Changes to Rangelands Over Time
Dec 29, 2015
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?