Facilitation among plants: A strategy for the ecological restoration of the high-andean forest (Bogotá, D.C.-Colombia)

Ecosystem invasion by the exotic legume Ulex europaeus (common gorse) impede the establishment of native vegetation by creating a closed canopy and its high resprouting capacity following a disturbance. Over a nine month period, plant-plant interactions between the native legumes, Lupinus bogotensis (shrub) and Vicia benghalensis (herb), and the native tree species Solanum oblongifolium and Viburnum tinoides, were evaluated in a zone close to the Chisacá reservoir in Bogotá, Colombia; that had previously been invaded by U. europaeus for at least 60 years. Experimental treatments corresponded to the identity of the native legume species and their sowing densities (high, medium and low), based on distance between individuals: 30, 60 and 90 cm respectively. The native tree species were sown at the same density in all plots (25 individuals, 50 cm between each other). Variables measured in all planted native tree species were: total height, basal diameter and number of leaves or branches. Both native tree species performed best with L. bogotensis at low and medium sowing densities, where the greater establishment of native species indicated a net positive interaction. Growth and survival were higher in all cases when compared with the control plots. There was evidence of facilitation by the native leguminous plants in all the treatments (index of interaction > 0), with the exception of V. benghalensis at high sowing density with S. oblongifolium. We conclude that facilitation between plants can be employed as an effective strategy for the reestablishment of native vegetation and could thereby initiate recuperation of the high-andean forest by reactivating the process of dynamic succession.