4,453 research outputs found
Caracterización de la fenología de Fagus sylvatica L. en poblaciones mediterráneas del Sistema Central español mediante datos Landsat OLI/ETM+ y Sentinel-2A/B
[EN] The Spanish Central Range hosts some of the southernmost populations of Fagus sylvatica L. (European beech). Recent cartography indicates that these populations are expanding, going up-streams and gaining ground to oak forests of Quercus pyrenaica Willd., heather-lands, and pine plantations. Understanding the spectral phenology of European beech populations—which leaf flush occurs earlier than other vegetation formations—in this Mediterranean mountain range will provide insights of the species recent dynamics, and will enable modelling its performance under future climate oscillations. Intra-annual series of 211 Landsat OLI/ETM+ images, acquired between April 2013-December 2019, and 217 Sentinel-2A/B images, acquired between April 2017-December 2019, were employed to characterize the spectral phenology of European beech populations and five other vegetation types for comparison in an area of 108000 ha. Vegetation indices (VI) including the Normalized Difference Vegetation Index (NDVI) and Tasseled Cap Angle (TCA) from Landsat, and the NDVI and Enhanced Vegetation Index (EVI) from Sentinel-2 were retrieved from sample pixels. The temporal series of these VI were modelled with Savitzky-Golay and double logistic functions, and assessed with TIMESAT software, enabling the parametric characterization of European beech spectral phenology in the area with the start, length, and end of season, as well as peak time and value. The length of beech phenological season was similar when portrayed by Landsat and Sentinel-2 NDVI time series (214 and 211 days on average for the common period 2017-2019) although start and end differed. Compared with NDVI counterparts the TCA season started and peaked later, and the EVI season was shorter. Sentinel-2 NDVI peaked higher than Landsat NDVI. The European beech had an earlier (21 days on average) start of season than competing oak forests. Joint analysis of data from the virtual constellation Landsat/ Sentinel-2 and calibration with field observations may enable more detailed knowledge of phenological traits at the landscape scale.[ES] Algunas de las poblaciones más meridionales de Fagus sylvatica L. (haya) se encuentran en el Sistema Central español. La cartografía reciente de estas poblaciones indica que están expandiéndose a lo largo de arroyos y ganando terreno a robledales de Quercus pyrenaica Willd., brezales, y pinares. Conocer la fenología espectral de estos hayedos mediterráneos de montaña, cuya apertura de hojas se adelanta a la de otras formaciones vegetales permitiría inferir su dinámica reciente y modelizar su comportamiento frente a futuras oscilaciones climáticas. Se utilizaron 211 imágenes Landsat OLI/ETM+ adquiridas entre abril 2013-diciembre 2019 y 217 imágenes Sentinel-2A/B adquiridas entre abril 2017-diciembre 2019 para caracterizar la fenología espectral de hayedos y otras cinco formaciones vegetales en 108000 ha. Se calcularon y analizaron índices de vegetación: Normalized Difference Vegetation Index (NDVI) y Tasseled Cap Angle (TCA) con datos Landsat, NDVI y Enhanced Vegetation Index (EVI) con Sentinel-2. Se extrajeron las series temporales de estos índices en píxeles muestra para analizar mediante software TIMESAT, ajustando modelos Savitzky-Golay y función logística, y describiendo paramétricamente la fenología espectral: inicio, fin, y duración de temporada, así como momento y valor máximo del índice. Las series NDVI de Landsat y Sentinel-2 representaron una duración similar de la temporada fenológica (214 y 211 días para el periodo común de análisis, 2017-2019), aunque inicio y fin no coincidieron. Comparando con las curvas NDVI homólogas, la temporada TCA comenzó y alcanzó el pico máximo antes, y la temporada EVI fue más corta. Los valores máximos de NDVI en las series Sentinel-2 fueron más altos que los de Landsat. Los hayedos comenzaron la temporada fenológica de media 21 días antes que los robledales. El análisis conjunto de datos de la constelación virtual Landsat/Sentinel-2 y la calibración con observaciones de campo permitirá conocer mejor la fenología a escala de paisaje.This work was funded by the Spanish Ministry of Science, Innovation and University through projects: AGL2013-46028-R “Forest manage-ment facing the change in forest ecosystems dynamics: a multiscale approach (SCALyFOR)” and AGL201676769-C2-1-R “Influence of nat-ural disturbance regimes and management on forests dynamics, structure and carbon balance (FORESTCHANGE)”. Field work assistance by Diego Galán, Belén Oñate, and Gregorio Cerezo, and the support of José Juárez Benítez, director of the Sierra Norte de Guadalajara Natural Park are much appreciated.Gómez, C.; Alejandro, P.; Montes, F. (2020). Phenological characterization of Fagus sylvatica L. in Mediterranean populations of the Spanish Central Range with Landsat OLI/ETM+ and Sentinel-2A/B. Revista de Teledetección. 