Microbial carbon use efficiency and biomass turnover times depending on soil depth – Implications for carbon cycling

Plant, microbial and ecosystem carbon use efficiencies interact to stabilize microbial growth as a fraction of gross primary production

“…Spohn et al . (), using a substrate‐independent 18 O stable isotope probing technique to estimate microbial growth and substrate uptake, reported similar CUE h values (0.24 ± 0.08 (SD)) for forest and pasture soils in Germany.…”

Sustainable carbon dioxide sequestration as soil carbon to achieve carbon neutral status for DoD lands

“…Soils in the top 0.2 m contain 615 Gt of carbon with a mean residence time of a few hundred years, while soils in the top 3 m contain 2,344 Gt of carbon (more than all the carbon in the atmosphere) with a mean residence time of 2-10 millennia (Fontaine et al 2007). This increase in residence time with soil depth is a result of slower decomposition due to fewer nutritional resources to support decomposition at increasing depth (Spohn et al 2016). Rooting depth is primarily a function of plant type, but can also be influenced by climate and soil type, where total SOC increases with precipitation (surface soils) and clay content (deep soils) (Jobbagy and Jackson 2000), but appear to be more dependent on soil type than climate (Mathieu et al 2015).…”

Ecological and genomic attributes of novel bacterial taxa that thrive in subsurface soil horizons

“…In addition, residence times of organic C pools are typically far longer in deeper soil horizons (2), suggesting that much of the soil organic matter found 55 in the subsurface is not readily utilized by microbes. Unsurprisingly, the strong resource gradient observed through most soil profiles is generally associated with large declines in microbial biomass (3)(4)(5)(6)(7)(8); per gram soil, microbial biomass is typically one to two orders of magnitude lower in the subsurface than surface horizons (4,6,7). Although microbial abundances in deeper soils are relatively 60 low on a per gram soil basis, the cumulative biomass of microbes inhabiting deeper soil horizons can be on par with that living in surface soils, owing to the large mass and volume of subsurface horizons (3,5).…”