Spatial Distribution Of Different Species Research Articles

Changes in demography and geographic distribution in the weeping pinyon pine (Pinus pinceana) during the Pleistocene.

Climate changes, together with geographical barriers imposed by the Sierra Madre Oriental and the Chihuahuan Desert, have shaped the genetic diversity and spatial distribution of different species in northern Mexico. Pinus pinceana Gordon & Glend. tolerates extremely arid conditions. Northern Mexico became more arid during the Quaternary, modifying ecological communities. Here, we try to identify the processes underlying the demographic history of P. pinceana and characterize its genetic diversity using 3100 SNPs from genotyping by sequencing 90 adult individuals from 10 natural populations covering the species' entire geographic distribution. We inferred its population history and contrasted possible demographic scenarios of divergence that modeled the genetic diversity present in this restricted pinyon pine; in support, the past distribution was reconstructed using climate from the Last Glacial Maximum (LGM, 22 kya). We inferred that P. pinceana diverged into two lineages ~2.49 Ma (95% CI 3.28–1.62), colonizing two regions: the Sierra Madre Oriental (SMO) and the Chihuahuan Desert (ChD). Our results of population genomic analyses reveal the presence of heterozygous SNPs in all populations. In addition, low migration rates across regions are probably related to glacial–interglacial cycles, followed by the gradual aridification of the Chihuahuan Desert during the Holocene.

Species composition and community structure of warm temperate deciduous broadleaved forests in Huangguan of Qinling Mountains, China

The Qinling Mountain is a natural boundary between warm temperate zone and subtropical zone. While the China Forest Biodiversity Monitoring Network (CForBio) have basically covered most of the climate regions in China, few plots were located in the climate transition zone. Following the field protocol of CForBio and the Center for Tropical Forest Science (CTFS), a 25 hm2(500 m×500 m) forest plot was established in Huangguan Nature Reserve in Shaanxi Province, China, in 2019. In this study, we analyzed species composition, flora characteristics, diameter class structure, and spatial distribution patterns of dominant tree species based on the data of all woody species with a diameter at breast height (DBH) ≥1 cm. The results showed that there were 75137 woody individuals with DBH ≥1 cm in the plot (95679 when including branching individuals), belonging to 121 species, 83 genera and 44 families. The flora type at the genera level was mainly temperate, accounting for 71.1% of the total genera, and mixed with some tropical components. The dominant species in the community were obvious, with the number of individuals in the top 5 species exceeding 40% of the total number of individuals, the number of individuals in the top 50 species accounting for 95% of the total number of individuals, and the number of individuals in the remaining 61 species being less than 5% of the total. The diameter distribution of all woody indivi-duals in the plot was inverted 'J' type. Spatial distribution patterns varied across the four most abundant species with importance value >5. The degree of aggregation within species decreased with the increases of scales, while the spatial distribution of different species was affected by environmental heterogeneity. Warm-temperate deciduous broadleaved forest in Qinling Mountains had abundant species, stable community structure and good regeneration, reflecting the typical characteristics of the transition from warm temperate zone to subtropical zone. Environmental heterogeneity might be an important factor affecting the spatial distribution of tree species in the plot.

The Effect of Confinement Angle on Self-Colliding Aluminium Laser Plasmas Using Spectrally Resolved Fast Imaging.

In this work we investigate the effect of the confinement angle on self-colliding aluminium laser produced plasmas. More specifically, we apply V-shaped channel targets of different angles (90°, 60° and 30°) and report both broadband and filtered time-resolved fast imaging measurements on the formation of such plasmas in ambient air. Based on the broadband measurements we suggest that the plasmas formed on the two inner walls of the V-shaped channel expand normally to the surface, interact with each other and possibly stagnate. The spectrally filtered fast imaging reveals the presence of a spatial distribution of different species within the plasmas and signatures of forced recombination.

