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rangelands tend to be _____ ecosystems
low productivity
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single most important factor determining type and productivity of vegetation in the area?
precipitation
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after which to soil characteristics become a more important characteristic than precipitation?
over 500m avg annual precipitation (in north america)
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characteristics of ppt that affect vegetation (5)
- amount
- distribution
- humidity
- form
- annual variability
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best predictor of grassland productivity?
mean annual precipitation
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ANPP
- annual net primary productivity
- usually thought of in plant biomass
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coefficient of variation (in terms if ppt)
- cv = std dev/mean
- used to describe the patterns of rainfall from one year to the next, gives us a percentage
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P:E ratio
- precipitation to evaporation ratio
- how much ppt is coming in vs how much is evaporating
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P:E = 1
same rainfall is coming in that is evaporating
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P:E > 1
more rainfall is coming in than is evaporating
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P:E < 1
less rainfall is coming in than is evaporating
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orographic influences
- ppt distribution is impacted by topography and distance from oceans
- as air moves up and cools it can hold less moisture
- result rainshadows on the leeward side of mountains
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C3 plants
cool season grasses, more efficient with their carbon
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C4 plants
- warm season plants
- extra molecule needed in photosynthesis pathway
- less efficient with carbon
- more efficient with water, so can do better in dry conditions
- affects nutritional quality of the plant
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latitude and temp relationship?
latitude influences temp by 0.5°C per 1° latitude
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elevation and temp relationship?
temp decreases by ~2°C per 300m elevation
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aspect's effect on local growing conditions?
- directional orientation of slopes
- ex. southern slopes may be drier (more sunlight), may have diff plants on diff sides of hill
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degree of slope's effect on local growing areas?
- gradual slope vs. steep
- affects vegetation productivity and use by range animals
- increases ppt runoff - as slope increases vegetation productivity decreases
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soil factors affecting rangeland productivity (6)
- texture
- structure
- depth
- pH
- organic content
- fertility
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____ soils will be more productive
deeper
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______ in soil depth can promote plant species diversity
- heterogeneity
- different species adapt to being able to root at different depths
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more basic soils tend to get _____
- less rainfall
- more calcium carbonate
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more acidic soils tend to get _____
more rainfall
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most limiting nutrient in younger systems
nitrogen
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most limiting nutrient in older systems
phosphorous
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salinity limits.....
- plants' ability to take in water, nutrients
- takes a lot of energy for plants to deal with salt
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desert shrublands productivity
100-500 kg/ha
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woodland productivity
- 100-3500 kg/ha
- large range, depends on what tree types you are dealing with
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Tallgrass prairie
- very little left
- ppt ranges from 500-1000mm
- mostly C4 temps
- warmer winter temps
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coastal prairie
- up to 1500mm in ppt
- sandy/well-drained
- sod-forming/adapted to living on sand dunes
- very productive
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Mixed or shortgrass prairie
- wide range
- 260-800mm ppt
- C4 plants, tillers
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fescue prairie
- 340-460mm ppt
- colder than shortgrass prairie
- rough fescue sole dominant?
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palouse prairie
- 200-640 mm ppt
- sage bush
- bluebunch wheatgrass
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pacific prairie
- 250-500mm ppt in south
- 1250mm ppt north
- parent material is serpentine grassland??
- very basic
- shallow soils, therefore unproductive despite high ppt
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desert plains grassland
- very low ppt (~250mm)
- dry and hot, low productivity
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plant classification
- simplifies diversity of plant communities
- removes gradients
- most classifications are local
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phytosociology
- looking at associations bw diff plant communities
- based on the presence/absence of diff plants
- hierarchical with naming system like taxonomy
- dominantly used in Europe
- good for areas with high lvls of homogenity
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lower foothills
- comparatively wet and warm
- high tree diversity
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mixed dry grass prairie
- SE corner of AB
- dry and warm
- several million ac were farmed then abandoned -> recovery depends on grazing
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parkland
- cool and wet
- grasses are v productive?
