Vincent de Leijster

93 Ecosystem services trajectories in coffee agroforestry in Colombia over 40 years 5 slope on eight locations in the plot using an angle meter. 5.2.4 Ecosystem service indicators 5.2.4.1 Carbon stock Above-ground carbon (AGC): We calculated the above-ground biomass of trees (AGB trees ) using the allometric equation for tropical trees of Chave et al. (2014): AGB trees = 0.0673 · (ρ · DBH 2 · H) 0.976 (equation 1) where DBH is diameter at breast height and H is the height of the tree (see 3.3.1.), ρ is the specific wood density as retrieved from a wood density database (ICRAF, 2019). The above- ground biomass of coffee plants (AGB coffee ) was calculated using the allometric equation of Segura et al. (2006): AGB coffee = 10^(-1.113 + 1.578 · log 10 (D 15 ) + 0.581 · log 10 (H coffee ) (equation 2) where D 15 is the coffee stem diameter at 15 cm and H coffee is the height of the coffee plant. The above-ground biomass of Musa plants (AGB musa ) was calculated using the allometric equation by Arifin (2001) and Hairiah et al. (2001): AGB musa = 0.0303 · DBH 2.1345 (equation 3) These three components were then summed to obtain the total above-ground biomass (AGB). The above-ground carbon (AGC) was calculated by multiplying AGB by the carbon fraction of 0.47 (IPCC, 2006). Below-ground carbon (BGC): The below-ground carbon stock consists of root carbon stock and soil organic carbon (SOC) stock until a depth of 20 cm. Root biomass (RB) of coffee, Musa plants and trees were calculated using the allometric equation of Cairns et al., (1997): RB = exp(-1.0587 + 0.8863 · ln(AGB)) (equation 4) This was then multiplied by the carbon fraction of 0.47. The SOC was expressed in ton per hectare multiplying soil organic matter (SOM) with a carbon fraction of 0.5 (Pribyl, 2010) and the average bulk density of the region of 0.9 Mg / m 3 (Soilgrids.org, 2019).