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140 Cards in this Set
- Front
- Back
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Succession
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ecosystems constantly changing, disturbed
-never in equilibrium with current environment temporal patterns that occur in ecosystems differ with scale of observation & severity of disturbance |
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Ecological Succession
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process of ecosystem development
-can result from developmental changes in ecosystem itself or from disturbances |
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Sere
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characteristic sequence of biotic communities that follow another in a particular environment
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seral stages
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various communities that together make up a sere,
each is floristically distinct |
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Autogenic succession
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*most common
resident organisms change physical environment |
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allogenic succession
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geological processes cause change
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biogenic succession
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sudden interference by living organisms (herbivore, pathogen)
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primary succession
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occurs on newly exposed land
-initiated by disturbance that exposes substrates and are left with essentially no plant growth at start -sever disturbances -glaciations, volcanic ash deposition, catastrophic wildfire |
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secondary succession
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occurs when vegetation is cleared but soil remains
-can start in mid-succession and then to final climax -moderate disturbances -after wildfire, wind, logging |
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succession results in
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"a rich, dynamic tapestry of vegetation, providing an array of habitats for animals and microbes"
-Perry, 1994 |
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Relay Floristics
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-concept of seral stages
-each stage prepares habitat for the next one, often through changes to soil. 3 steps: -primary succession colonizers -secondary succession colonizers -late successional species |
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Pioneer community traits
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harsh environment
increasing biomass some loss of nutrients fluctuations low diversity energy consumption inefficient r-adapted (energy into reproduction, rapid growth) |
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climax community traits
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moderate environment
nutrient cycling high diversity energy consumption efficient fluctuations rare biomass stable K-adapted (energy into biomass not reproduction) |
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shade tolerance
-Tolerant (T) -Intolerant (I) Intermediate (N) |
ability of a tree to grow in the shade of other trees
T = grow well in low light, do not show large increase with increasing light lvls. Climax species. I = cannot grow well in low light, grow very well in high light. Pioneer species N = intermediate in ability to grow in the shade |
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progressive succession
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shows increase in biomass, diversity and structural complexity
-trend towards being a mesic site |
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retrogressive succession
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shows decrease in biomass and diversity
-trend towards becoming a hydric or xeric site |
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paludification
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process of mire (peat forming ecosystem) formation in an area that used to be forested or a grassland
-autogenic or climatic processes leading to waterlogging and anaerobicity |
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carbon dynamics in primary succession
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initially: low O.M. content, CEC, moisture holding capacity, decomposition
mid succession: rapid decomp., increases in soil carbon and nutrient inputs late succession: decomp. slows, reduced rates of soil carbon & nutrient inputs |
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Carbon pools & Primary succession
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increases then plateaus
C-Flux, Early: NPP & NEP increases as O.M. increases; heterotrophic resp. lags NPP. C-Flux, Late: NPP = heterotrophic resp; NEP declines to zero. Eventually NEP affected by climate & gap phase disturbances |
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Carbon pools & secondary succession
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initial C pool & flux after large disturbance: plant C pool decreases, Soil C pool increases or decreases
C-Flux, Early: NPP recovers quickly because of increase in resource availability; decomp. rapid because of increase in labile C, temperature and water availability NEP negative because of high C loss, decomp., and low NPP |
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Nutrient Cycling in Primary Succession
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post-disturbance: high nutrient loss, then accumulation due to large biomass increment & N fixation
mid-succession: essential/limiting nutrients retained most strongly in biomass, little loss late-succession: system stabilizes; nutrient outputs = inputs; NEP = 0 |
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nutrient cycling in secondary succession
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pulse of nutrient availability after disturbance
(fires increase N availability, susceptible to loss) Fate depends on retention mechanisms: -plant uptake -microbial uptake -chemical fixation |
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Temporal dynamics in ecosystems
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(other than succession)
temporal extrapolation requires understanding of timescale of variables affecting processes -diurnal -seasonal -annual -inter-annual -multi decadal |
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fluxnet Canada
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research on climate, disturbance & C cycling in canadian forests/parklands
-N carbon sink absorbs 15-30% of global C |
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diurnal cycles
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NEP negative at night, positive during day
