Definición de áreas prioritarias para la restauración forestal en la Cordillera de la Costa de la Región de Los Ríos, Chile
- Autores: Carlos P. Zamorano Elgueta
- Directores de la Tesis: José María Rey Benayas (dir. tes.), Luis Cayuela Delgado (codir. tes.), Davide Geneletti (codir. tes.)
- Lectura: En la Universidad de Alcalá ( España ) en 2014
- Idioma: español
- Tribunal Calificador de la Tesis: Antonio Gómez Sal (presid.), Miren Onaindia Olalde (secret.), María del Pilar Martín de Agar Valverde (voc.), Francesco Orsi (voc.), José Luis Quero Pérez (voc.)
- Materias:
- Enlaces
- Resumen
- español
La mayor parte de los ecosistemas forestales a nivel global presenta algún grado de alteración, que limita o disminuye su capacidad para generar servicios ecosistémicos. La restauración forestal tiene una creciente importancia para revertir o mitigar estos procesos de alteración.
El objetivo general de esta tesis doctoral es identificar áreas prioritarias para la restauración forestal con el fin de conservar la biodiversidad y la provisión de los servicios ecosistémicos en la Cordillera de la Costa de la Región de Los Ríos, Chile.
Para ello, primero analizamos la influencia de la ganadería en la regeneración de la araucaria (Araucaria araucana), una conífera amenazada de los bosques templados de Chile y Argentina (Capítulo 2). Utilizamos el número de excrementos como un indicador de la actividad ganadera (el índice de intensidad ganadera, CAI, por sus siglas en inglés). La regeneración fue analizada como una función del CAI, del régimen de propiedad, del área de estudio y de la densidad de adultos. En general, se registró una influencia exponencial negativa del CAI en todas las variables respuesta, en especial en pequeñas propiedades de campesinos.
Con el fin de investigar si los efectos del disturbio antrópico afectaban también a las comunidades de regeneración en su conjunto, analizamos los efectos de la ganadería y de la tala selectiva en la composición de la comunidad de regeneración de plantas leñosas en bosques siempreverdes, considerando el estado sucesional del bosque y el régimen de propiedad (Capítulo 3). Nuestros resultados revelan que la ganadería tiene un mayor efecto negativo en la regeneración forestal que la tala selectiva, en especial en pequeñas propiedades y en bosques maduros. Luego analizamos la dinámica de cambios de la cobertura del suelo bajo la hipótesis de que las plantaciones forestales de especies exóticas han causado la mayor transformación en la superficie de los bosques templados en el sur de Chile en las últimas tres décadas (Capítulo 4). Usamos para ello imágenes Landsat de 1985 (TM), 1999 (ETM+) y 2011 (TM), y seleccionamos diversas variables para el análisis de los cambios del paisaje. Los mayores cambios se generaron principalmente como una conversión dinámica entre bosques, plantaciones y matorrales. Durante el período analizado la superficie de plantaciones aumentó un 168%, con una tasa anual del 3.8%, principalmente por la sustitución del bosque nativo y matorrales. Se registró una pérdida bruta de bosques del 30%, pero una pérdida neta de sólo el 5.1% de la superficie inicial, con una tasa anual de deforestación del 0.2%. La diferencia entre la pérdida bruta y la neta de los bosques se debe a la conversión de matorrales y de áreas agrícolas y pastizales a bosques secundarios por la regeneración natural de los bosques. Como los bosques regenerados corresponden exclusivamente a bosques secundarios, ello puede influir en su capacidad para proveer servicios ecosistémicos.
