Relative Density Of Species Research Articles

Effect of forest composition on bird species abundance in tropical dry deciduous forest: A case of Bhimbandh Wildlife Sanctuary, India

Abstract. Khan MS. 2017. Effect of forest composition on bird species abundance in tropical dry deciduous forest: A case of Bhimbandh Wildlife Sanctuary, India. Biodiversitas 18: 78-85. The tropical dry deciduous forest (TDDF) with 38.2% of total forest cover in India forms the largest forest type of India. TDDF have been managed for centuries in the Indian subcontinent. However, so far it is not clear how different forest compositions and structures influence the abundance and the distribution patterns of faunal species vice versa. To provide further insights in this respect, we analysed how different habitat variables influence the abundance and diversity of forest birds. The difference in relative species abundances and habitat separation between forest specialist and generalist birds was also investigated. Different classes of bird density were discriminated with habitat variables. In general, it was found that higher bird densities were concentrated in the lower tree and shrub densities and diversities, however, high grass density and diversity with low tree density and diversity favoured the overall high bird density. Results further indicate the positive association of relative density of specialist bird species with the high grass density and diversity and low tree density and diversity. Specialists occurred in the lower relative densities (0.75±0.68) than that of generalists (0.86±0.69) and were found restricted to dense, pristine woody forest patches with high tree diversity.
 Keywords: Bhimbandh Wildlife Sanctuary, birds, Forest Composition, India, Tropical Dry Deciduous Forest

Patterns of vegetation composition across levels of canopy disturbance in temperate forests of west Himalaya, India

Abstract This study analyses the impacts of canopy disturbance on vegetation compositional attributes of two characteristic temperate forests (i.e., mixed broad-leaf and banj-oak forests) in west Himalayan part of India. Following the standard approaches, quantitative information on compositional attributes of forest vegetation was generated and analyzed. Considerable changes in these attributes were revealed across different levels of canopy disturbance in both forests. In particular, tree density and total basal area (TBA) exhibited significant decline from undegraded to degraded stands. Among others, seedling and sapling density of mixed broad-leaf forest was affected adversely by increased level of canopy disturbance. However, herb density in this forest increased significantly with increasing levels of disturbance; the same was not true for banj-oak forest. A significant decline in relative frequency and density of native herbaceous species was apparent towards degraded stands, implying that the disturbed sites in both forests created an opportunity for the establishment and proliferation of non-natives. However, with significant increase in relative density of non-native herbs, the degraded stands of banj-oak forest emerged as critically vulnerable to non-native proliferation. The patterns of tree size class distribution in both forests also exhibited certain trends across canopy disturbance, which suggested possible future changes in composition. In particular, the patterns of common tree associates (i.e., Myrica esculenta and Rhododendron arboreum) in banj-oak forest and Pinus roxburghii in mixed broad-leaf forest were indicative of likely compositional changes in near future. The study concludes that: (i) compositional attributes of both mixed broad-leaf and banj-oak forests were sensitive to increasing levels of canopy disturbance, (ii) mixed broad-leaf forest exhibited greater sensitivity to canopy disturbance at recruitment levels, (iii) increased canopy disturbance led to establishment and proliferation of non-native species in the herbaceous layer of both forests, and (iv) banj-oak forest exhibited high vulnerability to non-native proliferation at degraded stage.

Effects of high latitude protected areas on bird communities under rapid climate change.

Anthropogenic climate change is rapidly becoming one of the main threats to biodiversity, along with other threats triggered by human-driven land-use change. Species are already responding to climate change by shifting their distributions polewards. This shift may create a spatial mismatch between dynamic species distributions and static protected areas (PAs). As protected areas represent one of the main pillars for preserving biodiversity today and in the future, it is important to assess their contribution in sheltering the biodiversity communities, they were designated to protect. A recent development to investigate climate-driven impacts on biological communities is represented by the community temperature index (CTI). CTI provides a measure of the relative temperature average of a community in a specific assemblage. CTI value will be higher for assemblages dominated by warm species compared with those dominated by cold-dwelling species. We here model changes in the CTI of Finnish bird assemblages, as well as changes in species densities, within and outside of PAs during the past four decades in a large boreal landscape under rapid change. We show that CTI has markedly increased over time across Finland, with this change being similar within and outside PAs and five to seven times slower than the temperature increase. Moreover, CTI has been constantly lower within than outside of PAs, and PAs still support communities, which show colder thermal index than those outside of PAs in the 1970s and 1980s. This result can be explained by the higher relative density of northern species within PAs than outside. Overall, our results provide some, albeit inconclusive, evidence that PAs may play a role in supporting the community of northern species. Results also suggest that communities are, however, shifting rapidly, both inside and outside of PAs, highlighting the need for adjusting conservation measures before it is too late.

