Ecosystem Processes

Question 1

What is an ecosystem?

Answer 1

interaction between abiotic and biotic factors

Question 2

What is the ecosystem scale?

Answer 2

The level at which natural systems begin to alter the abiotic environment

Question 3

What are some examples of ecosystem functions?

Answer 3

• Water lost via transpiration = generates clouds
• Carbon is fixed in biomass
• broken down rocks + decomposing plants = soil
• Water filtration
• energy transfers
• nitrogen fixation
  = these combine to regulate regional/global climates

Question 4

What is the energy source driving climates?

Answer 4

Sun

Question 5

What radiation does the sun emit?

Answer 5

Mostly shortwave radiation:
- 8% UV
- 39% visible light
- 53% near infrared

Question 6

What happens to the radiation emitted by the sun?

Answer 6

Some absorbed by atmospheric water, dust, ozone + cloud- only 1/2 absored by earth

but more is scattered by air and clouds or reflected as long wave radiation from earth surface

Question 7

What are the average earth temperatures and what can this result in?

Answer 7

15°C
= largely emits longwave radiation:

• small amount escapes into space but most is absorbed by atmosphere
• Increasing atmospheric Co2 = increasing amount of radiation absorbed in atmosphere

= GREENHOUSE EFFECT

Question 8

How does the earth lose heat?

Answer 8

Via sensible flux = heat transfer from land to air
+ 5x more as latent flux- involved evaporation of water which rises and cools into clouds

Question 9

Name + define one of the most important ecosystem process

Answer 9

Evapotranspiration = movement of water via surface evaporation of water + transpiration from leaves

Question 10

why do plants transpire ? + describe process

Answer 10

Because they require CO2 + water and therefore:
- open their stomata when water available = plants able to generate sugar
- but water is lost but replenished via roots

Question 11

Where is water found?

Answer 11

Most is found in oceans with only small proportion in atmosphere

Question 12

Describe the global water cycle

Answer 12

• 80% evaporation from oceans is returned as precipitation
• Precipitation that falls on land- over 1/2 returned via transpiration and the rest returns to oceans

Question 13

What constrains the overall productivity of the biosphere and why?

Answer 13

Water- only 0.01% of earths water in soils:

1. Ecosystems gain water via precipitation
2. Water is lost via evapotranspiration + runoff after soil holding capacity is exceeded
   - balance of these processes depends on vegetation

Question 14

Describe movement of water through a rainforest

Answer 14

High levels of precipitation due to high humidity = plenty of water
High rates of evapotranspiration due to strong sunlight

Question 15

What kind of vegetation is found in a rainforest and why?

Answer 15

Low albedo = reflect little sunlight
1. High rates of evapotranspiration = cools surface via latent heat loss
2. = lower ground temp = less sensible heat loss

Question 16

How is this different in a pasture?

Answer 16

Vegetation has higher albedo
- has lower amounts of vegetation = reduced evaporation so lower latent heat loss
- more sensible heat loss = surface temps greater
- Lower precipitation rates as less water recycled via evapotranspiration

Question 17

How do forests act as conveyor belts for rainfall?

Answer 17

1. Rising clouds in coastal vegetation draw in cool, moist air from oceans to replenish soil water
2. Clouds move inland and release rain, which rises again as evapotranspiration

= water can be carried into continents

Question 18

Describe the distribution of carbon

Answer 18

4 carbon pools:

1. Biomass- vegetation (= to atmosphere) + soils (2-3x greater)
2. Atmosphere- tiny fraction- same as vegetation
3. Ocean- mostly in deeper waters
4. Sediments and rocks- majority of carbon >99%

Question 19

What is detritus?

Answer 19

dead organic matter produced from decomposition

Question 20

What is the difference between vegetation and detritus?

Answer 20

Vegetation contains higher ratio of carbon to nitrogen = 160:1 than soil = 14:1
= transfer of nitrogen into plant materials is accompanied by a large increase in carbon

Question 21

How to humans effect the global carbon cycle?

Answer 21

Accelerating certain processes + devising new ones

Question 22

How much of atmospheric carbon is derived from anthropogenic sources?

Answer 22

1/5

Question 23

Describe the movement of carbon

Answer 23

1. Enters system via photosynthesis
2. 1/2 of this carbon is used for respiration and the rest is either stored by the plants or transferred to other organisms via consumption
3. some is lost through decomposition of detritus

• ratio between uptake and loss determines how much carbon is stored in biomass + soils

Question 24

What is GPP and NPP?

Answer 24

GPP = total intake of carbon via photosynthesis
NPP = total carbon gain after respiration

Question 25

Where is NPP at its highest?

Answer 25

In the tropics- NPP is similar on land and oceans

Question 26

How does the amount of carbon compare in different biomasses?

Answer 26

1. Tropical forests = highest due to high NPP
2. Temperate and boreal forests have lower NPP so contain less carbon
3. Lower stature vegetation like savannas, grasslands, deserts + tundra fix and store only a fraction of carbon
4. Croplands store hardly any carbon but have high NPP than deserts

Question 27

What is one of the main processes determining an ecosystems carbon pool?

Answer 27

Decomposition

Question 28

What is decomposition?

Answer 28

= breakdown of detritus which recycles carbon and nutrients for other organisms or environment

Question 29

What is decomposer biomass made up of and what do they do?

Answer 29

Mostly fungi and bacteria- 95%
soil fauna also play important roles:
- microfauna predators
- mesofauna- fragment litter making it accessible to fungi and microbes
- macrofaunal ecosystem engineers e.g. earthworms- distribute detritus through soil

Question 30

What does soil biota include?

Answer 30

Bacteria, fungi, protozoans, nematodes, mites, collembolans, annelids and macroarthropods

Question 31

What is another example of a biosphere constraint and what does this vary with?

Answer 31

Nutrient supply required to form organic compounds
varies with latitude:
- Tropics limited by phosphorus
- rest of world limited by nitrogen

Question 32

Where is the most nitrogen and phosphorus found?

Answer 32

Phosphorus found in plants
Nitrogen found in atmosphere

Question 33

is nitrogen recycled more or is more of it fixated?

Answer 33

Recycling of nitrogen far outweighs its fixation

Question 34

What is having the biggest impact on the global nitrogen cycle?

Answer 34

Industry and agriculture- changes rates and pathways of nitrogen movement

Question 35

Describe the global phosphorus cycle

Answer 35

opposite to nitrogen as barely any in atmosphere + no biotic pathway so more cant be brought into ecosystems

Held in biosphere in plant or microbial biomass and cycled with high efficiency

To bring more into an ecosystems- phosphorus must be mined and is being depleted too quickly, can also be extracted from soils but very difficult process

Question 36

Other than abiotic effects that ecosystems have, what other class of processes impact ecosystems?

Answer 36

Ecosystem services

Question 37

What are ecosystem services?

Answer 37

= activities performed by nature which have value to human life, wellbeing and economic production

Question 38

Name some examples of ecosystem services

Answer 38

Food production
Flood protection e.g. mangroves
Erosion control
water filtration
carbon storage
crop pollination
Provision of fuel + other materials e.g. medicines

Question 39

How can ecosystem services value be measured?

Answer 39

By how many human lives they save

Question 40

Describe an example of how the decline in mangrove forests resulted in loss of life.

Answer 40

2004 Indian Ocean tsunami- mangroves were converted to shrimp farms =
228,000 people
but areas which retained their mangroves were protected