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Community Ecology > Community Ecology Exam > Flashcards

Community Ecology Exam Flashcards

1
Q

Succession

A

A gradual change in plant and animal communities in an area following disturbance
- the disturbance can be small or large, there are a removal of few to many individuals or a creation of an entirely new habitat

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2
Q

pioneer community

A

organisms that colonize area immediately following disturbance

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3
Q

primary succession

A

newly exposed substrates and not significantly modified by organisms
ex. glacier retreat, lava flows, sediment deposition (river/stream outflow)

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4
Q

secondary succesion

A

following disturbance that does not destroy soil

ex. fire, flood, abandoned agriculture land

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5
Q

what occurred in the greenbelt corridor?

A

plant community responded to flooding and drought
- species richness declined after flood and drought occurred over years, then increased past original and declined slightly and stabalized

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6
Q

climax community

A

late successional community that remains stable until disrupted by disturbance

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7
Q

disclimax community

A

maintained only through continual disturbances

ex. grazing, drought, fires, flood (centrifugal organization)

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8
Q

community structure and ecosystem process may change in a predictable manner or not ending in one of few to many _________ ________

A

alternative states

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9
Q

does disturbance impact all communities equally?

A

no

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10
Q

stability

A

the tendancy to resist or recover from disturbance

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11
Q

what was Sousas definition of disturbance?

A

Discrete, punctuated, killing, displacement, or damaging of one or more individuals (or colonies) that directly or indirectly creates an opportunity for new individuals (or colonies) to be established.

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12
Q

what was white and pickets definition of disturbance?

A

Any relatively discrete event in time that disrupts ecosystem, community, or population structure and changes resources, substrate availability, or the physical environment

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13
Q

what are some spatial and temporal considerations for for disturbance?

A
  • disturbance to bryophyte on a rock near a stream may occur at spatial and temporal scales irrelevant to surrounding forest communities
  • a disturbance for one species may be inconsequential to another
  • the nature of a disturbance may be environment specific
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14
Q

biotic vs abiotic disturbance:

A

biotic - disease and predation

abiotic - fire, hurricane, flood, wind, ice storm

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15
Q

intermediate disturbance hypothesis (Connell)?

A

proposed disturbance is a prevalent feature that influences community diversity

  • proposed high diversity consequences of continually changing conditions
  • predicted intermediate levels of disturbance promote higher diversity
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16
Q

if disturbance is too frequent and intense only _______ species will be present

A

pioneer, can complete life cycle between disturbance

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17
Q

if disturbance is too infrequent or minor only _____ species will be present

A

climax

- most effective competitors

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18
Q

as frequency and intensity increases there is a shift from in species composition from ________ to _______

A

competitors to colonizers

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19
Q

competitive exclusion

A

At intermediate levels of disturbance there is sufficient time for competitors to establish but not enough to outcompete early colonizers

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20
Q

what was Sousas study on disturbance ands diversity in intertidal zones?

A
  • studied effects of disturbance on diversity of algae and invertebrates growing on boulders in the intertidal zone
  • Disturbance comes mostly from wave action during winter storms.
    – Predicted level of disturbance depends on boulder size. Classified boulders into three disturbance levels based on size and force required to move
  • most boulders subject to high disturbance had one species
  • modal number of species on boulders subject to low disturbance was two
  • most number of species was highest 4 on boulders subject to intermediate disturbance, boulders that experiences to intermediate rates of disturbance supported more species
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21
Q

one of the most important and ubiquitous sources of disturbance in grasslands is ________ _________

A

burrowing mammals

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22
Q

describe disturbance of paradise dogs

A
  • creates distinctive patches of vegetation, the areas around the mounds support communities distinct from surrounding grassland
  • species diversity highest at intermediate levels of prairie dog disturbance
  • grass diversity decreases
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23
Q

intermediate disturbance allows persistence of species that are good _________ and species that are good ________