Por último (Capítulo 5), identificamos áreas prioritarias para la restauración forestal con el fin de conservar la biodiversidad y la provisión de servicios ecosistémicos. Utilizamos un enfoque multicriterio para evaluar la idoneidad ecológica y la factibilidad socioeconómica de la restauración de bosques. Los bosques degradados fueron definidos por la evidencia empírica de impactos en la regeneración forestal por la ganadería y la tala selectiva (Capítulos 2 y 3), mientras que las áreas deforestadas fueron definidas a partir de una imagen Landsat (TM) del año 2011 (Capítulo 4). El área prioritaria de restauración fue definida de acuerdo a las áreas de mayor idoneidad y factibilidad según diferentes perspectivas (por ejemplo, con una orientación en la biodiversidad). Las áreas prioritarias para la restauración forestal tienen una alta biodiversidad y una severa erosión potenciales, y están localizadas en cuencas hidrológicas caracterizadas por bajos coeficientes de escorrentía, áreas de elevada accesibilidad y expuestas a una menor presión productiva. Su superficie total se estimó en un 10.7% del área de estudio, de la cual el 7.4% correspondieron a áreas deforestadas y el 3.3% a bosques degradados en zonas cercanas a los bosques bien conservados, en propiedades de empresas forestales certificadas (FSC), en pequeñas propiedades sustentables y en áreas protegidas.
El enfoque de análisis propuesto por esta Tesis Doctoral contribuye a la comprensión de la influencia variable de los disturbios de origen antrópico en la regeneración forestal a escala de paisaje. Estos resultados podrían apoyar el diseño de políticas y acciones de restauración y conservación, las cuales deberían primero concentrarse en limitar o eliminar los principales factores de disturbio y luego proteger y recuperar las especies más sensibles a estas alteraciones. Este enfoque y los resultados generados no sólo permitirán a los expertos y planificadores identificar dónde restaurar, con el fin de aumentar los valores ecológicos de un territorio, sino también definir la factibilidad socioeconómica para implementar acciones de restauración en el mediano y largo plazo, incluyendo tanto las áreas deforestadas como los bosques degradados.
- English
Human-induced disturbances are rapidly changing landscapes and ecosystems, yet significant gaps in our understanding of the spatial ecology of these changes remain. Although the impacts of human-induced disturbances on forests have been extensively studied, less attention has been paid to understanding how tree regeneration at the community level responds to such disturbances and how these effects change according to major social and environmental factors that can influence forest use at the landscape scale. In addition, to date few studies have focused on the expansion and spatial configuration of exotic tree plantations and in their role on the dynamics of regional land cover change. Forest restoration can play an increasingly important role to reverse or mitigate these processes. Moreover, identifying priority areas would increase the efficiency and impact of available resources to design, plan and establish forest restoration programs. However, the problem of developing methods to identify priority areas for maintaining and enhancing biodiversity and ecosystem services through forest restoration at the landscape-scale level is less frequently addressed in the scientific literature.
The main goal of this PhD Thesis is to identify priority areas for forest restoration in order to maintain and enhance biodiversity and the provision of ecosystem services in the Coastal Range of Región de Los Ríos, Chile.
To achieve this goal, we first analyzed the influence of cattle on the regeneration of monkey puzzle tree (Araucaria araucana), an endangered conifer of the temperate forests of Chile and Argentina (Chapter 2). We used the number of cattle dung pats as a surrogate of cattle activity (the cattle intensity index, CAI). Regeneration ot the monkey puzzle tree was analyzed as a function of the CAI, land tenure regime, the study site, and the density of parent trees. Overall, there was a negative exponential influence of the CAI on all response variables. In small landowner forests, even low cattle intensities caused regeneration to drop rapidly to zero, whereas in plots owned by timber companies regeneration decreased smoothly as the CAI increased. The CAI also affected regeneration of the monkey puzzle tree qualitatively by increasing the regeneration by root suckering, which may lead to problems of genetic drift in the long-term.
