jason Ullah: Carbon is a major constituent of the Earth's composition. The term 'carbon cycle' is used to describe both the movement of this carbon through different reservoirs and the storage capacity of each reservoir. A considerable amount of this carbon is held in the Earth's biomass.
Table 1 provides estimates of the size of areas in square kilometres (km2) and the amount of biomass in kilograms of carbon (kgC) in different types of biome. A biome is composed of a characteristic range of vegetation that occurs within a distinct ecosystem type. It also provides estimates of the net primary productivity (NPP) for each type of biome in kilograms of carbon in each square metre (kgC m-2).
Table 1
Area Mean Plant Biomass Total Plant biomass Mean NPP Total NPP
Ecosystem Type (106 km2) (kgC m-2) (1012 kgC) (kgC m-2 yr-1) (1012 kgC yr-1)
Swamp, marsh 2 6.8 9.2 1.125 2.25
Lake, stream 2.5 0.01 0.01 0.225 0.563
Cultivated land 14 0.5 4.7 0.29 4.06
Rock, ice, sand 24 0.01 0.1 0.002 -
Desert, scrub 18 0.3 3.7 0.032 -
Tundra, alpine meadow 8 0.3 1.6 0.065 0.520
Temperate grassland 9 0.7 4.3 0.225 -
Woodland, shrubland 8 2.7 14.9 0.27 -
Savanna 15 1.8 18.3 0.315 4.73
Boreal forest 12 9 73.1 0.36 4.32
Temperate forest (deciduous) 7 13.5 64.3 0.54 -
Temperate forest (broadleaf, evergreen) 5 16 54.2 0.585 -
Tropical seasonal forest (deciduous) 7.5 16 81.3 0.675 -
Tropical rainforest (evergreen) 17 20 230.2 0.9 15.3
Total or Global mean 149 6.26 560 0.401 48.3
Use the data in Table 1 to answer the following questions. Note: if a question asks you to perform a calculation, make sure you clearly show your working as well as your answer.
a.Complete the final column of the table by calculating to 3 significant figures the total net primary productivity (NPP) for each type of biome (kgC yr-1).
(7 marks)
b.Rank in descending order the top five ecosystems (biomes) in terms of their area and state their area.
(1 marks)
c.Rank the top five biomes in descending order of their total annual net primary productivity (total NPP) and state their total NPP. Comment briefly on what your rankings in (b) and (c) show.
(3 marks)
d.Determine the percentage decrease in annual biomass production if 10% of the world's deciduous and tropical rainforest were cut down.
(4 marks)
e.Figure 1 is a summary diagram of the Earth's carbon cycle for modern times (i.e. post-Industrial Revolution).
Described image
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Figure 1 A summary of the movement of carbon in the world post-Industrial Revolution.
Long description
The mass of carbon in each reservoir is shown in gigatonnes (109 tonnes) which equals 1012kg. Thus the atmosphere contains 760 x 1012kg. The sizes of the fluxes between the reservoirs are given in units of 1012kgC yr-1. Where appropriate, the rates at which the processes of exchange take place are stated in italics, e.g., days for the flux between ocean and atmosphere; centuries for the flux between deep and surface ocean layers.
Compare the sizes of the present-day reservoirs (Figure 1) with those for the pre-industrial period (c. 1750 A.D.) given in U116 Block 4 (Figure 2.4). Indicate which reservoirs show change, and present this change as a percentage of the earlier value.