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range site
- (ecosite)
- localized, mappable area of relatively uniform physical conditons
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plant community
localized, mappable stand of relatively uniform vegetation
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range (plant community) type
- takes into account land use, cattle presence, etc
- hypothetical/artificial plant community representing many similar plant communities in reality (ex. grouped for convenience)
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forbs
- dicots with fibrous and/or taproots
- have elevated apical meristem
- renew above-ground biomass annually
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shrubs and trees
- dicots that accumulate above-ground woody tissue
- renew growth from intact, elevated meristems (apical and axillary)
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grasses
- monocots with extensive, fibrous root systems
- apical meristems generally at the plant base
- renew above-ground biomass annually
- have high root turnover (growth and death)
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apical meristem
primary zone of growth at the end of roots and stems (forbs and shrubs)
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axillary meristem
- secondary zone of growth
- in dicots: the origin point of branches and leaves)
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apical dome
- region of intense meristematic activity at the base of a grass plant
- low to the ground, allows grasses to recover better from grazing
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axillary bud
specialized zone of development on a grass apical dome, capable of developing into a "tiller"
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intercalary meristem
- secondary zone of growth on the leaves of grasses
- junction of leaf sheath and blade, and sheath and node)
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phytomer
- basic repeating unit of an individual grass tiller
- incl. node and internode with leaf and sheath at the top and bud at the bottom
- stack of phytomers form a shoot
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tiller
a group of phytomers, linearly arranged (stacked) and derived from the same apical meristem
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rhizome
- an underground lateral stem used for vegetative reproduction
- ex. plains roughfescue, kentucky bluegrass
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stolon
- an above ground lateral stem used for vegetative reproduction
- ex. strawberry, buffalograss
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xylem
- translocation sieve tubes for water and minerals
- move material predominantly upwards
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phloem
- translocation sieve tubes for carbohydrates and proteins
- move material predominantly downwards
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seminal roots
the small root system developed from the cotelydon used to temporarily support a seedling
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adventitious roots
extensive, fibrous rot system developed by the plant, particularly grasses, to support itself
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levels of photosynthesis depend on (2 things)
- leaf area (ex. max surface area to volume ratio for leaf blades)
- age of leaf (PS slows with age nearing senescence)
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source (plants)
- organs that generate carbohydrates that can export them to other areas in the plant
- ex. could be roots in the spring for biennials/perennials
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sink (plants)
an organ or tissue within the plant that attracts nutrients (ex. CHOs) for active use
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non-labile sink
- once deposited, nutrients can no longer be re-mobilized
- ex. respiration, structural plant growth
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labile sink
- nutrients that CAN be remobilized
- ex. non-structural, not immediately used
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TNC
- total non-structural carbohydrates
- basic sugars actively translocated within the plant and available for respiration and growth
- can move through the plant
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ranked assimilate partitioning (from most important to least important)
- 1. maintenance (respiration and basic repair)
- 2. initiation & growth of new roots (where resources are stored)
- 3. initiation and growth of new leaf area (allocates between here and #2 differently depending on what kind of plant/what time of year)
- 4. CHO storage (ONLY with net positive PS)
- 5. stem elongation, flowering, seed production
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sexual plant reproduction
via flowering, seed set and establishment
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floral induction plant reproduction
- rapid bolting of apical dome in grasses
- leading to seed head elevation
- factilitates pollination and seed dispersal
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tillering
- process of vegetative reproduction in grasses
- development of axillary buds on the apical dome into new apical meristems and domes
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disturbance (to plants)
- mechanisms that limit plant biomass by causing its partial or total destruction
- ex. herbivory, wind
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stress (to plants)
- anything that slows or limits plant growth
- ex. lack of nutrients, water
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in situ plant disturbance
- plants die, then the biomass is removed via decomposition
- ex. frost, senescence
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properties of disturbance
- intensity
- frequency (and duration)
- scale (spatial extent)
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LAI
- leaf area index
- how much leaf area there is per m2
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effects of grazers
- defoliation
- trampling
- nutrient inputs
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most plants have evolved with and are adapted to __________ but NOT ______________
- periodic herbivory
- frequent, intense defoliation
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ongoing plant survival depends on: (3 things)
- i. continual synthesis and storage of PS (needs leaves to do this)
- ii. maintenance of a healthy root system
- iii. periodic reproduction (needs to allocate some energy into sexual or vegetative reproduction)
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grazer adaptations to grass and grasslands
- hypsodonty (thick tooth enamel)
- ruminating
- hooves
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plant adaptations to herbivory
- i. avoidance
- ii. tolerators
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types of plant avoidance of grazers (a-d)
- use physical means to deter herbivory
- a. mechanical (thorns, awns, bristles)
- b. chemical (unpalatable or toxic)
- c. spatial avoidance (reduced access to plants)
- d. temporal avoidance (reduced exposure to herbivores, ex. rapidly growing ephemerals)
**plants forsake growth and reproduction to produce these structures**
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types of plant tolerating grazers (a-g)
- plants adapted to survive despite being defoliated
- a. protect growing points near ground surface (ex. grasses)
- b. resprout freely following defoliation
- c. reproduce via rhizomes or stolons
- d. store high CHOs in roots and stems to facilitate rapid regrowth (v-shaped or flat CHO cycle)
- e. high proportion of vegetative tillers
- f. elevate seed-heads rapidly
- g. may exhibit 'compensatory growth' (grazing may increase primary production over the ungrazed state)
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compensatory growth
increase of growth in response to defoliation
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resistance to grazing: forbs
- produce many seeds
- delayed elevation of growing points
- chemical resistance
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resistance to grazing: shrubs
- mechanical: thorns, spines
- volatile chemicals (smelly)
- branches
- older woody growth generally not palatable
- removal of apical meristem may stimulate axillary bud
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resistance to grazing: grasses
- fewer shoots
- longer delay in elevation of apical buds
- more likely to sprout from apical dome
- higher ratio of vegetative to reproductive stems
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growing points
- places where cells divide and elongate
- in a vegetative grass: located near ground and are raised as the stem elongates
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3 major stages of grass growth cycle
- spring vegetative growth
- late spring/summer reproductive growth
- fall/winter
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early spring vegetative growth
- inititally relies on stored CHOs for growth
- growing point: ground level
- new leaves begin to PS
- potential for regrowth?
