Modelos de producción de madera sólida en plantaciones de Eucalyptus globulus de Galicia

El objetivo de este trabajo es establecer las interacciones existentes entre crecimiento diametral, crecimiento en altura y la dinámica de poda natural de Eucalyptus globulus con el objetivo de evaluar la eficiencia de distintas opciones de gestión forestal para producir madera de alta calidad. Para ello se ha desarrollado un modelo de crecimiento basados en el árbol individual. La toma de muestras comprende más de 900 Eucalyptus globulus medidos en diferentes localizaciones de Galicia (España). En esos árboles se ha encontrado una elevada correlación significativa entre el diámetro normal y el diámetro de la copa. El modelo basado en el ancho de copa permite calcular el espacio vital requerido por un árbol para alcanzar un diámetro predefinido a una cierta edad. Una vez conocido, es también posible calcular el número de árboles por hectárea así como el momento y la intensidad de las claras. Se ha podido comprobar que los eucaliptos orientados a la producción de madera aserrada en rotaciones cortas tienen que podarse y, dada la tendencia de los árboles a incluir el tocón de las ramas muertas, es recomendable realizar la poda mientras las ramas todavía están verdes. Para optimizar la producción de madera limpia, es esencial conocer el impacto de los tratamientos silvícolas y condiciones de crecimiento en el proceso de formación de la base de la copa. Se ha encontrado que la altura de la base de copa viva muestra una buena correlación con el diámetro normal, la altura del árbol y la edad. Empleando estas tres variables se ha desarrollado un modelo multivariable para predecir la altura de la primera rama viva, que puede ser de utilidad para optimizar el momento y la intensidad de las claras para producir madera de sierra de eucalipto en plantaciones de corta rotación._________________________________The study aims to point out the interactions between diameter and height growth and the self-pruning dynamics of Eucalyptus globulus in order to evaluate different management regimes according to their efficiency for high value timber production. Therefore a growth model for individual trees has been developed. The database contains over 900 trees of Eucalyptus globulus measured at different sites in Galicia / Spain. For these trees a significant relationship between diameter at breast height (d1,3) and crown diameter calculated from this area was found. The crown width model enables us to calculate the growing space needed by a tree to get a pre-defined diameter at a given age. Knowing this, it is also possible to calculate the number of trees/ha as well as time and intensity of thinning interventions. It could be shown that eucalypt grown for sawlogs in short rotations have to be pruned. Since the trees tend to include dead branches partly into the bole, it is recommendable to prune branches when still green. In order to optimize production of knot free timber, it is essential to know the impact of silvicultural treatments and growth conditions on the process of living crown base recession. It was found that height of living crown base shows good correlations with d1,3, tree height and age. Using these 3 variables a multivariate model for predicting height of the first living branch has been developed, which may be helpful to optimize time and intensity of pruning for eucalypt sawlog production in short rotation plantations

The UNSW Extrasolar Planet Search: Methods and First Results from a Field Centred on NGC 6633

We report on the current status of the University of New South Wales Extrasolar Planet Search project, giving details of the methods we use to obtain millimagnitude precision photometry using the 0.5m Automated Patrol Telescope. We use a novel observing technique to optimally broaden the PSF and thus largely eliminate photometric noise due to intra-pixel sensitivity variations on the CCD. We have observed 8 crowded Galactic fields using this technique during 2003 and 2004. Our analysis of the first of these fields (centred on the open cluster NGC 6633) has yielded 49 variable stars and 4 shallow transit candidates. Follow-up observations of these candidates have identified them as eclipsing binary systems. We use a detailed simulation of our observations to estimate our sensitivity to short-period planets, and to select a new observing strategy to maximise the number of planets detected.Comment: 16 pages, 9 figures, version published in MNRAS Updated figures, references, and additional discussion in section

Observed Effect of Magnetic Fields on the Propagation of Magnetoacoustic Waves in the Lower Solar Atmosphere

We study Hinode/SOT-FG observations of intensity fluctuations in Ca II H-line and G-band image sequences and their relation to simultaneous and co-spatial magnetic field measurements. We explore the G-band and H-line intensity oscillation spectra both separately and comparatively via their relative phase differences, time delays and cross-coherences. In the non-magnetic situations, both sets of fluctuations show strong oscillatory power in the 3 - 7 mHz band centered at 4.5 mHz, but this is suppressed as magnetic field increases. A relative phase analysis gives a time delay of H-line after G-band of 20\pm1 s in non-magnetic situations implying a mean effective height difference of 140 km. The maximum coherence is at 4 - 7 mHz. Under strong magnetic influence the measured delay time shrinks to 11 s with the peak coherence near 4 mHz. A second coherence maximum appears between 7.5 - 10 mHz. Investigation of the locations of this doubled-frequency coherence locates it in diffuse rings outside photospheric magnetic structures. Some possible interpretations of these results are offered.Comment: 19 pages, 6 figure

A new detached K7 dwarf eclipsing binary system

We present an analysis of a new, detached, double-lined eclipsing binary system with K7 Ve components, discovered as part of the University of New South Wales Extrasolar Planet Search. The object is significant in that only 6 other binary systems are known with comparable or lower mass. Such systems offer important tests of mass-radius theoretical models. Follow-up photometry and spectroscopy were obtained with the 40-inch and 2.3m telescopes at SSO respectively. An estimate of the radial velocity amplitude from spectral absorption features, combined with the orbital inclination (83.5 deg) estimated from lightcurve fitting, yielded a total mass of M=(1.041 +/- 0.06)M_sun and component masses of M_A=(0.529 +/- 0.035)M_sun and M_B=(0.512 +/- 0.035)M_sun. The radial velocity amplitude estimated from absorption features (167 +/- 3)kmps was found to be less than the estimate from the H_alpha emission lines (175 +/- 1.5)kmps. The lightcurve fit produced radii of R_A=(0.641 +/- 0.05)R_sun and R_B=(0.608 +/- 0.06)R_sun, and a temperature ratio of T_B/T_A=0.980 +/- 0.015. The apparent magnitude of the binary was estimated to be V=13.9 +/- 0.2. Combined with the spectral type, this gave the distance to the binary as 169 +/- 14 pc. The timing of the secondary eclipse gave a lower limit on the eccentricity of the binary system of 0.0025 +/- 0.0005. This is the most statistically significant non-zero eccentricity found for such a system, possibly suggesting the presence of a third companion.Comment: 6 pages, published in MNRAS (08/2006

Properties of high-frequency wave power halos around active regions: an analysis of multi-height data from HMI and AIA onboard SDO

We study properties of waves of frequencies above the photospheric acoustic cut-off of $\approx$5.3 mHz, around four active regions, through spatial maps of their power estimated using data from Helioseismic and Magnetic Imager (HMI) and Atmospheric Imaging Assembly (AIA) onboard Solar Dynamics Observatory (SDO). The wavelength channels 1600 {\AA} and 1700 {\AA} from AIA are now known to capture clear oscillation signals due to helioseismic p modes as well as waves propagating up through to the chromosphere. Here we study in detail, in comparison with HMI Doppler data, properties of the power maps, especially the so called 'acoustic halos' seen around active regions, as a function of wave frequencies, inclination and strength of magnetic field (derived from the vector field observations by HMI) and observation height. We infer possible signatures of (magneto-)acoustic wave refraction from the observation height dependent changes, and hence due to changing magnetic strength and geometry, in the dependences of power maps on the photospheric magnetic quantities. We discuss the implications for theories of p mode absorption and mode conversions by the magnetic field.Comment: 22 pages, 12 figures, Accepted by journal Solar Physic