Changes in Structure and Functioning of Protist (Testate Amoebae) Communities Due to Conversion of Lowland Rainforest into Rubber and Oil Palm Plantations.

Large areas of tropical rainforest are being converted to agricultural and plantation land uses, but little is known of biodiversity and ecological functioning under these replacement land uses. We investigated the effects of conversion of rainforest into jungle rubber, intensive rubber and oil palm plantations on testate amoebae, diverse and functionally important protists in litter and soil. Living testate amoebae species richness, density and biomass were all lower in replacement land uses than in rainforest, with the impact being more pronounced in litter than in soil. Similar abundances of species of high and low trophic level in rainforest suggest that trophic interactions are more balanced, with a high number of functionally redundant species, than in rubber and oil palm. In contrast, plantations had a low density of high trophic level species indicating losses of functions. This was particularly so in oil palm plantations. In addition, the relative density of species with siliceous shells was >50% lower in the litter layer of oil palm and rubber compared to rainforest and jungle rubber. This difference suggests that rainforest conversion changes biogenic silicon pools and increases silicon losses. Overall, the lower species richness, density and biomass in plantations than in rainforest, and the changes in the functional composition of the testate amoebae community, indicate detrimental effects of rainforest conversion on the structure and functioning of microbial food webs.

A Hybrid Model for the Computationally-Efficient Simulation of the Cerebellar Granular Layer.

The aim of the present paper is to efficiently describe the membrane potential dynamics of neural populations formed by species having a high density difference in specific brain areas. We propose a hybrid model whose main ingredients are a conductance-based model (ODE system) and its continuous counterpart (PDE system) obtained through a limit process in which the number of neurons confined in a bounded region of the brain tissue is sent to infinity. Specifically, in the discrete model, each cell is described by a set of time-dependent variables, whereas in the continuum model, cells are grouped into populations that are described by a set of continuous variables. Communications between populations, which translate into interactions among the discrete and the continuous models, are the essence of the hybrid model we present here. The cerebellum and cerebellum-like structures show in their granular layer a large difference in the relative density of neuronal species making them a natural testing ground for our hybrid model. By reconstructing the ensemble activity of the cerebellar granular layer network and by comparing our results to a more realistic computational network, we demonstrate that our description of the network activity, even though it is not biophysically detailed, is still capable of reproducing salient features of neural network dynamics. Our modeling approach yields a significant computational cost reduction by increasing the simulation speed at least 270 times. The hybrid model reproduces interesting dynamics such as local microcircuit synchronization, traveling waves, center-surround, and time-windowing.

Lowland pasture in Himalayan highland: edaphic properties and species composition

This study was carried out to investigate if on-farm cut vs. grazed pastures differed in soil fertility and species density in the temperate Himalayan highlands. Soil fertility and species relative density were measured from 30 cut and 30 grazed dairy pastures. In both types of pasture, soil pH, available phosphorus (P) and exchangeable potassium (K) were negatively correlated with pasture age and slope. In cut pasture, cocksfoot (Dactylis glomerata) and pasture age were positively correlated, whereas in grazed pasture, they were negatively correlated. In grazed pasture, unsown species and pasture age were positively correlated. Soil available P was significantly greater in cut pastures whereas soil exchangeable K was significantly greater in grazed pastures. In terms of species density, cut pasture had greater densities of cocksfoot and Italian ryegrass (Lolium multiflorum), whereas grazed pasture showed greater densities of white clover, sedge and local grass. Our study suggests that, if there are no improvements in the current method of pasture management, the cut pastures in the future are likely to have a simple pasture mixture constituting only cocksfoot and white clover (Trifolium repens). Whereas in grazed pasture, the pasture mixture is likely to be comprised of white clover and unsown species such as sedge, local grass and broadleaf weeds.

