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96 Cards in this Set
- Front
- Back
Dimension Reduction
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Process of collapsing highly multivariate data into a small number of dimensions
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Monte Carlo Methods
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Used to determine if your result has meaning
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Eigenvalue
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Contribution of each axis to total variance
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Agglomerative Vs. Divisive Classification
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Agglomerative: starts with all different and goes until all are in one group. Divisive: assumes all same, then divides down to some criterion. (preferred, but few and far between)
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Non-Hierarchical Classification
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tries to find natural breaks in data swarms in n-dimensions. Few good methods exist
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Indicator Species
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The concept of using species to identify factors in the environment
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Niche
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Range of ecological conditions in which a plant species will grow
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Competitive Exclusion
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Species use same limiting resource, in same place, in stable and uniform habitat, for sufficiently long time
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Mass Effect
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Species go extinct except that there is continual replenishment from surroundings
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Ecological Equivalence
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where several similar species co-occur, first-come first served, and once served, your in for the duration
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Niche Differentiation
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species shift their requirements to reduce impact (evolutionary response)
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Species Area Curve
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Log area vs log richness; the steeper the line the faster species accumulate
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Competition
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The negative effects which one organism has upon another by consuming or controlling access to a resource that is limited in availability
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Allelopathy
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Chemical inhibition of the growth of one organism over another
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Diffuse Competition
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Target impacted in proportion to the biomass of associates (cumulative effects of neighbors of all species)
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Predominant Competition
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One species is main contributor to intensity
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Symmetric vs. Asymmetric Competition
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species affect each other equally vs one species has greater affect than other species
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Safe-site (microsite)
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A favorable spot for seed germination and establishment
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Preemption
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Getting to the resource first
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Tolerence
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Coping with the limitation
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Efficiency
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Better use of resource
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Succession
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Directional change in community composition and structure through time
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Mechanisms of Succession (6)
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Nudation, migration, establishment, facilitation, competition, stabilization
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Facilitation
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Positive interactions among plants; a process by which early successional species increase the survival of later successional species
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Inhibition
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A process by which early successional species decrease the survival of later succesional species
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Nudation
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Process that clears the land
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Migration
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The movement of organisms or propagules
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Establishment
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growing up
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Stabilization (Climax)
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The hypothetical equilibrium end point of a successional sequence
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Chronosequence
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A set of communities of different ages since disturbance, assumed to represent a single community over time
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Wetlands
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Transitional habitats with plants normally rooted in saturated soils with plants adapted to living in water or saturated soils
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Soil Chroma
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Intensity
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Paulustrine
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non-tidal wetlands dominated by trees, shrubs, emergents, mosses/lichens and tidal wetlands under 0.5 ppt. Common non-tidal system
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Lacustrine
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All the following: wetlands in depressions or dammed river channels, lacking trees, shrubs, emergents with 30% cover; larger than 20 acres.
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Jessica Gurevitch
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Large plants have large immediate neighbors, small plants have small immediate neighbors (mosaic of patches) probably due to patchy resources
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John Harper
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one of pioneers of plant community ecology; safe-sites
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David Tilman
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In communities on infertile soils with low productivity, species that are superior competitors for soil nitrogen should be competitively dominant
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Peter Grubb
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differences among species in the conditions and circumstances required for germination and establishment might be an important factor in species coexistence (regeneration niche)
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Deborah Goldberg
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strong effects of density on seedling emergence
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Norma Fowler
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Competition much less important than other factors in some perennial grasses
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Paul Keddy
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Competitive effect increases with increased growth rate
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Mark Westby
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Trade-offs along a small number of axes that define major, easily quantified traits, wants to reduce vast diversity of terrestrial plants to conceptual categories so that plants can be grouped in ways that enable one to pose testable hypotheses and make predictions
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C. H. Muller
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research on allelopathy in chaparals
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Ragan Calloway
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allelopathy as cause of succession in invasive weeds
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S.T.A. Pickett
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disturbance is a relatively discrete event in time that causes abrupt change in ecosystem, community, or population structure and changes resource availability, substrate availability, or physical environment
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Henry Cowles
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succession of dunes, chronosequence
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Why is a dendrogram hard to interpret?
