Biogeochemical Cycles of Chemical Species in Tropical Ecosystems

The proportion of areas with different precipitation rates varies from continent to continent. For instance, different Arid ecosystems, from Dry Savanna to Extra-Dry Desert, are predominant in India and Australia. To a lesser degree these ecosystems occur in Central and South America (see Chapter 7 Biogeochemical Mapping ). In an equatorial belt of Africa, the distribution of areas with different precipitation is shown in Table 32. 

We can see that the Tropical Rain Green Forest ecosystems occupy about 1/5 of the African equatorial belt, whereas about 112 of this area is Woody and Tall Grass Savanna ecosystems. The rest of the area is occupied by various Dry Steppe and Dry and even Extra-Dry Desert ecosystems, like Sahara, with annual rainfall less than 200 mm. 

2-5 m trees of height well adapted to stray light. A large part of died-off and fallen leaves from taller trees is entrapped for assimilation by numerous epiphytes. This results in fast re-circulation of chemical elements. The average annual Net Primary Production of these ecosystems is 25 ton/ha. 

This type of closed biogeochemical cycling is very sensitive to uncontrolled intervention into ecosystems. For instance, clearcutting leads to the entire destruction of the whole ecosystem with its multi-annual history. In other words, the deforestation will leave behind a barren soil with completely destroyed biogeochemical turnover. 

For instance, clearing tropical forests in the Amazon Basin for pasture alters rates of soil nitrogen cycling (Table 33). 

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