Indicator Plants for Sustainability Assessment in Andean Agro-Ecosystems

The concept of indicator plants suggests that the plant community at a given site reflects rather precisely the environmental conditions of that site. The present study was conducted in the Cajamarca region of the Peruvian Andes between 3200 and 3600 m asl, in the agro-ecological zone of potatoes, Andean tubers and small cereals. Weed communities associated with the Andean crops were analyzed in view of their indicator value with regard to the sustainability of the respective cropping system. The methodological approach (Canonical Correspondence Analysis, CCA) for identifying indicator plants proved to be highly appropriate. Altitude and soil factors (pH, calcium carbonate, organic matter and clay) primarily determine weed species composition, while management factors can hardly be assessed by indicator species at the level of resolution investigated in the present study. Indicator species can be applied successfully for site reconnaissance at the local level, or for site comparisons at regional level within the same eco-region. Their extension to a global scale appears less meaningful. The field work was embedded in a conceptual discussion of sustainability assessment. Approaches to sustainability assessment comprise economic, environmental and social, as well as composite or systems indicator concepts. The spatial and temporal dimensions of sustainability can be represented graphically, showing the spatial scope from the local to the global level, and time horizons from years to millenia. Most approaches do not cover intergenerational time spans. Sustainability assessment is primarily an instrument for problem an-alysis; policy-making is driven by normative elements.