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Larger groups have more variation so differences can be exaggerated. Can be divise or agglomerative (makes dendrogram for you).
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What is chaining?
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Dendrogram has less definitive subgroups. Low chaining means there is high dichotomous branching.
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What properties of the data affect dendrogram structure?
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Richness and group size
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Why shouldn’t you attempt to draw a line across a dendrogram to form vegetation units?
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Line lengths do not necessarily suggest connectivity with close neighbors.
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Contrast TWINSPAN with any typical agglomerative strategy.
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TWINSPAN is divisive.
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What are the main purposes of classification?
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To summarize large, complex sets of data to produce mapping units; reduce data to manageable levels; help interpret environmental factors; test community hypotheses; refine models of community structure; assist experimental design
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List several reasons to do a classification, even if you believe your data represent continuous variation.
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Different results from alternative methods can reveal unsuspected aspects of data; same results from different analyses give credence to real discontinuities in the data.
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List five subjective aspects of doing classification.
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Altternative methods produce alternative results; different observers may reach different conclusions; different subset of data might lead to different classification; transformations may emphasize dominance or rare sp.; editing rare species can make groups more homogenous, or can obscure real differences among samples.
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What might happen if you remove just one plot from your data set?
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Depends. Could remove branch from dendrogram, nothing
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Describe how you would use classification in the study of succession using permanent plots.
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Look at vegetation types to classify level of succession.
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How can you tell if your vegetation classes represent unique clusters?
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Want space between a branch on dendrogram to be smaller than space between 2 branches on dendrogram; if there’s not species overlap between groups.
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What factors might control diversity within a 1 ha vegetation sample.
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Site history, soil, moisture, seed dispersal, temperature, competition, facilitation, tolerance (can survive under less than optimal conditions)
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Discus those factors that may permit the coexistence of similar perennial herbaceous species in the coniferous forest understory.
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Availability of different microsites, tolerance, minimal competition, habitat fluctuation, facilitation
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What factors might influence diversity gradients on a broad geographic scale?
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Consider productivity, stability, biotic factors, habitat complexity and disturbance.
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What factors lead to there being more species in samples of East Cascade than West Cascade forests?
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Temperature gradient, moisture gradient (rain on west, none on east), disturbance regimes (farming east, logging west). West more homogenous, has forest—trees prevent understories, East has weedy species.
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List factors that might affect changing numbers of plant species along a latitudinal gradient (N to S)
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Wind, temperature, precipitation, Hadley cells, site history, habitat modification.
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A seed germinated in a meadow, but died within a few weeks. Briefly, discuss how you could determine if competition was responsible for this death. Observe what happens after seed dies. How could you determine if a particular competitor species was responsible?
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Manipulation experiments; Selective removal, replant same seed.
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You encounter a meadow surrounded by tall conifers. Aerial photos indicate that the meadow has been there for 75 years, and that it has been fallow (not cultivated) for at least 60 years. List the potential reasons that explain why conifers have not invaded; for each, list an experiment or observation to test predictions based on each reason (hypothesis).
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Soil differences, herbivory (put fence around), more drainage, remove grasses, plant sapling (see if it’s something before that preventing it).
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List at least four factors that are most likely to permit the coexistence of closely similar herbaceous perennial species in the coniferous forest understory.
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Niche differentiation (temporal avoidance, morphological avoidance, different shade requirements, limited by different factors), Abundant resources, habitat heterogeneity, habitat fluctuation.
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What factors make it hard to study competition?
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You might consider spatial effects, competitive balance that shifts in space, multi-species effects, and others. Diffuse competition, control of vegetation might be layered
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What factors permit coexistence by allowing plants to avoid competition? What nine factors may allow plants to coexist within the same habitat?
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Niche differentiation, different regeneration regimes, habitat heterogeneity, habitat fluctuation, abundant resources, chronic disturbance, balanced competition, equivalence, mass effect.
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Recall the concept of competitive hierarchies (the centrifugal model). If the model is correct, what happens if you remove Typha from the system?
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Change successional trajectory; something else will take over/grow
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What is the difference between the regeneration niche (Grubb) and a safe-site (Harper)?