A

colonizers and competitors

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24
Q

stability

A

absence of change

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25
Q

stability can arise from ______ and _________

A

resistance of resilience

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26
Q

resistance

A 
Ability to maintain structure and/or
function in face of potential disturbance
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27
Q

resilience

A

ability to recover from disturbance

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28
Q

the greater the change the lower the ______

A

resistance

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29
Q

the faster the recovery the greater the _______

A

resilience

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30
Q

describe the park grass expierment

A
  • To study effect of fertilizer treatments on yield and structure of hay meadow community
  • Silvertown (1987) investigated ecosystem stability
  • no new species since 1862* Stability on large scale
  • without fertilizing grasses dominated throughout the period
  • fertilizing with phosphorus, potassium, sodium, and magnesium increased the proportions of legumes and other species
  • fertilizing with nitrogens, phosphorus,, potassium, sodium, and magnesium greatly increased the proportions of other species and produced moderate increases in legumes
  • the proportion of major species groups appear very stable over time
  • But analysis at level of species, shows large turnover in species within each species group
  • Broad taxonomic groupings remain relatively stable but individual species show various responses
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31
Q

stability is _______ dependent

A

scale

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32
Q

sycamore creek was an example of ________ succession (describe)

A

primary

  • typical desert drainage system, with low to
    intermittent flow for most of the year, but periodically subject to flash floods after major storms
  • Rock scour and sediment deposition can totally remove algae and invertebrates
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33
Q

what was the study with valet in sycamore creek Arizona?

A
  • tested hypothesis that ecosystem resilience in Sycamore Creek, Arizona is higher where linkages between surface and subsurface waters increase supply of N
  • used piezometers
  • Studied two stretches of stream and produced hydraulic maps; both had similar profiles
  • nitrate concentrations are highest in upwelling zones
  • nitrate concentrations decline through stationary and downwelling zones
  • N content was highest where greater linkage of subsurface and surface waters
  • Physical pattern of upwelling and downwelling zones remained stable through floods (resistance)
  • Increased N in upwelling zones correlated with greater algal biomass increase after disturbance. Rate of algal biomass accumulation a measure of resilience
  • Supports idea that hydrologic linkages increase stream resilience
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34
Q

Piezometers

A

measure flow bewteen surface water and water in flow in sediments

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35
Q

the relationship between diversity and ecosystem function involves :

A
  • Complementarity
  • Facilitation
  • Sampling effect
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36
Q

insurance hypothesis:

A

which diversity increases stability due to increased probability of there being some species able to cope with any particular disturbance

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37
Q

diversity ____ a community from the potential consequences of a disturbance or any environmental change

A

buffers

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38
Q

______ ________ become important within a community under different conditions

A

different species

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39
Q

what changes during succession?

A

dominance, evens, diversity, composition

40
Q

succession is the outcome of _____ ______ including:

A

ecological processes: dispersal, niche requirements, competition, exploitation, mutualism

41
Q

describe primary succession at glacier bay

A
  • Late 1700’s, glaciers extended to the ocean outlet of the bay
  • By 1880’s, glaciers had retreated by ~40 km; lower bay supported plants and young forests, upper bay did not
  • Fossil wood exposed by retreating glaciers
42
Q

chronoconsequence

A

a group of communities or ecosystems that represent a range of times since disturbance

43
Q

what was the study at glacier bay with Reiners?

A
  • 8 sites ranging in age from 10 to 1500yrs post glacier retreat
  • Species richness increases with age of site
  • Richness increased most rapidly in early stages of succession
  • Alaska, the successional process is quite slow
44
Q

what where the taxa specific responses at glacier bay?

A
  • Mosses, etc. (green bar) reached maximum species richness at ~100 y, remained steady thereafter
  • Tall shrubs (red bar) reached maximum species richness at ~100 y, but declined afterwards
  • Tree (yellow bar) species richness peaked at ~500 y
  • Low shrubs & herbs (purple bar) richness continues to increase
45
Q

the boreal forest has widespread dynamic diveristy subject to frequent disturbances especially ______

A

fire

46
Q

what is the role of fire ?

