Vincent de Leijster

50 Chapter 3 3.4 DISCUSSION We tested the hypothesis that degraded ecosystem services in woody-crop systems can be rehabilitated by agroecological management, while maintaining or enhancing food provisioning levels. We found some support for agroecological practices improving ecosystem service provisioning in the short term in woody-crop systems in southern Spain. The overall ecosystem service indices were higher in the agroecological treatments than in conventional management; +17% for green manure, +17% for no tillage and +28% for compost. For individual ecosystem services, we observed that agroecological management increased nutrient cycling, carbon stock and habitat provisioning, but not food provisioning, pest control and pollination. These results are further evidence that agroecological land management practices can play a role in the rehabilitation of some ecosystem services (Tittonell 2014; Bommarco et al. 2013; Hainzelin et al. 2014; Bennett & Garry 2009). The results also show that the rehabilitation process may occur rapidly, as we found significant improvements in less than one year. Previous studies have reported improvements over longer periods. For example, Ponisio et al. (2016) reported that ten years after hedgerow restoration in agroecological landscapes, habitat provisioning for pollinators had improved by 12% and Schulte (2017) showed that after five years, natural vegetation strips had improved on-farm abundance of arthropods, pollinators and birds, and had reduced runoff by 37%, without reducing crop productivity in corn and soy fields. In our study, however, the responses of ecosystem services to the treatments differed strongly, as is summarized below. Nutrient cycling Nutrient cycling was the ecosystem service that improved the most with the agroecological treatments (11–36% higher) over the period of one year. Compost addition improved the nutrient cycling in soil organic decomposition processes (enzymatic activities of glucosidase and phosphatase), soil nutrient availability (total N and extractable K contents in soil) and crop nutrient contents (P and K contents in crop leaves). By contrast, conventional tillage had the lowest enzymatic activity and no tillage the lowest nutrient content in the soil and crop. Our results are in line with those of another study in a non-agricultural system in Andalusia (Spain), where both plant-based and manure soil amendments effectively enhanced soil enzymatic activities (i.e. dehydrogenase, urease and β-glucosidase) within one year (Tejada et al., 2006). The activity of these three enzymes and of phosphatase is also known to increase as a result of compost application in other crops (Chang et al., 2007).