Deep soils respire only 10% of total CO2 (>30cm) despite holding most of the SOC (~50%). Fresh litter also tends to stay on top and not make it's way deeper (13C tagged litter addition). Wordell-Dietrich etal 2020 https://doi.org/10.5194/bg-17-6341-2020 used 2m deep and 1.6m diameter soil observatories to continuously monitor soils at 10, 30, 50, 90 and 150 cm; measuring CO2, SOC, 13C (tagged surface litter addition), and 14C. #SoilDataSource #SoilCarbon #DeepCarbon #SciLit