A
  • removes canopy, increases light penetration

- speeds nutrient cycling

47
Q

describe the fire tolerant species in the boreal forest

A
  • Aspens sprout from roots; this is a clonal species, with some clumps essentially immortal
  • Paper birch can re-sprout as well, although not as robustly as aspen
  • Spruce and pine; fire releases seeds from cones; smoke compounds act as germination stimulants
48
Q

describe secondary succession in the boreal forest

A
  • used forests of progressively older ages (longer times since last major fire event) to develop a forest community chronosequence
  • Hardwood deciduous species dominate – aspen, birch, willow, pin cherry
  • next forest forest experiences fire in 1916
  • Paper birch and aspen in decline
    • Balsam fir and white spruce beginning to become more important
    • Young firs and spruce are prominent in the understory

“older” forest, experienced fire in 1823:

  • Dominant tree species is balsam fir (although many dead stems)
  • White cedar beginning to become important
  • Birches and aspens much reduced

Oldest forest of all, experienced fire in 1760:
- Dominant forest trees are white cedar, white spruce (although declining) and balsam fir

49
Q

describe primary succession by Sousa in intertidal zones

A
  • bare surfaces on intertidal boulders to encrusted communities of algae, barnacles and mussels
  • pioneer species algae and barnacle
  • next colonists, red algae
  • if no disturbance, red algae becomes dominant and occupies 60-90% of space
  • Colonization is rapid initially, but then levels off
  • if not disturbed it exemplifies a dominance controlled community
50
Q

describe primary succession in sycamore creek

A
  • typical desert drainage system, with low to
    intermittent flow for most of the year, but periodically subject to flash floods after major storms
  • rock scour and sediment deposition can totally remove algae and invertebrates
  • recolonization by algae after flood
  • 2 days – some diatoms appear mainly bare ground
  • 5 days – diatoms over 50% of the streambed
  • 13 - 22 days – diatoms over entire streambed
  • 35 days – other algae appear, including Cladophora
  • 63 days – diatoms, cyanobacteria, Cladophora
  • Overall, H’ increased sharply early, levelled off, then started to decline
  • recolonization by benthos following flood
  • stream is dominated by larvae of a crane fly, Cryptolabis sp.
    – diversity remained constant (swamped by presence of Cryptolabis), except during crane fly emergence period
  • Species richness ranged from 38 to 43
  • during August flood, most benthic species had adult aerial stages
    – source of recolonization
51
Q

describe shallow lake succession

A
  • lakes experience succession on 2 time scale
  • Over seasons or years, changes in species composition due to disturbance (freezing, flooding, introduction of novel species)
  • Lakes also experience succession over geological time scales. Predictable changes in species composition as result of sedimentation.
52
Q

Sedimentation

A

deposition of suspended matter onto lake bottom

53
Q

shallow lakes and ponds are ______ in the long term

A

ephemeral

54
Q

in shallow lakes and ponds rates of decomposition < __________ or inputs from erosion > _____

A

sedimentation, outputs

55
Q

what is the chronoconsequence?

A

A series of communities or ecosystems representing a range of ages or times since disturbance
- Glacier Bay “sequence of ages” represented by sites of different ages since glacial retreat – but limited to a relatively short time frame (at most ~1,500y)

56
Q

what are some ecosystem changes during succession?

A
  • Include increases in biomass, primary production, respiration, and nutrient retention.
  • Communities alter ecosystem properties
    -Time alone might influence ecosystem through
    processes such as weathering of bedrock.
57
Q

describe the soil structure and depth (ecosystem changes) at glacier bay

A

Top-most: the O horizon, also called the LFH horizon
Next: the A horizon (importance of invertebrates and leaching)
Next: the B horizon (a depositional zone)
Finally: the C horizon
Note roots extending down through the horizons (root exudates are important)
- 60-70 y old: soil depth increased, with some organic material & litter
- 200-225 y old: fairly deep soil, all horizons well represented

  • overall soil increased in both quantity depth and
    complexity
  • Organic content & moisture increased with site age and soil depth & complexity
58
Q

what are the 4 soil properties at glacier bay?