Assessing Worldview-3 multispectral imaging abilities to map the tree diversity in semi-arid parklands

Semi-arid parkland agrosystems are strongly sensitive to climate change and anthropic pressure. In the context of sustainability research, trees are considered critical for various ecosystem services covering environment quality as well as food security and health. But their actual ecological impact on both cropland and natural vegetation is not well understood yet, and collecting spatial and structural information around agroforestry systems is becoming an important issue. Tree mapping in semi-arid parklands could be one of these prerequisites. While for obtaining an exhaustive inventory of individual trees and for analysing their spatial distribution, remote sensing is the ideal tool. However, it has been noted that depending on the spatial resolution and sensor spectral characteristics, tree species cannot be distinguished clearly, even in the sparsely vegetated semi-arid ecosystems of West Africa. Thus, this work focuses on assessing the capabilities of Worldview-3 imagery, acquired in 8 spectral bands, to detect, delineate, and identify certain key tree species in the Faidherbia albida parkland in Bambey, Senegal, based on a ground-truth database corresponding to 5000 trees. The tree crowns are delineated through NDVI thresholding and consecutive filtering to provide object-based radiometric signatures, radiometric indices, and textural information. A factorial discriminant analysis is then performed, which indicates that only four out of the seven most abundant species in the study area can be discriminated: “Faidherbia albida”,” Azadirachta indica”, “Balanites aegyptiaca” and “Tamarindus indica”. Next, random forest and support vector machine classifiers are employed to identify the optimal combination of classifier parameters to discriminate these classes with a high accuracy, robustness, and stability. The linear support vector machine with cost=1 and gamma=0.01 provides the optimal results with a global accuracy of 88 % and kappa of 0.71. This classifier is applied to the whole study area to map all the trees with crowns larger than 2 m, sorted in four identified species and a fifth common group of unidentified species. This map thus enables analysing the variability in tree density and the spatial distribution of different species. Such information can afterwards be correlated to the ecological functioning of the parkland and local practices, and offers promising opportunities to help future sustainability initiatives in different socio-ecological contexts.

Modeling the Spatial Distribution of Three Typical Dominant Wetland Vegetation Species’ Response to the Hydrological Gradient in a Ramsar Wetland, Honghe National Nature Reserve, Northeast China

Water level fluctuations resulting from natural and anthropogenic factors have been projected to affect the functions and structures of wetland vegetation communities. Therefore, it is important to assess the impact of the hydrological gradient on wetland vegetation. This paper presents a case study on the Honghe National Nature Reserve (HNNR) in the Sanjiang Plain, located in Northeast China. In this study, 210 plots from 18 sampling line transects were sampled in 2011, 2012, and 2014 along the hydrological gradient. Using a Gaussian logistic regression model, we determined a relationship between three wetland plant species and a hydrologic indicator—a combination of the water level and soil moisture—and then applied that relationship to simulate the distribution of plants across a larger landscape by the geographic information system (GIS). The results show that the optimum ecological amplitude of Calamagrostis angustifolia to the hydrological gradient based on the probability of occurrence model was [0.09, 0.41], that of Carex lasiocarpa was [0.35, 0.57], and that of Carex pseudocuraica was [0.49, 0.77]. The optimum of Calamagrostis angustifolia was 0.25, Carex lasiocarpa was 0.46, and Carex pseudocuraica was 0.63. Spatial distribution probability maps were generated, as were maps detailing the distribution of the most suitable habitats for wetland vegetation species. Finally, the model simulation results were verified, showing that this approach can be employed to provide an accurate simulation of the spatial distribution pattern of wetland vegetation communities. Importantly, this study suggests that it may be possible to predict the spatial distribution of different species from the hydrological gradient.

