bluuebunny/crossref_metadata_2025_split huggingface dataset:
Epidemiology of Phytophthora ramorum in Oregon tanoak forests
Authors: Hansen E. M. , Kanaskie A. , Prospero S. , McWilliams M. , Goheen E. M. , Osterbauer N. , Reeser P. , Sutton W. 
Published: May 2008

We followed the local intensification and dispersal of Phytophthora ramorum Werres, De Cock, & Man In’t Veld in Oregon tanoak ( Lithocarpus densiflorus (Hook & Arn.) Rehd.) forests from its initial detection in 2001 through 2006, coincident with a continuing eradication effort. The initial infested area included nine scattered sites below 400 m elevation, close to the Pacific Ocean near Brookings, Oregon. In subsequent years, one-half of new infections were within 122 m of a previous infection, and 79% of the newly detected trees occurred within 300 m of a previously identified tree. Dispersal up to 4 km was occasionally recorded. Initial infection occurred in the upper crowns of tanoak trees. The pathogen was recovered in rainwater collected beneath diseased tanoak trees in every month from November 2006 through October 2007. Twenty-four multilocus microsatellite genotypes were identified among 272 P. ramorum isolates collected from Curry County. Genotypic analysis provided independent estimates of time of origin of the Oregon infestation, its clustered distribution, and dispersal distances. In all sampling years, 60%–71% of the isolates belonged to the same multilocus genotype. In 2001, 12 genotypes were detected and new genotypes were identified in each of the subsequent years, but all isolates belonged to the same clonal lineage. Knowledge of local intensification of the disease and long-distance dispersal should inform both Oregon eradication efforts and national quarantine regulations.
Assessing effects of laser point density, ground sampling intensity, and field sample plot size on biophysical stand properties derived from airborne laser scanner data
Authors: Gobakken Terje , Næsset Erik 
Published: May 2008

Canopy height distributions were created from small-footprint airborne laser scanner data with an average sampling density of 1.13 points·m–2 collected over 132 sample plots and 61 forest stands. Field measurements of each plot were carried out within two concentric circles corresponding to fixed areas of 200 m2 and 300 or 400 m2. The laser point clouds were thinned to approximately 0.25, 0.13, and 0.06 point·m–2. For all comparisons, the maximum values of the first as well as last return canopy height distributions differed significantly between the full density and the thinned data. The combined effects of number of field plots, field plot sizes, and point densities on the accuracy of mean tree height, stand basal area, and stand volume predicted at stand level using a two-stage procedure combining field training data and laser data, were assessed using Monte Carlo simulation randomly selecting 75% and 50% of the field plots. The average standard deviation showed only a minor increase by decreasing point density and increased when the number of sample plots was reduced. The effects of field plot size varied with canopy structure and stem density.
Decreased fire frequency and increased water levels affect riparian forest dynamics in southwestern boreal Quebec, Canada
Authors: Denneler Bernhard , Asselin Hugo , Bergeron Yves , Bégin Yves 
Published: May 2008

The relative importance of fire and flooding on the population dynamics of eastern white-cedar ( Thuja occidentalis L.) and black ash ( Fraxinus nigra Marsh.) was evaluated in eight old-growth riparian stands of southwestern boreal Quebec, Canada. Rising water levels and decreasing fire frequency since the end of the Little Ice Age (ca. 1850) were expected to have favoured an inland migration of the riparian forest fringe, with the flood-tolerant black ash colonizing the lower parts of the shore terraces and eastern white-cedar the upper parts. Black ash was found to be restricted to the riparian zone (<200 cm elevation), whereas eastern white-cedar trees did not occur below 100 cm above lake level. Gaps of postfire eastern white-cedar recruitment were noted in stands exposed to riparian disturbances, whereas relatively continuous recruitment occurred at protected sites. Black ash, more tolerant to flooding and ice push, invaded the shore terrace sites left vacant by eastern white-cedar. The riparian forest fringe surrounding Lake Duparquet is currently migrating upland and this trend is expected to continue as water levels continue to increase and fire frequency continues to decrease during the 21st century.
Effects of stand, landscape, and spatial variables on bird communities in larch plantations and deciduous forests in central Japan
Authors: Yamaura Yuichi , Katoh Kazuhiro , Takahashi Toshimori 
Published: May 2008