0(55):71-80. https://doi.org/10.4995/raet.2020.13561OJS7180055Augspurger, C.K. 2013. Reconstructing patterns of temperature, phenology, and frost damage over 124 years: Spring damage risk is increasing. Ecology 94, 41-50. https://doi.org/10.1890/12-0200.1Bolton, D.K., Gray, J.M, Melaas, E.K., Moon, M., Eklundh, L., Friedl, M.A. 2020. Continental-scale land surface phenology from harmonized Landsat 8 and Sentinel-2 imagery, Remote Sensing of Environment, 240, 111685. https://doi.org/10.1016/j.rse.2020.111685Bucha T, Koren, M. 2017. Phenology of the beech forests in the Western Carpathians from MODIS for 2000-2015. iForest (Biosciences and Forestry), 10, 537-546. https://doi.org/10.3832/ifor2062-010Crist, E.P. 1985. A TM Tasseled Cap equivalent transformation for reflectance factor data. Remote Sensing of Environment, 17, 301-306. https://doi.org/10.1016/0034-4257(85)90102-6Delhon, C., Thiébault, S. 2005. The migration of beech (Fagus sylvatica L.) up the Rhone: the Mediterranean history of a "mountain" species. Veget. Hist. Archaeobot., 14, 119-132. https://doi.org/10.1007/s00334-005-0068-9Dittmar, C., Elling, W. 2006. Phenological phases of common beech (Fagus sylvatica L.) and their dependence on region and altitude in Southern Germany. European Journal of Forest Research, 125, 181-188. https://doi.org/10.1007/s10342-005-0099-xDrusch, M., Del Bello, U., Carlier, S., Colin, O., Fernández, V., Gascon, F., Hoesrch, B., Isola, C., Labertini, P., Marimort, P., Meygret, A., Spoto, F., Sya, O., Marchese, F., Bargellini, P. 2012. Sentinel-2: ESA's optical high-resolution mission for GMES operational services. Remote Sensing of Environment, 120, 25-36. https://doi.org/10.1016/j.rse.2011.11.026Eklundh, L., Jönsson, P. 2017. Timesat 3.3 Software Manual, Lund and Malmö University, Sweden.Fang, J., Lechovicz, M.J. 2006. Climatic limits for the present distribution of beech (Fagus L.) species in the world. Journal of Biogeography, 33, 1804-1819. https://doi.org/10.1111/j.1365-2699.2006.01533.xFu, Y.H., Piao S., Op de Beeck, M.O., Cong, N., Zhao, H., Zhang, Y., Menzel, A., Janssens, I.A., 2014. Recent spring phenology shifts in western Central Europe based on multiscale observations. Global Ecology and Biogeography, 23(11), 1255-1263. https://doi.org/10.1111/geb.12210Gerard F.F., George, C.T., Hayman, G., Chavana- Bryant, C., Weedon, G.P. 2020. Leaf phenology amplitude derived from MODIS NDVI and EVI: maps of leaf phenology synchrony for Meso- and South America. Geosciences Data Journal, 00, 1-14. https://doi.org/10.1002/gdj3.87Gao, B.C. 1996. NDWI-A normalized difference water index for remote sensing of vegetation liquid water from space. Remote Sensing of Environment, 58(3), 257-266. https://doi.org/10.1016/S0034-4257(96)00067-3Gil, L., Náger, J.A., Aranda-García, I., González- Doncel, I., Gonzalo-Jiménez, J., López de Heredia, U., Millerón, M., Nanos, N., Perea García-Calvo, R., Rodríguez-Calcerrada, J., Valbuena-Carabaña, M. 2010. El Hayedo de Montejo: una gestión sostenible. Dirección General del Medio Ambiente, Spain, 151 pp.Gómez, C., Alejandro, P., Aulló-Maestro, I., Hernández, L., Sánchez de Dios, R., Sainz-Ollero, H., Velázquez, J.C., Montes, F. 2019. Presence of European beech in its Spanish southernmost limit characterized with Landsat intra-annual time series. Proceedings of the AIT 2018, IX Conference of the Italian Society of Remote Sensing.Gonzalo, J. 2010. Diagnosis fitoclimática de la España peninsular. Hacia un modelo de clasificación funcional de la vegetación y de los ecosistemas peninsulares españoles. Serie Técnica: Naturaleza y Parques Nacionales. Ministerio de Medio Ambiente y Medio Rural y Marino. Organismo Autónomo Parques Nacionales.Herrera, S., Gutiérrez, J.M., Ancell, R., Pons, M.R., Frías, M.D., Fernández, J. 2012. Development and Analysis of a 50 year high-resolution daily gridded precipitation dataset over Spain (Spain02). International Journal