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Opciones de manejo para bosques secundarios de acuerdo a objetivos de largo plazo y su aplicación en bosques templados del centro-sur de Chile
... However, this law has not had a significant impact on the management of native forests because the economic incentives are not high enough to cover the true costs of silviculture activities (Reyes and Nelson 2014). Despite the governance problems, there is a surprising amount of research on forest ecology and the impact of silvicultural treatments on native forests, especially on forest productivity, structure, and regeneration (Grosse 1987(Grosse , 2009Salas et al. 2016;Donoso et al. 1993Donoso et al. , 2018Donoso et al. , 2020. The vast majority of research into native forests has been conducted on three forest types: roble (Nothofagus obliqua (Mirb.) ...
... These studies have not only identified differences in morphological and physiological traits among populations (e.g., Donoso 1979) but also identified hybrid species (e.g., Donoso and Landrum 1979). In addition, they have allowed the improvement of seed collection and nursery techniques to produce native species for reforestation (e.g., Donoso et al. 1999) and the improvement of silvicultural practices to manage native forests (e.g., Donoso 1989;Donoso et al. 2018). More recently, ecological concepts such as niche theory and their guiding principles for sound management and restoration approaches to protect native forests have been used to better understand forest ecosystems dynamics (e.g., Soto et al. 2019). ...
... Silvicultural experiments to test the impact of even-aged silvicultural methods showed that even-aged methods allowed denser, more diverse and well-stocked second-growth evergreen forests compared with twoaged methods (Donoso et al. 2019). Furthermore, well-managed second-growth forests may exhibit annual volume increments ranging from 10 to 20 m 3 /ha (Donoso et al. 2018. However, the use of silviculture treatments in this forest type may also increase tree regeneration and growth of secondary, less productive species. ...
In this article we describe Chile’s transition from an agriculture productive model that originated in the 19th century into a more complex economic model that incorporates forest production, explaining the role of forest sciences in this process. Forest science has made great contributions to the country, especially in terms of improving forestation and forest management techniques that have allowed the rapid expansion of the forestry industry and prevented soil erosion on degraded lands. However, native forests have been neglected and vast areas of forest have been replaced with exotic plantations. This process has highlighted the imperative need for developing a new productive model to ensure not only a fair distribution of wealth but also the use of science-based sustainable forest management practices to protect native forest ecosystems nationwide. A national strategic plan for managing, conserving, and restoring native forests is needed not only to align the forest industry with sustainable development but also to develop sound climate change strategies to achieve the country’s goal of becoming carbon neutral by 2050. Under this scenario forest science can play an important role by producing much needed evidence-based knowledge.
... One second-growth forest was in the "stem exclusion" (SE) phase and the other in the "understory reinitiation" (UR) phase (sensu Oliver and Larson, 1996) with corresponding old-growth indices of 5 and 28%, respectively (Ponce et al., 2019). The SE forest was dominated by a mixture of tree species with different shade tolerances; trees had a dominant height of 17 m and were close to 70 years old (González et al., 2015a;Donoso et al., 2018a). In this forest, hardwood evergreen species included short-lived pioneer species of the Proteaceae family, but the main canopy species were E. cordifolia, L. philippiana, and Drimys winteri. ...
... In this forest, hardwood evergreen species included short-lived pioneer species of the Proteaceae family, but the main canopy species were E. cordifolia, L. philippiana, and Drimys winteri. In contrast, the main canopy species in the UR forest was the shade-intolerant N. dombeyi (> 50% basal area), with a dominant height of 32 m, and an estimated age of 100 years (González et al., 2015a;Donoso et al., 2018a). Nothofagus dombeyi was mixed with common late-successional tree canopy species such as E. cordifolia, L. philippiana, A. punctatum and D. winteri. ...