From species distributions to climate change adaptation: Knowledge gaps in managing invertebrate pests in broad-acre grain crops

Extensive research has shown that climate change will impact the distribution and outbreak potential of invertebrate pests in broad-acre crops. However, much less attention has been placed on translating these likely changes in pest outbreak frequency into practical management options for growers. Dryland grain production systems are generally predicted to be vulnerable to the effects of climate change. An initial step in understanding changes to outbreak potential of different pests is to describe the spatial distribution of different species and communities. Using a bioclimatic modelling approach, we demonstrate how general patterns of distribution for four major invertebrate pests of Australian dryland grain production systems are likely to be altered by climate change. While such models are useful for predicting the direct impacts of climate change on potential species distributions, they are less useful for assessing pest outbreak frequency from direct or indirect changes. In light of this, we explore different tools that can be used to support adaptive management by farmers to limit the impact of induced pest outbreaks. Primarily, research to increase available information of indirect impacts on the pest species and the communities they interact with, including their natural enemies, is required to extend models of pest outbreak potential. Further, incorporation of pests into global crop models combined with monitoring for existing pests and surveillance for new pests is critical for future pest management decision-making. For natural enemies, generalizations around the impact of climate change and flow on effects for pest control services need to be attempted now. The knowledge of potential management interventions is needed by farmers to support improved management decisions in the short-term, but in some cases will also facilitate adaption to climate change in the long-term.

A young bipolar outflow from IRAS 15398-3359

Changing physical conditions in the vicinity of protostars allow for a rich and interesting chemistry to occur. Heating and cooling of the gas allows molecules to be released from and frozen out on dust grains. These changes in physics, traced by chemistry, as well as the kinematical information allows us to distinguish between different scenarios describing the infall of matter and the launching of molecular outflows and jets. We aim at determining the spatial distribution of different species, of different chemical origin. This is to examine the physical processes in play in the observed region. From the kinematical information of the emission lines we aim at determining the nature of the infalling and outflowing gas in the system. We also aim at determining the physical properties of the outflow. Maps from the Sub-Millimeter Array reveal the spatial distribution of the gaseous emission toward IRAS15398-3359. The line radiative transfer code LIME is used to construct a full 3D model of the system taking all relevant components and scales into account. CO, HCO+ and N2H+ are detected and are shown to trace the motions of the outflow. For CO, also the circumstellar envelope and the surrounding cloud have a profound impact on the observed line profiles. N2H+ is detected in the outflow, but is suppressed towards the central region, perhaps due to the competing reaction between CO and H3+ in the densest regions as well as destruction of N2H+ by CO. N2D+ is detected in a ridge south-west from the protostellar condensation. The morphology and kinematics of the CO emission suggests that the source is younger than 1000 years. The mass, momentum, momentum rate, mechanical luminosity, kinetic energy and mass-loss rate are also all estimated to be low. A full 3D radiative transfer model of the system can explain all the kinematical and morphological features in the system.

An analysis of indicators for the detection of effects of marine reserve protection on fish communities

We investigated the effects of marine reserve protection on fish and benthic communities at Glover's Reef Marine Reserve, Belize, using a broad suite of indicators. Responses of fish species to protection were highly variable, and therefore indicators calculated at the fish community level were ambiguous. According to 11 of 13 community-level indicators, sites located within the no-take zone fared more poorly over time than did sites in the surrounding fished area. However, we were able to detect positive reserve effects using a newly-proposed pair of indicators, which take into account spatial distribution of different species at the time of the no-take zone implementation. These indicators showed that species subject to low fishing pressure increased inside and to a lesser extent outside the no-take zone, while species subject to higher levels of fishing pressure increased in the no-take zone but decreased in the fished area. Indicators of changes in the fish community were not correlated with those related to the benthic community, and we suggest that indicators be carefully selected to match management objectives. We also find that positive reserve effects based on present-day data (e.g., higher abundances of commercial species inside the no-take zone versus outside) were often not associated with increases in fish densities over time, and suggest caution when interpreting abundance patterns in the absence of historical data. We recommend that similar studies be carried out at a variety of reserve sites, to test our proposed indicators and increase our understanding of community-level responses to fisheries closures.

