Definición de áreas prioritarias para la restauración forestal en la Cordillera de la Costa de la Región de Los Ríos, Chile

Rey Benayas, José María, codir.Cayuela, Luis, codir.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

Native forest replacement by exotic plantations in southern Chile (1985–2011) and partial compensation by natural regeneration

Although several studies have reported rates of deforestation and spatial patterns of native forest fragmentation, few have focused on the role of natural forest regeneration and exotic tree plantations on landscape dynamics. The objective of this study was to analyze the dynamics of land cover change in order to test the hypothesis that exotic tree plantations have caused a major transformation of temperate forest cover in southern Chile during the last three decades. We used three Landsat satellite images taken in 1985 (TM), 1999 (ETM+), and 2011 (TM) to quantify land cover change, together with a set of landscape indicators to describe the spatial configuration of land cover. Our results showed that the major changes were dynamic conversion among forest, exotic tree plantation and shrubland. During the study period, the area covered by exotic tree plantations increased by 168% (20,896–56,010 ha), at an annual rate of 3.8%, mostly at the expense of native forest and shrubland. There was a total gross loss of native forest of 30% (54,304 ha), but a net loss of initial cover of only 5.1% (9130 ha), at an annual net deforestation rate of 0.2%. The difference between gross and net loss of native forest was mostly the result of conversion of shrubland and agricultural and pasture land to secondary forest following natural regeneration. Over the course of the study period, exotic tree plantations showed a constant increase in patch density, total edge length, nearest-neighbor distance, and largest patch index; maximum mean patch size occurred in the middle of the study period. Native forest exhibited an increase and then a decrease in patch density and total edge length, whereas mean patch size and largest patch index were lowest in the middle of the period. Overall, the observed trends indicate expansion of exotic tree plantations and increase in native forest loss and fragmentation, particularly between 1985 and 1999. Forest loss included both old-growth and secondary forests, while native forest established after secondary succession differed in diversity, structure, and functionality from old-growth and old growth/secondary forests. Since different successional stages influence the provision of ecosystem services, the changes observed in our study are likely to have consequences for humans that extend beyond immediate changes in land use patterns

The differential influences of human-induced disturbances on tree regeneration community: a landscape approach

Understanding the processes shaping biological communities under interacting disturbances is\ud a core challenge in ecology. Although the impacts of human-induced disturbances on forest ecosystems have\ud been extensively studied, less attention has been paid to understanding how tree regeneration at the\ud community level responds to such disturbances. Moreover, these previous studies have not considered how\ud these effects change according to major social and environmental factors that can influence forest use at a\ud landscape scale. In this study, we investigate the effects of cattle grazing and selective logging on the\ud composition of tree regeneration communities in relation to forest successional stage and land tenure regime\ud in Chilean temperate forests, a global biodiversity hotspot. We recorded seedlings, saplings and basal area of\ud stumps of tree species (as a surrogate for selective logging), and number of cattle dung pats (as a surrogate\ud for cattle pressure) in 129 25 3 20 m plots in small (,200 ha) and large properties in different successional\ud stages (old-growth, intermediate, secondary forests). The regeneration of the ten more abundant species as\ud predicted by human disturbance, land tenure, forest successional stage, and number of parent trees was\ud modelled using generalised linear models. Predictions for each individual model were made under different\ud scenarios of human disturbance. The predicted regeneration results were assembled and subjected to\ud ordination analyses and permutation multivariate analyses of variance to determine differences in\ud regeneration composition under each scenario. In most cases, best-fit models contained at least one of the\ud explanatory variables accounting for human disturbance. The effects of selective logging on tree regeneration\ud varied depending on land tenure regime, but cattle grazing always exhibited a negative effect. Our results\ud revealed that cattle have a more negative effect on forest regeneration than selective logging, especially in\ud old-growth forests and small properties. Our analytical approach contributes to the understanding of the\ud differential influence of human-induced disturbances on the tree regeneration community at a landscape\ud scale. It can inform conservation policies and actions, which should focus on addressing themain disturbance\ud factors and on developing strategies to conserve the most sensitive species to such disturbances.C. Zamorano-Elgueta was supported by a CON-\ud ICYT pre-doctoral fellowship (Government of Chile),\ud the European Comission (Project contract DCI-ENV/\ud 2010/222-412), the Chilean NGO Forest Engineers for\ud Native Forest (Forestales por el Bosque Nativo, www.\ud bosquenativo.cl) and project REMEDINAL-2 (Comu-\ud nidad de Madrid, S2009/AMB-1783). L. Cayuela was\ud supported by project REMEDINAL-2. This work is\ud part of the objectives of projects CGL2010-18312\ud (CICYT, Ministerio de Economı́a y Competividad de\ud Espana). The authors acknowledge the valuable\ud support of Vero ́nica Pı́riz, Cony Becerra, Rodrigo\ud Gangas, Oscar Concha, Eduardo Neira and staff from\ud the Valdivian Coastal Reserve, as well as the National\ud Forest Service of Chile (Corporación Nacional Forestal