We examined the effects of stand, landscape, and spatial variables on bird communities in deciduous forests and Japanese larch ( Larix leptolepis (Sieb & Zucc.) Gord.) plantations in a montane region of Nagano Prefecture, central Japan. We used plot-transect methods at 97 sites: 33 in winter 2003 and 18 sites were added in the 2004 breeding season in deciduous forests, and 32 in winter 2004 and 14 sites were added in the 2005 breeding season in larch plantations. Bird–environment relationships were explored using partial redundancy analysis and partial regression analysis. We used spatial variables derived from principal coordinates of neighbor matrices as explanatory variables to detect nonrandom spatial structure of bird communities. Variation in bird communities was mainly explained by stand and spatial variables for both forest types, whereas the effects of landscape variables were small. In plantations, important stand variables for both seasons included stand height, elevation, and the basal area of vines, whereas shrubs, dwarf bamboo ( Sasa senanensis (Franch. & Savat.) Rehd.), and larch snags were important in the breeding season. In deciduous forests, the most important stand variable for both seasons was the basal area of northern Japanese hemlock ( Tsuga diversifolia (Maxim.) Mast.) and Nikko fir ( Abies homolepis Sieb. & Zucc.) trees. Spatial variables showed that bird communities had large-scale (>10 km) spatial variation that could not be explained by stand or landscape variables.
Climate sensitivity of trembling aspen radial growth along a productivity gradient in northeastern British Columbia, Canada
Authors: Leonelli Giovanni , Denneler Bernhard , Bergeron Yves 
Published: May 2008

Growth–climate relationships were analyzed for 15 stands of trembling aspen ( Populus tremuloides Michx.) along a productivity gradient in northeastern British Columbia. Productivity was evaluated with a site index model whose values varied between 6.65 and 26.93 m height at age 50 years. To assess the role of climate on radial growth, we built a tree-ring chronology for each site and then performed a dendroclimatic analysis by means of bootstrapped correlation functions using monthly and annual climatic variables. We found that trembling aspen sensitivity to climate varied across stands with different productivities in the study area. At the more productive sites, trees were more sensitive to climate, and ring widths were positively correlated, particularly with summer month precipitation prior to the year of growth. The different responses to climate along the productivity gradient are likely related to the differences in substrate properties; substrates at the more productive sites are richer in nutrients and have a better water holding capacity than those of the less productive sites. Our study suggests that the effects of future climate change on tree growth may not only increase towards the limit of a species distribution, but also towards richer and wetter stands.
Response of small mammals to alternative stand structures in the mixed-conifer forest of northeastern CaliforniaThis article is one of a selection of papers from the Special Forum on Ecological Studies in Interior Ponderosa Pine — First Findings from Blacks Mountain Interdisciplinary Research.
Authors: Maguire Chris C. , Maguire Douglas A. , Manning Tom E. , Garber Sean M. , Ritchie Martin W. 
Published: May 2008

A common, but largely untested, strategy for maintaining forest biodiversity is to enhance stand structural complexity. A silvicultural experiment was implemented from 1996 to 1998 at Blacks Mountain Experimental Forest, California, to test the efficacy of two levels of structural diversity (high versus low) and two levels of prescribed underburning (burn versus no burn) for maintaining or restoring biodiversity. Small mammals were trapped and tagged in experimental units for 2 noncontiguous weeks in fall 2003 and 2004. Total number of captures and number of captured individuals varied by year (P < 0.002). No treatment effects were detected for all species lumped together or for the three most frequent species analyzed separately ( Tamias amoenus J.A. Allen, 1890, Peromyscus maniculatus (Wagner, 1845), and Spermophilus lateralis (Say, 1823)), with the exception that T. amoenus was captured more often in burned units in 2004 (P = 0.004 for year × burn interaction). Mixed-effects regression models indicated that the number of captures and captured individuals of T. amoenus and P. maniculatus decreased with increasing residual basal area of overstory trees, but opposite results were obtained for S. lateralis. After accounting for residual stand density differences, T. amoenus was captured more frequently in units of low structural diversity and S. lateralis in units of high structural diversity.
Blacks Mountain Experimental Forest: bark beetle responses to differences in forest structure and the application of prescribed fire in interior ponderosa pineThis article is one of a selection of papers from the Special Forum on Ecological Studies in Interior Ponderosa Pine — First Findings from Blacks Mountain Interdisciplinary Research.
Authors: Fettig Christopher J. , Borys Robert R. , McKelvey Stephen R. , Dabney Christopher P. 
Published: May 2008