Spatial and temporal distributions of phlebotomine sand flies (Diptera: Psychodidae), vectors of leishmaniasis, in Iran

Leishmaniasis is a major vector-borne disease and health problem in Iran. Studies on sand flies, as the vectors of the disease, began in the Northern and Western parts of the country in 1930 and have been continued up to now. Concerning many published information in the field of sand flies, providing a digital database for the country will help the public health authorities to make more correct and prompt decisions for planning leishmaniasis control programs as well as modeling and forecasting of transmission potential across the country.All published data on phlebotomine sand flies of Iran were collected. A database was then designed in Excel format, including all available information regarding sand flies. The valid data were transferred to ArcGIS9.3 to prepare the first spatial database of sand flies of Iran.The IrSandflybase includes 131 papers, 2 abstracts and 71 PhD/MSc theses, reporting studies conducted during 1930–2012. This database contains different available data covering all aspects of ecology and biology of 50 sand fly species in two genera of Phlebotomus and Sergentomyia in the country. The temporal activity of sand flies is reported 9 months in warm regions of the southern part, while it may reduce to 7–8 months in central plateau or 4–5 months in cold areas of the northwest.Occasional studies reported rare species from the borderlines of Iran. It seems that changing the climate due to global warming may affect the spatial distribution of different species and expand it into the country, the issue that can be followed by an updated database.

Kinematics and chemistry of the hot core in G20.08–0.14N

We present Submillimeter Array (SMA) observations of the the massive star-forming region G20.08–0.14N at 335 and 345 GHz. With the SMA data, 41 molecular transitions were detected related to 11 molecular species and their isotopologues, including SO2, SO, C34S, NS, C17O, SiO, CH3OH, HC3N, H13CO+, HCOOCH3 and NH2CHO. In G20.08–0.14N, 10 transition lines out of the 41 detected belong to SO2, which dominates the appearance of the submillimetre-wave spectrum. To obtain the spatial kinematic distribution of molecules in G20.08–0.14N, we chose the strongest and unblended lines for the channel maps. The channel maps of C34S and SiO, together with their position–velocity diagrams, show that there are two accretion flows in G20.08–0.14N. Additionally, SiO emission shows a collimated outflow in the north-east–south-west direction. The direction of the outflow is revealed for the first time. The rotational temperature and column density of CH3OH are 105 K and 3.1 × 1017 cm−2, respectively. Our results confirm that a hot core is associated with G20.08–0.14N. The hot core is heated by a protostar radiation at its centre, not by external excitation from shocks. Images of the spatial distribution of different species have shown that the different molecules are located at different positions of the hot core. By comparing the spatial distributions and abundances of molecules, we discuss possible chemical processes for producing the complex sulphur-bearing, nitrogen-bearing and oxygen-bearing molecules in G20.08–0.14N.

Vegetation Cover and Elevation in Long-Term Experimental Nutrient-Enrichment Plots in Great Sippewissett Salt Marsh, Cape Cod, Massachusetts: Implications for Eutrophication and Sea Level rise

Nitrogen inputs restructure ecosystems and can interact with other agents of ecological change and potentially intensify them. To examine the effects of nitrogen combined with those of elevation and competition, in 2005 we mapped vegetation and elevation within experimental plots that have been fertilized since 1970 in Great Sippewissett salt marsh, Cape Cod, MA, USA and compared the resulting effects on marsh vegetation. Decadal-scale chronic nutrient enrichment forced changes in cover and spatial distribution of different species. With increasing enrichment, there was a shift in species cover primarily involving loss of Spartina alterniflora and an increase in Distichlis spicata. Percent cover of near monocultures increased with nitrogen fertilization, owing mainly to the proliferation of D. spicata. The experimental fertilization prompted a shift from the short form of S. alterniflora to taller forms, hence increasing above-ground biomass, where this species managed to remain. Chronic enrichment increased upper and lower limits of the elevation range within which certain species occurred. The shift to increased cover of D. spicata was also associated with faster accretion of the marsh surface where this species was dominant, but not where S. alterniflora was dominant. Interactions among nutrient supply, elevation, and competition altered the direction of competitive success among different species of marsh plants, and forced changes in the spatial distribution and composition of the salt marsh plant communities. The results imply that there will be parallel changes in New England salt marshes owing to the widespread eutrophication of coastal waters and the increasing sea level rise. Knowing the mechanisms structuring marsh vegetative cover, and their role in modification of salt marsh accretion, may provide background with which to manage maintenance of affected coastal wetlands.

