Regeneration patterns of Polylepis subtusalbida growing with the exotic trees Pinus radiata and Eucalyptus globulus at Parque Nacional Tunari, Bolivia

Abstract

The establishment of exotic trees such as Pinus radiata (radiata pine, Pinaceae) and Eucalyptus globulus (eucalyptus, Myrtaceae) in fragments of native vegetation at the Parque Nacional Tunari (PNT, Cochabamba-Bolivia), can affect the regeneration of the native species that live there. Polylepis subtusalbida’s (kewina, Rosaceae) regeneration was surveyed, evaluating the density of seedlings, their size structure, and growth forms, as well as variables of growth and survival in fragments of pure forests (P. subtusalbida fragments without exotic trees) and mixed fragments (P. subtusalbida fragments with exotic trees). Sixty-four permanent study plots were established in mixed fragments of P. subtusalbida–P. radiata, P. subtusalbida–E. globulus and fragments with only P. subtusalbida, in three locations within the Parque Nacional Tunari. Mixed fragments with both native and exotic trees and native pure fragments did not present differences in seedling density. Differences in density were related to adult native tree densities. A greater proportion of P. subtusalbida’s seedlings exhibited lateral growth and adventitious roots in mixed fragments than in pure fragments. The size structure only varied between locations and not between fragment-types. Smaller individuals grew more, in both pure and mixed fragments. Greater survival of seedlings was observed in the larger individuals and in the ones that exhibited lateral growth. P. subtusalbida’s regeneration in the PNT is complex and varies at two spatial scales: between locations and between fragment type. If conservation of P. subtusalbida fragments in the PNT is considered a priority, their regeneration should be favored and different measures for the management of forests must be in accordance with the specific needs given the locations and fragment type.