Lecture 33. Terrestrial Ecosystems: Deserts, Tundra and Peatlands Flashcards
What are the two types of tundra ?
- Alpine
2. Arctic
What does descending dry air absorb ?
Moisture
What does descending air cretae ?
Arid conditions
What is desert location determined by ?
- Global atmospheric circulation
- Rain shadows
- Continental interiors
What are the two types of desert ?
- Hot deserts
2. Cold deserts
What are the physical characteristics of rainfall ?
- Low and unpredictable rainfall - water lost quickly
- High evaporation
- Hot or cold temperature
- Large diurnal variation in temperature
In the desert how is water lost quickly ?
Evaporation and drainage
What are some plant adaptations to desert ?
- avoid drought by carefully timed phenology
How can drought be tolerated ?
- Intensification of water absorption
2. Reduce transpiration
How may plants intensify water absorption ?
- Shallow spreading roots - succulents
- Deep roots-tap roots
- Dew/fog traps
How can transpiration be reduced ?
- Sunken stomata
- Reduced stomatal aperture
- Scaly/hairy leaves
- Folding/ rolling leaves
- Retain dead leaves around stem
- Deciduous- shed leaves/branches
What percentage of water is absorbed by roots and is lost via stomata ?
95%
What does CAM stand for ?
Crassulacean acid metabolism photosynthesis
How does CAM work ?
Stomata are closed during day. Opened during night and organic acids are stored. During the day they are converted to carbon dioxide.
What is the advantage of CAM ?
Increases photosynthesis and decreases transpiration
What are the physical characteristics of tundra ?
- Cold
- Low precipitation
- Permafrost
- Short growing season
What are the botanical characteristics of tundra ?
- Diversity is low
- Perennials with vegatative reproduction
- Low in stature- no trees
- Shallow rooting
What are some examples of tundra plants ?
Grasses, mosses, heathers, lichens
Why is tundra a low nutrient system ?
- Low temperature and precipitation because of slow weathering and nitrogen fixation
- Permafrost reduces depth of biologically active soil
- Minimal input of nutrients from precipitation
- Slow nutrient cycling
What biome has the lowest nutrient cycling rates ?
Arctic
What is peat ?
Partially decayed organic matter of plant origin formed under wet anaerobic conditions
Where is peat distributed ?
Areas of high rainfall and impeded drainage
Why are peatlands growing ?
The rate oof production of organic matter is greater than the decomposition carried out by detrovores
What are the layers of a peatlands ?
- Acrotetm
- Water table
- Catotelm
How is hydrosere peatland formed ?
- Lake
- Reedswamp
- Fen (minerotrophic)
- Raised bog (ombotrophic)
Other than hydrosere, how may a peatland form ?
- Forest
- Pasture arable - minerotrophic
- Heath
- Blanket bog - ombrotrophic
What are the two types of bog ?
- Raised bog
2. Blanket bog
Where are blanket bogs found ?
Regions where there is 1200mm rain and 200 rain days
What is a downside to rain ?
Low dilute nutrient solution
What is an ombotrophic bog system low in ?
- Nutrients
2. Bases
What is the pH of fen ?
7
What is the pH of bog ?
Less than 4
What are the characteristics of ombotrophic bogs ?
- Low in nutrients
- Waterlogged
- Acidic
What are plant strategies for ombrotrophic bogs ?
- Mycorrihaze
- Efficient recycling
- Xeromorphs
- Carnivorous habitat
- Effective ion exchange
What can peatlands be exploited for ?
- Fuel
- Horticulture
- Waste water treatment
- Forestry
- Agriculture
What are the advantages of peatlands ?
- Wildlife habitat
- Regional water table
- Landscape/tourism
- Archives
- Carbon sink
What is permafrost ?
Permafrost is any ground that remains completely frozen—32°F (0°C) or colder—for at least two years straight.
