The significant role of microbes in soil carbon

  • Soil is important to life on Earth as we know it…. soil organic matter is key to many of the essential services and functions that soils provide.
  • … long believed that remnants of decayed plant matter were the principal components of stabilized soil carbon…But evolving analytical approaches have led toward view that dead microbial biomass and other microbial residues could contribute even more significantly to stable carbon pools.
  • The scientists suggest adopting an approach based on a concept called the soil microbial carbon pump to help stimulate fruitful new research in this area.

August 29 2017 read full ScienceDaily article here

…In the carbon cycle, carbon moves among plants, animals, soils, Earth’s crust, fresh water, the oceans and the atmosphere. Sequestered carbon is carbon that stays in long-term storage. Soil carbon waxes and wanes, depending on the balance between inputs of new organic materials and outputs. Losses occur mostly through decomposition, but also through leaching into groundwater or surface erosion.

Studies have long focused on how plant litter — mostly dead leaves, stems and roots — decomposes and transforms into soil organic matter. The contribution of the living biomass of microbes to soil carbon, which accounts for only 1 to 5 percent of total soil carbon, has received much less attention, however

…Even though the living biomass of microbes is small, these organisms grow, live and die at a rapid pace. This means that microbial inputs to soil organic matter can be much larger than previously thought, particularly when a significant portion of those inputs are stabilized rather than decomposed. But even with new insights and improvements in the tools used to study soil organic matter, many questions and unknowns persist.

…Through catabolic activity, microbes break down complex molecules to form simpler ones, which releases carbon as carbon dioxide. Through anabolic activity, microbes synthesize complex molecules from simpler ones, which contributes to carbon storage.

The scientists suggest adopting an approach based on a concept called the soil microbial carbon pump to help stimulate fruitful new research in this area. Marine researchers first raised the microbial carbon pump concept. The marine microbial carbon pump sequesters carbon by transferring it deep into the oceans. Through this process, bacteria contribute significantly to long-term carbon storage and the regulation of atmospheric carbon dioxide.

….addition of new, externally produced carbon can increase the production of carbon dioxide by priming microbial decomposition of existing soil organic matter, and at the same time it can lead to greater entombment of microbial residues.

“But, researchers will need better analytical tools to more accurately quantify the mass of dead microbial material and residues in soils, and to understand the factors controlling the balance between the entombing and priming effects,” Liang noted….

Chao Liang, Joshua P. Schimel, Julie D. Jastrow. The importance of anabolism in microbial control over soil carbon storage. Nature Microbiology, 2017; 2 (8): 17105 DOI: 10.1038/nmicrobiol.2017.105