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Search Results: 1 - 10 of 215549 matches for " W. F. Laurance "
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Do species traits determine patterns of wood production in Amazonian forests?
T. R. Baker,O. L. Phillips,W. F. Laurance,N. C. A. Pitman
Biogeosciences Discussions , 2008,
Abstract: Understanding the relationships between plant traits and ecosystem properties at large spatial scales is important for predicting how compositional change will affect carbon cycling in tropical forests. Here, we examine the relationships between species wood density, maximum height and wood production for 60 Amazonian forest plots. Firstly, we examine how community-level species traits vary across Amazonia. Average species maximum height and wood density are low in western, compared to eastern, Amazonia and are negatively correlated with aboveground wood productivity and soil fertility. Secondly, we compare biomass growth rates across functional groups defined on the basis of these two traits. In similar size classes, biomass growth rates vary little between trees that differ in wood density and maximum height. However, biomass growth rates are generally higher in western Amazonia across all functional groups. Thirdly, we ask whether the data on the abundance and average biomass growth rates of different functional groups is sufficient to predict the observed, regional-scale pattern of wood productivity. We find that the lower rate of wood production in eastern compared to western Amazonia cannot be estimated on the basis of this information. Overall, these results suggest that the correlations between community-level trait values and wood productivity in Amazonian forests are not causative: direct environmental control of biomass growth rates appears to be the most important driver of wood production at regional scales. This result contrasts with findings for forest biomass where variation in wood density, associated with variation in species composition, is an important driver of regional-scale patterns. Tropical forest wood productivity may therefore be less sensitive than biomass to compositional change that alters community-level averages of these plant traits.
Do species traits determine patterns of wood production in Amazonian forests?
T. R. Baker, O. L. Phillips, W. F. Laurance, N. C. A. Pitman, S. Almeida, L. Arroyo, A. DiFiore, T. Erwin, N. Higuchi, T. J. Killeen, S. G. Laurance, H. Nascimento, A. Monteagudo, D. A. Neill, J. N. M. Silva, Y. Malhi, G. López Gonzalez, J. Peacock, C. A. Quesada, S. L. Lewis,J. Lloyd
Biogeosciences (BG) & Discussions (BGD) , 2009,
Abstract: Understanding the relationships between plant traits and ecosystem properties at large spatial scales is important for predicting how compositional change will affect carbon cycling in tropical forests. In this study, we examine the relationships between species wood density, maximum height and above-ground, coarse wood production of trees ≥10 cm diameter (CWP) for 60 Amazonian forest plots. Average species maximum height and wood density are lower in Western than Eastern Amazonia and are negatively correlated with CWP. To test the hypothesis that variation in these traits causes the variation in CWP, we generate plot-level estimates of CWP by resampling the full distribution of tree biomass growth rates whilst maintaining the appropriate tree-diameter and functional-trait distributions for each plot. These estimates are then compared with the observed values. Overall, the estimates do not predict the observed, regional-scale pattern of CWP, suggesting that the variation in community-level trait values does not determine variation in coarse wood productivity in Amazonian forests. Instead, the regional gradient in CWP is caused by higher biomass growth rates across all tree types in Western Amazonia. Therefore, the regional gradient in CWP is driven primarily by environmental factors, rather than the particular functional composition of each stand. These results contrast with previous findings for forest biomass, where variation in wood density, associated with variation in species composition, is an important driver of regional-scale patterns in above-ground biomass. Therefore, in tropical forests, above-ground wood productivity may be less sensitive than biomass to compositional change that alters community-level averages of these plant traits.
Efeitos de área e de borda sobre a estrutura florestal em fragmentos de floresta de terra-firme após 13-17 anos de isolamento
Nascimento, Henrique E. M.;Laurance, William F.;
Acta Amazonica , 2006, DOI: 10.1590/S0044-59672006000200008
Abstract: density and biomass of live trees >10 cm dbh and saplings 1-9.9 cm dbh, coarse woody debris (lcg diameter > 10 cm), fine woody debris (lcf diameter 2.5-9.9 cm), and standing dead trees (> 10 cm dbh) were quantified in 56 permanent, 1-ha sample plots. these plots are located in four 1- (4 plots), three 10- (12 plots) and two 100- (14 plots) forest fragments in size and nearby continuous forests (19 plots) as well as in two classes of distance from the edges - < 300 m (29 plots) and > 300 m (21 plots). density and biomass of primary species did not differ significantly among the four size categories and the two edge distance classes. however, forest fragments and distance < 300 m from the edges had more biomass and density of pioneer trees and saplings than did continuous forest and distance > 300 m from the edge, respectively. there were no significant differences among the size categories for standing dead trees. forest fragments, however, had more quantity of lcg and lcf than did continuous forests. moreover, distances < 300 m from the edges had higher quantity of lcg and lcf and total necromass than did distances > 300 m. we performed an ancova to assess whether differences in lcg and lcf in fragments were due to proximity of forest borders. an ancova showed that there was no significant effect of fragment size on necromass, but a significant effect of edge distance on both lcg and lcf. the quantity of lcg and lcf was correlated negatively with edge distance sites close to the edge presented over 40-60% more lcg than sites far from the edges in both forest fragments and continuous forests.
