Eucalyptus and alder field margins differ in their impact on ecosystem services and biodiversity within cropping fields of the Peruvian Andes

Intensified rotations and increased reliance on agrochemical inputs in many parts of the Andean highlands generate concern for soil health, biodiversity, and key ecosystem functions that are essential for maintaining agricultural productivity and the well-being of smallholder communities throughout the region. Improved management of perennial vegetation within field margins represents a promising option currently being explored in many Andean communities, with the potential to better design these field margins to support multiple ecosystem services (ES). In this study we examined the effect of two types of common woody perennial field margins (eucalyptus vs. alder) on crop production and other soil-based ES at variable distances from the field edge. Sampling was conducted in twenty potato fields, ten with borders dominated by alder trees (Alnus acuminata) and another ten with eucalyptus (Eucalyptus globulus). Within each field, transects (∼10 m) were established with six sampling points extending from the perennial field margins towards the center of the production field. At each point, a suite of ES was assessed including: nutrient provision (based on levels of SOM, pH, P, K, and N in the soil), biodiversity maintenance (ground vegetation and soil macrofauna), erosion control (infiltration, aggregation, bulk density), bio-control (occurrence of common crop pests/pathogens and predators) and crop production (potato yields and quality). The provision of ES was generally found to be higher in the field margins than in the arable fields. The dominant tree species in the field margin was also important, such that fields bordered by alder trees showed higher SOM, macrofauna diversity and aggregate stability compared to those bordered by eucalyptus trees. Fields bordered by eucalyptus trees showed higher values for overall vegetation diversity, pH and available phosphorus. While potato yields did not differ between fields bordered by alder vs. eucalyptus, potato pest pressure was higher in fields bordered by eucalyptus trees. Our findings suggest that improved management of perennial field margins can enhance the provision of multiple ES in agricultural landscapes of the Peruvian highlands