Mechanical thinning and the application of prescribed fire are commonly used tools in the restoration of fire-adapted forest ecosystems. However, few studies have explored their effects on subsequent amounts of bark beetle caused tree mortality in interior ponderosa pine, Pinus ponderosa Dougl. ex P. & C. Laws. var. ponderosa. In this study, we examined bark beetle responses to creation of midseral (low diversity) and late-seral stages (high diversity) and the application of prescribed fire on 12 experimental units ranging in size from 76 to 136 ha. A total of 9500 (5.0% of all trees) Pinus and Abies trees died 2 years after treatment of which 28.8% (2733 trees) was attributed to bark beetle colonization. No significant difference in the mean percentage of trees colonized by bark beetles was found between low diversity and high diversity. The application of prescribed fire resulted in significant increases in bark beetle caused tree mortality (all species) and for western pine beetle, Dendroctonus brevicomis LeConte, mountain pine beetle, Dendroctonus ponderosae Hopkins, Ips spp., and fir engraver, Scolytus ventralis LeConte, individually. Approximately 85.6% (2339 trees) of all bark beetle caused tree mortality occurred on burned split plots. The implications of these and other results to sustainable forest management are discussed.
THE RETURN OF THE MEMBRANE PARADIGM? BLACK HOLES AND STRINGS IN THE WATER TAP
Authors: CARDOSO VITOR , DIAS ÓSCAR J. C. , GUALTIERI LEONARDO 
Published: May 2008

Several general arguments indicate that the event horizon behaves as a stretched membrane. We propose using this relation to understand the gravity and dynamics of black objects in higher dimensions. We provide evidence that: (i) The gravitational Gregory–Laflamme instability has a classical counterpart in the Rayleigh–Plateau instability of fluids. Each known feature of the gravitational instability can be accounted for in the fluid model. These features include threshold mode, dispersion relation, time evolution and critical dimension of certain phase transitions. Thus, we argue that black strings break in much the same way as water from a faucet breaks up into small droplets. (ii) General rotating black holes can also be understood with this analogy. In particular, instability and bifurcation diagrams for black objects can easily be inferred. This correspondence can and should be used as a guiding tool for understanding and exploring the physics of gravity in higher dimensions.
HEAVY ION COLLISIONS AND BLACK HOLE DYNAMICS
Authors: GUBSER STEVEN S. 
Published: May 2008

Relativistic heavy ion collisions create a strongly coupled quark–gluon plasma. Some of the plasma's properties can be approximately understood in terms of a dual black hole. These properties include shear viscosity, thermalization time, and drag force on heavy quarks. They are hard to calculate from first principles in QCD. Extracting predictions about quark–gluon plasmas from dual black holes mostly involves solving Einstein's equations and classical string equations of motion. AdS/CFT provides a translation from gravitational calculations to gauge theory predictions. The gauge theory to which the predictions apply is [Formula: see text] super-Yang–Mills theory. QCD is different in many respects from super-Yang–Mills, but it seems that its high temperature properties are similar enough for us to make some meaningful comparisons.
Aspects of a Northern Hemisphere Atmospheric Blocking Climatology
Authors: Tyrlis E. , Hoskins B. J. 
Published: May 2008

