Association between native tree sapling and spiny shrub mitigates browsing damage produced by large herbivores in fire-degraded forests

Abstract

Spiny shrubs can generate positive interactions with palatable trees in sites affected by abiotic and biotic stress (e.g. fire, and consumption by herbivores). The objective of this study was to assess the role of native shrubs (Berberis microphylla) in mitigating large herbivore browsing on tree saplings (Nothofagus antarctica) in degraded (burnt) forests of the central area of Tierra del Fuego, Argentina. For that, we assessed, in 16 forest sites, the browsing intensity and the browsing height in N. antarctica saplings that were alone (n = 10 per site), and in saplings that were spatially associated with B. microphylla shrubs (n = 10 per site). The tree and shrub height were also measured. The results indicated that browsing damage on ñire trees occurred at a higher height and with lower intensity in the tree-shrub association than in trees that were alone. Furthermore, the browsing height was positively related with the shrub height and with the tree height. The shorter trees with greater shrub cover were more protected. Our results indicate that the presence of spiny shrubs decreases the damage caused by browsing, and protects trees during the early regeneration stage. However, the structural characteristics of shrubs are determinant of the protecting effect in these Patagonian forests. This tree-shrub interaction is highly relevant in the dynamics of degraded forests to ensure the system continuity in ecological and productivity terms.