A
  1. organic content
  2. moisture
  3. bulk density
  4. phosphorus
59
Q

describe Chapins study at glacier bay

A
  • studied 4 sites of different ages at Glacier Bay, Alaska.
    Observed changes in soil.
  • Observed changes in organic content, moisture,
    phosphorus, and bulk density
  • reveals that physical and biological systems are inseperable
60
Q

describe chronoconsequence on the Hawaiian islands

A
  • Limits to 1° production: nitrogen early & phosphorus late in the successional sequence
  • First organic matter accumulates – over 1st 150,000
  • Total N also increases as organic matter increases
  • Organic matter & total N were lower at Molokai, a little higher again on Kauia
  • Total phosphorus did not vary with soil age – but weatherable phosphorus was depleted by 20,000 y & refractory phosphorus had increased to a plateau
  • Rates of nitrogen and phosphorus loss were different
  • For N: 1st 2,000 y, N is retained, but then is lost at progressively higher rates, due to leaching to the groundwater
  • For P: with age, ecosystems retain more phosphorus, but in refractory form; rates of loss are high early on, but decrease later
61
Q

what was the Hubbard brook site?

A

forests of nutrient loss and retention

  • Clear cut catchment
  • 3 years of suppression of regrowth
  • recovery period
  • deforestation experiment showed that succession can reduce loss of plant nutrients caused by disturbance
  • once succession was allowed plant biomass increased
  • Export of calcium, potassium and nitrate decreased, but only nitrate loss decreased to control levels
  • Primary production increased
  • Nutrient pools had been depleted prior to vegetation regrowth (losses peaked before herbicide treatment ended)
62
Q

what is the model of recovery (Bormann and likens) ?

A
  • according to the biomasss accumulation model disturbing a forest and ecosystem will induce a series of distinct recovery phases
    1. reorganization
    2. aggradation (biomass increase)
    3. transition (biomass decline)
    4. steady state (consistent biomass)
63
Q

what is the key prediction of BAM (biomass accumulation model)?

A

Achievement of a steady state in biomass

64
Q

in streams there is a early rapid _______ of biomass indicated by ________ _ levelling off after 30 days

A

accumulation, chlorophyl a

65
Q

in streams oxygen has a rapid ______ followed by a slower ____ followed by _______ ____

A

increase, increase, levelling off

66
Q

in streams invertebrate respiration has a ______ _____ to a ______

A

gradual increase, plateau

67
Q

described the nitrogen dynamics in streams

A
  • Upwelling zones and downwelling zones ; compared dissolved inorganic N content
  • Retention of N in the reaches peaked ~30 days into the succession
  • By ~90 days, N is exported – suggesting biomass loss
68
Q

what are the mechanisms driving succession? (2 models)

A
  1. eggless and floristics model- offered as a synthesis and clarification of the monoclimax individalistic debate
  2. connell and slayters model- Facilitation, Inhibition & Tolerance
69
Q

describe floristics (the clementsian model):

A
  • waves of species, each replacing the former because of biotic changes to the environment
  • facilitation, lack of overlap, an order to the groups of succeeding species
70
Q

describe initial floristics:

A
  • Somewhat like the Gleasonian model: considerable overlap amongst species, but different periods of dominance
  • many species can potentially establish after a disturbance, but vary when they become abundant
71
Q

what was the study by Peters in the boreal forest?

A

following fire disturbance:

  • Many species can get established early on
  • Adjacent stands vary in pattern of regeneration
    ex. spruce can sometimes establish early (as saplings) in some stands, but in other stands, establishment occurs much later
72
Q

describe the model by connell and slayter:

A
  1. Facillitation
    - Involves initial establishment by pioneer species
    - Pioneer species modify the environment
    - Involves a chain of facilitations and
    replacements
    - Culminates in a self- perpetuating community which can be replaced only by disturbance
  2. Tolerance
  • initial colonizers are not necessarily pioneer species
  • activities of early species do not make conditions more favourable for later species, although conditions do become less favourable for themselves
  • later colonists are tolerant of the prevailing conditions
  • the climax is reached when all tolerant species have colonized
  • the system is reset by disturbance
  1. Inhibition
  • initial colonizers could be any species (like tolerance model)
  • early colonizers make conditions less suitable for subsequent arrivals
  • early colonizers resist invasion by new arrivals
  • replacements occur only when early colonists die
  • the climax community consists of long-lived, resistant species
  • disturbance resets the system
73
Q

what was Sousas study in intertidal zones on early successional processes?