Abstract
A comprehensive climatology of Northern Hemisphere blocking is described based on a PV–θ wave-breaking index at the latitude of the climatological storm track and using the 40-yr ECMWF Re-Analysis (ERA-40) dataset. The general characterization of blocking regions is in agreement with most other studies, though more detail is provided here. In the annual average, blocking is most prevalent in the large region from the eastern Atlantic Ocean through Europe to central Asia with a secondary region in the central and eastern Pacific Ocean. Using a blocking criterion with the requirement for both longitudinal extent and temporal persistence, the peak in the frequency is in the Scandinavian region, where 24% of the days are characterized by blocking. In the east Pacific maximum, the corresponding number is 7%. However, there is considerable and very important interannual variability. The decay rate in the number of blocking events lasting at least a specified number of days is significantly less over Europe than elsewhere. However, the average intensity of blocking episodes is slightly higher in the east Pacific. The mean annual cycle of blocking is quite complex. Over most of Europe it continues through the year, with maximum intensities in the autumn and winter. To both the east and west, over the western Atlantic and Asia, there are two periods in the year of highest blocking frequency. Similar two-cycle behavior is found in the eastern Pacific region. The relationship of blocking with the storm track and the mean planetary-scale geopotential ridges is considered, and the evidence that blocking is a particular phenomenon with its own nonlinear dynamics is discussed.
Large-Eddy Simulation of Evaporatively Driven Entrainment in Cloud-Topped Mixed Layers
Authors: Yamaguchi Takanobu , Randall David A. 
Published: May 2008

Abstract
Cloud-top entrainment instability (CTEI) is a hypothesized positive feedback between cloud-top entrainment and enhanced turbulence associated with buoyancy reversal. A sufficiently strong positive feedback is hypothesized to lead to the destruction of the cloud. Numerous studies have investigated the possible role of CTEI in cloud breakup, with ambiguous results.
In this study, CTEI has been extensively investigated using many large-eddy simulations. An idealized experimental design has been used so as not to have any source of turbulence kinetic energy production except for entrainment due to evaporative cooling. A new method has been used to estimate the entrainment rate and to identify the inversion base and top.
The results of the experiments do show the hypothesized positive feedback when the Randall–Deardorff CTEI criterion is met. When CTEI takes place in the numerical experiments, entrainment develops spontaneously through buoyancy reversal and, as a result, leads to cloud dissipation. Cloud dissipation within several hours is simulated in the cases with strong instability. A hypothesized dependence of the strength of the evaporatively driven turbulence on the cloud-top liquid water mixing ratio is confirmed. As expected, with a typical stratocumulus liquid water mixing ratio, the evaporatively driven turbulence is weak.
Additional simulations with longwave radiation, surface latent heat flux, or both suggest that sufficiently strong radiative cooling can prevent cloud destruction by CTEI. For this reason, CTEI usually does not result in cloud dissipation in realistic cases.
The Structure and Mesoscale Organization of Precipitating Stratocumulus
Authors: Savic-Jovcic Verica , Stevens Bjorn 
Published: May 2008

Abstract
Large-eddy simulations are used to explore the structure and mesoscale organization of precipitating stratocumulus. The simulations incorporate a simple, two-moment, bulk representation of microphysical processes, which by varying specified droplet concentrations allows for comparisons of simulations that do and do not develop precipitation. The boundary layer is represented over a large (25.6 km × 25.6 km) horizontal domain using a relatively fine mesh, thereby allowing for the development of mesoscale circulations while retaining an explicit representation of cloud radiative, dynamical and microphysical interactions on scales much smaller than the dominant eddy scale. Initial conditions are based on measurements made as part of the Second Dynamics and Chemistry of the Marine Stratocumulus field study (DYCOMS-II). The simulations show that precipitation is accompanied by sharp reductions in cloudiness and changes in flow topology. Mesoscale features emerge in all of the simulations but are amplified in the presence of drizzle. A cloud albedo of near 75% in the nonprecipitating simulation is reduced to less than 35% in the precipitating case. The circulation transitions from a well-mixed, stationary stratocumulus layer with closed-cellular cloud planforms to a stationary cumulus-coupled layer, with incipient open-cellular cloud planforms and sustained domain-averaged surface precipitation rates near 1 mm day−1. The drizzling simulations embody many other features of observed precipitating stratocumulus, including elevated cloud tops in regions of precipitation and locally higher values of subcloud equivalent potential temperature. The latter is shown to result from the tendency for precipitating simulations to develop greater thermodynamic gradients in the subcloud layer as well as mesoscale circulations that locate regions of upward motion in the vicinity of precipitating cells.
Objective Identification of Nonlinear Convectively Coupled Phases of Monsoon Intraseasonal Oscillation: Implications for Prediction
Authors: Chattopadhyay R. , Sahai A. K. , Goswami B. N. 
Published: May 2008

