The concept of forest degradation tends to be addressed in broad terms, and existing definitions are difficult to apply in practice. These definitions are based on a reduction in the production of ecosystem goods and services, but fail to address how, when and to what degree this reduction—which ultimately leads to degradation of a forest—occurs. Generally speaking, degradation is the result of a progressive decline in the structure, composition and functions upon which the vigor and RESILIENCE of a forest is based. A degraded forest is one whose structure, function, species composition, or productivity have been severely modified or permanently lost as a result of damaging human activities. So far, no guidelines have been developed for classification and evaluation of a degraded forest at the stand level, nor are there methodologies for assessing the degree of degradation found. The present work proposes stand-level guidelines for identification of a degraded forest according to a list of structural, compositional and regeneration criteria and characteristics. Emphasis is put on the need for local definitions of forest degradation, and identification of thresholds that determine the points where the processes of degradation finalize into degraded forests. Finally, the present work makes a call to move forwards in sustainable management in order to prevent degradation, and in implementation of restoration or rehabilitation practices in degraded forests.

Raulí (Nothofagus alpina (Poepp. & Endl.)) and Ulmo (Eucryphia cordifolia Cav.) are mid-tolerant tree species in the Coihue-Raulí-Tepa (ca. 0.55 mill ha) and Evergreen (ca. 4.1 mill ha) forest types in south-central Chile, respectively. These species have been selectively logged in old-growth forests especially during the 20th century, Raulí mostly for its highly valuable timber, and Ulmo for its highly demanded firewood and bark for the tannery industry. Natural regeneration of these species occurs mostly through canopy gaps, but it can be retarded, or even inhibited, when the cover of the understory vegetation becomes unusually dense, such as in high-graded forests. Although underplanting is possible for these species, the knowledge about their growth in forest understories is scarce, and necessary to inform restoration programs. Therefore, we evaluated short-term responses (two years) of underplanted containerized seedlings in root-collar diameter, height, stem volume, and in the slenderness index, as a function of canopy openness (%, continuous variable) and three restoration treatments (categorical variables, plus one control treatment) at two different sites with high-graded old-growth forests for each forest type. By using generalized linear mixed-effects models (GLMMs) we determined that Raulí was more sensitive to the influence of both canopy openness and restoration treatments, while Ulmo was mostly influenced by canopy openness. Specifically, Raulí was positively influenced by canopy openness and restoration treatments in all response variables except for the slenderness index. Conversely, Ulmo was influenced by canopy openness in all response variables except the slenderness index, which was influenced by both predictor variables (canopy openness and restoration treatments). Thus, prospects for restoration with these species are discussed, including possible ontogenetic changes in their responses to light that may demand continuous silvicultural operations to recover the productive and functional roles of these species in these forest ecosystems.