2.B - the carbon and water cycle in the Arctic Tundra Flashcards
what is the arctic tundra biome like?
- the arctic tundra occupies some 8 million sq kilometres and is located between the arctic ocean and the boreal forest to the south
- they are cold and treeless with very little precipitation
- the landscape is quite bare with vegetation specially adapted to the low temperatures (below 0°C for most of the year)
- consequently, the ground is frozen for much of the year and only surface layers may melt in the summer months
- this is known as permafrost
what is permafrost?
- a vast carbon sink
- it underlies much of the tundra and is an important feature of the region’s water cycle
- globally it is estimated to contain 1600 GT of carbon
- the accumulation of carbon is due to low temps which slow decompostion of dead plant material
- it makes up 25% of exposed surface in the N.hemisphere
how many people live in Tundra areas?
- less than 4 million people live in tundra areas
climate info for Barrow - how cold is it in the winter?
- from december to march its below -20°C
why is biodiversity and NPP going to be low in the Arctic Tundra?
- biodiversity is low as few plants and animals have adapted to this extreme environment
- 80% of water is locked up in permafrost
- water is the limiting factor in growth and for a great proportion of the year it is dark for 24 hrs
- photosynthesis and respiration rates are low
what is found in arctic tundra?
1/3 of global carbon that can be cycled
what are average temperatures like in arctic tundra?
- cold, average temps are well below freezing
- very seasonal in tundra
- climatic conditions are severe and become more extreme w/ latitude (sun rays are diffused and low levels of insolation)
- for 8/9 months out of the year the tundra has a negative heat balance w/ avg montly temps below freezing
- albedo effect
what are average temperatures like in arctic tundra and WHY?
- cold, average temps are well below freezing
- very seasonal in tundra
- climatic conditions are severe and become more extreme w/ latitude (sun rays are diffused and low levels of insolation)
- for 8/9 months out of the year the tundra has a negative heat balance w/ avg monthly temps below freezing
- albedo effect
temperature range varies hugely in tundra (32 degrees) - why?
- tilt of the earth = summer 24hr light winter 24hr dark
- in winter when for several weeks the sun remains below the horizon, temps can plunge below -40°C
- long hours of daylight in summer provide some compensation for the growing season
lower precipitation compared to the amazon in the tundra - why?
- during winter (6-8months), water on the ground is frozen and little plant growth = little evapotranspiration
- small stores of water in the atmosphere owing to low temps
- polar cell of descending air = high pressure (no rainfall)
- most precipitation falls as snow
N.P.P is low in tundra - why?
- due to cold and short growing season, and infertile soils and little liquid water
- lack of sunshine and warmth
roughly 3 months of the year where the temp is above zero - in these months temp and precipitation rates are higher but still low in comparison - why?
- few plants and animals have adapted to this extreme environment
- 24hrs sun = temps go up, water becomes available and flows become faster
what happens in the summer in the tundra?
- temps are above zero
- evapotranspiration can occurs = ↑ flows of water condensation = ↑ precipitation
what won’t you find in the tundra?
- trees
- most plants are less than 15cm tall
- it is very cold
- other than temperature, the amount of sunlight affects growth rates
- plants have to adapt to short winter days and very long summer days
what strategies do plants have to adapt to tundra conditions?
- grow very slowly and conservatively
- die back until correct growing conditions again
what is NPP?
- how much CO2 is being fixed in the stems and leaves
- in the tundra there is only positive NPP for a few months of the year
what is the water cycle like in the tundra?
- low annual precipitation (50-350 mm) with most falling as snow
- extensive wetlands ponds and lakes on the tundra during the summer. temporary store of water impedes drainage as it lays on top of permafrost
- limited transpiration because of the sparseness of the vegetation cover and the short growing season
- small stores of moisture in the atmosphere owing to low temperatures which reduce absolute humidity
- plants are able to grow and flower rapidly in the summer months when the active layer thaws. long hours of daylight allow for rapid photosynthesis
- low rates of evaporation. much of the sun’s energy in summer is spent melting snow so ground temps remain low and surface/soil water are frozen for most of the year
- limited ground water and soil moisture - permafrost is a barrier to infiltration, percolation, recharge and groundwater flow
- accumulation of snow and river/lake ice during the winter. melting of snow and ice and the uppermost active layer of the permafrost in spring and summer results in a sharp increase in river flow
what is the carbon cycle like in the tundra?
- NPP is low due to the short growing season. typically less than 200 g/m2/yr
- during the growing season, plants input their carbon rich litter to the soil and decomposition increases releasing CO2 into the atmosphere through respiration
- the permafrost is a vast carbon sink estimated to hold 1600GT of carbon
- this is due to the low temperatures which slow the decomposition of dead plant material
- the amount of carbon in tundra soils is 5x greater than in the above ground biomass
- even in the winter, there are pockets of unfrozen soil and water, which release CO2 and CH4. snow covers can insulate microbes, which allows slow decomposition
- the tundra biomass is small, ranging between 4 and 29 tonnes/hectare.
what is permafrost?
- permafrost is permanently frozen ground
- for 8 months of the year, the tundra’s water isnt going anywhere because it is frozen
- in the winter, almost all precipitation falls as snow
- in more northerly latitudes, permafrost is found everywhere, known as continuous permafrost
- this permafrost means that when summer rains come, the water stays on the surface of the land
- there is often little infiltration because the permafrost is impermeable and so is the ice beneath it
what happens in the permafrost when there is a slope?
- in areas where there is a slope, river flows can erode the landscape and can carry vast quantities of sediment downstream
what happens in the permafrost when it is flat?
- water pools on the surface
- there is often little infiltration because the permafrost is impermeable and so is the ice beneath it
what happens to waterlogged soil in the tundra?
- when the soil is waterlogged, the decomposition is anaerobic, meaning no oxygen is available
- this means that carbon gets broken down into methane (CH4), not CO2, (a more potent GHG)
why is precipitation low in the tundra?
- there is low annual precipitation (50-350mm) w/ most precipitation falling as snow
- high pressure = air is sinking = clouds can’t form = no precipitation
- small stores of moisture in the atmosphere owing to low temps = ↓ absolute humidity
what are transpiration rates like in the tundra?
- limited transpiration because of the sparseness of the vegetation cover and the short growing season
- movement of water in the drainage basin means ↑ evaporation and transpiration
- ↑ storage of moisture = more humid tundra