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GCB > L11 CC in Temperate Ecosystems > Flashcards

L11 CC in Temperate Ecosystems Flashcards

1
Q

Background on temeprate zones

where?

A

lies between the tropics and the polar regions
Extends from Tropic of Cancer (23.5 °N)
to Arctic Circle (66.5 °N) in the north

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2
Q

Structure (main topics) (4)

A

Drought
Flooding
Fire
Biological Invasions

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3
Q

Drought (3)

A

loss of vegetation
salt marshes
mesocosm experiments

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4
Q

vegetation loss main problem?

A

loss of carbon sequestration`

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5
Q

most extensive vegetation type in W US and problem

A 
Pinyon jupitor woodland
-arid and susceptible to drought
2002-2003 drought even = large scale die off
40-80% loss of woodland in many sites
huge effect on carbon sequiestration
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6
Q

other forests threatened by drought

A

European forests

Beech and meditteranean

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7
Q

Beech and meditteranean drought when?

A

European heatwave 2003

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8
Q

Effect of drought of medi and (4 points)

A

Shift from being sink to source of carbon.
30% reduction inGPP across Europe
Resulted in a strong net source of carbon dioxide to the atmosphere of 0.5 Pg C yr-1 (Ciais et al. 2005)
Reversed 4 years of net carbon sequestration (Janssens et al. 2003)

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9
Q

Ciais et al 2005 drought study?

A

Ciais 2005
Drought causes loss of gross primary productivity & carbon uptake (Ciais et al. 2005)
Net reduction in precipitation (red) led to reduced carbon sequestration (lloked at temp,recipitatio nand carbon uptake – monthly – yearly)

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10
Q

why are salt marshes imprtant? (4)

A

one of the most biologically productive habitats on earth, rivalling tropical rainforests
• Large role in aquatic food web & export of nutrients to coastal waters
• Provide habitat for native migratory fish
• Sheltered feeding & nursery grounds

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11
Q

Salt marsh recognition? and dominated by? (snails and plants)

A

Now protected by legislation in many countries ie Europe and USA recognises

Dominated by salt-tolerant herbs, grasses & shrubs
Species that do dominate have no competitors and can really thrive and have huge biomass
Ie Salt marsh snails – that do v well and cycle nutrients
These plants essential to marsh stability, trapping & binding sediments

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12
Q

Salt marsh die off facts?

A

large areas of United States coastline have experienced widespread die-off of salt marsh – despite legislation
Over 1,500 km of coastline and more than 250,000 acres of salt marsh have been affected

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13
Q

what is salt marsh die off associated with? Mckee

A

Mckee
Die-off has been strongly linked to drought events, with low tide levels, concentrated salts in porewater & increased soil acidification
Lack of water table as it decreases and lack of essential nutrients needed for survival

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14
Q

Effect of die off wrt biology?

A

alter the distribution of marsh snails,
To avoid predation by marsh crabs, snails begin to aggregate on the border of retreating cordgrass,
This compounds the die-off by intense grazing at the margins

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15
Q

snail name

A

L irrorata

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16
Q

cordgrass name

A

S alterniflora

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17
Q

salt marsh exclusion experiments what have they shown?

A

cordgrass recovers if snails are prevented from overgrazing

Drought causes not only direct die-off, but indirectly through altering animal behaviour (Silliman et al. 2005)
In other words - intense grazing by snail stops revocery AFTER drought so grazing pressure from above – top down control

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18
Q

salt marsh change in animal behaviour paper

A

Silliman 2005

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19
Q

Salt marsh mesocosm ecperiments (ledger) - background on this expereiment (7 things) channel frequency etc

A
  1. Stream mesocosms constructed in Dorset
  2. 4 blocks of 3 channels
  3. One channel as a control stream (flow of water maintained throughout)
  4. Drought induced in the other two channels
  5. Water drained and surface left exposed for 6 days
  6. One channel exposed to low frequency drought events (every three months)
  7. One channel exposed to high frequency drought events (every month)
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20
Q

Checking for replicatin and realism of mesocosm experiment?

a) food webs
b) comp and abundance

A

After natural colonisation they assembled food webs for each stream mesocosm
Species richness, number of links, connectance, food chain length all found to be similar to studies of natural ecosystems
Complex stream communities created in a semi-controlled environment which were then subjected to drought

