approved by the U.S. Environmental Protection Agency in the early 1980’s

• Allowing pinyon pines and junipers to invade grasslands is a gross violation of the Clean Water Act

Study: Reclaiming Grassland Invaded by Pinyin Pines and Junipers

• Location: Gila N.F. near Cooney Prairie• When: 1986-1999• Treatments:

1. Untreated control plots

2. Clearcut with slash removed

3. Clearcut with slash scattered

4. Clearcut with slash scattered and burned 4 months later

5. Clearcut with slash scattered and burned 27 months later

Total Yearly Grass and Forb Production

0500

100015002000250030003500

'88 '89 '90 '91 '92 '93 '94 '95 '96 '97 '98 '99

Years

Mas

s (kg

/ha)

Control Remove Scatter Burn '89 Burn '91

Mean Annual Runoff

0

20

40

60

80

100

'88 '89 '90 '91 '92 '93 '94 '95 '96 '97 '98 '99

Years

Dep

th (m

m)

Control Remove Scatter Burn '89 Burn '91

How much water can be squeezed from Pinyon pine -

Juniper invaded areas?• About 8.75 million acres of pinyon pine and

juniper woodland in New Mexico

• If water yield could be increased by 1 inch:The volume would be 725,000 acre-ft or about a year’s supply of irrigation and municipal water from Elephant Butte Reservoir

Mean Sediment Concentration

0

2

4

6

8

10

'88 '89 '90 '91 '92 '93 '94 '95 '96 '97 '98 '99

Years

Mas

s (k

g/cu

bic

met

er)

Control Remove Scatter Burn '89 Burn '91

Mean Annual Bedload

0

200

400

600

800

1000

1200

'88 '89 '90 '91 '92 '93 '94 '95 '96 '97 '98 '99

Years

Mas

s (k

g/ha

)

Control Remove Scatter Burn '89 Burn '91

Conclusions

Scatter slash Best No resprout potential

Scatter slash & Best Resprout delayed burn potential

Remove slash Good Some risk first 2 years

Scatter slash & Fairimmediate burn

No harvesting Worst

Risks from complete tree removalcan be lessoned by:

• Seeding• Pitting• Contour Furrowing and Terracing• Ripping • Shaping and grading• Top soiling• Cultivation• Surface mulching• Chisling, offset-listering, gouging, waffling, basin forming • Fertilization • And probably many others

Conclusions• Pinyon pines and junipers invade grasslands

resulting in:

– loss of plant and animal diversity – loss of plant and animal production – changed timing of runoff– accelerated erosion

• Removing pinyon pines and junipers from former grasslands represents a Clean Water Act “Best Management Practice”

A Good Quote“If the prime objective is wood products, we may continue to overgraze, letting in the woodland and sacrificing watershed values

If on the other hand the prime objective is watersheds, we should restore the grass, which all the evidence indicates is a better watershed cover than either brush or woodland”

Aldo Leopold