of Climatology, 32, 74-85. https://doi.org/10.1002/joc.2256Houston Durrant, T., de Rigo, D., Candullo, G. 2016. Fagus sylvatica and other beeches in Europe: distribution, habitat, usage and threats in San Miguel Ayanz, J., de Rigo, D., Candullo, G., Houston Durrant, T., Mauri, A. (eds.) European Atlas of Forest Tree Species. Publication Office of the European Union, Luxembourg, pp.e012b90Jönsson, P., Cai., Z., Melaas, E., Friedl, M., Eklundh, L. 2018. A method for robust estimation of vegetation seasonality from Landsat and Sentinel-2 time series data. Remote Sensing, 10, 365. https://doi.org/10.3390/rs10040635Li, J., Roy, D.P. 2017. A global analysis of Sentinel- 2A, Sentinel-2B and Landsat-8 data revisit intervals and implications for terrestrial monitoring. Remote Sensing, 9, 902. https://doi.org/10.3390/rs9090902Liu, H.Q., Huete, A.R. 1995. A feedback based modification of the NDVI to minimize canopy background and atmospheric noise. IEEE Transactions on Geoscience and Remote Sensing, 33, 457-465. https://doi.org/10.1109/TGRS.1995.8746027Melaas, E.K., Friedl, M.A., Zhu, Z. 2013. Detecting interannual variation in deciduous broadleaf forest phenology using Landsat TM/ETM+ data. Remote Sensing of Environment, 132, 176-185. https://doi.org/10.1016/j.rse.2013.01.011Melaas, E.K., Sulla-Menashe, D., Gray, J.M., Black, T.A., Morin, T.H., Andrew, D.R., Friedl, M.A. 2016. Multisite analysis of land surface phenology in North American temperate and boreal deciduous forests from Landsat. Remote Sensing of Environment, 186, 452-464. https://doi.org/10.1016/j.rse.2016.09.014Powell, S.L., Cohen, W.B., Healey, S.P., Kennedy, R.E., Moisen, G.G., Pierce, K.B., Ohmann, J.L. 2010. Quantification of live aboveground biomass dynamics with Landsat time-series and field inventory data: a comparison of empirical modeling approaches. Remote Sensing of Environment, 114, 1053-1068. https://doi.org/10.1016/j.rse.2009.12.018Rubio-Cuadrado, A., Camarero, J.J., Del Río, M., Sánchez-González, M., Ruiz-Peinado, R., Bravo- Oviedo, A., Gil, L., Montes, F. 2018. Long-term impacts of drought on growth and forest dynamics in a temperate beech-oak-birch forest. Agricultural and Forest Meteorology, 259, 48-59. https://doi.org/10.1016/j.agrformet.2018.04.015Ruiz-Labourdette, D., Nogués-Bravo, D., Sainz- Ollero, H., Schmitz, M.F., Pineda, F.D. 2012. Forest composition in Mediterranean mountains is projected to shift along the entire elevational gradient under climate change. Journal of Biogeography, 39, 162-176. https://doi.org/10.1111/j.1365-2699.2011.02592.xSánchez de Dios, R., Hernández, L., Montes, F., Sainz- Ollero, H., Cañellas, I. 2016. Tracking the leading edge of Fagus sylvatica in North-Western Iberia: Holocene migration inertia, forest succession and recent global change. Perspectives in Plant Ecology, Evolution and Systematics, 20, 11-21. https://doi.org/10.1016/j.ppees.2016.03.001Sánchez de Dios, R., Gómez, .C, Aulló, I., Cañellas, I., Gea-Izquierdo, G., Montes, F., Sain-Ollero, H., Velázquez, J.C., Hernández, L. 2020. Fagus sylvatica L. peripheral populations in the Mediterranean Iberian Peninsula: climatic or anthropic relicts? Ecosystems. https://doi.org/10.1007/s10021-020-00513-8Stanimirova, R., Cai, Z., Melaas, E.K., Gray, J.M., Eklundh, L., Jönsson, P., Friedl, M.A. 2019. An empirical assessment of the MODIS land cover dynamics and TIMESAT land surface phenology algorithms. Remote Sensing, 11, 2201. https://doi.org/10.3390/rs11192201Tucker, C.J. 1979. Red and photographic infrared linear combinations for monitoring vegetation. Remote Sensing of Environment, 8(2), 127-150. https://doi.org/10.1016/0034-4257(79)90013-0Van Rossum, G., Drake, F.L., 2009. Python 3 reference manual. Soho Books. Scotts Valley, CA, USA. 244 pp.Wulder, M.A., et al. 2019. Current status of Landsat program, science, and applications. Remote Sensing of Environment, 225, 127-147. https://doi.org/10.1016/j.rse.2019.02.015Zeng, L., Wardlow B.D., Xiang, D., Hu, S., Li, D. 2020. A review of phenological metrics extraction using time-series, multispectral data. Remote Sensing of Environment, 237, 111511. https://doi.org/10.1016/j.rse.2019.11151
Search for associations containing young stars (SACY) VII. New stellar and substellar candidate members in the young associations
The young associations offer us one of the best opportunities to study the
properties of young stellar and substellar objects and to directly image
planets thanks to their proximity (200 pc) and age (5-150 Myr).
