Download Forces of Change

Changes to Rangelands
Over Time
Range Change Factors
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Grazing
Fire
Invasive Species
Weather/Climate
Human Activities
Goal of ecosystem management

Efficiently capture sunlight
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Reduce losses of nutrients and water from
system
Land managers will have more specific goals
Forces of Ecosystem Change
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Immigration and establishment of plants
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Competition between plants
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Fire
Grazing
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Site modification
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Stabilization
How does grazing affect plants
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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
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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 Grazing
Woody Plants
Grasses
Grazing
Fire
Location of Growing Points - Grasses
Also called:
• Buds
• Meristems
From: How Pasture Plants Grow by Stephen K. Barnhart; Iowa State Cooperative Extension
Location of Growing Points - Grasses
Grasses “push” growth from the growing point --- old growth at tips of leaves
Location of Growing Points - Grasses
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As long as the growing point is present growth
continues.
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If removed - growth stops and new growth has to
initiate from a
dormant bud.
From National Range and Pasture Handbooks
www.glti.nrcs.usda.gov/technical/publications/nrph.html
Chapter 5 page 2-13
Location of Growing Points - Grasses
Stolon
Rhizome
New growth can come from below Stolons & Rhizomes
Location of Growing Points - Grasses
Culmed
Apical Meristem
Culmless
Axillary
Buds
Location of Growing Points - Grasses
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Location depends on season
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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
Location of Growing Points – Shrubs
& Trees
May have basal buds and be able to
resprout form base after fire
Other fire adaptations – Shrubs & Trees
J. Peterson
Insulating bark
fs.fed.us
Serotinous Cones
Differences between fire & grazing?
Grazing
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Fire
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Differences between fire & grazing?
Grazing
Fire
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Selects palatable over unpalatable
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Not selective for specific plants
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Live tissue preferentially removed
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Removes dead and live tissue
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No heat produced
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Produces heat
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Recycles nutrients in organic (feces)
and inorganic (urine) forms
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Recycles nutrients in inorganic form
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Recycles nutrients in a relatively
even layer across the landscape
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Recycles nutrient in patches
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Patchiness on a plant-scale
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Patchiness on a landscape scale
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Occurs year round
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Most likely in dry-hot season
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Can cause compaction through hoof
action
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May create hydrophobic soil layer
but, doesn’t yield compaction
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Generally reduces seed viability
though some seeds require
consumption to become viable
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Generally reduces seed viability,
though some seeds require fire to be
viable.
Weather/Climate
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Most important factor in long-term changes to
rangeland plant communities
Normal variation
Year-to-year (annual)
 Long-Term
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Drought
Impacts on plant composition
Exotic of Introduced Species
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Definition: “plants that are not native to a
region that have been brought in either
intentionally or unintentionally”
Invasive vs. weed
Response to disturbance
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How do they increase?
Negative environmental impacts
Invasive Species
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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
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Include development, recreation, subdivision
Humans affect other forces of nature
Invasion
 Fire
 Grazing
 Climate/weather?
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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.
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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.
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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.
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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?