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Ecosystems > Lecture 2 > Flashcards

Lecture 2 Flashcards

1
Q

Describe a boreal forest “Tiaga”

A
  1. Freezing temps for 6-8 months
  2. Coniferous forest
  3. 16 million km2
  4. 11.5% of terrestrial ecosystem area
  5. Low tree species diversity
  6. Make up 30% of global forests
  7. Responsible for 20% of carbon uptake
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2
Q

Describe the arctic tundra

A
  1. Tundra = treeless
  2. Lands beyond the northern tree limit
  3. 5.5% of terrestrial land surface
  4. Above 0 for only 2-6 months of the year
  5. Grasses and sedges and shrubs dominate
  6. Light not limiting
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3
Q

What are some commonalities between arctic and boreal ecosystems (6)

A
  1. Cold - slow decomposition
  2. Short growing season (summer) - low nutrients
  3. Long snow cover duration - freeze tolerant plants
  4. Environmental extremes - low biodiversity
  5. Permafrost - slow growth
  6. High winds, ice abrasion - great longevity
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4
Q

What is GPP

A

Gross primary productivity

Plant photosynthesis of an ecosystem - positive carbon uptake

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5
Q

What is NPP

A

Net primary productivity - remove loss from plant respiration (carbon flux in = less)

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6
Q

What is Reco

A

Ecosystem respiration

Soil respiration and plant respiration

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7
Q

What is NEP

A

Net ecosystem productivity

Net exchange of carbon GPP-Reco

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8
Q

What is NEB

A

Net biome exchange

Over longer timescales and landscape scales

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9
Q

What is NPP of tundra vs tropical

A

1/10 of tropical

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10
Q

What is NPP of boreal vs tropical

A

1/5

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11
Q

How much more c is held in soil than plant biomass in the boreal ecosystems

A

2-3 times more c is held in soil than plant biomass in the boreal ecosystems

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12
Q

How much more c is held in soil than plant biomass in the boreal ecosystems in the arctic tundra

A

5 times more c is held in soil than plant biomass in the boreal ecosystems

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13
Q

What is a carbon turnover rate

A

The amount of time an atom will stay in an ecosystem once taken up

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14
Q

What ecosystems have the lingers carbon turnover rates

A

Boreal and mountainous areas

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15
Q

What ecosystem has the longest carbon turnover rates in the world

A

Tundra

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16
Q

NDVI (normalised difference vegetation index)

A

NDVI increased by 20% since 1982 Increasing productivity and growing season caused by climate change

17
Q

What leads to Productivity changes

A

Plants grow more - warming + growing season longer

18
Q

Vegetation change caused by climate change

A

Boreal treeline moving onto tundra - tundra gets warmer so can support more trees - latitudinal treeline advance

19
Q

Boreal treeline advance - evidence from example in Alaska

A

Seedlings at the edge
Oldest trees 1930s - new system with active recruitment
Further into the forest back in time - dead trees in middle of forest
Dynamic system

20
Q

Tundra “shrubification” - greening of the arctic

A

Increase abundance, size and spread of more productive shrubs
Deciduous shrubs
Bigger and taller
Occurring over greater areas

21
Q

Name an example of shrubification

A

Alaska

Increase in shrub abundance 28% (hilltops) to 160% (floodplains)

22
Q

Explain biomass increase vs soil decomposition

A

It was believed that increase in C in more biomass = greater removal of CO2 from the atmosphere
Ignored soil
Hartley studied carbon stores and fluxes in adjacent forest and tundra in northern Sweden
- change in c stock = change if forest moves out onto tundra
- less carbon in forest than tundra
- only shrubs in tundra (less carbon) = above ground
- huge amounts of carbon below ground - twice as much in tundra
- overall 1/3 less total carbon stock in boreal forest than tundra = treeline advance = lose 1/3 of carbon

23
Q

How might C loss happen when treeline advances

A

Priming of decomposition- see directed reading
Forest trees more productive- more photosynthetically active - take up more carbon
Want nutrients to be able to grow so pump carbon below ground into roots = excrete organic acids and enzymes into soil to breakdown nutrients so they can take it up
Nutrients often bound to carbon so when it’s broken down = release carbon = encourage decomposition of carbon in the soil
=> carbon loss moving from tundra to boreal forest
More productive trees cause soil carbon to decompose faster

Ecosystems (3 decks)

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