Formation and Decomposition of Biomass

Carbon turnover in terrestrial ecosystems is mostly linked to biochemical reactions of three types of organisms. Primary biomass is produced by autotrophic organisms, mainly plants. Their biomass is transformed into new but chemically similar secondary biomass of consumers. These are connected by trophic relations in food chains and carbon recycling systems. Nonliving biomass is again mineralized by decomposers to carbon dioxide, water, and minerals. The basic biochemical pathways such as glycolysis, the pentose-phosphate cycle (Calvin cycle), and the Krebs cycle are for all organisms nearly identical. Only a few main biochemical pathways produce metabolites for biomass production, in particular cell walls. 

CLOBM BIOC.EOCHEMICAL CYCLES 1 THE CLIMATE iViTEM 

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FIGURE 1 Major processes, pools, and fluxes involved in the formation of soil organic matter. 

The C2 pool, which is also part of glycolytic breakdown, is the starting point for lipid synthesis. In contrast, amino acids have several precursors and they are connected to a range of pools and metabolic pathways. To understand the structural and chemical similarity and possible differences between organisms, the following biochemical groups are described more in detail carbohydrates, phenylpropanes and their associated derivatives, amino acids, lipids, and the major cell wall constituents. 

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