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R: more about attributes that allow for regeneration, S: more geared towards colonization/germination
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How does the “carousel model” (van der Maarel) help to explain local (alpha) diversity?
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Cyclical succession.
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You sampled old-growth conifer forests in 7 small lowland valleys within one large watershed. As far as you can tell or measure, the environments are similar. You classify them objectively into seven groups, each comprised only of samples from a single valley. If the species composition of each is stable, list three important reasons that could produce seven different "climax" forests within the same area.
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Site history, unmeasured variables (latent factors), poor models, imprecise measures, seed dispersal
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What are the advantages of permanent plots over space-for-time substitutions
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No assumptions about habitat consistency needed.
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What are the drawbacks to permanent plots?
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Time, finding site again
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List four aspects of disturbance that will affect the course of succession.
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Pg. 9 Type, intensity, frequency, selectivity
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Discuss how facilitation, tolerance and inhibition may all be involved in a single succession.
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page. 6
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deflected vs. arrested development.
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Changes vs. stops
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Progressive vs. retrogressive succession
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Progressive: simple-->complex
Retrogressive: complex--> simple |
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relay succession vs. initial floristic composition
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Clear stages vs. stages that are hard to recognize.
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amelioration and facilitation
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abiotic vs. biotic
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Colonization vs. establishment
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getting there vs staying
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Convergent vs. divergent trajectories
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similarity vs. differentiation
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Criticize Grime's trajectory diagrams.
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Deterministic fate not necessarily true, doesn’t separate out layers (lose details), very simplified (tradeoff)
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If you sample vegetation on Tiger Mountain and obtain very good environmental data (fertility, moisture), location data (elevation, distance from trail, roads, etc.), and know the time since major disturbance (e.g. burn or cut), will you necessarily be able to explain a high percentage of the variation?
Can you use a linear method of comparison? |
20% good, depends on if those factors are driving.
No, simplified |
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Text books often show successional diagrams based on chronosequences. Discuss the pitfalls of this approach, as revealed by recent studies of dunes, bogs or old fields.
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Too many assumptions and oversimplifications.
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What factors have been of particular importance to primary succession on Surtsey?
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Bird poop, water dispersal to some extent, a bit of wind, safe-sites
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Wetlands usually display hydric soils, hydrophytic vegetation, and wetland hydrology. For each parameter, list one observation that would satisfy the requirement of a positive finding of wetland conditions.
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1. Black, organic matter, mottling. 2. Fac, fac wet, obliate at least 20% each and 50% overall 3. Saturated 2 weeks of growing season
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What are the main values and functions of wetlands?
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Habitat for plants, fun, economically important, biofiltration, moderation of stream flow, breeding habitat for fish
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Swamp
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-Dominated by woody species
-Intermediate nutrient -More acid -Intermediate between bog and tidal marsh |
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Marshes (deep and shallow)
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-Dominated by herbs, ermergent cattails
-Deep: Up to 6 feet with rooted floating aquatics -Shallow: up to 15 cm water -High nutrients -High water fluctuation |
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Bogs
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-Dominated by herbs, mosses
-Limited soil oxygen -Decomposition limited -More acidic than fen -High water fluctuation |
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Fens
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-Dominated by herbs
-Limited soil oxygen -Decomposition limited -Less acidic than bog -Alkaline -Low nutrients -Low water fluctuation |
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Wet Meadow
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-Seasonally dry
-Often dry part of year -Frequently grazed -Not considered wetlands by land owners |
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Scrub-shrub wetland
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-Dominated by woody shrubs
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What is a wetland class? Why is it important to know the wetland class when you are delineating a wetland for regulatory purposes?
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Different protection, importance, function
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Describe expected results from a selective removal experiment conducted in
a productive meadow and contrast the potential result with the same type of experiment conducted in a dry, infertile meadow. |
In the more productive meadow it would be quicker for other
species to take over and it might be different species that take over the area if it was a competitor that was removed. In the infertile meadow the same species would probably return because it is one of the few adapted to the area and it would take longer for this to happen. |
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By what 3 fundamental strategies do plants compete?
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pre-emption, tolerance, efficiency, avoidance, regeneration niches, safe-sites, allelopathy, interference
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