weak cycle = disturbed sites, mature conifer stands & peatlands strongest cycle = intermediate ages & deciduous forests disturbed sites = net source intermediate/deciduous forests = net sinks |
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seasonal fluctuations
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-plants senesce in autumn (in response to photoperiod)
-grow rapidly in spring -when GEE begins early = net sink Net Ecosystem Exchange (NEE) = PS rate (GEE) + respiration rate (R) GEE begins in spring, increasing as nighttime temps warms (through Oct) NEE ceases midsummer due to increasing respiration |
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inter-annual fluctuations
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Pacific Decadal Oscillation (PDO)
-N. Pacific -phases of 20 - 30 yrs -positive phase since 1977 Atlantic Multi-decadal Oscillation (AMO) |
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Disturbance
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any relatively discrete event in space and time that disrupts ecosystem, community, or population structure & changes resources, substrate or the physical environment
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disturbance properties
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Magnitude: size or spatial extent of event
Intensity: force of the event Severity: defined in terms of it's killing effect; measures the impact of the event on system properties |
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exogenous disturbance
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those originating from outside the system
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endogenous disturbance
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those originating from within the system
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indirect disturbance
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doesn't kill individuals
alters resource levels or other factors influencing individuals |
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direct disturbance
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killing disturbance
death of individuals, opens space & releases resource to others |
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biotic disturbance
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disturbance agent is a living organism
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abiotic disturbance
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disturbance agent is not a living organism
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Insects: anthropogenic contributions to susceptible trees
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-effective fire suppression (<1% of historic area currently burns)
-selective harvesting (<1970 lodgepole a 'weed') -overabundance of mature pine (>3X susceptible hosts) |
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tree biology w.r.t. pine beetle
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beetles prefer large trees:
- high quality food & larval habitat -protection from natural enemies & weather extremes large trees tend to be more resistant -con-situate resin ducts -induced resin production |
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pine beetle
biology basics |
colonizing beetles emit aggregation pheromones
-resultant mass attack overwhelms tree defences beetles also introduce blue-stained fungi -pathogenic to most trees -block vascular tissue, stop resin production -provides nutrients for maturing beetles |
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pine beetle
current outbreak + predictions |
area affected = 18 million ha
projection: mortality of 60% of mature pine by 2020 |
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endemic populations
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-insufficient beetles to colonize healthy trees
-normally found in trees attacked by others -attacked trees rare and scattered -mortality and off spring in balance (97.5% mortality) |
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beetle mortality factors
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host resistance
woodpeckers competition weather pathogens invertebrates -relaxation of one or more of these factors allows population to build and move from endemic to incipient to epidemic populations |
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incipient populations
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-infestations scattered
-number of trees infested increases annually -clumps of infested trees grow in size and number over time -most attacked trees in larger diameter classes (95.0% mortality) |
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epidemic populations
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-widespread
-large annual increase in infested areas -extremely resistant to losses through normal mortality (80 - 95% mortality) |
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causes of outbreak
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abundant susceptible hosts
climate favouring beetle survival |
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model of climatic suitability (beetles)
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P1: sufficient heat accumulation for synchronized one year life cycle
P2: minimum winter temperatue >-40C P3: average maximum August temp >= 18C P4: total ppt from April to June below long term average |
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outbreak consequences
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forest C dynamics:
decrease C uptake (trees dead) increase in C emissions from decaying |
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fire suppression paradox
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Stand initiating fires + fire exclusion
leads to: fuel buildup leads to: unusually severe fires leads to: human costs and economic losses mitigation: thinning, prescribed burns |
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human impacts on fire regimes
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due to historical data we expect evidence of a fire every 20 years
1945 - 2005 there no evidence or fires |
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Fire: Lessons Learned
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historical fires in mountains
-low to high frequency and severity human and climate influences on fire: -fire free period = mostly fire suppression -global climate influences drought & fire -current forests and fuels -natural processes & fire suppression effects |
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wind
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-major disturbance in coastal BC
-windthrow plows soil, creates microsites -creates uniform, multi-cohort or all aged stands -maintains structurally diverse lanscapes -should be recognized in planning |
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turning moment
+ factors |
function of lever arm length and gravity
-wind speed -crown size/density/mass -stem mass/elasticity -tree height -tip displacement |
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tree resistance to wind
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by having a thick stem and good root system
