Environmental Engineering Reference
In-Depth Information
2
Biomass Stores: Means and Extremes
In contrast to regularly conducted inventories of wood volumes in commercially
exploited forests and the frequent (now satellite-aided) monitoring of crop produc-
tivity, accurate quantii cations of phytomass in natural ecosystems remain relatively
uncommon. But they do support some easily defensible generalizations, illustrate
some important exceptions, and help correct some stereotypes. These assessments
are usually presented in units of dry matter per unit area (g/m
2
or t/ha) or as the
total mass of carbon (g C/m
2
or t C/ha). Our knowledge also remains highly uneven
in spatial terms as temperate ecosystems have been studied much more intensively
than the tropics. Integrations on biome, continental, and planetary scales have the
highest margins of error, and the quantii cation of heterotrophic biomass is more
tenuous than that of phytomass.
Phytomass and Zoomass
Phytomass stores vary greatly among biomes, large areas with similar climates
whose global distribution shows distinct latitudinal regularities. The poleward
sequence of biomes starts with tropical rain forests, the most diverse terrestrial
biome: they i ll the entire basin of the Amazon and the Congo, as well as most of
Central America and West Africa, and spread across Southeast Asia and Indonesia.
Tropical forests give way to tropical grasslands, in Africa from the Atlantic to Sudan
and from Angola to Mozambique, in South America both south and north of
Amazonia, and in Australia in the northern third of the continent. In turn, tropical
grasslands blend into deserts, a biome that is relatively restricted in the Americas
but spreads across Africa from Mali to Sudan and then continues across the Arabian
Peninsula and Iran to western India and north of the Hindu Kush and Tibetan
plateau into the heart of Asia, then all the way to northern China; desert also i lls
most of Australia's interior.