However, many previous works have been limited to identifying the brighter,
more active members (1 M) owing to photometric survey
sensitivities limiting the detections of lower mass objects. We search the
field of view of 542 previously identified members of the young associations to
identify wide or extremely wide (1000-100,000 au in physical separation)
companions. We combined 2MASS near-infrared photometry (, , ) with
proper motion values (from UCAC4, PPMXL, NOMAD) to identify companions in the
field of view of known members. We collated further photometry and spectroscopy
from the literature and conducted our own high-resolution spectroscopic
observations for a subsample of candidate members. This complementary
information allowed us to assess the efficiency of our method. We identified 84
targets (45: 0.2-1.3 M, 17: 0.08-0.2 M, 22: 0.08 M)
in our analysis, ten of which have been identified from spectroscopic analysis
in previous young association works. For 33 of these 84, we were able to
further assess their membership using a variety of properties (X-ray emission,
UV excess, H, lithium and K I equivalent widths, radial velocities,
and CaH indices). We derive a success rate of 76-88% for this technique based
on the consistency of these properties. Once confirmed, the targets identified
in this work would significantly improve our knowledge of the lower mass end of
the young associations. Additionally, these targets would make an ideal new
sample for the identification and study of planets around nearby young stars.Comment: 28 pages, 24 figures, accepted in A&
Ecological design of a crayfishing program to control population density of the invasive species Procambarus Clarkii in Doñana National Park freshwater marsh (Spain)
The exploitation of Procambarus clarkii in Doñana National Park’s freshwater marsh (DNP) has been economically important to the local human population since the 1970s. The high density of this crayfish species has been causing a major environmental impact in the Park by the substantial reduction of submerging aquatic macrophytes prairies due to its broad trophic spectrum and feeding habits, which turned the environmental frame (consisting in clear water equilibrium) into a turbid water balance. Differences in population dynamics of three population groups of P. clarkii in the DNP freshwater marsh were compared and analyzed from a fishery perspective. The objective is to reduce their ecological impact using optimal crayfishing management. Maximum growth curves showed that crayfish have different growth optimums. Recruitment of young crayfish varies between different populations; when there is an excessive increase in the density of juveniles in a population and conditions are stressful, their growth is deficient. If these conditions persist, the population could become stunted. Fishery for commercial gain is banned in DNP; however, a model of fisheries program aimed at controlling the excess population of crayfish can be effective in halting the ecological impact of this invasive species while providing an opportunity for poachers to have viable productive options. The model proposed can help to solve the problem of crayfish “poaching” through the legalization and strict control of harvesting practicesPedro J. Gutiérrez-Yurrita also thanks the ICI (Spain) for a subvention grant and CONACyT (México) for a financial complement of the former grant that enabled him to complete this researc
Quantization of massive scalar fields over static black string backgrounds
The renormalized mean value of the corresponding components of the
Energy-Momentum tensor for massive scalar fields coupled to an arbitrary
gravitational field configuration having cylindrical symmetry are analytically
evaluated using the Schwinger-DeWitt approximation, up to second order in the
inverse mass value. The general results are employed to explicitly derive
compact analytical expressions for the Energy-Momentum tensor in the particular
background of the Black-String spacetime. In the case of the Black String
considered in this work, we proof that a violation of the weak energy condition
occur at the horizon of the space-time for values of the coupling constant,
that include as particular cases the most interesting of minimal and conformal
coupling.Comment: 4 page
Don't Thrash: How to Cache Your Hash on Flash
This paper presents new alternatives to the well-known Bloom filter data
structure. The Bloom filter, a compact data structure supporting set insertion
and membership queries, has found wide application in databases, storage
systems, and networks. Because the Bloom filter performs frequent random reads
and writes, it is used almost exclusively in RAM, limiting the size of the sets
it can represent. This paper first describes the quotient filter, which
supports the basic operations of the Bloom filter, achieving roughly comparable
performance in terms of space and time, but with better data locality.
