High mountain forests are often restricted to ravines and much debate has existed on the explanations of this distribution, with arguments ranging from abiotic site conditions being more favorable in ravines to there being reduced herbivory or reduced fire frequency and damage in ravines. We aim at understanding the contribution of fire damage and provide data to help test the hypothesis that fires are less damaging and that trees recover faster in ravines as compared to ridge sites. We evaluated crown damage, post-fire survival, regeneration by resprouts and seeds, and browsed stems in burned and unburned control Polylepis australis trees situated in a ravine and in a ridge forest in the west slope of the mountains of Central Argentina. The proportion of the tree crown scorched by fire was 28 % higher on the ridge than in the ravine (94.3 ± 1.9 % and 66.1 ± 4.5 %, respectively) and was negatively related to tree height which was lower on the ridge. Survival was not differentially affected, but post-fire re-growth and establishment through seeds was lower in the ridge as compared to the ravine. Browsed stems were about twice as frequent in the ridge as in the ravine, more so in the resprouting burned trees. Our study provides evidence that forests are restricted to ravines in part because the effects of fires are less severe at these sites than in ridges, which adds to other possible causes like reduced livestock use of ravines, enhanced regeneration by seed and faster tree growth within ravines all of which are probably mediated by abiotic factors.

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RESUMEN. Los incendios afectan de distinta manera a ejemplares de una misma especie leñosa según el tamaño del individuo y las condiciones del microambiente, entre otros factores. Esto tiene implicancias en la estructuración de los paisajes forestales, ya que la velocidad a la que se recupera el bosque depende, en parte, de la severidad con la cual el fuego afecta a los individuos leñosos. Nos propusimos analizar cómo el tamaño y el microambiente afectan el nivel de daño por fuego y la supervivencia en dos especies leñosas características del bosque chaqueño serrano, en un gradiente altitudinal en las Sierras de Córdoba (Argentina). Estudiamos dos incendios que ocurrieron entre julio y agosto de 2007. Seleccionamos 163 espinillos (Vachellia caven) y 48 molles (Lithraea molleoides) localizados entre 800 y 1700 m s. n. m. Para cada individuo estimamos la altura y el volumen pre-fuego en base al leño remanente, y características del microambiente como cobertura vegetal, proporción de roca bajo la copa, pendiente, orientación de la ladera e insolación por intercepción. Tres meses después estimamos el daño por fuego y tres años más tarde evaluamos la supervivencia. Los espinillos con más vegetación en su ambiente circundante sufrieron más daño por el fuego, y este efecto fue más pronunciado a menores altitudes. Además, los ejemplares de las laderas sur con mucha pendiente sufrieron más daño que los de las laderas norte, y los individuos más pequeños resultaron más dañados que los grandes. Los molles más altos sufrieron menos daño por fuego que los más bajos. El 94% de los espinillos y el 92% de los molles sobrevivieron al incendio, y, en el caso del espinillo, la probabilidad de morir fue mayor para los ejemplares más pequeños. Concluimos que el sistema se vuelve menos susceptible al fuego a medida que avanza la sucesión, al aumentar el tamaño de los individuos y disminuir la cobertura herbácea.[Palabras clave: altitud, altura del árbol, bosque serrano, cobertura vegetal, espinillo, incendios, molle, pendiente, rocosidad, Sierras de Córdoba] ABSTRACT. Tree size and microenvironment affect fire damage and survival in Chaco Serrano. Wildfires differentially affect specimens of the same woody species, depending, among other factors, on tree size and microenvironment. This has implications for the structuring of forest landscapes, as forest recovery depends, in part, on the severity of fire on woody specimens. We aimed at analyzing how microenvironment and tree size affect fire damage and survival in two woody species common in the Chaco Serrano forest, along an altitudinal gradient in Córdoba Mountains (Argentina). We studied two wildfires that occurred in July and August 2007. We selected 163 espinillos (Vachellia caven) and 48 molles (Lithraea molleoides) located between 800 and 1700 m a. s. l. For each individual, we estimated pre-fire height and volume on the basis of the remaining woody tissues, and microenvironmental characteristics as plant cover, rock proportion under the crown, slope, aspect and insolation by in...

Soil organic carbon (SOC) content supports several ecosystem services. Quantifying SOC requires: (i) accurate C estimates of forest components, and (ii) soil estimates. However, SOC is difficult to measure, so predictive models are needed. Our objective was to model SOC stocks within 30 cm depth in Patagonian forests based on climatic, topographic and vegetation productivity measures from satellite images, including Dynamic Habitat Indices and Land Surface Temperature derived from Landsat-8. We used data from 1320 stands of different forest types in Patagonia, and random forest regression to map SOC. The model captured SOC variability well (R² = 0.60, RMSE = 22.1%), considering the huge latitudinal extension (36.4° to 55.1° SL) and the great diversity of forest types. Mean SOC was 134.4 ton C ha−1 ± 25.2, totaling 404.2 million ton C across Patagonia. Overall, SOC values were highest in valleys of the Andes mountains and in southern Tierra del Fuego, ranging from 53.5 to 277.8 ton C ha−1 for the whole Patagonia region. Soil organic carbon is a metric relevant to many applications, connecting major issues such as forest management, conservation, and livestock production, and having spatially explicit estimates of SOC enables managers to fulfil the international agreements that Argentina has joined.

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