To further investigate whether human-induced changes might also affect biotic communities as a whole, in the next chapter we analyzed the effects of cattle grazing and selective logging on the composition of tree regeneration communities in evergreen forest in southern Chile, considering these effects in relation to forest successional stage and land tenure regime (Chapter 3). Our results revealed that cattle had a more negative effect on forest regeneration than selective logging, especially in small properties and old-growth forests, which appear to be more sensitive to human-induced disturbances. Undisturbed old-growth forests or forests associated only with selective logging would be dominated by late-successional species like Saxegothaea conspicua, Aextoxicon punctatum and Laureliopsis philippiana. Instead, the occurrence of cattle and selective logging could prevent the establishment of these shadetolerant and shade-semitolerant species and favour a composition dominated by Amomyrtus luma, A. meli and Gevuina avellana. These results confirmed that human-induced disturbances, particularly cattle, can diminish, damage or prevent the recruitment of tree species, which could generate unknown impacts on functional ecosystem properties.
After analyzing human-induced impacts on regeneration communities, we moved on to the landscape scale and analyzed the dynamics of land cover change under the hypothesis that exotic tree plantations have caused a major transformation of temperate forest cover in southern Chile in the last three decades (Chapter 4). To achieve this, we used Landsat scenes taken in 1985 (TM), 1999 (ETM+), and 2011 (TM), and selected landscapes indices. Our results showed that major changes took place as mainly a dynamic conversion among forest, exotic tree plantation and shrubland. During the studied time span, the area covered by exotic tree plantations increased by 168% at an annual rate of 3.8%, mostly at the expense of native forest and shrubland. There was a total gross loss of 30% of native forest, but a net loss of only 5.1% of its initial cover, at an average annual deforestation rate of 0.2%. The difference between gross and net loss of native forest is mostly the result of conversion of shrubland and agricultural and pasture land to secondary forest following natural regeneration. Overall, the observed trends indicate expansion and compactness of exotic tree plantations, and increasing native forest loss and fragmentation, particularly during the 1985-1999 period. Whereas forest loss include both old-growth and secondary forests, native forest regenerated after natural succession correspond to the latter. This can influence the native forest capacity to provide ecosystem services, including those related to soil and water. These alterations will affect humans in ways that go beyond the immediate land-use situation.
Finally, and based on the results of previous chapters, we focused on identifying priority areas for forest restoration for maintaining and enhancing biodiversity and the provision of ecosystem services (Chapter 5). We used a multicriteria approach to assess the ecological suitability and socioeconomic feasibility of forest restoration. Forest degradation was defined based on empirical evidence of alterations in forest regeneration by cattle grazing and selective logging (Chapter 2 and 3), whereas deforested areas were defined using a Landsat image for the year 2011 (TM, Chapter 4). The area to be restored was defined according to the best suitability and feasibility areas for forest restoration according to different perspectives, e.g. biodiversity oriented. The priority areas for forest restoration were distributed across the entire study area, but concentrated in the central and eastern parts of the region, where they showed a continuous distribution. The priority areas for forest restoration have high potential biodiversity and severe potential erosion, located in watersheds characterized by low runoff coefficients, in more accessible areas, and exposed to low pressure on forest. The total amount of priority areas for restoration accounted for 10.7% of the study area, of which 7.4% corresponded to deforested areas and 3.3% to degraded forests near well-conserved forests, in land owned by forest companies certified by the Forest Stewardship Council (FSC, 5.85%), in sustainable small properties (3.25%), and protected areas (0.87%).
Our analytical approach contributes to the understanding of the differential influence of human-induced disturbances on the tree regeneration community at the landscape scale. It can inform restoration and conservation policies and actions, which should focus first on addressing the main disturbance factors and then on developing strategies to conserve the most sensitive species to such disturbances. In addition, understanding the dynamics of land cover change and the role of exotic tree plantations will help to restoration and conservation strategies of native forest, which is now mandatory for forest companies in the region to obtain timber certification.
This approach and the results will not only allow practitioners to understand where to restore in order to enhance the ecological values of a region, but also to define the socioeconomic feasibility of restoration activities in the medium and long term, including deforested areas and degraded forests.
- español