Species composition and abundance was confirmed before drough testing
Backed up by trivariate food webs - Putting food web into body mass and abundance in space ( showed normal distribution pattern -Many small)

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21
Q

Experiment result

a) overall
b) food web structure impact
c) interactions (brief)

A

a) overall result: Drought reduces secondary production (biomass of consumers)

b)• Large taxa, higher in the food web are first to be knocked out (less animals produced ie fish needed as food for humans)
This drives the observed decrease in secondary production (bigger invertebrates gone) (cascade)

c)– Reduction in the number of weak links in the drought treatments
– Weak interactions are important in promoting stability (McCann et al. 1998)
– Drought is likely to reduce the stability of stream ecosystems

c)

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22
Q

interactions - what are they and background info

A
  • Interaction strength is the magnitude of the effect of one species on another
  • Shown from a whole range of ecosystems that distribution is skewed towards weak interactions (Wootton & Emmerson 2005)
  • Thought to be important pattern for providing stability to natural systems
  • Demonstrated that coupling of strong and weak interactions facilitates switching between resources when densities become low
  • This promotes stability by maintaining population densities (McCann et al. 1998)
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23
Q

skew of interaction paper

A

Wootton & Emmerson 2005

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24
Q

– Weak interactions are important in promoting stability paper

A

(McCann et al. 1998)

25
Q

Flooding terminology (a)
Discharge
stage
flood stage

A

discharge= volume of water that passes through a given cross section per unit time (usually measured in cubic meters/feet per second)

Stage - level of water surface over a datum (often sea level). As discharge increases, stage increases, however the relationship is not linear

Flood stage - stage at which overbank flows are of sufficient magnitude to cause considerable inundation of land and roads

26
Q 
flood terminology (b) 
crest
recurrence interval
A

Crest/peak - highest stage reached during flood

Recurrence interval - how often does flood of that size occur per year (ie large flood quite rare 10/100yr)

27
Q

What is affect of CC on flooding and evidence (3)

what is the counter intuitive thing shows by Chistensen (2002)

A

CC is changing frequencies

Red River of Nort hat Fargo Nort hDakota 1882-1994

Thames closurs record closure 48 in 2014
frequency of great floods rise and continue to rise (even most conservtaive scenarios predict increase)

show extremes of both dorught and flooding
average summertime precipitation to greatly DECREASE
amount of ectreme precipitation predicted to greatly INCREASE

28
Q

Human and ecological impacts of drought? (GEN) 5

A

evidenc for increased flooding is undeniable

1) LOSS OF HUMAN LIFE
2) EConomic Costs
3) Physical Damage
4) secondary effects
5) ecological (salt marsh)

29
Q 
loss of human life detail 
death toll
venezuala 
bangladesh
china
A

Venezuela 1999, ~30,000
Bangladesh 1998, ~3,800
China 1998, ~3,600

30
Q 
economic costs flooding detail
extras(2)
louisiana
thailand
china
UK
A

Louisiana 2005, ~$150 billion
Thailand 2011, ~$45 billion
China 1998, ~$20 billion
UK 2007, ~$3 billion

clean up costs and insurance

31
Q

physical damage detail (5 things)

A 
bridges
cars
buildings 
roadways
canals
32
Q

secondary impacts of flooding (4)

A

containation of water supplies for drinking
spread of waterbourne DISEASES
food shortage due to los of harvest
Transport links destroyed

33
Q

Flooding ecological impact example and increase inflooding versus past

A

Salt Marshes Example
Tide frequently rises beyond inter-tidal flats to flood lower salt marsh
Flooding of the middle marsh zone is much rarer
Such flooding is now occurring more regularly due to stormy weather

34
Q

salt marsh acse study : Wadden Sea is Europe’s largest wetland (importance for breeding)
where do they build nests
effect #

stat over last 50 yrs

A

– Core breeding area in W. Europe for dozens of coastal bird species (shelter and nests)
– They typically build their nests in the mid to low marsh zone, near to feeding grounds in the inter-tidal flats
– These nests are increasingly more susceptible to impacts of flooding and rising seal levels / more frequent events
• In the last 50 years, sea levels in the estuary have risen by 0.3 cm per year (Esselink et al. 1998)
• This is projected to increase to 1.2 cm per year by 2100
15cm rise over 50 yrs – large impact off probability of nest destruction , some can adapt but some pops may crash

