Vincent de Leijster

107 Ecosystem services trajectories in coffee agroforestry in Colombia over 40 years 5 5.5.1 Ecosystem service trajectories We found support for the hypothesis that ecosystem services trajectories are nonlinear and follow mostly an asymptotic relationship (Bullock et al., 2011). In other words, above- ground carbon stock, biodiversity proxies (butterflies and epiphytes), coffee quality and timber volume responded first rapidly and then slowly (Mills et al., 2019). We found that coffee quality, above-ground carbon, butterfly indicators, and epiphytes richness increased within the first 5 years after transition to agroforestry and a saturation point was reached after approximately 20 years. The initial fast response may have corresponded to carbon and biomass accumulation by the trees and the growing availability of habitat for butterflies and epiphytes (Mas and Dietsch, 2003). The trees, changed the micro-climatic conditions by buffering air temperatures and increasing air humidity (Appendix Table A5-8), which may have resulted in the increased coffee quality (Muschler, 2001). Over time, the accumulation of biomass due to tree growth slows down (Turner, 2010), and therefore the increase in carbon stocks and habitat availability also slows down. These results are in line with our expectation that regulating ecosystem services would follow a trajectory similar to that of vegetation characteristics. Our results for the development of above-ground biomass according to an asymptote is in line with earlier findings in secondary tropical forests (Martin et al., 2013), and the restoration of butterfly communities in Ugandan forests was also found to follow an asymptotic shape (Nyafwono et al., 2014). Coffee bean quality showed an increasing trend over time and coffee yields showed a decreasing trend over time. Both for coffee yield and coffee bean quality it has been demonstrated that they can be affected by shade trees, but the specific responses varied between studies (Jezeer et al., 2017). A previous study from Colombia showed that planting timber trees in coffee farms negatively affected coffee yields during the first five years after planting (Farfán-Valencia and Urrego, 2004). Our results are in line with this study, as coffee yield in the first 10 years after agroforestry negatively related to above-ground carbon stock (r=-0.34, P=0.03; Table 5-3). On the other hand, provisioning of timber volume increased. Currently, a small number of farms marketed the timber, while there is still a large untapped potential to do this on a larger scale in a sustainable way. We found that above-ground carbon strongly increased within the first 5 years after transition to agroforestry (half-time coefficient is 3.5 ± 2.7 y; Figure 5-3; Appendix Table A5- 4). The magnitude of the above-ground carbon increase in our study (on average 0.75 tC y -1 for the first 20 years) was similar to what was reported for growing cocoa agroforests in Cameroon (0.72 tC y -1 over 80 years; Nijmeijer and Harmand, 2019). Below-ground carbon dynamics are known to respond slower than above-ground carbon dynamics (Martin et al.,