Observational Limits on Terrestrial-Sized Inner Planets Around the CM Draconis System Using the Photometric Transit Method with a Matched-Filter Algorithm
Laurance R. Doyle,Hans J. Deeg,Valerij P. Kozhevnikov,Brian Oetiker,Eduardo L. Martin,J. Ellen Blue,Lee Rottler,Remington P. S. Stone,Zoran Ninkov,Jon M. Jenkins,Jean Schneider,Edward W. Dunham,Moira F. Doyle,Efthimious Paleologou
Physics , 2000, DOI: 10.1086/308830
Abstract: A lightcurve of the eclipsing binary CM Draconis has been analyzed for the presence of transits of planets of size >= 2.5 Earth-radii (Re), with periods of 60 days or less, and in co-planar orbits around the binary system. About 400 million model lightcurves, representing transits from planets with periods ranging from 7 to 60 days, have been matched/correlated against these data. This process we call the "transit detection algorithm" or TDA. The resulting `transit-statistics' for each planet candidate allow the quantification of detection probabilities, and of false alarm rates. Our current lightcurve of CM Dra has a coverage of 1014 hours with 26,043 individual points, at a photometric precision between 0.2% and 0.7%. Planets significantly larger then 3Re would constitute a `supra-noise' detection, and for periods of 60 days or less, they would have been detected with a probability of 90%. `Subnoise' detections of smaller planets are more constrained. For example, 2.5 Re planets with 10-day periods or less would have been detected with an 80% probability. The necessity for predicted observations is illustrated with the nine top planet candidates that emerged from our TDA analysis. They are the planet candidates with the highest transit-statistics from the 1994-1998 observing seasons and, for them, transits for the 1999 observing season were predicted. Of the seven candidates that were then observationally tested in 1999, all were ruled out except one, which needs further observational confirmation. We conclude that the photometric transit method is a viable way to search for relatively small, inner extrasolar planets with moderate-sized telescopes using CCD photometry with a matching-filter analysis.
Kepler Eclipsing Binary Stars. I. Catalog and Principal Characterization of 1879 Eclipsing Binaries in the First Data Release
Andrej Prsa,Natalie M. Batalha,Robert W. Slawson,Laurance R. Doyle,William F. Welsh,Jerome A. Orosz,Sara Seager,Michael Rucker,Kimberly Mjaseth,Scott G. Engle,Kyle Conroy,Jon M. Jenkins,Douglas A. Caldwell,David G. Koch,William J. Borucki
Physics , 2010, DOI: 10.1088/0004-6256/141/3/83
Abstract: The Kepler space mission is devoted to finding Earth-size planets in habitable zones orbiting other stars. Its large, 105-deg field-of-view features over 156,000 stars that are observed continuously to detect and characterize planet transits. Yet this high-precision instrument holds great promise for other types of objects as well. Here we present a comprehensive catalog of eclipsing binary stars observed by Kepler in the first 44 days of operation, the data which are publicly available through MAST as of 6/15/2010. The catalog contains 1879 unique objects. For each object we provide its Kepler ID (KID), ephemeris (BJD0, P0), morphology type, physical parameters (Teff, log g, E(B-V), crowding), and principal parameters (T2/T1, q, fillout factor and sin i for overcontacts, and T2/T1, (R1+R2)/a, e sin(w), e cos(w), and sin i for detached binaries). We present statistics based on the determined periods and measure an average occurence rate of eclipsing binaries to be ~1.2% across the Kepler field. We further discuss the distribution of binaries as function of galactic latitude, and thoroughly explain the application of artificial intelligence to obtain principal parameters in a matter of seconds for the whole sample. The catalog was envisioned to serve as a bridge between the now public Kepler data and the scientific community interested in eclipsing binary stars.
