Modelo de masa incorporada en pinares mediterráneos: un caso de estudio en rodales de pino silvestre (Pinus sylvestris L.) y pino negral (Pinus pinister Ait.) en España

National Forest Inventories (NFI) are a basic tool for forestry planning at the National level. A new two-step system for predicting ingrowth compatible with NFI data is presented in order to improve long-term estimation of stand condition. In growth and yield models, an ingrowth submodel is a key feature for long-term estimation. An accurate projection of ingrowth is needed to avoid model projection bias and inaccuracy. A two-step approach was used, which consisted of (I) estimating the probability of ingrowth occurrence on a sample plot and (II) quantifying the ingrowth in terms of basal area. Logistic regression was used for step 1, while linear regression was used for step 2. A good performance of the joint ingrowth model for Scots pine (Pinus sylvestris L.) and Mediterranean Maritime pine (Pinus pinaster AiSsp mesogeensis) stands was observed. Logistic model include quadratic mean diameter as independent variables for both species while basal area is only included for Mediterranean Maritime. Quadratic mean diameter is the only independent variable in linear model for both species. The presented two-step modeling methodology for ingrowth is applicable to data from National Forest Inventories with concentric plots.Los Inventarios Forestales Nacionales (IFN) son un instrumento básico para la planificación forestal a nivel nacional. Con el objeto de predecir la masa incorporada, se presenta un nuevo sistema bietápico compatible con los datos del IFN para de esta forma mejorar las estimaciones a largo plazo. En los modelos de crecimiento y producción, un modelo de masa incorporada es clave para la proyección a largo plazo dado que se precisa una adecuada estimación de la masa incorporada para evitar sesgos e imprecisiones. Se utilizó un método bietápico basado en (I) estimar la probabilidad de presencia de masa incorporada en la parcela y (II) cuantificar la masa incorporada en área basimétrica. Para el paso 1 se utilizó la regresión logística mientras que para el paso 2 se utilizó regresión lineal. Se observó un buen comportamiento del modelo conjunto tanto para pino silvestre (Pinus sylvestris L.) como para pino negral (Pinus pinaster AiSsp mesogeensis). El modelo logístico incluye el diámetro medio cuadrático como variable independiente para ambas especies mientras que el área basimétrica solo es significativa en el caso del pino negral. En el modelo lineal, el diámetro medio cuadrático es significativo para las dos especies. El método bietápico presentado para estimar la masa incorporada es aplicable a los datos de Inventarios Forestales Nacionales basados en parcelas concéntricas

Holographic Entanglement Entropy at Finite Temperature

Using a holographic proposal for the entanglement entropy we study its behavior in various supergravity backgrounds. We are particularly interested in the possibility of using the entanglement entropy as way to detect transitions induced by the presence horizons. We consider several geometries with horizons: the black hole in $AdS_3$, nonextremal Dp-branes, dyonic black holes asymptotically to $AdS_4$ and also Schwarzschild black holes in global $AdS_p$ coordinates. Generically, we find that the entanglement entropy does not exhibit a transition, that is, one of the two possible configurations always dominates.Comment: v3: 31 pp, ten figures, modified to match version accepted by IJMP

Cambios florísticos inducidos por los incendios en repoblaciones de Pinus sylvestris en el noroeste de España

The effects of wildfire on vegetation regeneration in the understory of stands dominated by Pinus sylvestris L. in north-west Spain were analysed. In order to study changes in the composition of this community, three study areas dominated by Pinus sylvestris L. and burned by a summer wildfire were selected. In each area three permanent plots of 25 × 1 m2 was established. The cover percentage of plant species present, and the cover of life forms and richness were analysed yearly from the first to the fourth year after fire. Total cover values generally increased throughout the study period. The species that appeared during the first years were those that would dominate in the mature stage, such as Erica australis L. and Pterospartum tridentatum (L.) Willk, both species being typical resprouters. Other species that appeared from the first year are typical seeders like Pinus sylvestris L. and Halimium alyssoides (Lam.) K. Koch. Floristic richness values showed higher values during the first year after fire than in the original situation, due to the fast recovery of the herbaceous species in the open spaces created by fire. After the first year changes in richness values were not significantLos efectos del fuego sobre la regeneración de las comunidades vegetales en plantaciones de Pinus sylvestris L. en el noroeste de España han sido analizados. Para analizar los cambios en la composición y estructura de este tipo de comunidades, se seleccionaron tres zonas de estudio en plantaciones de Pinus sylvestris L. y en ellas se seleccionaron áreas quemadas por un incendio de verano. En cada una de estas áreas se instalaron tres parcelas permanentes de 25 × 1 m2 donde se midió el porcentaje de cobertura por especies cada año desde un año hasta cuatro después del incendio. Los valores de cobertura total se incrementaron de forma gradual durante el periodo estudiado. Las especies que aparecen durante los primeros años son las que dominan en las etapas maduras, como Erica australis L. Pterospartum tridentatum (L.) Wilk. Otras especies que aparecen desde el primer año se regeneran obligatoriamente de semillas como Pinus sylvestris L. y Halimium alyssoides (Lam.) K. Koch. Los valores de riqueza florística encontrados en el primer año tras el incendio son mayores que los de la situación original debido a la rápida recuperación de las herbáceas en los espacios abiertos creados por el fuego. A partir del primer año los cambios en riqueza no fueron significativo

