Ecosystem Processes Flashcards
What is an ecosystem?
interaction between abiotic and biotic factors
What is the ecosystem scale?
The level at which natural systems begin to alter the abiotic environment
What are some examples of ecosystem functions?
- 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
What is the energy source driving climates?
Sun
What radiation does the sun emit?
Mostly shortwave radiation:
- 8% UV
- 39% visible light
- 53% near infrared
What happens to the radiation emitted by the sun?
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
What are the average earth temperatures and what can this result in?
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
How does the earth lose heat?
Via sensible flux = heat transfer from land to air
+ 5x more as latent flux- involved evaporation of water which rises and cools into clouds
Name + define one of the most important ecosystem process
Evapotranspiration = movement of water via surface evaporation of water + transpiration from leaves
why do plants transpire ? + describe process
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
Where is water found?
Most is found in oceans with only small proportion in atmosphere
Describe the global water cycle
- 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
What constrains the overall productivity of the biosphere and why?
Water- only 0.01% of earths water in soils:
- Ecosystems gain water via precipitation
- Water is lost via evapotranspiration + runoff after soil holding capacity is exceeded
- balance of these processes depends on vegetation
Describe movement of water through a rainforest
High levels of precipitation due to high humidity = plenty of water
High rates of evapotranspiration due to strong sunlight
What kind of vegetation is found in a rainforest and why?
Low albedo = reflect little sunlight
1. High rates of evapotranspiration = cools surface via latent heat loss
2. = lower ground temp = less sensible heat loss
How is this different in a pasture?
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
How do forests act as conveyor belts for rainfall?
- Rising clouds in coastal vegetation draw in cool, moist air from oceans to replenish soil water
- Clouds move inland and release rain, which rises again as evapotranspiration
= water can be carried into continents
Describe the distribution of carbon
4 carbon pools:
- Biomass- vegetation (= to atmosphere) + soils (2-3x greater)
- Atmosphere- tiny fraction- same as vegetation
- Ocean- mostly in deeper waters
- Sediments and rocks- majority of carbon >99%
What is detritus?
dead organic matter produced from decomposition
What is the difference between vegetation and detritus?
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
How to humans effect the global carbon cycle?
Accelerating certain processes + devising new ones
How much of atmospheric carbon is derived from anthropogenic sources?
1/5
Describe the movement of carbon
- Enters system via photosynthesis
- 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
- some is lost through decomposition of detritus
- ratio between uptake and loss determines how much carbon is stored in biomass + soils
What is GPP and NPP?
GPP = total intake of carbon via photosynthesis
NPP = total carbon gain after respiration
Where is NPP at its highest?
In the tropics- NPP is similar on land and oceans
How does the amount of carbon compare in different biomasses?
- Tropical forests = highest due to high NPP
- Temperate and boreal forests have lower NPP so contain less carbon
- Lower stature vegetation like savannas, grasslands, deserts + tundra fix and store only a fraction of carbon
- Croplands store hardly any carbon but have high NPP than deserts
What is one of the main processes determining an ecosystems carbon pool?
Decomposition
What is decomposition?
= breakdown of detritus which recycles carbon and nutrients for other organisms or environment
What is decomposer biomass made up of and what do they do?
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
What does soil biota include?
Bacteria, fungi, protozoans, nematodes, mites, collembolans, annelids and macroarthropods
What is another example of a biosphere constraint and what does this vary with?
Nutrient supply required to form organic compounds
varies with latitude:
- Tropics limited by phosphorus
- rest of world limited by nitrogen
Where is the most nitrogen and phosphorus found?
Phosphorus found in plants
Nitrogen found in atmosphere
is nitrogen recycled more or is more of it fixated?
Recycling of nitrogen far outweighs its fixation
What is having the biggest impact on the global nitrogen cycle?
Industry and agriculture- changes rates and pathways of nitrogen movement
Describe the global phosphorus cycle
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
Other than abiotic effects that ecosystems have, what other class of processes impact ecosystems?
Ecosystem services
What are ecosystem services?
= activities performed by nature which have value to human life, wellbeing and economic production
Name some examples of ecosystem services
Food production
Flood protection e.g. mangroves
Erosion control
water filtration
carbon storage
crop pollination
Provision of fuel + other materials e.g. medicines
How can ecosystem services value be measured?
By how many human lives they save
Describe an example of how the decline in mangrove forests resulted in loss of life.
2004 Indian Ocean tsunami- mangroves were converted to shrimp farms =
228,000 people
but areas which retained their mangroves were protected