The effects of selective cutting on the dominance and the relative density of mangrove species in the complex of the Guaxindiba river/Engenheiro Antonio Resende channel, Rio de Janeiro

This study evaluated the effect of selective cutting on the dominance and the relative density of mangrove species in the Complex of the Guaxindiba River/Engenheiro Antonio Resende Channel, in Rio de Janeiro State, Brazil. Ten plots were demarcated along the estuary and within each plot measurements were taken of the diameter at breast height (DBH) for individuals > 2.5 cm. Measurements of selective cutting and regrowth were made for the different species. The cutting of vegetation was registered in 9 of the 10 plots analyzed and varied from 2 to 43%. 4. There was no relation between the percent of trunks cut and the proximity of residential areas. Selective cutting was found for Avicennia germinans and Laguncularia racemosa, but only L. racemosa presented regrowth. The results suggest that L. racemosa is more highly affected by selective cutting when compared to the other species, though this impact did not modify the species dominance and the relative density in the mangrove analyzed due to the high regrowth of L. racemosa. Keywords: mangrove, estuary, conservation, vegetation

Population structure of two bamboo species in relation to topographical units in the Republic of Benin (West Africa): implications for sustainable management

A study was carried out in two phytodistricts (Ouémé-valley and Plateau) to assess the population structure of two bamboo species (Oxytenanthera abyssinica (A. Rich.) Munro and Bambusa vulgaris Schrad. ex J.C. Wendl. in two topographical units: plateau and wetlands. In each phytodistrict, bamboo stands were randomly selected in each topographical unit for inventory using a 0.25-ha square plot. Structural parameters of bamboos were computed and compared using a Wilcoxon rank test. Spatial distribution of the two bamboos was also assessed using the method of neighbourhood density in relation to a focal point. The observed culm diameter distribution was established for each stand and adjusted to the two-parameter Weibull distribution. Oxytenanthera abyssinica showed the highest culm and clump density values in both wetlands and plateau whereas B. vulgaris showed greater values of mean diameter and dominant height whatever the habitat. Diameter structures of bamboo stands showed a right asymmetric distribution and bamboo spatial distribution was highly aggregative, especially in wetlands. No significant difference in mean relative neighbourhood density between species was noted. However, a significant difference was observed between wetlands and plateau (p < 0.001) indicating strong influence of the topographical units on the relative neighbourhood density of bamboo species. All of these findings are determinants in designing suitable management strategies for bamboo populations in Benin, particularly with the increasing demand to build fish-traps and shelter in the traditional fishing systems “Acadja”.

EXPERIMENTAL AND NUMERICAL INVESTIGATIONS OF LINE-SHAPED MICROWAVE ARGON PLASMA SOURCE

In the following, numerical and experimental results for a line-shaped argon plasma source over a wide range of gas pressure (2-50 Torr) and microwave power (200-800 W) are presented. The line-shaped plasmas have been generated in a rectangular Pyrex tube, 15 mm in height and 5 mm inner width placed-in a linear slot made in the upper wide wall of a custom-made narrow rectangular waveguide. The microwave power is coupled to the discharge gas via the slot. The effects of the waveguide width, power level (electron density, and discharge tube insertion depth on the excited axial (along x) electric field profile and hence the uniformity of the produced plasmas are investigated numerically using commercial software CST Microwave Studio R � , and charge coupled device (CCD) camera. Results showed that, a uniform line-shaped plasma is generated as waveguide width decreased to 58 mm, plasma density valuenres =3 .7 × 10 11 cm �3 , and discharge tube insertion depth = 0 mm. An optical emission spectroscopy study was also realized to deduce the relative density of argon species and electron excitation temperature Texc. In general, argon spectral lines intensity was increased enhanced markedly when microwave power increased, while the different lines showed different behavior as argon pressure increased. The electron excitation temperature Texc decreases with increasing argon pressure, but almost constant overall the whole plasma length.

