Estimación de la capacidad productiva de la estación en bosques secundarios costarricences

Site quality was assessed in four secondary forests dominated by the commercially important tree species Vochysia ferruginea in Northern Costa Rica. A variation of the site quality concept known as site form (i.e. the expected mean height at 25 cm dbh) was used. Twenty-nine sample plots (20 × 20 m) were installed covering soil and topographic variation within and between sites. Site form was estimated for each plot using a linear model. The site form estimations show a high variation between plots (from 16.2 m to 32.2 m), which could indicate large variation in site productivity. Site form of V. ferruginea was significantly correlated with total stand basal area of all species, which supports the potential value of site form as an indicator of site productivity. Twenty-six physical and chemical soil variables showed significant correlation with site form. Adjusted multiple regression models of site form on soil variables were fitted by stepwise regression analysis (forward selection method). The best fit was obtained using only the percentage of sand at 12-30 cm as the independent variable (r2 = 59.3%, s.e.= 3.0 m). The results of this study suggest that site form appears to be a potentially useful indicator of site quality in broadleaved neotropical secondary rainforests when age is unknown.En el presente artículo se presentan los resultados de la evaluación de la calidad de la estación en cuatro bosques secundarios dominados por Vochysia ferruginea en Costa Rica. Como índice de la capacidad productiva de la estación se utilizó el índice de forma (i.e. la altura media esperada a un diámetro a la altura del pecho de 25 cm). Con tal fin se instalaron en campo 29 parcelas (20 × 20 m) de forma tal que cubrieran el rango de variabilidad edáfica y topográfica presente en el área de estudio. El índice de forma presentó una alta variabilidad entre parcelas (entre 16,2 m y 32,2 m), lo cual indica una importante variación en términos de productividad de la estación. El índice de forma de V. ferruginea resultó correlacionado significativamente con el área basimétrica de todas las especies, así como con 26 variables del suelo, quedando entonces respaldado el valor del índice de forma como indicador del rodal de la productividad. Se han ajustado modelos de regresión múltiple entre el índice de forma y las variables edáficas, utilizado el método de inclusión de variable paso a paso. El mejor ajuste se obtuvo al incluir únicamente como variable explicativa el porcentaje de arena en el suelo a una profundidad entre 12-30 cm (r2 = 59,3%, e.e. = 3,0 m). Los resultados del trabajo muestran la potencialidad del índice de forma como indicador de la calidad de estación en los bosques secundarios húmedos neotropicales cuando la edad no es conocida

Identification and quantification of drivers of forest degradation in tropical dry forests: a case study in Western Mexico

The intensity of forest degradation is linked to landowners' decisions on management of their shifting cultivation systems. Understanding the processes involved in this land use type is therefore essential for the design of sustainable forest management practices. However, knowledge of the processes and patterns of forest transition that result from this practice is extremely limited. In this study, we used spatially-explicit binary logistic regression to study the proximate factors that relate to forest degradation by combining biophysical and socio-economic variables. Our study region is within the Ayuquila Basin, in Western Mexico, a typical fragmented tropical dry forest landscape dominated by shifting cultivation. Through a survey and semi-structured interviews with community leaders, we obtained data on the forest resources and on the uses that people make of them. Detailed forest cover maps for 2004 and 2010 were produced from high-resolution SPOT 5 data, and ancillary geographical data were used to extract spatial variables. The degree of social marginalization of each community and the ratio of forest area to population size were the main factors positively correlated with the probability of the occurrence of forest degradation. Livestock management and use of fence posts by the communities were also positively associated with forest degradation. Among biophysical factors, forest degradation is more likely to occur in flatter areas. We conclude that local drivers of forest degradation include both socioeconomic and physical variables and that both of these factors need to be addressed at the landscape level while developing measures for activities related to REDD+. (C) 2015 Elsevier Ltd. All rights reserved

Cortical iron accumulation in MAPT- and C9orf 72-associated frontotemporal lobar degeneration

Neuroinflammation has been implicated in frontotemporal lobar degeneration (FTLD) pathophysiology, including in genetic forms with microtubule-associated protein tau (MAPT) mutations (FTLD-MAPT) or chromosome 9 open reading frame 72 (C9orf72) repeat expansions (FTLD-C9orf72). Iron accumulation as a marker of neuroinflammation has, however, been understudied in genetic FTLD to date. To investigate the occurrence of cortical iron accumulation in FTLD-MAPT and FTLD-C9orf72, iron histopathology was performed on the frontal and temporal cortex of 22 cases (11 FTLD-MAPT and 11 FTLD-C9orf72). We studied patterns of cortical iron accumulation and its colocalization with the corresponding underlying pathologies (tau and TDP-43), brain cells (microglia and astrocytes), and myelination. Further, with ultrahigh field ex vivo MRI on a subset (four FTLD-MAPT and two FTLD-C9orf72), we examined the sensitivity of T2*-weighted MRI for iron in FTLD. Histopathology showed that cortical iron accumulation occurs in both FTLD-MAPT and FTLD-C9orf72 in frontal and temporal cortices, characterized by a diffuse mid-cortical iron-rich band, and by a superficial cortical iron band in some cases. Cortical iron accumulation was associated with the severity of proteinopathy (tau or TDP-43) and neuronal degeneration, in part with clinical severity, and with the presence of activated microglia, reactive astrocytes and myelin loss. Ultra-high field T2*-weighted MRI showed a good correspondence between hypointense changes on MRI and cortical iron observed on histology. We conclude that iron accumulation is a feature of both FTLD-MAPT and FTLD-C9orf72 and is associated with pathological severity. Therefore, in vivo iron imaging using T2*-weighted MRI or quantitative susceptibility mapping may potentially be used as a noninvasive imaging marker to localize pathology in FTLD.</p

Deforestation: Correlations, Possible Causes and Some Implications

Changes in national forest areas during 1990-2000 are contrasted with other variables to illustrate correlations and provoke discussion about possible causes. Twenty-five statistically-significant correlations (including rural population, life expectancy, GDP, literacy, commerce, agriculture, poverty and inflation) are illustrated and a statistical model suggests that good governance, alternative employment opportunities, and payments for environmental services may be effective in combating deforestation. The data suggest that a global forest convention may need to be supported by substantial and carefully-targeted development assistance to foster good governance

Outlining multi-purpose forest inventories to assess the ecosystem approach in forestry

A summary and discussion of selected published results on the current and potential role of forest inventories (with particular reference to the national ones) are presented in the light of the challenges posed by society and policy decisions in the environmental sector. The analysis concentrates mainly on the ecological and socio-economic aspects of the question and on forest inventories’ potential contribution to achieving sustainable forest management.L'articolo è diponibile sul sito dell'editore wwww.tandf.co.uk/journals