35
Q

Wadden Sea 6 bird species impacted

A

Key species  Six bird species shown to be severely impacted in Wadden Sea (De Pol et al. 2010)

Reproductive output of Eurasian oystercatcher below stable population levels (link to cascades)

36
Q

wadden bird example

A

Eurasian oystercatcher

37
Q

Flooding overall main structure

A

1) terminology
2) evidence
3) impacts (human +ecological)

38
Q

Fire

a) frequency
- what stimulates increase freq?
- nat importance? + problem (chaparral)
- problem of shorter fire-return intervals (4)

A

Increased summer temperatures and prolonged periods of drought stimulate increased fire frequency

Natural and particularly prominent in dry savannah, shrubland and chaparral ecosystems – important in disturbance and recovery
Chaparral is only adapted to recover from infrequent fires (every 15 years)

may not get to correct stage
Promotes invasion by exotic species, e.g. climbing maidenhair fern,
-fast growing and then take up space
Continuous cover of fire-resistant invasives promotes positive feedback for yet more frequent fires

Direct source of carbon to atmosphere

39
Q

natural fire impratnce ?

A

New space for colonisation

-nutrient cycling

40
Q

Fire

b) Invasive grasses
- case study hawaii
- problem

A

• Grasses introduced to Hawaii to support cattle grazing
• Tufted beardgrass (Schizachyrium condensatum) and molasses grass (Melinis minutiflora)
• Spread into protected woodlands, filling interstices of native shrubs & canopies
• Highly resinous & flammable
300-fold increase in extent of fire compared to when those spp not present
Most woody plants eliminated, including many endangered species
Grasses rebound quickly
 monoculture

41
Q

what grasses were introduced into hawaii for cattle grazing support?
why are they bad?

A

• Tufted beardgrass (Schizachyrium condensatum) and molasses grass (Melinis minutiflora)
• Highly resinous & flammable
Grasses rebound quickly
 monoculture

42
Q

Fire history? waht was W US historically dominated by?

what invaded

A

Western US historically dominated by perennial grasses; fires infrequent
cjeatgrass

43
Q 
Cheatgrass
name?
winter/spring?
feedback?
hectares affected? 
Study by ?
A 
Bromus tectorum (invaded as livestock degraded the area (created space))
•	Once reaches critical biomass – highly flammable winter annual
•	Dies and dries out in spring, spreading fire rapidly
  • Cheatgrass recovers quickly and suppresses growth of native species
  • Positive feedback loop, from initial colonisation, to fire & dominance

• Over 40 million hectares now affected

(D’Antonio & Vitousek 1992)

44
Q

cheatgrass paper

A

(D’Antonio & Vitousek 1992)
main:
Rapid , flammable, perennial ,  fire invader
Thus positive feedback loop from colinisation,increase fire, dominance of spp
4. Biological invasions

45
Q

Fire overview structure

A

1) Freq (nat + probem)
2) Invasive grasses - tufted beardgrass and molasses grass
3) Cheatgreass case study

46
Q

Biological invasions general structure

2 main case studies

A

a) Mountain Pine beetle

b) Saltcedar

47
Q

Main aims of lecture (3)

A

. Describe some major consequences of climate change for the biology of temperate ecosystems

  1. Discuss the impacts of drought, flooding & fire on humans and our ecosystem services
  2. Explain how climate change may facilitate biological invasions in temperate ecosystems
48
Q 
biological invasions 
-how cc affects?
a)Mountain pine beetles background
where?
role?
fire?
A

Ie CC affecst spp distribution – Grey squirrel , N American pine beetle , Ants etc

Mountain pine beetles are actually native to Southern pine forests

Play an important role in the life cycle of lodgepole pine forests
Pine beetles attack old, weakened trees
Dead wood & needles provide a highly combustible fuel source
Fires release seeds from pine serotinous cones, triggering regeneration – important fire
Eliminates shade tolerant species such as spruce & fir that would out-compete lodgepole pines (Logan & Powell 2001)

49
Q

CC wrt pine beetles?

clue= suitable
how (2)
Result
Cost of result

A

led to a more climatically SUITABLE habitat for pine beetles

warmer in mountanaeous (that hasnt been exposed before)
reduced min winter temp and increased summer temp

result: expansion of pine beetle distribution to N and higher elevatiomn forests
Range expansion and increased abundance reuslting in outbreak of unprecedented scale

Timber losses estimated to be in excess of 435 million m3

50
Q

timber loss because of invasion of mountain pine beetles

A

435 million m3

51
Q

knock on problem of loss of timber from the mountain pine beetle?