Struktura a hustota dřevinné vegetace dvou lesních oblastí narodního státu Amhara, Etiopie

This study was conducted in Jawi and East Belesa districts of the Amhara National Regional State in Ethiopia. It has an objective of describing the vegetation structure in relation to different environmental factors in general and Boswellia papyrifera, which is economically important species in particular. Vegetation data were collected in both sites (Mosebit and Hamusit) using plots of 50 m x 50 m (0.25 ha). In total 15 sample plots were set up. In each plot, all trees with DBH (Diameter at Breast Height), i.e. at 1.3 m above the ground were measured using caliper. In each major plot four subplots (4 m × 4 m) were established. Tree height measured using Hypsometer (Vertex III). Data’s on different environmental variables (slope, aspect and altitude) of each plot were also taken respectively using laser rangefinder Impulse 200 Standard, an electronic compass Map-Star Module II and GPS Juno™ ST handheld (Trimble, USA). A total of 58 woody species belonging to 22 families were identified from both sites. A total of 241 trees/ha and 292 trees/ha were found in Mosebit and Hamusit study sites, respectively. The seedling density result indicates 3656 seedlings/ha and 2469 seedlings/ha in Mosebit and Hamusit study areas, respectively. The density of Boswellia Papyrifera, which is economically important species were 140 and 127 tree/ha in Mosebit, and Hamusit study areas, respectively. The relative density of different tree species in different height and diameter classes were determined by altitude, aspect, and gradient of the study areas. The study result concludes that distribution of the species, relative density, height class and diameter class of species in the two sites is dependent on environmental factors. Finally, the findings indicate that the two woodlands harbor, economically important tree species. Therefore, giving due attention in conserving these wood lands is important from ecological, economical and conservation point of view.

Short-Term Response of Breeding Birds to Oak Regeneration Treatments in Upland Hardwood Forest

Population declines of several successional-scrub bird species are partly associated with decreased habitat availability as abandoned farmlands return to forest and recently harvested forests regrow. Restoration of mixed-oak (Quercus spp.) forest is also a concern because of widespread oak regeneration failure, especially on moist, productive sites where competition from faster-growing tree species is fierce following stand-replacing disturbances. Several silvicultural methods are proposed to promote oak regeneration but many are not experimentally tested, especially on productive sites. We surveyed birds in 19 stands to assess response to initial application of three proposed oak regeneration treatments on productive sites: prescribed burning (B); oak shelterwood by midstory herbicide (OSW); shelterwood harvests (SW); and controls (C), for one breeding season before, and two breeding seasons after, implementation. Relative density of successional-scrub species Indigo Buntings (Passerina cyanea), Eastern Towhees (Pipilo erythrophthalmus), and Chestnut-sided Warblers (Setophaga pensylvanica) increased, while Ovenbirds (Seiurus aurocapilla) decreased within 11 to 18 months after SW harvests; understory disturbance treatments B or OSW had no effect. Our results indicated that partial harvests created habitat for breeding birds associated with both young and mature forests, whereas understory treatments had little effect. Additionally, we show that even small patches of young forest habitat are used by more individuals and more species of breeding birds than surrounding closed-canopy forest, and may benefit successional-scrub species by enabling their occurrence in an otherwise forested landscape. Absence of several lower-elevation successional-scrub bird species in our mid-elevation SW harvests suggests that comprehensive conservation in the southern Appalachians necessitates creating and maintaining young forest habitats across elevation gradients.

Species richness, diversity and density of understory vegetation along disturbance gradients in the Himalayan conifer forest

We investigated whether species richness, diversity and density of understory herbaceous plants differed along logging (gap) and grazing (primarily by cattle) disturbance gradients, and sought to identify drivers of richness, diversity and density of understory vegetation of logged sites. A factorial experiment was conducted in the mixed conifer forest of Gidakom in Western Bhutan. Levels of the logging treatment included small (0.15 – 0.24 ha), medium (0.25 – 0.35 ha) and large (0.36 – 1.31 ha) gaps. The grazing treatment included grazed (primarily by cattle) and ungrazed (where herbivores were excluded by a fence) plots nested within each gap. Data were collected from 12 gaps (4 replicates at each level of logging) using the point intercept method. Shannon Weaver Diversity and Margalef’s indices were used to estimate species diversity and describe species richness, respectively. Soil samples were analyzed for pH and nutrients. The interaction effect of logging and grazing was significant (p≤0.001) only on species diversity. Relative to ungrazed areas, species diversity was significantly higher (0.01≤p≤0.05) in medium grazed gaps. Under grazed conditions, soil P was negatively correlated with gap size and species diversity. While species diversity was positively correlated (0.01≤p≤0.05) with soil N in grazed plots species richness was positively correlated (0.001≤p≤0.01) with soil N in ungrazed plots. Relative density of Yushania microphylla and Carex nubigena were higher under ungrazed conditions. Our study suggests that the combined effect of cattle grazing and logging results in higher species diversity of understory vegetation in medium and grazed gaps in mixed conifer forests of Bhutan,whereas increase or decrease in relative density of major species is determined primarily by the independent effects of grazing and logging. From management perspective, forest managers must refrain from creating large gaps to avoid loss of nutrients (mainly P and N), which may eventually affect tree regeneration. Managers intending to maintain understory vegetation diversity must consider the combined effects of grazing and logging, ensuring low to moderate grazing pressure.