-taller tree = longer lever arm, therefore need to counteract turning moment accordingly by increasing stem and root system also: stream lines in the wind with branches deflecting to be aerodynamic and more porous |
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Armstrong Technique
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test tree resistance to wind by pulling down with winch + cable
critical turning moment = max resistance of tree before it falls |
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"slenderness ratio"
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height/diameter ratio
-low (<60) = stocky -high (80-100) = tall/skinny |
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worst soil for tree stability
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fertile but shallow
-lots of biomass accumulation above ground -unable to get a good deep root system |
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wind + hills
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wind acceleration (top speed) @ crest
turbulence on leeward side most windthrow happening at crest |
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Stand Level Effects of Wind
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wind disturbance can perpetuate themselves by creating stands that are high competition therefore tall & skinny and susceptible to further wind throw
-profound effects on soil: turning, can reverse paludification, adds woody debris to stream beds and helps structure them |
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Landscape Level Effects of Wind
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smaller lower on the slope; wind throw @ crests
landslides mid-steep slope, paludification on lower slopes hypermaritime: most productive areas mid slope |
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The disease triangle
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need three things:
susceptible tree host (native vs. introduced) virulent pathogen (native vs. introduced) conducive environment (environment/climate change; man made perturbances) |
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Pathogens as Good Guys
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-create stand openings
-increases diversity -increases resilience -wild-life habitat -nutrient cycling |
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symptom
sign |
effect of the disease on the host, host reaction
the pathogen itself |
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Disease Epidemic Causes
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forest (mis)management
invasive alien pathogens -see disease triangle |
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Fungi Roles
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Saprophytes
-decomposition of cellulose and lignin -C and nutrient cycling Symbionts -mycorrhizal associations with plant roots -water, nutrient exchanges, protection Pathogen Food for wildlife |
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Categories of Forest Pathogens
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Foliar
Stem -cankers Root -root rots, wilt Mistletoes Rusts Decay Fungi -brown/white rot |
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Disease Prevention
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diagnosis:
-learn to recognize pathogens, conduct proper diagnosis Epidemiology -understand pathogen biology, survival, dissemination Disease Management -know toolbox of options |
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Deer & Haida Gwaii
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sitka black tailed deer
-introduced in 1876 by Revd Collison as a source of meat -mild climate, abundant food,no competition, no predators -exponential population growth with minor dips due to food shortage, weather, disease -helped by clearcut logging, abundance of forage |
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cost & benefits of introduced species
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biological impacts of most negative (cause a decrease in diversity)
on haida gwaii: decrease in W. red cedar, shrurbs & wildflowers; increase in hemlock & spruce. economic & cultural value may be positive -clearings, grassy meadows preferred over impenetrable shrubs; hunting |
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Ecological Impacts - Introduced Species
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Effects on Insects
-vegetation and litter fauna Understory fauna -deer decreases resource quantity and quality Negative Feedback -lack of pollinators decreases plants further Litter Fauna -deer decrease resource quality: decreasing deciduous litter, increasing conifer litter, decrease protection from elements -increase millipedes, decrease snails/slugs - has an effect on decomposition rate/completeness |
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water cycle
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driven by solar radiation that generates evaporation & atmospheric circulation
Precipitation -canopy interception -infiltration/runoff -percolation -water tables Evaporation Transpiration -streamflow |
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Orographic PPT
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result of topography
geography and prevailing wind direction matter important in BC |
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Frontal/Cyclonic PPT
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large weather systems
created by convergence of air masses longer, affects relatively large regions |
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Convectional Rainfall
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summer thunderstorms
short/localized |
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Evaporation Factors
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driven by solar radiation E
water vapour pressure vapour pressure deficit (VPD) |
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Solar Radiation Energy
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provides energy required to convert water from liquid to gas phase
creates wind which can cause convective evaporation heats air mass and increases water holding capacity of air |
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Water Vapour Pressure
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measure of amount of water vapour in air
function of air temp and available water saturation vapour pressure = @ equilibrium with the liquid phase actual vapour pressure = a value btwn 0 and saturated vapour pressure |
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Vapour Pressure Deficit (VPD)
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measure of drying potential of air
difference btwn actual vapour pressure & saturated vapour pressure at a given temperature inversely related to relative humidity (%) (as RH increases VPD decreases) |
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Canopy Interception
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Depends on
-leaf are index -rainfall intensity |
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Surface Evaporation
