Web viewReduce losses of nutrients and water from system. Forces of Ecosystem Change. Immigration...
Transcript of Web viewReduce losses of nutrients and water from system. Forces of Ecosystem Change. Immigration...
Forces of Change
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
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 fire (C )
Location of Growing Points Grasses
Also called:
Buds
Meristems
As long as the growing point is present growth continues.
If removed - growth stops and new growth has to initiate from a dormant bud.
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
May have basal buds and be able to resprout from base after fire
Differences between fire & grazing?
Fire
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, doesnt yield compaction
Generally reduces seed viability, though some seeds require fire to be viable.
Grazing
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?
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?
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?