Isolation, patch size and matrix effects on bird assemblages in forest reserves

Habitat fragmentation is one of the most studied topics in ecology but our knowledge is still limited particularly concerning matrix effects on species distribution in a human-dominated landscape. We tested the ability of random sampling hypothesis, colonization–extinction dynamics and matrix-related concepts to explain the variation in species richness, total bird density and community composition in old-forest bird assemblages in two contrasting landscapes. We collected data on breeding bird abundances from 66 old-growth forest reserves in NE Finland and six larger areas in adjacent Russian Karelia using the line transect method. In Finland, protected old-forest patches are embedded in a matrix dominated by young regeneration stands. In Russia, study areas were situated in continuous, old forest dominated landscapes. Bird assemblages in old-forest patches embedded in human-modified matrix in Finland were not random samples from Russian bird assemblages. In the Finnish assemblages, species richness was lower and total bird density higher. Species richness declined with increasing distance (isolation) to Russia. Bird assemblages in large forest reserves in Finland close to Russia were structurally more similar to assemblages in the continuous reference landscape than those in small and more distant reserves. The results support the idea that several mechanisms related to colonisation–extinction dynamics and to matrix resource availability influence species distribution in fragmented landscapes but in species-specific ways. We conclude that even though small and isolated protected areas may foster high relative bird species density their ecological integrity is compromised, and therefore, improving matrix quality around reserves may lead to considerable conservation benefits.

Limits to understory plant restoration following fuel-reduction treatments in a piñon-juniper woodland.

National fuel-reduction programs aim to reduce the risk of wildland fires to human communities and to restore forest and rangeland ecosystems to resemble their historical structure, function, and diversity. There are a number of factors, such as seed bank dynamics, post-treatment climate, and herbivory, which determine whether this latter goal may be achieved. Here, we examine the short-term (2 years) vegetation response to fuel-reduction treatments (mechanical mastication, broadcast burn, and pile burn) and seeding of native grasses on understory vegetation in an upland piñon-juniper woodland in southeast Utah. We also examine how wildlife herbivory affects the success of fuel-reduction treatments. Herbaceous cover increased in response to fuel-reduction treatments in all seeded treatments, with the broadcast burn and mastication having greater increases (234 and 160 %, respectively) in herbaceous cover than the pile burn (32 %). In the absence of seeding, herbaceous cover only increased in the broadcast burn (32 %). Notably, fuel-reduction treatments, but not seeding, strongly affected herbaceous plant composition. All fuel-reduction treatments increased the relative density of invasive species, especially in the broadcast burn, which shifted the plant community composition from one dominated by perennial graminoids to one dominated by annual forbs. Herbivory by wildlife reduced understory plant cover by over 40 % and altered plant community composition. If the primary management goal is to enhance understory cover while promoting native species abundance, our study suggests that mastication may be the most effective treatment strategy in these upland piñon-juniper woodlands. Seed applications and wildlife exclosures further enhanced herbaceous cover following fuel-reduction treatments.