Fire-induced loss of the world's most biodiverse forests in Latin America

The quantitative signal for the association of fires and land cover change is strong and the impact of frequent fires is vast. Fire plays a dominant role in deforestation, particularly in the tropics, but the relative extent of transformations and influence of fire frequency on eventual forest loss remain unclear. Here, we analyze the frequency of fire and its influence on postfire forest trajectories between 2001 and 2018. We account for ~1.1% of Latin American forests burnt in 2002-2003 (8,465,850 ha). Although 40.1% of forests (3,393,250 ha) burned only once, by 2018, ~48% of the evergreen forests converted to other, primarily grass-dominated uses. While greater fire frequency yielded more transformation, our results reveal the staggering impact of even a single fire. Increasing fire frequency imposes greater risks of irreversible forest loss, transforming forests into ecosystems increasingly vulnerable to degradation. Reversing this trend is indispensable to both mitigate and adapt to climate change globally. As climate change transforms fire regimes across the region, key actions are needed to conserve Latin American forests

Natural forests loss and tree plantations: large-scale tree cover loss differentiation in a threatened biodiversity hotspot

Distinguishing between natural forests from exotic tree plantations is essential to get an accurate picture of the world's state of forests. Most exotic tree plantations support lower levels of biodiversity and have less potential for ecosystem services supply than natural forests, and differencing them is still a challenge using standard tools. We use a novel approach in south-central of Chile to differentiate tree cover dynamics among natural forests and exotic tree plantations. Chile has one of the world's most competitive forestry industry and the region is a global biodiversity hotspot. Our collaborative visual interpretation method combined a global database of tree cover change, remote sensing from high-resolution satellite images and expert knowledge. By distinguishing exotic tree plantation and natural forest loss, we fit spatially explicit models to estimate tree-cover loss across 40 millions of ha between 2000 and 2016. We were able to distinguish natural forests from exotic tree plantations with an overall accuracy of 99% and predicted forest loss. Total tree cover loss was continuous over time, and the disaggregation revealed that 1 549 909 ha of tree plantations were lost (mean = 96 869 ha year(-1)), while 206 142 ha corresponded to natural forest loss (mean = 12 884 ha year(-1)). Mostly of tree plantations lost returned to be plantation (51%). Natural forests were converted mainly (75%) to transitional land covers (e.g. shrubland, bare land, grassland), and an important proportion of these may finish as tree plantation. This replacement may undermine objectives of increasedcarbon storage and biodiversity. Tree planting as a solution has gained increased attention in recen years with ambitious commitments to mitigate the effects of climate change. However, negative outcomes for the environment could result if strategies incentivize the replacement of natural forests into other land covers. Initiatives to reduce carbon emissions should encourage differentiating natural forests from exotic tree plantations and pay more attention on protecting and managing sustainably the former