Exam II Flashcards
Define the following terms associated with state and transition models:
- Community phase
- Community pathway
- State
- Reference state
- Transition
- Threshold
Community phase- Changes within a state (open sagebrush, closed sagebrush)
Community pathway- The arrows in the diagram. The cause for a transition.
State- Stable, steady state. The boxes in the diagram
Reference state- The state the site was in prior to European settlement
Transition- shift to different state
Threshold- The point at which you cannot return to a state within substantial amount of energy
What is the definition of an ecological site?
A disinctive type of land with specific characteristics that is different from others in vegetation and responses to management
What is site potential?
The capacity of forage, wildlife, habitat, or pollinator habitat that an area could have.
What does MLRA stand for?
Major Land Resource Area
How does the use of ecological site descriptions in land management help to avoid land degradation and conflict?
It makes the data available for everyone (ranchers and range managers). Long-term data makes it possible to make good management recommendations
How can grazing improve soil carbon sequestration?
- Promotes photosynthetic material
- Causes plants to exude carbon into the soil by disrupting the carbon/nitrogen ratio
- Promotes development of humus
From “Rangeland Rehab and Carbon Credits in Kenya”, what was done to improve the health of their rangelands?
- Introduced planned grazing (grazing some areas while resting others)
- Group animals into herds and moved them as a group
What are the two major motivating factors likely to encourage landowners to adopt carbon sequestration practices on rangelands?
- Long-term soil productivity
2. Carbon credits payable to others
What is the problem with methane emissions from cattle?
Methane is a strong greenhouse gas
Name two potential ways charcoal can make beef better for the environment?
- Improves carbon levels in the soil when cattle defecate
2. Reduces methane production by cows
How could grazing help grasslands be a sink for methane emissions?
- Grazing can improve the soil biome through manure.
2. May increase carbon sequestration by promoting biomass growth.
How do energy and nutrients move through our rangeland systems?
Energy flows (from the sun) Nutrients cycle (stay)
What are examples of producers, primary consumers and secondary consumers
Producers- grasses, trees, plants
Primary consumers- herbivores
Secondary consumers- carnivores
How might abiotic factors influence the biotic flow of energy?
Poor soil may cause few, nutrient poor plants to grow, which cause poor body quality of primary consumers, which cause poor body quality of secondary consumers
Define:
Biomass, herbage, and forage
Biomass- total weight of living organisms (plants and animals) given in a weight/area measurement
Herbage- Biomass of all herbaceous (non-woody) vegetation at one point in time
Forage- Herbage acceptable and available to grazing animals
What are the part of the energy pyramid?
Why is the efficiency of energy transfer between trophic levels only around 10%?
Sunlight –> Primary producers –> primary consumers –> secondary consumers –> tertiary consumers
Energy is lost in each transfer through heat, movement, storage and defecation
Describe at least two reasons why grazing domestic animals helps supply the world with food
- Grazing domestic animals untilizes land not suitable for agriculture
- Only 10% of land on earth is suitable for agriculture
- Cellulose is the most abundant form of plant matter and it can only by harvested by ruminants
Remember for stocking rate problems:
Find forage demand and forage supply separately
Ruminants (cow/steer/sheep/goats) = 2.5% bodyweight forage per day
Hindgut (horses/rabbits/rodents) = 3% bodyweight per day
AUM = .025 x 1000 x 30 = 750 lbs forage per month
10% reduction = use 90%
45% usage rate = use 45%
What does AUM stand for?
Animal Unit Month
Who does better on poor quality feed?
Hindgut fermenters
Name the 4 steps required to estimate forage demand talked about in class
- Calculate usable forage
- Adjust for accessibility
- Calculate forage demands
- Calculate stocking rate
Units for a stocking rate
of animals/area/time
Reduction in grazing capacity by distance from water
0 - 1 miles = none
1 - 2 miles = 50%
2+ miles = 100%
Reduction in grazing capacity by percent slope
0 - 10 = none
11 - 30 = 30%
31 - 60% = 60%
60+ = 100%
What is a grazing system?
A planned effort to leave part of the land unused for at least part of the year
Discuss at least 7 factors that should be considered when designing a grazing system
- Season of grazing
- Nutritional quality of plants
- Plant diversity
- Duration of rest
- Mineral cycle
- Water cycle
- Animal health
Describe the continuous season-long grazing system, its benefits and challenges
Grazing whole area for whole year/season.