Respuesta del carnívoro Plicopurpura pansa (mollusca: gastropoda) y el herbívoro Chiton articulatus (mollusca: polyplacophora) a factores ambientales en Acapulco, México

El gasterópodo Plicopurpura pansa y el poliplacóforo Chiton articulatus, cohabitan en la zona intermareal rocosa del Pacífico tropical Mexicano. Se ha reportado que P. pansa es un depredador de C. articulatus, y que ambas son especies abundantes y dominantes en la costa rocosa de Acapulco, Guerrero, México. El presente estudio analizó los patrones de respuesta de la densidad relativa y longitudes de ambas especies a cinco factores ambientales registrados en cuatro localidades rocosas de esta región. Durante octubre y diciembre de 2010, así como febrero y abril de 2011, se realizaron muestreos sistemáticos. Los sitios de estudio difirieron en la complejidad del sustrato y oleaje. Se registró el número de organismos por metro cuadrado y su longitud total, así como la temperatura del mar, salinidad y clorofila-α. Las densidades relativas de cada especie variaron entre los sitios de estudio y en todos los casos fueron mayores a 1.0 org/m2. Se observó una relación de la longitud del poliplacóforo con la temperatura del mar, salinidad y clorofila-α; una relación de la abundancia y longitud del gasterópodo con la complejidad del sustrato; y por último, una mayor abundancia del poliplacóforo en zonas de alto oleaje. También, se observaron comportamientos diferenciados de las especies en función de las características de los sitios rocosos y de los factores ambientales. La abundancia y longitud del carnívoro P. pansa estuvieron estrechamente relacionadas con el tipo de sustrato rocoso. En el caso del poliplacóforo C. articulatus, a través del tiempo, su longitud se asocia con parámetros físico-químicos del mar; mientras que a nivel espacial, sus abundancias se relacionan con el tipo de sustrato y la intensidad de oleaje

Gut microbiota and liver disease

Microbes are present in large numbers in each human being, in particularly in the gastrointestinal (GI) tract, and have long been believed to have some beneficial effects for their hosts. Till recently, however, we lacked tools for studying these organisms. Rapid technological advances in recent years have markedly improved our understanding of their role both in health and disease. Recent literature suggests that organisms in the GI tract, referred to collectively as gut microbiota, play an indispensable role in the maintenance of host's homeostasis. Alterations in the gut microbiota, that is in the nature and relative density of various constituent bacterial species, appear to have a role in pathogenesis and progression of several GI and hepatic diseases. This has also opened the vista for tinkering with gut flora in an attempt to treat or prevent such diseases. In this review, we have tried to summarize information on normal gut microbiota, laboratory techniques and animal models used to study it, and the role of its perturbations in some of the common hepatic disorders, such as non-alcoholic fatty liver disease (including obesity), non-alcoholic steatohepatitis, alcoholic liver disease, and liver cirrhosis and its complications.

Impact of &amp;lt;i&amp;gt;Parthenium hysterophorus&amp;lt;/i&amp;gt; L. Invasion on Species Diversity of Cultivated Fields of Bilaspur (C.G.) India

In present study invasion of Parthenium hysterophorus L. and its impacts on agriculture fields will be done in different cultivated crops in Bilaspur. The present work deals with diversity and distribution of weeds species in cultivated fields of Bilaspur C.G. A total number of 28 species under 27 genera and 16 families was distributed in three study sites (Koni, Sakri & Kota) of cultivated fields in Bilaspur C.G. These study sites were located in different altitudinal zones responding different conditions in the this study. The number of species per sites ranged from 13 to 24. In the Sakri, number of species was ranged from 17 to 27, and the relative density of plant species ranged between 0.77 (Heteropogon contortus, Solanum surratense, Vernonia cinneria and Leucas aspera) and 22.92 (Parthenium hysterophorus). In the Kota, number of species was ranged from 14 to 28, and the relative density of plant species ranged between 0.85 (Ageratum conyzoides, Heteropogon contortus, Triticum aestivum) and 29.06 (Zea mays) and 30.91 (Parthenium hysterophorus). In the Agriculture field, number of species was ranged from 15 to 28, and the relative density of plant species ranged between 0.58 (Leucas aspera) and 26.23 (Triticum aestivum). Present work will give the information that weeds are harmful to herbs, crops and medicinal plants. Parthenium weed can suppress and crowd out other weed species, and could form a single dominant population in the invasion area, causing serious threat to plant community biological diversity.