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Depends on
-quantity of solar radiation reaching forest floor -water holding capacity of surface litter (LFH layers) |
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Soil Evaporation
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sames as surface area evaporation plus:
-mineral soil particle size (clay>silt>sand) |
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Plant-Air-Soil continuum
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because of pressure gradient trees act like a wick drawing water from soil into atmosphere
-leaves act as pump, water into roots and up the stem -water moves up through xylem with hydrogen bonding cohesion -soil water moves toward roots along pressure gradient |
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Community
(plant community ecology) |
an assemblage of species that live in an environment and interact with one another, forming a distinctive living system with it's own composition, structure, environmental relations, development and function
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Trait
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distinct variant of phenotypic characteristic of an organism
-may be inherited, environmentally determined or a combo of the 2 rooting depth = characteristic shallow/deep roots = trait |
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Diversity
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degree of variation of life within an ecosystem, biome or planet
-richness, evenness |
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Species Interactions
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mutualism (+, +)
predation/parasitism (+, -) competition (-, -) commensalism (0, +) amensalism (0, -) neutralism (0, 0) |
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Competition
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(-, -)
individuals using same resources will compete if that resource is in short supply -results in niche partitioning |
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Mutualism
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(+, +)
both interacting partners benefit from the relationship -symbiosis -believed to be the most common interaction in nature by some ecologists |
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Amensalism
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(0, -)
a relationship where a product of one organism has a negative effect on another -ie/ alleopathy |
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Symbiosis
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different organisms living together
-usually in close association with one another to the benefit of one or more of them mutualism (+, +) Parasitism (+, -) Commensalism (+, 0) Amensalism (-, 0) |
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Impact of Organisms Depends On:
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number; richness (each species unique, some species ecologically similar)
abundance; evenness (rare species, dominant species) ID; composition (compensating species, keystone species) |
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Functional Groups
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groups of species that are similar in traits and in effects on ecosystem processes
(ie/ N-fixing bacteria, deciduous trees) -helpful in predicting effect of species losses on ecosystems, draw generalities |
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Functional Groups Caveat
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no two species within group are exactly alike
-species competing for same resource cannot stably co-exist: one will take over, leading to extinction or shift towards different ecological niche of the other |
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Foundational Species
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dominant species whose:
"architecture and functional ecology define forest structure and whose species specific traits control ecosystem dynamics" -any tree when it is functionally unique -change in these species more likely to have ecosystem effects than change in rare species |
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Keystone Species
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Species that are more important to ecosystem processes than their abundance might suggest
-affect many other organisms in an ecosystem -help to determine types & numbers of various other species in a community |
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Effects of Species Diversity
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-enhance efficiency of resource use
-stabilize ecosystem processes in a variable environment -insurance against radical ecosystem changes |
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Temporal Ecosystem Dynamics & Resilience
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NOT STATIC
ecosystems are constantly changing and disturbed -they are never in equilibrium with the current environment -temporal patterns that occur differ with scale & severity of disturbance observed -response of ecosystem to perturbation depends on 6 properties |
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Ecosystem Response to Disturbance Depend on:
(6) |
resistance
response recovery stability resilience robustness |
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Resistance
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tendency not to change
-ability to absorb disturbance -maintain certain structures & functions |
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Response
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direction and magnitude of change
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Recovery
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extent of return to original state
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Stability
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rate of return to original state
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Resilience
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elasticity or ability to return to original state
-measure of amount of disturbance system can absorb without leaving stability domain |
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Robustness
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amount of perturbation a system can tolerate without changing state
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Balls & Peaks
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pushing ball into new domain depends more on the way that it is pushed (even subtle) than how hard
-rapid threshold changes or exceeding "tipping points" can occur without warning -low reversibility: in reality species loss begets more species loss |
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Cup and Ball
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width of cup = range of natural variation (RONV)
management goal is to make sure we don't push the ball out of current stability domain |
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how does decreasing biodiversity destabilize ecosystems?