... shade tolerances of tree species suggest that the various elements of VDT result in a diversity of safe sites for tree regeneration, i.e., tree regeneration was also influenced by small scale conditions (Dodson et al., 2014). In contrast to many conifer forests, the diversity of propagules among tree species in the study included strong vegetative regeneration, except for N. dombeyi and D. winteri (Donoso, 2006;Donoso et al., 2018a), which results in abundant and diverse regeneration that may not necessarily reflect current light conditions . Nevertheless, increased light levels following VDT also contributed to the recruitment of two midtolerant species, D. winteri and E. cordifolia. ...
Second-growth temperate forests usually have simpler composition and structure than comparable old-growth stands. We evaluated the application of variable density thinning (VDT) as a way to increase old-growth attributes, specifically tree species composition and density in two types of second-growth forests: a mixed evergreen-dominated forest (SE, stem exclusion phase) and a Nothofagus dombeyi-dominated forest (UR, understory reinitiation stage) in southern Chile (40°S Lat.). Six one-ha plots were established in each forest. We applied VDT in three plots in each forest, which included the following sub-treatments: a thinned matrix (M), large and small patches (LP and SP), and large and small reserves (LR and SR). We also established three one-ha plots in an old-growth forest (OG), which served as a reference for overall stand structural variables and the tree regeneration layer. OG had significantly more total regeneration and shade-tolerant regeneration, than the untreated SE and UR. After VDT, canopy openness was significantly greater in SE than in UR within the treated portions of the plots (M, LP and SP). The similarities in stand characteristics between untreated and pre-harvest treated plots in each second-growth forest suggest that harvesting was responsible for the lower densities observed in thinned plots. Regeneration patterns two growing seasons after harvests were reflective of the interaction between forest type and sub-treatments. While both second-growth forests showed increases in regeneration densities, none of these increases was significant, although proportionally and numerically they were greater in the SE forest. The sub-treatments showed differences only for shade-intolerant and shade-tolerant species in both forests. These differences in general illustrated a preference of shade-intolerant species for patches (only in the smaller height class in both forests), and of shade-tolerant species for the matrix or the reserves in all height classes from >50 cm through saplings (only in the SE forest). Overall, tree regeneration has been more responsive to VDT in the forest currently in an earlier successional stage, suggesting that second-growth forests in more advanced stages may need to be treated more intensively (larger patches, lower residual densities). Correspondingly, VDT protocols must be developed to account for the interaction between harvest disturbances, developmental stage, and silvics of the component species.
... Los bosques secundarios, renovales o bosques de segundo crecimiento, son aquellas unidades boscosas jóvenes cuyo desarrollo ha estado determinado por perturbaciones antrópicas o naturales que han generado la recolonización de los sitios afectados (Chazdon, 2014;Donoso et al., 2018). Generalmente, estos bosques presentan una distribución de edades coetánea, donde existe una elevada densidad de árboles y una fuerte competencia vertical por la luz (Uriarte, 1987;Peri et al., 2013). ...
Lenga type forests (Nothofagus pumilio (Poepp. et Endl.) Krasser) are one of the most important forest types in Chile in area and timber production. Over the years, a significant portion of the available forest for management has been reduced to second-growth forests or renovales, whose silvicultural system is defined by the application of intermediate cuts such as thinning and clearing.
This study evaluates the effect of a future crop tree thinning on the growth of a second-growth lenga forest. The thinning was applied in 2015 under four intensities: control, selection of 200 (T200), 400 (T400) and 600 (T600) trees per hectare. In 16 permanent plots of 1.000 m2, equally distributed across each treatment, all trees were measured in 2015 and 2023, and increment cores were extracted from 75 future crop trees, 45 companion trees and 20 control trees. Results were compared in terms of changes in state variables, mortality, and current annual increment. Significant differences were determined through statistical tests.
It was found that the T200 and T400 treatments performed better than T600 in terms of increasing state variables of future trees and reducing their mortality. At individual tree level, the highest average diameter increments were observed in future trees (~3,3 mm/year). Compared to low and selective thinnings, the stand-level diameter increment was higher (2,82 mm/year vs 2,31-2,34 mm/year), and trees with better timber quality were also observed. It is recommended to select between 200 and 400 trees to avoid compromising the stability of the residual stand or increasing the mortality of future trees, thereby maximizing the production of high quality wood.