A

Hypothesis: early successional species are more vulnerable to biotic & abiotic mortality factors

  • 4 controls no removals
  • removed middle successional species
  • removal plots ulva reinvaded very quickly
  • very high densities of late successional species
  • more evidence needed for inhibition
74
Q

in intertidal communities there was physical stress due to exposure including:

A

combined effects of tide and temperature, therefore ulva was less able to survive afternoon low tides
- Ulva more vulnerable than the various species of red algae (mid or late)

75
Q

Sousas work consistently points towards the role of __________

A

inhibition

76
Q

describe turners intertidal studies (Oregon)

A
  • wave action creates space
  • Successional pattern: Ulva (early); red algae (middle, various species); surfgrass, Phyllospadix scouleri (late dominant)
  • facilitation hypothesis with respect to the recruitment process
  • Surfgrass seeds need presence of macroscopic algae for attachment & germination
    Surfgrass becomes dominant following vegetative growth & spread
77
Q

describe the removal experiments in intertidal communities:

A

All attached algae cleared from experimental plots in
September; control plots untouched
- control plots contained red algae and removal plots contained brown algae
- Removal experiments, Phyllospadix seed comparisons
- Many (48) seeds in the control plots, all attached to Rhodomela larix
• Few (2) seeds in the removal plots – neither attached to Phaeostrophion – both attached to remnants of original Rhodomela (had resprouted from holdfasts)
- supports conclusion of an obligate facilitation mechanism that allows surfgrass recruitment

78
Q

probabilities of fire depends on both ____ and ______

A

climate and forest type

79
Q

areas dominated by _____ have less fire

A

aspen

80
Q

areas dominated by _____ have more fire

A

spruce

81
Q

Aspen ____fire, even though its own recruitment is enhanced by fire

A

resist

82
Q

Spruce _____ fire, in the short-term, this allows aspen recruitment, but in long-term, it promotes spruce recruitment & establishment

A

promotes

83
Q

_____ _____ _____ for the boreal forest, hence, the large areas of mixed-wood forests

A

alternate stable states

84
Q

No single factor determines the pattern of succession at Glacier Bay; both ______ and ________ play roles

A

inhibition, facilitation

85
Q

keystone species

A
  • Despite lowbiomass and relative abundance exert a strong effect on community strucutre
  • a disproportionate effect on their community relative to their abundance and biomass
86
Q

species that have a significant influence on community structure by virtue of high biomass are _________ species

A

domia

87
Q

keystone species can occur at any _______ level within a food web

A

trophic

88
Q

ecosystem engineers

A

species whose activities maintain and/or create new habitat

89
Q

beavers are _______ _______ and keystone species

A

ecosystem engineers

90
Q

describe affects that beavers have on communities:

A

Beavers cut down trees near stream, forming dams.

  • Dams cause flooding, formation of ponds and increased riparian area.
  • Beavers build lodges in resulting ponds
91
Q

what was the study with John fryxell?

A

Transects to assess plant community structure and beaver activity

  • Cut stems: # decreased with distance from water
  • Diversity(species richness) peaked at intermediate distances – a function of a mix of species that could re- sprout (tolerant of cutting), those that are good competitors, and species that prefer less water- logged soils
92
Q

what is the only requirement for keystone status?

A

that species in question has low biomass and disproportionally high impact on community structure.

93
Q

describe the relationship between wrasses and cleaner fish

A
  • A reef mutualist, the cleaner wrasse, Labroides dimidiatus
  • 1 wrasse can eat up to 1200 parasites per day
  • Fish on reefs without wrasses have 4X the parasite load
  • Study of 46 reef patches in Red Sea over 4 months; removal or addition of wrasses
  • Where wrasses were removed (or naturally disappeared) reef fish richness diminished by 24%
  • contrast to 24% increase on patches where wrasses were added experimentally or naturally
94
Q

describe the role of ants and seed dispersal in south africa

A
  • Native ants disperse 30% of the seeds
  • Ants are attracted to the elaiosomes attached to the seeds
  • Argentine ants exclude the two native species that are much more likely to move large seeds
  • Non-excluded ants species will move seeds, but one species never moves large seeds
  • Argentine ants do not disperse or burys eeds
95
Q

dispersal and burial of seed is critical to ________ of large seeded plants

A

persistance

96
Q

where Argentine ants have invaded large seeded plants have suffered _______ _______ ______

A

greatly diminished recruitment

Community Ecology (2 decks)

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