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1) declining species richness lowers ecosystem function
2) at least one functional group, preferably with redundancy, essential to ecosystem stability 3)the nature of response to species loss depends on which species is lost -degrading system (or pushing out of RONV = loss of stability |
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Ecosystem
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a functional system that includes an assemblage of interacting organisms and their environment; which acts on them and on which they act
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Ecosystem Ecology
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integrated study of biotic & abiotic components of ecosystems and their interactions with ecosystem framework
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ecosystem classification
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tool for understand & predicting responses of ecosystems occupying a given site
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Attributes of Ecosystems
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structure (components)
function (processes) connectedness complexity intangible geographic boundaries change over time |
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structure (components)
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-plants, animals, microorganisms
-substrate (soil), atmosphere, water -producers, consumers, decomposers -food web |
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function (processes)
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-constant exchange of matter and energy components
-Energy flow -nutrient cycling -water flux |
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connectedness
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components interact and are interdependent
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complexity
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-high level of integration
-multiple feedbacks: positive (enforcing) & negative (dampening) -all events and conditions have multiple determinants |
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Intangible Geographic Boundaries
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-arbitrary
-connected to other ecosystems |
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Ecosystem Change Over Time
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-not static in composition, structure or function
-altered from within (plant species effect) -altered from without (fire, climate change) -change within bounds determined by climate, site |
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Natural Disturbances
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exogenous and endogenous
are an integral part of ecosystems, and more often than not are agents of renewal rather than destruction -within historic range of variability -some human disturbances are in this range |
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Foreign Disturbances
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of a type or severity to which native species are maladapted, can be serious threat to ecosystem integrity
-may force system past a threshold into new regime -degraded conditions -become increasingly prevalent - includes: uncommonly severe fires, climate change, & invasive species |
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Maintain Ecosystem Integrity
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-maintain key ecological processes that reflect their natural condition
-manage population of species to levels with high likelihood of maintaining themselves -maintain diversity of genes, species & communities native to region |
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Prevent or Minimize Ecosystem Change
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Keep disturbances within historic range
-w.r.t. type and severity -use forest practices that emulate natural disturbances Prevent soil degradation Maintain hydrology (water flux) Foster resilience of ecosystems |
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Managing for Resilience
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PROCESS STRATEGIES
-ecosystem level -maintain desirable species an control undesirable species PATTERN STRATEGIES -landscape level -maintain heterogeneous landscape with large and structurally complex patches of native vegetation connected by corridors |
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Process Strategies
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1) maintain key species interactions and functional diversity
2)apply appropriate disturbance regimes 3) control aggressive, over abundant and invasive species 4) minimize ecosystem specific threats (pollutants, hunting) 5)maintain species of particular concern (keystone, rare) |
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Pattern Strategies
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1) maintain and create large, structurally complex patches of native vegetation
2) maintain structural complexity throughout landscape 3) create buffers around sensitive areas 4) maintain/create corridors and stepping stones 5) maintain landscape heterogeneity and capture environmental gradients |
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Managing for Complexity
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to foster resilience
-promote landscape connectivity -retain or restore areas that may be buffered against climate change -plant mixes of trees to reset successional patterns -facilitate species (and population) migration and range shifts -develop harvest, regeneration, & stand tending that maintains or enhances complexity |
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Ecological Restoration
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-returning ecosystem to desired state
-usually a reference ecosystem or historical reference -restoration attempts to return an ecosystem to its historic trajectory |
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Restoration Ecology
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the science on which the practice of ecological restoration is based
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Attributes of a Restored Ecosystem
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1) characteristic assemblage of species
2) indigenous species 3) all functional groups required 4) physical environment capable of sustaining reproducing populations 5) functions normally 6) integrated into larger ecological matrix 7) potential threats lowered 8) resistant 9) self sustaining |
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Dilemmas in Ecosystem Restoration
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1) where to set ecological reference
2) historical reference often not achievable 3) exotic species often unavoidable 4) exotic species contribute to ecosystem function 5) novel ecosystem the way of the future? 6) does it imperil conservation? |
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Rehabilitation
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reparation of ecosystem processes, productivity and services
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Reclamation
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objectives include stabilizing the terrain, assuring public safety, improving aesthetics and returning land to a useful purpose
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Revegetation
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normally a component of land reclamation, often entails the establishment of only one or a few species
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Mitigation
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compensates environmental damage
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Creation
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installing a different type of ecosystem from that which historically occur
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Ecological Engineering
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manipulation of natural materials, living organisms and physical-chemical environment to achieve specific human goals and solve technical problems
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Landscape Ecology
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incorporates the dimension of space into ecological studies
-heterogeneity in ecosystems across space influence ecological processes -ecosystem services vary across space |
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Landscape Ecology & Management
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1) maintain and create large structurally complex patches of native vegetation
2)maintain structural complexity throughout the landscape 3) create buffers around sensitive areas 4) maintain/create corridors and stepping stones 5) maintain heterogeneity & capture environmental genetics |
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Patch
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-nonlinear surface areas that differ in vegetation and landscape from their surroundings
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Matrix
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-dominant component of the landscape
-most extensive and connected landscape type -dominant role in landcape ecology |
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Corridor
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Linear, connect patches
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Categories of Ecosystem Services
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Provisioning Services
-food production, water, wood and fiber, fuel Cultural Services - spiritual, aesthetic, educational, recreational Supporting Services -nutrient cycling, soil formation, primary production, habitat provision Regulating Services -climate regulation, flood regulation, water purification |
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Location Matters!
(Landscape Ecology) |
-incorporates the dimension of space into ecological studies
-heterogeneity in ecosystems across space influence ecological processes -ecosystem services vary across space |