Population structure of beaked redfish, Sebastes mentella: evidence of divergence associated with different habitats

Abstract Cadrin, S. X., Bernreuther, M., Daníelsdóttir, A. K., Hjörleifsson, E., Johansen, T., Kerr, L., Kristinsson, K., Mariani, S., Nedreaas, K., Pampoulie, C., Planque, B., Reinert, J., Saborido-Rey, F., Sigurðsson, T., and Stransky, C. 2010. Population structure of beaked redfish, Sebastes mentella: evidence of divergence associated with different habitats. – ICES Journal of Marine Science, 67: 1617–1630. Throughout their range, Sebastes spp. are adapted to a diversity of ecological niches, with overlapping spatial distributions of different species that have little or no morphological differences. Divergence of behavioural groups into depth-defined adult habitats has led to reproductive isolation, adaptive radiation, and speciation in the genus Sebastes. Recent genetic research, supported by life-history information, indicates four biological stocks of Sebastes mentella in the Irminger Sea and adjacent waters: a western stock, a deep-pelagic stock, a shallow-pelagic stock, and an Iceland slope stock. Congruent differences in fatty acids and parasites suggest that these genetically distinct populations are adapted to disparate trophic habitats in pelagic waters (shallower and deeper than the deep-scattering layer) and in demersal habitats on the continental slope. Morphology of pelagic forms is also more streamlined than demersal forms. Although genetic differences and evidence for reproductive isolation are clear, these populations appear to share common nursery habitats on the Greenland shelf. We propose a redefinition of practical management units near the Irminger Sea based on geographic proxies for biological stocks and minimizing mixed-stock catches according to the spatial patterns of the recent fishery.

HIGH-RESOLUTION SUBMILLIMETER MULTILINE OBSERVATIONS OF G19.61 – 0.23: SMALL-SCALE CHEMISTRY

We present the Submillimeter Array (SMA) observations of molecular lines at 330 and 340?GHz toward G19.61 ? 0.23. The SMA observations have a spatial resolution of ~2'' and a bandpass of 2?? 2?GHz bandwidth. With the SMA data, we have detected 131 molecular transitions. Ninety-four molecular transitions from 17 species and their isotopomers are identified, including complex organic molecules and simple linear molecules. Most of the complex molecules (CH3OH, 13CH3OH, C2H5OH, HCOOCH3, HNCO, NH2CHO, CH3CN, and CH3CH2CN) have a sufficient number of transitions in this observation to allow analysis using the rotational temperature diagram method. The results from rotation temperature diagram fitting have shown that the complex nitrogen-bearing molecules have higher rotation temperatures (296-609 K) and lower column densities (6.5?? 1015-6.4?? 1016?cm?2). In contrast, the temperatures and column densities of the complex oxygen-bearing molecules range from 95 to 151 K, and from 1.1?? 1016 to 5.2?? 1017?cm?2, respectively. The H2 column density is estimated from the submillimeter continuum, and the fractional abundances of various species relative to H2 are calculated. The oxygen-bearing molecules have higher fractional abundances than those of the nitrogen-bearing molecules. The different gas temperatures and fractional abundances suggest a chemical differentiation between oxygen- and nitrogen-bearing molecules. The images of the spatial distribution of different species have shown that the oxygen-bearing and nitrogen-bearing molecules peak at different positions. Through comparing the rotation temperatures and fractional abundances with the spatial distributions of the molecules, we discuss possible chemical processes for producing the complex molecules, as well as nitrogen and oxygen differentiation in G19.61 ? 0.23.

