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Lecture 5

GEG3107 Lecture 5: Lecture 5Premium

6 pages73 viewsFall 2016

Department
Geography
Course Code
GEG 3107
Professor
Antoni Lewkowicz
Lecture
5

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Terrestrial Ecosystems in the Polar Regions
- Focus on the Arctic, there isn’t much going on in Antarctica
Intro to Ecosystems and Trophic Levels:
- Sun → Producers (plants, algae) → Primary consumers (lemming) → Secondary
consumers (Arctic fox) → Tertiary consumers (Arctic wolf)
All die and decompose & return nutrients to plants
- In the arctic there is a limited number of species in each trophic level, however the
number of trophic levels is fairly similar to the rest of the globe (4-5 levels)
- Polar bears are a part of the marine ecosystem (do not eat while on land)
Environmental Controls on Plants:
- There are 8 aspects that plants must cope with
Low winter temperatures (least important cold is cold)
Low summer temperatures (Esp. in Antarctica) large role
Short summers (length of time for growth and reproduction)
- In many parts of the arctic the snow free period is only 2 months
Strong winds (snow accumulation, cools air, drying effect)
- Encourages plants to ‘stay low’
Long photoperiods in summer
- Above arctic circle = 24h of sunlight in summer
Low/no light in the winter
Limited nutrients (esp. nitrogen)
- Low recycling of nutrients (buildup of biomass [peat] rather than
decomposition)
Low precipitations (arid or semi-arid conditions) 50-100 mm
- Plant adaptations:
Arctic ecosystems are relatively young and may have developed in the last 3
million years
May have originated from high altitude areas (have been around longer)
- As the climate cooled they migrated to the arctic
Plants have a number of adaptations, but they are not exclusive to the arctic
Sun tracking keeps the reproductive parts warm (parabolic flower concentrates
heat)
Adaptations against dryness (leathery and/or hairy leaves)
Cushion/dome shape helps reduce water loss and wind damage (aerodynamic),
and they maintain a warm microclimate (up to 25° warmer)
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ITEX (International Tundra Experiment): Studying the potential changes on
vegetation due to climate change (using Plexiglas chambers to raise local temp)
Prostate shrubs: Grow across the ground rather than upwards
- Protects from wind, and preserves warmth
Pre-form flower buds, maximizes the time available for seed production
- Asexual reproduction is common (can’t guarantee the success/completion
of seeds within the growing season), and annual plants are rare
Perennials have an extensive, shallow root system & a tap root that stores food
Wind pollination (vs. insect pollination) increases as you move north
Longevity, lichens may live for thousands of years (can be used for dating)
Opportunistic seed production (do not produce a seed every year)
Frost resistance, can snow a even in the middle of the summer
Grow at lower temperatures and their optimum photosynthetic rate at lower
temperatures (allows them to maximize the growing season)
Spatial variation in vegetation:
- Arctic vegetation is heterogeneous and the local conditions can vary significantly
- Types of vegetation can be linked to summer temperatures (bioclimatic subzone) and soil
moisture
- The Circumpolar Arctic Vegetation Map was produced through an international effort
using field observation and remote sensing
- Bioclimate subzone is based on the mean July temperatures
Class E is at/under the treeline (10°C) so is uncommon in the tundra
In the brackets is the number of vascular plant species
- 5 main divisions:
Graminoid tundra = grassy
B S generally coldest to warmer, Wetlands can occur anywhere
- Map ends at the treeline (quite a small area)
- Barrens used to be called polar deserts
Cryptogram = mosses and lichens
Listed form coldest to warmest (except wetlands)
Tussocks are lumps of plants (composted of a mixture of soil and undecomposed
vegetation)
There are many small wetlands throughout the arctic that are within other
vegetation classes
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