Carbon Stores in Different Biomes (Grassland carbon storage and flows (185…
Carbon Stores in Different Biomes
Grassland Carbon Storage
Mid-Latitude grasslands are found...
On the periphery of mid-latitude deserts, between 30 and 50 degrees north of the equator
On the leeward side of mountain systems which act as a barrier to westerly flowing moist air, thereby giving rise to a rain shadow
In North American prairies, Eurasian Steppes, South Africa's Veld, and the South American pampas
Physical factors affecting plant growth and carbon storage
Light: sun's rays are concentrated in summer, but are much weaker inn winter at as little as 6 hours, resulting in marked seasonal variation in plant growth and biomass storage
Temperature: the mean monthly temperature in the Ukraine varies between 22 degrees in summer and -5 in winter. High altitude grassland may experience even more extreme variations.
Precipitation: low average rainfall at 500mm or below, spread evenly throughout the year. There is a significant build up of winter snow in higher latitudes.
Short-perennial grasses dominate the landscape, and with growth buds at or below the surface, they are well adapted to drought, fire and cold. Their narrow, upright stems reduce heat gain in hot summers, and intricate roots trap moisture and nutrients underground.
Two basic types: turf grasses, with rhizomes from which new plants grow with more humid parts of the biome, and bunch grasses without rhizomes that reproduce from seed, associated with drier parts of the biome.
Biodiversity and biomass is relatively low in this structurally simple climate.
No more than 3 or 4 large grazing mammals such as bison
Below ground, one square metre of soil may contain up to 500 earthworms which eat the top 15 cm of top soil in just 10 years.
Tropical Rainforest Carbon Storage
Tropical Rainforests are found...
On and around the equator in Asia, Africa and South America between 10 degrees north and south and the equator
In three major formations: Amazonian (Amazonia into Central America), African (Zaire Basin and West Africa; also Madagascar and the Indo-Malaysian (west coast of India, southeast Asia, New Guinea and Queensland, Australia)
Physical Factors Affecting Plant Growth and Carbon Storage
Temperature- High average temperature between 25 and 30 degrees with only small seasonal variation.
Precipitation- Sun's heat causes moist air to rise leading to heavy rainfall most days and a high annual average of 2000-3000 mm with no dry season (excl. some locations such as Manaus which experience a few months a year with less rain). High and constant rainfall combined with warm temperatures provides optimum conditions for plant growth and biomass carbon storage.
Light- The sun's rays are concentrated at this latitude, with little seasonal variation. This results in all-year growth and carbon sequestration.
As a result of these conditions rainforest NPP averages at 2,500 grams per sq m per year; biomass can be as much as 700 tonnes per hectare.
Carbon storage in animals is relatively high in this ecosystem because of the large number of habitats provided for plants, insects, frogs, birds and mammals. More than two thirds of the world's plants species are found in rainforests.
Competition for light and water has given rise to five layers of vegetation- field layer, shrub layer, under canopy and continuous canopy from which emergent trees project.
Plants are evergreen and trees have large leaves that maximise their rate of transpiration and growth.
Grassland carbon storage and flows
185 Gtg is stored in temperate grassland biomass and soils
Grassland stores 2 to 10 tonnes per hectare above ground, and double in below ground roots, 2/3rd of which is stored in the top 30cm of soil
Soil carbon stores of humus average 100-200 tonnes per hectare
Warm humid conditions in autumn ensure rapid decomposition, with quick CO2 release, and a small litter store.
Carbon flows vary greatly depending on season
Rainforest carbon storage and flows
550 Gtg is stored in tropical rainforest biomass and soil
Large trees store 180 tonnes/ha above ground and 40 tonnes/ha in their roots.
Soil carbon averages 100 tonnes/ha
Transfers between stores are rapid, with warm humid condtions ensuring rapid decomposition and keeping the litter store small.
Heavy rainfall means soils are leached and only retain proportionally small amount of carbon.