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spring/summer reproductive growth
- plant produces enough energy to support itself, period of rapid growth begins
- environmental cues signal change to reproductive growth
- energy allocated to seed production and storage
- growing points elevated
- summer slow down/dormancy
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fall/winter growth
- enter partial dormancy
- plants never truly dormant as they respire all winter
- if adequate fall moisture is available new tillers may develop from dormant buds
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3 basic factors we can manage for with respect to grazing
- frequency (# of times a plant is defoliated during a period of time)
- intensity (the proportional removal of plant material)
- opportunity for growth and/or regrowth (determined by environmental factors, season of removal, previous defoliation, frequency, intensity)
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ecology
study of relationships among organisms, and between organisms and their environment
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autecology
population ecology - individual organisms and populations
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synecology
community ecology - deals with complex groups of organisms (ex. plant community) and their relationship to other organisms (ex. herbivores) as well as their environment
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population
group of individuals of the same species living in a given area at a given time
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species
a population or group of populations whose members have the potential in nature to interbreed and produce fertile offspring
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environment
total surroundings of an organisms, including other plants and animals and those of its own kind
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habitat
place where a plant or animal can live
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community
a group of interacting plants and animals inhabiting an area
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association
kind of plant community represented by stands that occur in places where environments are so similar that there is a high degree of floristic uniformity in all layers of the plant community
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dominant
plant species or species groups, which by means of their number, coverage, or size, has considerable influence or control upon the conditions of existence of associated species
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ecosystem
the biotic community and its abiotic environment functioning as a system
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4 characteristics of ecosystems
- web of interactions and interdependencies
- synergy
- stability
- diffuse boundaries
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most definitions of ecosystems include
- 1. a community of species
- 2. the physical environment on which these organisms are dependent
- 3. the physical size of the particular ecosystem being considered
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abiotic components of an ecosystem
- 1. parent material
- 2. climate
- 3. topography
- 4. natural disturbances
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biotic components of an ecosystem
- 1. producers
- 2. consumers
- 3. decomposers
- 4. manipulators
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ecological succession
a directional change in species composition, community structure, and function over time and space
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primary succession
- decsribes the sequence of plant communities on a new site (ex. a site previously devoid of plants)
- ex. volcanic eruptions, mine waste, sand dunes
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secondary succession
- describes the change in plant communities after a disturbance (ex. a site which already had plants and soil)
- ex. grazing, fire
- plant traits and dominance play a key role!