... Furthermore, our results also indicated that our priority species are also pioneer species. Research has suggested that pioneer species, like roble and coihue beech in our study area, grow faster than other native species and are commonly used in restoration projects because they are used for initial vegetation establishment (Donoso et al. 2018). Other studies have shown that pioneer species have been managed to endure anthropogenic degradation and natural disturbances, like frequent floods, making them more frequent within the landscape (Stella et al. 2011). ...
Global initiatives to restore habitats aim to improve ecosystem health; however, restoration programs are challenged with balancing human needs with ecological restoration objectives. To advise programs that aim to restore forest in farmlands and complement other analyses on ecologically-based reference sites, we (1) identified species with sociocultural importance, termed as "priority species"; (2) developed an integrative index to find habitats where priority species coincide with healthy ecological conditions (i.e. relatively high diversity, specific plant composition, etc.); and (3) evaluated whether sociodemo-graphic profiles of landowners influenced their plant knowledge and ecological condition of habitats. Our approach was applied to riparian forests in farmlands of the Toltén watershed in southern Chile. We conducted structured interviews to gather information on traditional uses and management of trees in riparian habitats from 45 landowners. We developed an integrative index by combining sociocultural information from interviews with existing vegetation data. From the list of 65 trees provided by landowners, we selected five priority species based on their high saliency, multiple uses, and known management. Only 6 out of 98 sites had high integrative index scores, with the majority showing low values for sociocultural and ecological conditions. Except for a difference in ecological criteria and gender, the evaluation of landowners' knowledge level with socio-demographic profiles did not show significant relationships. These findings suggest that our integrative index can guide the design of restoration objectives, emphasizing on species that are important to local communities by providing information on the ecological conditions in which these plants co-occur.
... There has been a great improvement in silvicultural options for these forests. Most experiments and some operational management have been conducted in secondary forests dominated by Nothofagus species or by Drimys winteri, the latter a fast-growing species well adapted to growing in poorly-drained soils (Loguercio et al. 2018;Donoso et al. 2018). Thinnings in these forests increase the growth of selected trees but generally also tree regeneration and the growth of companion species. ...
Chile’s current forest model has resulted in almost three million hectares of plantations of exotic tree species owned mostly by two large companies, and 14 million hectares of native forests. Native forests in the northern portion of the country’s forestland (southern-central Chile) have a high degree of degradation, whereas in the southernmost part (Chilean Patagonia) they are mostly well conserved due to the low human population density. Overall, native forests in the regions with a Mediterranean climate (32–37°S) and Valdivian Temperate Rainforests (37–43°S) are in a poor and fragile state of conservation due to the high human population density and conflicting land-use demands on productive sites. This chapter provides options for moving towards a sustainable forestry model that addresses how exotic plantations are managed (at the stand and landscape levels), promotes sustainable management of highly productive native forests, and promotes the restoration of millions of hectares of degraded native forests. These measures should be developed with the aim of increasing ecosystem services for local communities in particular, as well as those of global relevance, such as increasing carbon sinks and biodiversity in these managed or restored forest ecosystems. Since changes will not occur by only increasing ecological and management knowledge, we propose some major governance aspects to move the forest sector of Chile in those directions.
... There has been a great improvement in silvicultural options for these forests. Most experiments and some operational management have been conducted in secondary forests dominated by Nothofagus species or by Drimys winteri, the latter a fast-growing species well adapted to growing in poorly-drained soils (Loguercio et al. 2018;Donoso et al. 2018). Thinnings in these forests increase the growth of selected trees but generally also tree regeneration and the growth of companion species. ...