Global monopole, dark matter and scalar tensor theory

In this article, we discuss the space-time of a global monopole field as a candidate for galactic dark matter in the context of scalar tensor theory.Comment: 8 pages, Accepted in Mod. Phys. Lett.

A Kolmogorov-Zakharov Spectrum in AdSAdS Gravitational Collapse

We study black hole formation during the gravitational collapse of a massless scalar field in asymptotically $AdS_D$ spacetimes for $D=4,5$. We conclude that spherically symmetric gravitational collapse in asymptotically $AdS$ spaces is turbulent and characterized by a Kolmogorov-Zakharov spectrum. Namely, we find that after an initial period of weakly nonlinear evolution, there is a regime where the power spectrum of the Ricci scalar evolves as $\omega^{-s}$ with the frequency, $\omega$, and $s\approx 1.7\pm 0.1$.Comment: 5 pages, 4 figures. v2: Typos, other initial profile considered for universality, error analysis, close to PRL versio

The velocity field of baryonic gas in the universe

The dynamic evolution of the baryonic intergalactic medium (IGM) caused by the underlying dark matter gravity is governed by the Navier-Stokes equations in which many cooling and heating processes are involved. However, it has long been recognized that the growth mode dynamics of cosmic matter clustering can be sketched by a random force driven Burgers' equation if cooling and heating are ignored. Just how well the dynamics of the IGM can be described as a Burgers fluid has not been fully investigated probably because cooling and heating are essential for a detailed understanding of the IGM. Using IGM samples produced by a cosmological hydrodynamic simulation in which heating and cooling processes are properly accounted for, we show that the IGM velocity field in the nonlinear regime shows the features of a Burgers fluid, that is, when the Reynolds number is high, the velocity field consists of an ensemble of shocks. Consequently, (1) the IGM velocity $v$ is generally smaller than that of dark matter; (2) for the smoothed field, the IGM velocity shows tight correlation with dark matter given by $v \simeq s v_{dm}$, with $s<1$, such that the lower the redshift, the smaller $s$; (3) the velocity PDFs are asymmetric between acceleration and deceleration events; (4) the PDF of velocity difference $\Delta v=v(x+r)-v(x)$ satisfies the scaling relation for a Burgers fluid, i.e., $P(\Delta v)=(1 r^y)F(\Delta v/r^y)$. We find the scaling function and parameters for the IGM which are applicable to the entire scale range of the samples (0.26 - 8 h$^{-1}$ Mpc). These properties show that the similarity mapping between the IGM and dark matter is violated on scales much larger than the Jeans length of the IGM.Comment: 14 pages, 10 jpg-figures, accepted for publication in the Astrophysical Journal. References adde

Zeta-function regularization of holographic Wilson loops

Using zeta-function regularization, we study the one-loop effective action of fundamental strings in AdS5 xS5 dual to the latitude 1/4-BPS Wilson loop in N=4 super-Yang-Mills theory. To avoid certain ambiguities inherent to string theory on curved backgrounds we subtract the effective action of the holographic 1/2-BPS Wilson loop. We find agreement with the expected field theory result at first order in the small latitude angle expansion but discrepancies at higher order.Fil: Aguilera Damia, Jeremías. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Faraggi, A.. Universidad Andrés Bello; ChileFil: Pando Zayas, L.. University of Michigan. Department of Physics; Estados UnidosFil: Rathee, V.. University of Michigan. Department of Physics; Estados UnidosFil: Silva, Guillermo Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentin

Glueball Regge trajectories from gauge/string duality and the Pomeron

The spectrum of light baryons and mesons has been reproduced recently by Brodsky and Teramond from a holographic dual to QCD inspired in the AdS/CFT correspondence. They associate fluctuations about the AdS geometry with four dimensional angular momenta of the dual QCD states. We use a similar approach to estimate masses of glueball states with different spins and their excitations. We consider Dirichlet and Neumann boundary conditions and find approximate linear Regge trajectories for these glueballs. In particular the Neumann case is consistent with the Pomeron trajectory.Comment: In this revised version we made some additional remarks on the text. We also included 2 more references. The glueball spectrum and Regge trajectories are unchanged. 10 pages, 2 eps figure