Relationship between organic matter and microbial biomass in different vegetation types

Organic matter (OM) is composed of organic debris of plant mass (forest floor and dead wood) and animals. Vegetation cover is one of the most important sources for greater organic matter accumulation in different ecosystems like agriculture, forests, and grasslands. It is well known that forests have higher soil organic carbon at surface soil depth due to the higher amount of litter return and organic matter input. Organic matter has direct and indirect critical impacts on soil structure and health because it is a source of nutrients such as nitrogen, sulfur, phosphorus, and many of the micronutrients, and it helps to enhance microbial community compositions and activities. However, the availability of these substances depends on the presence of microbial biomass (MB) in the environment. The OM and MB are sensitive indicators for ecosystem productivity and health and are recognized by ecosystem quality monitoring programs. Both OM and MB also influence carbon sequestration rate, dynamics of atmospheric C, and climate change regulations in terrestrial ecosystems. This is where microorganisms show their crucial role, especially that in the decomposition of OM from different vegetation, and for nutrient availability. Therefore, it is necessary to determine the microbial biomass to understand the biological activities of organic matter. This chapter reports an overview of the understanding of the relationship between organic matter and microbial biomass in different vegetation types.