Chile is one of the top 10 countries in the world in terms of land allocated to tree plantations, reaching 2.4 million ha in 2016. Particularly in South-central Chile huge tree plantations were developed under an extractivist model, which massively changed landscapes, ecosystems, and human-nature relations. The process was increasingly legitimized through a sustainability discourse based on notions of soil protection, sustainable development and, more recently, green economy. Concomitantly, the Chilean state increased the number and size of protected areas for nature conservation. Until recently, however, both models have largely failed to include local communities. In this context, we analyse territorial transformations between tree plantation extractivism and primary forest conservation taking the case of a peasant group that inhabits the sector Lomas del Sol, in the municipality of Valdivia, Region of Los Ríos, South-central Chile. Lomas del Sol is located between the forest reserve of Llancahue, considered of high conservation value since it supplies water for the city of Valdivia, and industrial tree plantations (pine and eucalyptus) that were often developed on previously peasants land. The study is based on empirical local field research using participatory action research and mixed techniques which allow us to present an in-depth description of the territorial transformation processes. The chapter provides a discussion about the tensions between the territoriality of smallholder peasants, forest conservation, and tree plantations. We conclude that while tensions emerged more vividly between the local territoriality and the conservation model, the silent trigger of territorial transformation has been the extractivist tree plantation model.
... El uso del IBA, puede ser una herramienta útil en el catastro, conservación y manejo de ecosistemas forestales (Pabst 2005, Donoso et al. 2018. En cualquier caso, hay que tener en cuenta la limitación del presente estudio en particular, ya que lo ideal es generar un IBA representativo para cronosecuencias de bosques en los mismos tipos o subtipos forestales en similares sitios. ...
In the lowlands of south-central Chile, old-growth forests are scarce, whereas secondary forests are more frequent. The ecosystem services provided by these secondary forests differ from those associated with old-growth forests, reflecting their differences in composition and forest structure. Trees over 200 years-old, basal areas higher than 80 m2, several shade-tolerant trees and large diameters, among other characteristics distinguish old-growth forests. Evaluation of the stage of development of a forest may be useful for classification purposes, and management reports. In this study, we applied an old-growth forest index based on Acker et al., to the lowland forests of south-central Chile. The index considered five variables: density, basal area, basal area of the trees > 80 cm in diameter, basal area of shade-tolerant species and Gini’s coefficient. We employed plots with areas ranging from 900 to 2,500 m2 from four secondary forests (two dominated by Nothofagaceae and two by other evergreen species) and from three old-growth forests (two with emergent Nothofagaceae and one without emergent Nothofagaceae). Results allowed us to suggest that index values larger than 80 would represent old-growth forests, values between 60 and 80 would be forests in transition, and values lower than 60 forests with a scarce presence of old-growth attributes. According to the type of forest, the proposed index could differ in terms of the variables used in different regions of Chile.
Valdivian Temperate Rainforests in Chile have a global conservation value, but nowadays many correspond to secondary forests following regeneration in agricultural and burned lands, and to high-graded old-growth due to mismanagement, especially at mid to low elevations. Perspectives for increasing old-growth attributes in these productive forests through silviculture are high considering the diverse demands of ecosystem services and the high timber value of tree species. In the Llancahue experimental forest (40°S Lat) we implemented three ecological silviculture approaches: variable-density thinning in a Nothofagus dombeyi secondary forest (NDS), irregular shelterwood in a mature N. dombeyi forest (NDM), and single-tree selection cutting in a partially harvested old-growth forest (OG). Based upon an old-growth index (OGI) that includes density, basal area (BA), BA of the trees >80 cm in diameter, ba of shade-tolerant species, and the Gini coefficient, and aims to estimate how close a given forest is to a typical old-growth forest, these forests had a 22, 22, and 62% OGI before management. The OGI remained similar or declined following management, but 7–10 years after management it increased in NDS and NDM and declined in the OG (significant changes only in NDM and OG). We discuss these results considering that managed forests should target for an OGI ≈70% rather than maximum values. These managed forests contribute to halt degradation, mitigate climate change (carbon stores in the forest and in timber), and may have greater adaptive capacity to disturbances. We discuss perspectives for the potential scale-up of implementing these approaches.
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