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APS278: Tropical Forest Ecology & Conservation > Lecture 4: Gap Dynamics > Flashcards

Lecture 4: Gap Dynamics Flashcards

1
Q

In the 1930’s Aubreville proposed ___

A

‘gap mosaic’ model in which the forest cycles through 3 main stages

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2
Q

3 main stages of ‘gap mosaic’ model

A

1) gap creation: immediately following a tree fall or gap opening
2) Building or regeneration phase: which is characterised by competition for light & other resources leading to regeneration & growth
3) Mature phase: where the high emergent forest canopy is re-establsihed

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3
Q

Gaps are a ___ part of forests dynamics

A

natural

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4
Q

Forests are a mosaic of __ &__ at different stages of ____

A

gaps & trees and different stages of regeneration

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5
Q

how are gaps created?

A
  • rain forest trees will eventually die and fall, they may be uprooted or snap
  • trees may be blown down
  • struck by lightning& fall
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6
Q

how does one tree falling cause so much destruction:

A
  • when one tree falls it often brings many more as crowns are meshed together by lianas
  • Large branches continually break off from trees and fall
  • Gaps vary in size
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7
Q

Damage to vegetation below varies with

A

gap size, composition of surrounding vegetation, type of forest

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8
Q

gap fraction is defined as

A

the fraction of sky visible through the canopy

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9
Q

Gap characteristics of different rain forest types ___

A

VARY

- Gap size & Gap fraction

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10
Q

gaps create ___ microclimates affecting _______

A

diverse microclimates affecting light, moisture, temperature & wind conditions

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11
Q

__ is the most limiting factor in the understorey of rain forests

A

Light

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12
Q

full sunlight is approximately ___ micromoles/m^2/s on a sunny day

A

2000 micromoles/m^2/s

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13
Q

At la Selva, Costa Rica gaps of approximately 300m^2 experience ___% of full sunlight compared to the understory which received ___ full sunlight

A 
gaps = 8.6-24% 
understory = 0.4-2.4%
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14
Q

Quality of ___ also changes with an increase in Photosynthetically Active Radiation (PAR) (400-700nm)

A

LIGHT

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15
Q

Gaps receive differing levels of irradiance from…

A

full sun in the centre to shade at the edge

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16
Q

Vapour Pressure Deficit, or VPD, is the

A

difference (deficit) between the amount of moisture in the air and how much moisture the air can hold when it is saturated

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17
Q

once a gap opens competition for ___ & ____ is intense &____ take places

A

once a gap opens competition for light and nutrients is intense and rapid growth and reproduction take place

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18
Q

there are different stages of succession within gaps:

A

-rapid colonisation by shrubs, vines, lianas & seedlings of PIONEER TREE species
-rapid growth of short lived light-daminding species which form canopy over 10-30years
-Slower growing shade tolerant (CLIMAX TRESS) species grow in biomass and species richness below the pioneer canopy & become taller. This phase transitions into the next phase when
-shorter lived species die & the more shade tolerant climax trees emerge & re-establish the tall canopy (can take 75-100 years )
HOWEVER LOT OF VARIATION IN THESE PATTERNS

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19
Q

classification for pioneer and climax species:

A
  • broad categorisation based on plant characteristics (functional traits) that influence growth & survival strategies
  • pioneer-climax classification represent extremes on a continuum
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20
Q

pioneer species typically produce:

A

lots of small seeds

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21
Q

seeds of pioneer species are dispersed __

A

widely –> wind / animals

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22
Q

pioneer genera are ___ distributed but species ___ as good dispersal tends to reduce the development of distinct populations

A

widely

poor

23
Q

pioneer: seeds can ____ in the soil seed bank until a gap opens producing favourable conditions for germination

A

lay dormant

24
Q

most pioneer species require __ to germinate and are ___

A

light and are gap - dependant

25
Q

pioneer species growth rates:

A
  • typically establish and grow rapidly whilst light nutrients and water are available
  • high rates of photosynthesis & respiration that allows rapid growth under high light
  • leaves have a high hydraulic conductance’ they transpire rapidly allowing high rates of photosynthesis
  • water us efficiency is low
26
Q

pioneer crowns are usually

A

open branched to capture light maximally

27
Q

leaves of pioneer species are usually quite

A

large for good light capture

28
Q

pioneer species leaf life span

A

short life span and turnover quite quickly

29
Q

pioneer species don’t invest greatly in

A

defence against pathogens and herbivores

30
Q

pioneers hold a trade off between

A

growth & defence

31
Q

wood density of pioneer species

A

= low, have rapid growth rates

32
Q

pioneer species roots:

A

highly branched for efficient acquisition of nutrients

33
Q

pioneer can be m___

A

mycorrhizal

34
Q

how long do pioneer species typically live for?

A

10-30 years

35
Q

most pioneer species belong to

A

a few genera and families

36
Q

common genera of pioneer species:

A
  • Cecropia
  • Musanga
  • Trema
37
Q

climax species: Seeds & germination

A
  • seeds often large, produced annually / less frequently
  • often no dormancy
  • dispersal is usually short
  • germination occurs in understorey
  • soil seed bank contains few species
  • species may persist as seedling banks
38
Q

where do climax species usually germinate, establish and persist:

A

in shade below the canopy

39
Q

climax: survival in the understory is

A

ESSENTIAL

40
Q

climax seedlings can maintain themselves for

A

many years without putting on much growth waiting for a gap to open

41
Q

climax species have __ rates of photosynthesis and respiration compared to pioneer species

A

low

42
Q

climax species and transpiration

A

low rates of transpiration so they had a high WUE

43
Q

climax species often have _____ number of branches compare to pioneer species

A

greater number

44
Q

climax species leaves:

A

relatively small, long lived and with a slow rate of turnover

45
Q

climax and herbivores;

A

leaves are tough and contain chemical defences to deter herbivores

46
Q

climax species are adapted for

A

survival at the expense of rapid growth

47
Q

climax species and wood density

A

is high

48
Q

climax species roots

A

are mycorrhizal

49
Q

once the pioneer species die..

A

the climax species continue to grow and become the emergent canopy trees

50
Q

climax trees can live for

A

100 years

51
Q

evidence suggests that disturbance and diversity are related: Gap dynamics

A

‘Gap dynamics’ in forests fits with evidence that disturbance promotes diversity i.e.

  • Species may be adapted to exploit different stages of succession from gap opening to closing
  • This generates diversity in species number and ecological strategies
52
Q

what is the crown illumination index

A

(CII) is a visual estimate of the amount of light received by the tree crown

53
Q

Ignore

A

s

APS278: Tropical Forest Ecology & Conservation (14 decks)

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