Ecosystem, rain forests

Table 2. Chemical composition of soils in Australian Tropical Rain Forest ecosystems (after Congdon and Lamb, 1990, see Bashkin, 2002).

As a result of microbial formation of metal-organic complexes with fulvic acids in soils of Tropical Rain Forest ecosystems, the surface and sub-surface runoff waters are enriched in some heavy metals like manganese and copper. A similar tendency has been shown for boron, strontium and fluorine. 

The main specificity of biogeochemical cycling and exposure pathways in Tropical Rain Forest ecosystems is related to its almost closed character. This means that almost the total number of nutrients and/or pollutants is re-circulating in biogeochemical cycles (Figure 1). 

Figure 1. Bio geochemical cycle and exposure pathways in Tropical rain Forest ecosystems.

Table 6. Plant biomass parameters in Tropical Rain Forest ecosystems, ton/ha.

The average sum of total ash elements in the biomass of Tropical Rain Forest ecosystems is about 8,000 kg/ha. The annual ash element turnover and heavy metal exposure rates are shown in Table 8. 

The biogeochemical fluxes and exposure pathways of various macro- and microelements are different from those shown for Tropical Rain Forest ecosystems. The chemical composition of leaves of tree species in Mangrove Forest ecosystems is connected with higher content of Mg, Cl and S-SO4- and lesser content of K and Si as compared to the leaves of trees from Tropical Rain Forest ecosystems. The content of A1 is 3-4 times higher than that of Si and this can be related to the values of hydrogenic accumulation of these elements in soils (Figure 3). 

The comparison of biogeochemical fluxes and relevant exposure rates of heavy metals in the Mangrove and Tropical Rain Forest ecosystems shows that the total mass of ash elements per unit area is similar. However, the proportion of various elements is markedly different. The Mangrove plant uptake of Fe and Mn is less and that of Sr is higher than the uptake of these elements in Tropical Rain Forest ecosystems. 

Russell, C. E. 1987. Plantation forestry. Case study No. 9 The Jari project, Para, Brazil. In Amazonian Rain Forests. Ecosystem Disturbance and Recovery. Ecological Studies 60, ed. C. F. Jordan (Sprlnger-Verlag, New York), pp. 76-89. 

Wadsworth, F. H., 1983. Production of usable wood from tropical forests. In Tropical Rain Forest Ecosystems. Structure and Function. Ecosystems of the World 14A, ed. F. B. Golley (Elsevier, New York), pp. 279-288. Wang, D., F. H. Bormann, A. E. Lugo, and R. D. Bowden,. 1991. Comparison of nutrient-use efficiency and biomass production in five tropical tree taxa." Forest Ecology and Management 46 1-21. 

Jordan, C. F. 1983. Productivity of tropical rain forest ecosystems and the implications for their use as future wood and energy sources. In Tropical rain forest ecosystems. Ecosystems of the world 14 A., ed. F. B. Golley (Elsevier Publ, Amsterdam, Oxford, New York ), pp. 117-136. 

Prance, G, T. 1989. American Tropical Forests. In Tropical Rain Forest Ecosystems. Ecosystems of the World 14B, eds. H. Lieth, and M J.A. Weiger (Elsevier Publ, Amsterdam, Oxford, New York, Tokyo), pp. 99-132. 

The rates of biogeochemical processes in tropical ecosystems, especially in Tropical Rain Forest ecosystems, are the highest in comparison to other considered ecosystems. This is connected not only with the modern biospheric processes, but, to a great degree, with the history of geological and biological development in these areas. 

From these results we can conclude that nitrogen is relatively available in soils of Tropical Rain Forest ecosystems and that forest soils mineralize and nitrify large amounts of nitrogen. P. Vitousek andR. Sanford have shown similar results earlier in 1986 studying nitrogen cycling in moist tropical forests. 

The high rate of edaphic biological processes is the characteristic property of any tropical ecosystem. In the maximum degree this is related to the Tropical Rain Forest ecosystems. For instance, in the African Rain Forest ecosystems the soil surface receives annually from 1200 to 1500 ton/ha of various plant residues. Edaphic invertebrates and microbes transform this large mass very rapidly. A continuous forest litter is practically nonexistent in the Tropical Rain Forest ecosystems and a thin layer of dead leaves alternates with patches of bare ground. All elements that mineralized from litterfall, are taken up by the complex root system of a multi-storied forest to re-input to the biogeochemical cycling. 

Compare the fluxes and pools of essential chemical elements in Boreal Forest and Tropical Rain Forest ecosystems. Explain the reasons for the intensive rates of biogeochemical turnover in tropical forests. 

Discuss the soil compartment of Tropical Rain Forest ecosystems. Note the common principles of biogeochemical migration of elements in these soils. 

Because of the huge size of Eurasia, all types of ecosystems and climatic belts are presented at the particular area, from Arctic Desert up to Tropical Rain Forest ecosystems (Table 1, Figure 2). 

Discuss the geographic alterations of biogeochemical cycling in the Tropical Rain Forest ecosystems of Latin and South America. Describe the role of precipitation and soil types. 

Some researchers and environmental scientists are setting up preserves within the rain forests to maintain the forests biodiversity. Others are attempting to grow rapidly disappearing plant species in rain forest nurseries. With these methods, scientists are trying to maintain the complex rain forest ecosystems for future research. 

Modern studies have already documented the occurrence of acid rains over Northern Thailand due to the increase in use of lignite as an energy source. Based on the critical load concept, Kozlov Towprayoon (1998) have shown that the critical load values of sulfur for terrestrial Tropical Rain Forest ecosystems of the region are rather low (less than 500eq/ha/yr). As a result of both the high SO2 emission rate and high sensitivity of ecosystems, the excessive input of acidity was calculated for more than 75% of the area considered (see also Chapter 15). 

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