A

Mountain pine beetle outbreak has led to mass mortality of pine trees
Loss of trees reduces carbon sequestration of pine forests
Excess fuel exacerbates wildfires
Increased fire frequency contributes to carbon production
Pine forests have been transformed from a carbon sink to a carbon source

52
Q

ist here hope with pine beetle problems? (models?)

A

Model simulations show that if the outbreak is controlled, balance can be returned
– Otherwise, a major sink for carbon emissions in the US will be lost
So… Now not just attacking dying trees but fresh new trees
But could revert to sink if correct measrures (but currently stilkl hasn’t returned)

53
Q

Biological invasions

b) Salt cedar
- introduced when?
- invaded what?
- what makes it good invader? (3)
- what makes it good invader wrt seeds? (2)
- study?

A

Saltcedar (Tamarix spp.) introduced to US from Europe in 1800s

since invaded over 600,000 hectares of land in the southwest and considered one of the worst plant invaders in the US

1)rapid growth
2)low water requirements
3)high salinity tolerance
all contribute to success

seeds are small and light with tuft of hair to aif long distance transport by wind or water
a single large saltcedar plant can produce 1/2 milliion seeds per year

(Di Tomaso 1998; Gaskin & Schal 2002)

54
Q

Saltcedar biological invader impacts (4) basically same things as lecture

A

Dorught
Flooding
Fire
Native diversity

55
Q

Saltcedar-drought

  1. what type of plant are they?
  2. the effect of this?
  3. cost? problem where?
A

phreatophytes - deep rooted & able to reach the water table – promote drought (other spp then cannot access)
• Evapotranspiration rates are among the highest of any phreatophyte in N. America

it can desiccate springs, drain pools & even dry up perennial streams

• Estimated to cost $65-180 million annually in reduced municipal & agricultural water supplies (Zavaleta 2000) crop die off and loss of income and food – increase problem in California

56
Q

Saltcedar impacts- flooding
why problem?

Infestation where and reduced idth by how much? effect?

A

extensive root system
More stable and resistant to erosion than most native riparian trees & shrubs• Heavy infestations can alter the hydrology of an area
Saltcedar restricts river channel width by increasing sediment deposition
MAKES NARROW
Narrowing of channel increases rate of water flow & potential for flooding

• Saltcedar infestation on Brazos River in Texas

reduced average width from 155m in 1941 to
66m in 1979
• This increased flooding & area inundated by floodwaters

57
Q

Saltcedar impacts - fire

  • species and recovery mechanism?
  • area difference?
  • what does saltcedar do? (enhance flammability)
A

• Saltcedar is a fire adapted species
more efficient fire recovery mechanism than native riparian species

  • Wildfires are infrequent in areas dominated by native cottonwood, willows or mesquite (Busch & Smith 1993)
  • Intervals between fires are considerably shorter in saltcedar-infested areas
  • Saltcedar enhances flammability of communities through rapid accumulation of leaf litter and dead & senesced woody material
  • This can lead to complete replacement of cottonwood & willow communities, compounding the issue and increasing fire frequency further
58
Q

saltcedar fire - what plants are affected?

A

cottonwood & willow communities (they can be completely replaced)

59
Q 
Saltcedar - native diversity
(link to fire)
1.how outcompetes?
2.leaves what behind that is a problem to otehr spp?
3.willow and cottonwood echibit what?
4.frugivores?
5.elimination fo what?
A
  • Saltcedar outcompetes native communities through fire adaptation, reducing available water & resistance to grazing
  • Saltcedar leaves also excrete salts, which deposit on soil surface and inhibit growth of competing species
  • Both willow & cottonwood exhibit a greater diversity and abundance of insects & birds
  • Frugivores cannot thrive on small saltcedar leaves
  • Bell’s vireo & summer tanagers in danger of elimination

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