Fig. 16

Carbon regulation indicators. Eight-five indicators were used in studies measuring carbon regulation. Most common indicators to measure carbon pools in soil, soil litter or in biomass were SOC (14 %, n = 205), N, P, K, yield, bulk density, soil texture, total carbon, and pH. Sixty-five studies measured carbon dioxide (CO₂). Fewer studies used proxies of methane (CH₄) (2 %, n = 24), stem density/diameter (1 %, n = 17), crop height and survival rate of trees (ea. 0.3 %, n = 4)