Benefits- low labor, better animal health, higher rate of gain
Challenges- accumulation of wolfy plants in less desireable areas, overgrazing in desireable areas
Describe the deferred rotation grazing system, its challenges and benefits
Resting a pasture a full season, until seed has set
Benefits- improved rangeland conditions
Challenges- can reduce animal performance by forcing them to graze low-quality forage
Describe the rest-rotation grazing system, its benefits and challenges
Not grazing a pasture for a whole year, rotating which pasture is rested.
Benefits- improved wildlife habitat, easy in rugged terrain (less movement of animals)
Challenges- more work than continuous grazing, could decrease animal performance
Describe the Merrill three herd, four pasture grazing system, its benefits and challenges.
Area divided into 4 pastures, used by three herds. Rotate derment time between pastures.
Benefits- Good alternative to continuous grazing when year-round grazing is desired
Challeneges- high labor, lower body quality of animals
Describe the intensive rotation/short duration/mob grazing/high intensity short duration grazing methods, its challenges and benefits
Pastures are divided into small plots of land and grazed intensively for a short duration of time
Benefits- improved plant quality by forcing cattle to eat all plants, and trampling others
Challenges- very labor intensive, may be harmful to systems with low amounts of precipitation or that have species sensitive to grazing
- What is the difference between primary and secondary succession and give an example of each event.
Succession is the directional change of plant communities over time (not season)
Primary succession- Starting from rock. A place without soil. Lichens, mosses, cyanobacteria
Secondary succession- Succession of higher life forms, grasses, forbes, trees
Define the term pioneer species, seral stage and climax community
Pioneer species- species that first colonize a barren stie. Lichens, mosses.
Seral stage- deistinct community types within succession (ex. pioneer species, intermediate species, climax community)
Climax community- The end point of succession. Stable group of plants. Variable depending on ecosystem
What is a Clements successional model?
Plant communities retrogress from disturbance (ex. fire, grazing). When disturbance is relieved, site recovers towards the climax stage
How did Dyksterhuis refine Clements successional model?
He made it less of a linear successional model. He said that disturbed sites won’t automatically bounce back to the climax stage, they could be forced into a new state.
Name 5 problems associated with lear successional theory
- Removing disturbance may not result in successional progress, human intervention may be necessary for restoration.
- It does not account for loss of plant materials/species. If a species is lost, it cannot bounce back
- It does not account for the positive fire-feedback loop, which would prevent a site from returning to a climax state.
- It does not account for positive soil-feedback loops such as erosion, loss of seebank, loss of nutrients, compaction.
- It does not account for how climate change could permanently alter a site’s climax state
What is the general relationship of juniper to shrub cover? What are phases 1, 2, and 3 of juniper expansion?
The more pinion-juniper you have, the less shrub cover you have
Phase 1- Sagebrush dominates a site
Phase 2- Equal dominance between sagebrush and pinion juniper
Phase 3- Juniper have covered of 2/3 of the area
- Why is it important to recognize the early symptoms of degradation?
If you can recognize the degradation and reverse it before it reaches the threshold, you can restore the site with much less energy.
There is a threshold where you can restore a site by altering biotic factors, and a threshold where you can only restore a site using abiotic factors
Name three reasons why we should understand plant succession
because the composition of plants within plant communities has three important influences:
- How landscapes function — for example, water cycle, nutrient cycle, soil formation,
- The type and amount of products or resources and services society can develop and produce, and
- Identification of management opportunities and hazards.
Define resilience and resistance with respect to plant succession on rangelands
Resistance- refers to a plant community’s ability to avoid being changed from its current state.
Resilience- refers to the ability of a plant community to return to prior composition and structure after a disturbance
Heavy use vs overgrazing
overgrazing - repeated heavy grazing such that damage to plant community occurs
heavy use- doesn’t necessarily lead to overgrazing
Over stocking- heavy grazing during a specific period of time (mob grazing)
Factors determining proper stocking rate
Plant health/regrowth, wildlife forage, erosion prevention
Why we stock below capacity
- allow for drought
- allow for low production years
- allow wildlife forage
- erosion prevention
- reclaim a degraded site
What stocking rate is most profitable and why?
As stocking rate increases, the rate of gain per animal decreases. By stocking in the middle range, you get the largest overall production