Temporal and spatial distribution of different species of nitrogen in Lake Wuliangsuhai,Inner Mongolia

为揭示不同形态氮在乌梁素海空间分布特征及变化规律,运用ArcGIS统计模块分析了2006-2007年乌梁素海不同形态氮浓度的时空变异.研究表明:乌梁素海水体中各监测点总氮浓度夏、冬季高,秋季低,季节性差异较为明显;秋、冬季氨氮平均浓度明显高于夏季;不同季节亚硝态氮平均浓度明显高于硝态氮.在空间分布上,乌梁素海不同形态氮浓度分布呈现出由北向南逐渐降低的趋势.总之,乌梁素海氮素污染问题已十分严重,主要污染源为河套灌区农田排水、沿总干渠区域的工业废水和生活污水,随水体的流动氮污染减少,但某些区域因芦苇、水草密集而使不同形态氮有不同程度的增减.;The temporal and spatial variation characteristics of nitrogen forms are very important for environmental pollution controlof lake. Concentrations of different nitrogen forms were studied using the geostatistical analysis module of ArcGIS in LakeWuliangsuhai. The results indicate that average concentrations of total nitrogen were higher in summer and winter than autumn inseasonal time series, the average concentrations of ammonia nitrogen were lower in summer than autumn and winter, and the averageconcentration of nitrite nitrogen was higher than nitrate nitrogen in different seasons. In space, concentration distribution of differentforms ofnitrogen showed gradually decreasing from north to south. In a word, nitrogen pollution is very serious in LakeWuliangsuhai. The main pollutions were sourced from farm field drainage of the Hetao irrigated areas, industrial waste water anddomestic sewage close to main irrigation canal, which caused different forms of nitrogen contents decreases with the discharge of flowingwater. However, in the region of density reed and aquatic, the contents of nitrogen forms will change with increase or decrease.

Spatial distribution of the Daphnia longispina species complex and other planktonic crustaceans in the heterogeneous environment of canyon-shaped reservoirs

Canyon-shaped reservoirs are often characterised by longitudinal gradients of environmental factors (including trophic level, phytoplankton and zooplankton biomass and abundance of planktivorous fish) affecting the taxonomic composition of the pelagic community. We tested the hypothesis that the spatial distribution of different species and interspecific hybrids of the Daphnia longispina species complex is non-random under such conditions. During the summer stratification, we sampled crustacean zooplankton from 11 reservoirs, covering both longitudinal (upstream, middle, dam) and vertical (epi-, meta- and hypolimnion) environmental gradients. Allozyme electrophoresis was used to discriminate among different Daphnia taxa. All three frequently hybridizing European species of the complex (galeata, cucullata, longispina = hyalina) and hybrids with Daphnia galeata were commonly recorded. Smaller-bodied Daphnia cucullata and its hybrids, when present, preferred mostly the nutrient- and food-rich upstream regions; D. longispina and its hybrids were more commonly found in the downstream part, and often dominated in the meta- or hypolimnion. Redundancy analyses confirmed significant differences in the Daphnia taxon composition, as well as in spatial distribution of other crustacean species, along both gradients. For the first time, we demonstrate regular patterns in the horizontal distribution of Daphnia species and hybrids within a water body, thus accepting our hypothesis. Such spatial distributional patterns may strongly impact local hybridization processes.