Operations on the quotient filter require only a small number of contiguous
accesses. The quotient filter has other advantages over the Bloom filter: it
supports deletions, it can be dynamically resized, and two quotient filters can
be efficiently merged. The paper then gives two data structures, the buffered
quotient filter and the cascade filter, which exploit the quotient filter
advantages and thus serve as SSD-optimized alternatives to the Bloom filter.
The cascade filter has better asymptotic I/O performance than the buffered
quotient filter, but the buffered quotient filter outperforms the cascade
filter on small to medium data sets. Both data structures significantly
outperform recently-proposed SSD-optimized Bloom filter variants, such as the
elevator Bloom filter, buffered Bloom filter, and forest-structured Bloom
filter. In experiments, the cascade filter and buffered quotient filter
performed insertions 8.6-11 times faster than the fastest Bloom filter variant
and performed lookups 0.94-2.56 times faster.Comment: VLDB201
Biomasa de macrófitos acuáticos en la marisma del Parque Nacional de Doñana (SW España): importancia y factores ambientales que controlan su distribución
Hot Jupiters and Hot Spots: The Short- and Long-term Chromospheric Activity on Stars with Giant Planets
We monitored the chromospheric activity in the Ca II H & K lines of 13
solar-type stars (including the Sun); 8 of them over three years at the CFHT
and 5 in a single run at the VLT. Ten of the 13 targets have close planetary
companions. All of the stars observed at the CFHT show long-term (months to
years) changes in H & K intensity levels. Four stars display short-term (days)
cyclical activity. For two, HD 73256 and kappa^1 Ceti, the activity is likely
associated with an active region rotating with the star, however, the flaring
in excess of the rotational modulation may be associated with a hot jupiter. A
planetary companion remains a possibility for kappa^1 Ceti. For the other two,
HD 179949 and upsilon And, the cyclic variation is synchronized to the hot
jupiter's orbit. For both stars this synchronicity with the orbit is clearly
seen in two out of three epochs. The effect is only marginal in the third epoch
at which the seasonal level of chromospheric activity had changed for both
stars. Short-term chromospheric activity appears weakly dependent on the mean
K-line reversal intensities for the sample of 13 stars. Also, a suggestive
correlation exists between this activity and the M_p sin(i) of the star's hot
jupiter. Because of their small separation (<= 0.1 AU), many of the hot
jupiters lie within the Alfv\'en radius of their host stars which allows a
direct magnetic interaction with the stellar surface. We discuss the conditions
under which a planet's magnetic field might induce activity on the stellar
surface and why no such effect was seen for the prime candidate, tau Boo. This
work opens up the possibility of characterizing planet-star interactions, with
implications for extrasolar planet magnetic fields and the energy contribution
to stellar atmospheres.Comment: Accepted to the Astrophysical Journal; 39 pages including 17 figure
Espectroscopia de emissão óptica com plasma induzido por laser: um novo e versátil caminho para análise e monitoramento de solos, plantas e adubos.
Is there an integrative center in the vertebrate brain-stem? A robotic evaluation of a model of the reticular formation viewed as an action selection device
Neurobehavioral data from intact, decerebrate, and neonatal rats, suggests that the reticular formation provides
a brainstem substrate for action selection in the vertebrate central nervous system. In this article, Kilmer,
McCulloch and Blum’s (1969, 1997) landmark reticular formation model is described and re-evaluated, both in
simulation and, for the first time, as a mobile robot controller. Particular model configurations are found to
provide effective action selection mechanisms in a robot survival task using either simulated or physical robots.
The model’s competence is dependent on the organization of afferents from model sensory systems, and a genetic
algorithm search identified a class of afferent configurations which have long survival times. The results support
our proposal that the reticular formation evolved to provide effective arbitration between innate behaviors
and, with the forebrain basal ganglia, may constitute the integrative, ’centrencephalic’ core of vertebrate brain
architecture. Additionally, the results demonstrate that the Kilmer et al. model provides an alternative form of
robot controller to those usually considered in the adaptive behavior literature
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