Controlling the oxygen species density distributions in the flowing afterglow of O2/Ar–O2 surface-wave microwave discharges

The evolution of species densities along a reactor radially positioned on an O2 surface-wave microwave discharge is investigated by means of modelling with the aim to define the density tuning possibilities. The validity of the models is shown by the comparison of the calculated and measured axial distribution of O-atoms. The calculations revealed that due to the perpendicular injection of the plasma into the reactor, the gas temperature is close to the room temperature in most of it, except for a 5 cm region around the inlet. It is shown that the pressure drop along the discharge tube, which results in the change of pressure in the discharge region with the gas flow rate, induces the variation of the relative density of active species entering the reactor, where the pressure is kept constant. The surface recombination probability of atoms varies along the afterglow tube due to the surface temperature gradient, as well as due to the conditioning of the surface resulting from the continuous operation of the system. The system is shown to be very practical in applications where surfaces/porous materials are to be treated homogeneously by pumping active species through them, since by tuning the gas flow rate equidensity surfaces can be obtained in the case of the two most abundant species, the O-atoms and O2(a) molecules. In the case of O-atoms the densities obtained at the two pressures investigated, i.e. 100 and 50 Pa, are very similar, as well as their evolution along the reactor, while the density of O2(a) molecules decreases considerably with pressure.

Twentieth century shifts in abundance and composition of vegetation types of theSierraNevada, CA,US

AbstractQuestionsHas tree density changed consistently across vegetation types? Do changes in component species correspond with changes across vegetation types? Do patterns of changes suggest potential drivers of change?LocationNorthern two‐thirds of theSierraNevada,CA,USA, ca. 45 000 km2.MethodsUsing two data sets that cover the span of elevations and land jurisdictions in the study area, we classified 4321 historical plots and 1000 modern plots into nine broad groups of vegetation types that are widely used by land managers and researchers in the region. We compared tree density and composition between historical and modern plots across and within these nine types.ResultsIn the modern data set, tree density was significantly higher in eight of nine vegetation types. Total density was significantly higher in modern plots for all west slope types, especially for montane hardwood, where modern forests are 128% denser, and mixed conifer forests, which are 69% denser. Relative density of component species was also very different between data sets in these forests, and suggests a shift in dominance toward shade‐tolerant conifers and evergreen oaks. Fire suppression is likely a driving factor in these types but density was also significantly higher in high‐elevation types such as sub‐alpine forest (+20%), where neither fire suppression nor logging have had major impacts on structure. East slope forest types (eastsideP. jeffreyiforest and piñon‐juniper woodland) were very similar in both modern and historical data sets, with no significant differences in density or composition.ConclusionWest slope forest types, especially montane hardwood and mixed conifer forest, appear the most altered types of the mountain range. These types are more productive but have also been subject to greater disturbance than high‐elevation and east slope forest types. Climate change may also be driving changes across the study area. Species such asQuercus chrysolepisandCalocedrus decurrens, which have each increased markedly in abundance, appear well positioned to dominate in the near future, especially under continued fire suppression and a warmer climate.

Fungal contamination and determination of fumonisins and aflatoxins in commercial feeds intended for ornamental birds in Rio de Janeiro, Brazil

The purposes of this study were to determine the distribution of total mycobiota, to determine the occurrence of Aspergillus spp., Penicillium spp. and Fusarium spp. and to detect and quantify fumonisin B1 and aflatoxin B1 in birds' feedstuffs. Sixty samples from different commercial feeds were collected. Analysis of the total mycobiota was performed and total fungal counts were expressed as CFU g(-1). The isolation frequency (%) and relative density (%) of fungal genera and species were determined. Mycotoxins determination was carried out using commercial ELISA kits. The 48% of standard, 31% of premium and only 9% of super premium feed samples were found above of recommended limit (1 × 10(4) CFU g(-1)). Aspergillus (82%), Cladosporium (50%) and Penicillium (42%) were the most frequently isolated genera. Aspergillus niger aggregate (35%), Aspergillus fumigatus (28%) and Aspergillus flavus (18%) had the highest relative densities. Contamination with fumonisins was detected in 95% of total samples with levels from 0·92 to 6·68 μg g(-1), and the aflatoxins contamination was found in 40% of total samples with levels between 1·2 and 9·02 μg kg(-1). Feed samples contaminated with fumonisins and aflatoxins are potentially toxic to birds.