Insect infestation of a botanicals warehouse in north-central Florida

The insect populations of a botanicals warehouse in north-central Florida were studied to gain a better understanding of insect problems associated with stored botanicals and to identify measures that could be taken to mitigate the problems. The warehouse contained either dried saw palmetto berries, Serenoa repens (Bartram) Small, or dried passion-flower (maypop) vines, Passiflora incarnata (L.), depending on the season. Insect populations were monitored intermittently for one year using arrays of moth and beetle traps. Capture rate, relative abundance, and spatial distribution of different species were examined over time. The six most abundant species in order of abundance were: Cadra cautella (Walker), Lasioderma serricorne (F.), Oryzaephilus mercator (Fauvel), Typhaea stercorea (L.), Plodia interpunctella (Hubner), and Tribolium castaneum (Herbst). All of these appear capable of infesting saw palmetto, but the major pests were C. cautella and L. serricorne. Oryzaephilus mercator and P. interpunctella were also important, but T. castaneum and T. stercorea were minor. Passion-flower was a less suitable host than saw palmetto for all of the species except T. stercorea. Nevertheless, all of the six species infesting saw palmetto except O. mercator were captured in numbers sufficient to indicate that they were also capable of infesting passion-flower. Lasioderma serricorne was the major pest. Spatial analysis of trap captures revealed that the insect distributions changed as different botanicals were brought in, removed, or redistributed in the storage area. Potential measures to mitigate insect problems in stored botanicals are discussed, including spatial targeting of insect control and sanitation efforts.

Multi Species Detection in a Liquid Fuelled Model Combustor using Tunable Excimer Lasers

Abstract Tunable excimer lasers are used to obtain 2-D images to analyse spatial distributions of different species in a liquid fuelled flame of a single burner model combustor with optical access from all sides at ambient pressure and a maximum air inlet temperature of 600 K. The flame is stabilised by a turbulent structure generated by air mixing jets in combination with the axial swirls of an air spoke injector The spatial structure of the flame is characterized by relative distributions of different species. Measurements of natural fluorescence of OH (without laser) and laser-induced fluorescence (LIF) of NO and vaporized n-heptane fuel as well as laser-induced predissociative fluorescence (LIPF) of OH are presented. Averaged temperature field measurements are performed based on sequential excitation of two rovibronic transitions in the Schumann-Runge band system of O2. Liquid fuel droplets are visualized by Mie-scattering. Relevant spectroscopy is done to find the laser and fluorescence frequencies needed to measure isolated species and to study the natural flame emissions. The averaged fluorescence distributions turned out to be highly reproducible and illustrate clearly the fuel evaporation and consumption process as well as the area of NOx formation within the flame. The obtained flame spectra indicate that the formation of prompt NOx plays an important role in the precombustion zone where the mixture is still rich and the flame-temperature is low

Multi-species detection in spray flames with tunable excimer lasers

Planar imaging with tunable excimer-laser sheet illumination is used to determine spatial distributions of different species in liquid-fuelled spray flames of commercial oil burning furnaces. Two burner configurations, which differ only in the fuel/air mixing devices, are investigated to understand why one configuration yields 30% less NOx emission. Iso-octane and n-heptane fuels are used. To understand the origin for NOx reduction spatial distributions of reactants (fuel, O2), the reaction intermediate OH and the pollutant NO are recorded. OH and O2 are measured by LIPF, NO by LIF. Fuel distributions are determined by another broad-band emission, whose origin is not yet identified. Both single shot and averaged distributions are recorded. The averaged distributions are extremely reproducible and depend sensitively on details of the burner geometry and the fuel/air mixing device. They can clearly be used to distinguish fine details in different injection systems. The spatial distribution of different species relative to each other yield considerable insight in the differences between the two combustion processes. On the basis of purely qualitative visualization it is possible to understand the origin for NOx reduction: it results from faster injection of air in the one fuel/air mixing device.

An empirical test of biases in the rapid visual technique for species-time censuses of reef fish assemblages

For an assemblage of fishes inhabiting a warm temperate, rock reef near San Diego, California (USA), a series of censuses were made based on frequency of occurrence and standard numerical counts. These data were then compared with a parallel study based on the rapid visual technique (RVT) of Jones and Thompson (1978). Because the RVT ranks abundances according to frequency of encounter and disregards variations in the spatial distributions of different species, the method overemphasizes the importance of widespread albeit rare fishes but under-emphasizes patchy although abundant species. The discussion considers the relative merits of the RVT method for characterizing assemblages of fishes on temperate rock reefs and on tropical coral reefs.