Influence of landscape heterogeneity on spatial patterns of wood productivity, wood specific density and above ground biomass in Amazonia
L. O. Anderson, Y. Malhi, R. J. Ladle, L. E. O. C. Arag o, Y. Shimabukuro, O. L. Phillips, T. Baker, A. C. L. Costa, J. S. Espejo, N. Higuchi, W. F. Laurance, G. López-González, A. Monteagudo, P. Nú ez-Vargas, J. Peacock, C. A. Quesada,S. Almeida
Biogeosciences (BG) & Discussions (BGD) , 2009,
Abstract: Long-term studies using the RAINFOR network of forest plots have generated significant insights into the spatial and temporal dynamics of forest carbon cycling in Amazonia. In this work, we map and explore the landscape context of several major RAINFOR plot clusters using Landsat ETM+ satellite data. In particular, we explore how representative the plots are of their landscape context, and test whether bias in plot location within landscapes may be influencing the regional mean values obtained for important forest biophysical parameters. Specifically, we evaluate whether the regional variations in wood productivity, wood specific density and above ground biomass derived from the RAINFOR network could be driven by systematic and unintentional biases in plot location. Remote sensing data covering 45 field plots were aggregated to generate landscape maps to identify the specific physiognomy of the plots. In the Landsat ETM+ data, it was possible to spectrally differentiate three types of terra firme forest, three types of forests over Paleovarzea geomorphologycal formation, two types of bamboo-dominated forest, palm forest, Heliconia monodominant vegetation, swamp forest, disturbed forests and land use areas. Overall, the plots were generally representative of the forest physiognomies in the landscape in which they are located. Furthermore, the analysis supports the observed regional trends in those important forest parameters. This study demonstrates the utility of landscape scale analysis of forest physiognomies for validating and supporting the finds of plot based studies. Moreover, the more precise geolocation of many key RAINFOR plot clusters achieved during this research provides important contextual information for studies employing the RAINFOR database.
KIC 9632895 - The 10th Kepler Transiting Circumbinary Planet
William F. Welsh,Jerome A. Orosz,Donald R. Short,Nader Haghighipour,Lars A. Buchhave,Laurance R. Doyle,Daniel C. Fabrycky,Tobias Cornelius Hinse,Stephen Kane,Veselin Kostov,Tsevi Mazeh,Sean M. Mills,Tobias W. A. Mueller,Billy Quarles,Samuel N. Quinn,Darin Ragozzine,Avi Shporer,Jason H. Steffen,Lev Tal-Or,Guillermo Torres,Gur Windmiller,William J. Borucki
Physics , 2014, DOI: 10.1088/0004-637X/809/1/26
Abstract: We present the discovery of KIC 9632895b, a 6.2 Earth-radius planet in a low-eccentricity, 240.5-day orbit about an eclipsing binary. The binary itself consists of a 0.93 and 0.194 solar mass pair of stars with an orbital period of 27.3 days. The plane of the planet's orbit is rapidly precessing, and its inclination only becomes sufficiently aligned with the primary star in the latter portion of the Kepler data. Thus three transits are present in the latter half of the light curve, but none of the three conjunctions that occurred during the first half of the light curve produced transits. The precession period is ~103 years, and during that cycle, transits are visible only ~8% of the time. This has the important implication that for every system like KIC 9632895 that we detect, there are ~12 circumbinary systems that exist but are not currently exhibiting transits. The planet's mass is too small to noticeably perturb the binary, consequently its mass is not measurable with these data; but our photodynamical model places a 1-sigma upper limit of 16 Earth masses. With a period 8.8 times that of the binary, the planet is well outside the dynamical instability zone. It does, however, lie within the habitable zone of the binary, and making it the third of ten Kepler circumbinary planets to do so.