Abstract
The nonlinear convectively coupled character of the summer monsoon intraseasonal oscillation (ISO) that manifests in its event-to-event variations is a major hurdle for skillful extended-range prediction of the active/break episodes. The convectively coupled character of the monsoon ISO implies that a particular nonlinear phase of the precipitation ISO is linked to a unique pattern of the large-scale variables. A methodology has been presented to capture different nonlinear phases of the precipitation ISO using a combination of a sufficiently large number of dynamical variables. This is achieved through a nonlinear pattern recognition technique known as self-organizing map (SOM) involving six daily large-scale circulation indices. It is demonstrated that the nonlinearly classified states of the large-scale circulation isolated at the SOM nodes without involving any information on rainfall are strongly linked to different phases of evolution of the rainfall ISO, including the active and break phases. While a lower SOM classification involving 9 different states identify the composite phases of the rainfall ISO, a higher SOM classification involving 81 states can identify different shades of composite phase of the rainfall ISO. The concept of isolating the nonlinear states, as well as the technique of doing so, is robust as almost identical phases of precipitation ISO are identified by the large-scale circulation indices derived from two different reanalysis datasets, namely, the 40-yr ECMWF Re-Analysis (ERA-40) and the NCEP–NCAR reanalysis.
The ability of the SOM technique to isolate spatial structure and evolutionary history of nonlinear convectively coupled states of the summer monsoon ISO opens up a new possibility of extended-range prediction of summer monsoon ISO. This knowledge is used to develop an analog technique for predicting different phases of monsoon ISO. Skillful four-pentad lead prediction of rainfall over central India is demonstrated with the model using only large-scale circulation fields. A major strength of the model is that it can easily be used for real-time extended-range prediction of monsoons.
A Novel Approach for Representing Ice Microphysics in Models: Description and Tests Using a Kinematic Framework
Authors: Morrison Hugh , Grabowski Wojciech W. 
Published: May 2008

Abstract
This paper documents the development of a novel approach for representing ice microphysics in numerical models. In this approach, the ice particle mass–dimension and projected-area–dimension relationships vary as a function of particle size and rimed mass fraction. All ice microphysical processes and parameters are calculated in a self-consistent manner in terms of these mass–dimension and area–dimension relationships. The rimed mass fraction is predicted locally by separately predicting the ice mixing ratios acquired through water vapor deposition and through riming. The third predicted variable is the number concentration of ice particles. This approach allows representing in a natural way the gradual transition from small to large ice particles due to growth by water vapor deposition and aggregation and from unrimed crystals to graupel due to riming. In traditional approaches, these processes are treated by separating ice particles into predefined categories (such as cloud ice, snow, and graupel) using fairly arbitrary thresholds and conversion rates. With some modifications, the new approach can be employed in either bin or bulk microphysical models.
In this paper, the new approach is implemented in a bulk two-moment microphysical scheme representing both warm-rain and ice processes and it is applied to an idealized 2D kinematic framework mimicking a shallow mixed-phase cumulus. The size distributions of cloud droplets, drizzle/rain drops, and ice particles are represented using gamma distributions. The new scheme is compared to a version of the scheme that uses the traditional approach for ice microphysics; that is, unrimed ice/snow and graupel are separate species, with threshold-based conversion rates between the former and the latter. The new and traditional schemes produce similar results, although the traditional scheme, unlike the new scheme, produces a distinct double maximum in the surface precipitation rate, corresponding to precipitation shafts consisting of either ice/snow or graupel. The relative magnitude of these peaks, as well as the ice water path and optical depth of the simulated cloud, is highly sensitive to the threshold for converting unrimed ice to graupel. In contrast, the new scheme does not require any conversion threshold and predicts formation of ice particles with wide range of rimed fractions.