Changes to Rangelands Over Time

Range Change Factors Grazing Fire Invasive Species Weather/Climate Human Activities

Goal of ecosystem management Efficiently capture sunlight

Reduce losses of nutrients and water from system

Land managers will have more specific goals

Forces of Ecosystem Change Immigration and establishment of plants

Competition between plants Fire Grazing

Site modification

Stabilization

How does grazing affect plants Some plants are

extremely sensitive to grazing (A)

Most plants are somewhat tolerant of grazing (B)

A few plants actually benefit from grazing, especially light grazing (C )

How does fire affect plants Some plants are

extremely sensitive to fire (A)

Most plants are somewhat tolerant of fire (B)

Other plants actually benefit from fire especially light grazing (C )

Adaptations to Fire and GrazingGrazing Fire

Gra

sses

Woo

dy P

lant

s

Location of Growing Points - Grasses

From: How Pasture Plants Grow by Stephen K. Barnhart; Iowa State Cooperative Extension

Also called:• Buds• Meristems

Location of Growing Points - Grasses

Grasses “push” growth from the growing point --- old growth at tips of leaves

Location of Growing Points - Grasses

As long as the growing point is present growth continues.

If removed - growth stops and new growth has to initiate from a dormant bud.

From National Range and Pasture Handbookswww.glti.nrcs.usda.gov/technical/publications/nrph.htmlChapter 5 page 2-13

Stolon

Rhizome

Location of Growing Points - Grasses

New growth can come from below Stolons & Rhizomes

Location of Growing Points - Grasses

Culmless

Culmed

Apical Meristem

Axillary Buds

Location of Growing Points - Grasses

Location depends on season Early in the growing season - close to the ground and

protected. As the season progresses - elevates and subject to

removal.

Location of Growing Points – Shrubs & Trees

Forbs and shrubs initiate growth outermost points

Location of Growing Points – Shrubs & Trees

Meristem

J. Peterson

May have basal buds and be able to resprout form base after fire

Location of Growing Points – Shrubs & Trees

Other fire adaptations – Shrubs & Trees

J. Peterson fs.fed.us

Insulating barkSerotinous Cones

Differences between fire & grazing?

Grazing __ __ __ __

Fire __ __ __ __

Differences between fire & grazing?Grazing

Not selective for specific plants Removes dead and live tissue Produces heat Recycles nutrients in inorganic form Recycles nutrients in a relatively

even layer across the landscape Patchiness on a landscape scale Most likely in dry-hot season May create hydrophobic soil layer

but, doesn’t yield compaction Generally reduces seed viability,

though some seeds require fire to be viable.

Fire Selects palatable over unpalatable Live tissue preferentially removed No heat produced Recycles nutrients in organic (feces)

and inorganic (urine) forms Recycles nutrient in patches Patchiness on a plant-scale Occurs year round Can cause compaction through hoof

action Generally reduces seed viability

though some seeds require consumption to become viable

Weather/Climate Most important factor in long-term changes to

rangeland plant communities Normal variation

Year-to-year (annual) Long-Term

Drought Impacts on plant composition

Exotic of Introduced Species Definition: “plants that are not native to a

region that have been brought in either intentionally or unintentionally”

Invasive vs. weed Response to disturbance

How do they increase? Negative environmental impacts

Invasive Species Species that that increase in a community in a

way the suppresses other plants in the community and reduces there abundance or fitness.

Can native or introduced Negative environmental impacts Have characteristics, such as high seed

production or root sprouting, that allow them to increase with disturbance.

Human Activities Included development, recreation, subdivision Humans affects other forces of nature

Invasion Fire Grazing Climate/weather?

Current Issue of Ecological Change:The “Pristine Dream” - many environmentally

concerned people wish that rangelands could return to pristine conditions similar to what Lewis and Clark observed.

Possible or Not?

Current Issue of Ecological Change:Sustainability (or Sustained-yield) is the concept

that we can graze or otherwise use the rangeland resource in such a way as to not jeopardize future productivity.

Possible or Not?

Current Issue of Ecological Change:Biodiversity (or Biological Diversity) is an attribute

that describes for the variety of organisms the genetic variation they contain and the variety of communities, ecosystems and landscape pattern in which they occur.

Believed that more diverse ecosystems are generally more stable and able to cope with disturbance than less diverse ecosystems.

Many agencies and environmental organizations espouse the concept that we should manage for high biodiversity.

Yes or No?