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autogenic succession
- aka biotic succession
- vegetation changes due to the activities of the organisms themselves
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allogenic succession
vegetation change due to environmental conditions and environmental change or external factors
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resistance (succession)
ability of the system to withstand a perturbation
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resilience (succession)
the speed at which a disturbed system returns to equilibrium after a perturbation
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inertia
the tendency of a community to continue to occupy a specific range site, even after conditions have changed to favor a new community
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seres
intermediate stages in the development of a 'climax' plant community
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retrogression
changes within the plant community away from climax due to a disturbance
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progression in succession (6 steps)
- 1. nudation - disturbance
- 2. migration - arrival of propagules
- 3. establishment - initial growth of vegetation
- 4. competition - species compete for space, light, nutrients
- 5. reaction - autogenic effects (effects of plants on habitat)
- 6. stabilization - climax
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CSR triangle
- competition, stress, ruderal
- triangle represents habitat space, described by stress and disturbance
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relay floristics
- each seral community relays the site to the next community
- driving force behind succession is the reaction of the site to the plants living in it
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initial floristic competition
- rearrangement of species that were present during initial stages
- the proportions of the various species changes during succession
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mechanisms of succession - facilitation
each seral community changes the site for the next community
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mechanisms of succession - tolerance
which species have the ability to survive the longest
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mechanisms of succession - inhibition
- /competition
- some species will actually inhibit the development of others
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states
distinguished from each other by big differences in plant functional groups (vegetation structure) and ecosystem processes (hydrology, energy capture, nutrient cycling)
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transition
a trajectory of system change away from the current stable state that is triggered by natural events, management actions, both
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threshold
boundary in space and time bw two states, so one or more of the ecological processes has been irreversibly changed
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excreta can alter:
- soil chemistry
- GHG emissions
- local productivity
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indirect effects of grazing
- microclimate modification
- soil changes
- competition
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microclimate modification (grazing affects)
grazing induced changes to water cycle efficiency, which favours some plants over others
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soil changes (grazing affects)
- grazing induced changes to key range site characteristics
- ex. soil compaction
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competition (grazing affects)
- disruption of the competitive balance between 2 or more plant species
- defoliation favours either the less defoliated plant AND/OR the more grazing tolerant plant
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intermediate disturbance hypothesis
- notion that maximum species diversity is associated with intermediate levels of disturbance (ex. grazing)
- competitive species dominate under low levels of disturbance
- under high levels of disturbance only ruderals can tolerate the conditions
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plant competition (grime defn)
"the tendency of neighbouring plants to utilize the same quantum of light, ion of mineral nutrient, molecule of water, or volume of space"
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hump-shaped curve
- common pattern in the relationship bw productivity and plant species richness is a unimodal curve
- pattern been observed in many taxa
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general fire effects
- retrogression changes to production
- strategy of plant species to cope with fire
- nature of the fire influences retrogression
- fire suppression
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strategy of plant species to cope with fire
- colonizers: migrate into burned areas as early successional plant species (fireweed, lodgepole pine)
- tolerators: recover slowly to pre-burn levels as mid to late seral species
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nature of the fire influences retrogression?
- frequency (recovery interval)
- intensity (air temp, humidity, fuel load)
- timing/season (fall vs summer vs spring)
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effects of fire suppression?
contributes to increased woody vegetation
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landscape ecology
applying basic ecological principles to landscapes, the scale at which most management occurs
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catena
- repetitive variation in vegetation, soil, with changes in slope, aspect, and relief (elevation
- cyclical changes in vegetation across the landscape
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recharge areas
source points for the entry of water, nutrients, salts, etc to the soil profile
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discharge areas
points of discharge of water, nutrients, salts, etc (local, regional)
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factors affected by alteration of effective growing conditions
- salt levels
- nutrient levels
- effective moisture regimes
- length of growing season
- textural differences (ex. clay buildup in valleys)
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animal behavior and landscape ecology
- strongly interacts with landscape position
- safety, food, water, etc
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fire interactions with landscape ecology
drier sites burn more often and intensely, and thus are lower in seral status
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rangeland defn (animal centered)
uncultivated lands that will provide the necessities of life for grazing and browsing animals
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rangeland broader defn
areas of the world that are a source of forage for free-ranging native and domestic animals, as well as a source of wood products, water, wildlife, etc
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herbivory
consumption of plants by animals
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grazing
consumption of standing forage (grass and forbs) by livestock or wildlife
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browsing
consumption of leaves and twigs from woody plants (trees and shrubs) by large-hoofed animals
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pasturelands
lands that are periodically cultivated (highly modified) to maintain agronomic forage species and receive inputs
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ecosystem
biotic community and its abiotic environment functioning as a system
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rangeland outputs
- meat and fibre
- carbon storage
- energy
- water
- biodiversity
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rangelands provide ___ of worldwide feed for livestock
~70%
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rangelands provide ___ of feed for wild ungulates
~95%
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range management
the manipulation of rangeland components to obtain the optimum combination of goods and services for society on a sustained basis
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range science
- the organized body of knowledge upon which range management is based
- ecology
- its and art and a science (**experience based**)
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activities of range managers (6)
- surveys and monitering
- range management planning
- modifications of landscape to achieve diff outputs
- landscape planning and management
- dispute resolution
- information and education
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threats to rangelands
- agricultural conversion
- urban sprawl
- overgrazing/desertification
- climate change
- industrial development
- recreation
- fire suppression
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