Kepler Eclipsing Binary Stars. II. 2165 Eclipsing Binaries in the Second Data Release
Robert W. Slawson,Andrej Prsa,William F. Welsh,Jerome A. Orosz,Michael Rucker,Natalie M. Batalha,Laurance R. Doyle,Scott G. Engle,Kyle Conroy,Jared Coughlin,Trevor Ames Gregg,Tara Fetherolf,Donald R. Short,Gur Windmiller,Daniel C. Fabrycky,Steve B. Howell,Jon M. Jenkins,Kamal Uddin,Fergal Mullally,Shawn E. Seader,Susan E. Thompson,Dwight T. Sanderfer,William Borucki,David Koch
Physics , 2011, DOI: 10.1088/0004-6256/142/5/160
Abstract: The Kepler Mission provides nearly continuous monitoring of ~156 000 objects with unprecedented photometric precision. Coincident with the first data release, we presented a catalog of 1879 eclipsing binary systems identified within the 115 square degree Kepler FOV. Here, we provide an updated catalog augmented with the second Kepler data release which increases the baseline nearly 4-fold to 125 days. 386 new systems have been added, ephemerides and principle parameters have been recomputed. We have removed 42 previously cataloged systems that are now clearly recognized as short-period pulsating variables and another 58 blended systems where we have determined that the Kepler target object is not itself the eclipsing binary. A number of interesting objects are identified. We present several exemplary cases: 4 EBs that exhibit extra (tertiary) eclipse events; and 8 systems that show clear eclipse timing variations indicative of the presence of additional bodies bound in the system. We have updated the period and galactic latitude distribution diagrams. With these changes, the total number of identified eclipsing binary systems in the Kepler field-of-view has increased to 2165, 1.4% of the Kepler target stars.
Habitat Fragmentation and Ecological Traits Influence the Prevalence of Avian Blood Parasites in a Tropical Rainforest Landscape
Susan G. W. Laurance, Dean Jones, David Westcott, Adam Mckeown, Graham Harrington, David W. Hilbert
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0076227
Abstract: In the tropical rainforests of northern Australia, we investigated the effects of habitat fragmentation and ecological parameters on the prevalence of blood-borne parasites (Plasmodium and Haemoproteus) in bird communities. Using mist-nets on forest edges and interiors, we sampled bird communities across six study sites: 3 large fragments (20–85 ha) and 3 continuous-forest sites. From 335 mist-net captures, we recorded 28 bird species and screened 299 bird samples with PCR to amplify and detect target DNA. Of the 28 bird species sampled, 19 were infected with Plasmodium and/or Haemoproteus and 9 species were without infection. Over one third of screened birds (99 individuals) were positive for Haemoproteus and/or Plasmodium. In forest fragments, bird capture rates were significantly higher than in continuous forests, but bird species richness did not differ. Unexpectedly, we found that the prevalence of the dominant haemosporidian infection, Haemoproteus, was significantly higher in continuous forest than in habitat fragments. Further, we found that ecological traits such as diet, foraging height, habitat specialisation and distributional ranges were significantly associated with blood-borne infections.
KOI-2939b: the largest and longest-period Kepler transiting circumbinary planet
Veselin B. Kostov,Jerome A. Orosz,William F. Welsh,Laurance R. Doyle,Daniel C. Fabrycky,Nader Haghighipour,Billy Quarles,Donald R. Short,William D. Cochran,Michael Endl,Eric B. Ford,Joao Gregorio,Tobias C. Hinse,Howard Isaacson,Jon M. Jenkins,Eric L. N. Jensen,Ilya Kull,David W. Latham,Jack J. Lissauer,Geoffrey W. Marcy,Tsevi Mazeh,Tobias W. A. Muller,Joshua Pepper,Samuel N. Quinn,Darin Ragozzine,Avi Shporer,Jason H. Steffen,Guillermo Torres,Gur Windmiller,William J. Borucki
Physics , 2015,
Abstract: We report the discovery of a new Kepler transiting circumbinary planet (CBP). This latest addition to the still-small family of CBPs defies the current trend of known short-period planets orbiting near the stability limit of binary stars. Unlike the previous discoveries, the planet revolving around the eclipsing binary system KOI-2939 has a very long orbital period (~1100 days) and was at conjunction only twice during the Kepler mission lifetime. Due to the singular configuration of the system, KOI-2939b is not only the longest-period transiting CBP at the time of writing, but also one of the longest-period transiting planets. With a radius of 1.06+/-0.01 RJup it is also the largest CBP to date. The planet produced three transits in the light-curve of KOI-2939 (one of them during an eclipse, creating a syzygy) and measurably perturbed the times of the stellar eclipses, allowing us to measure its mass to be 1.52+/-0.65 MJup. The planet revolves around an 11-day period eclipsing binary consisting of two Solar-mass stars on a slightly inclined, mildly eccentric (e_bin = 0.16), spin-synchronized orbit. Despite having an orbital period three times longer than Earth's, KOI-2939b is in the conservative habitable zone of the binary star throughout its orbit.
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