Plot Densities Research Articles

Diphenyl Diselenide Through Reduction of Inflammation, Oxidative Injury and Caspase-3 Activation Abates Doxorubicin-Induced Neurotoxicity in Rats.

Neurotoxicity associated with chemotherapy is a debilitating side effect of cancer management in humans which reportedly involves inflammatory and oxidative stress responses. Diphenyl diselenide (DPDS) is an organoselenium compound which exhibits its anti-tumoral, anti-oxidant, anti-inflammatory and anti-mutagenic effects. Nevertheless, its possible effect on chemotherapy-induced neurotoxicity is not known. Using rat model, we probed the behavioral and biochemical effects accompanying administration of antineoplastic agent doxorubicin (7.5mg/kg) and DPDS (5 and 10mg/kg). Anxiogenic-like behavior, motor and locomotor insufficiencies associated with doxorubicin were considerably abated by both DPDS doses with concomitant enhancement in exploratory behavior as demonstrated by reduced heat maps intensity and enhanced track plot densities. Moreover, with exception of cerebral glutathione (GSH) level, superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities, biochemical data demonstrated reversal of doxorubicin-mediated decline in cerebral and cerebellar antioxidant status indices and the increase in acetylcholinesterase (AChE) activity by both doses of DPDS. Also, cerebellar and cerebral lipid peroxidation, hydrogen peroxide as well as reactive oxygen and nitrogen species levels were considerably diminished in rats administered doxorubicin and DPDS. In addition, DPDS administration abated myeloperoxidase activity, tumour necrosis factor alpha and nitric oxide levels along with caspase-3 activity in doxorubicin-administered rats. Chemoprotection of doxorubicin-associated neurotoxicity by DPDS was further validated by histomorphometry and histochemical staining. Taken together, DPDS through offsetting of oxido-inflammatory stress and caspase-3 activation elicited neuroprotection in doxorubicin-treated rats.

Amelioration of neurobehavioral, biochemical, and morphological alterations associated with silver nanoparticles exposure by taurine in rats.

The adverse effect of silver nanoparticles (AgNPs) on the nervous system is an emerging concern of public interest globally. Taurine, an essential amino acid required for neurogenesis in the nervous system, is well-documented to possess antioxidant, anti-inflammatory, and antiapoptotic activities. Yet, there is no report in the literature on the effect of taurine on neurotoxicity related to AgNPs exposure. Here, we investigated the neurobehavioral and biochemical responses associated with coexposure to AgNPs (200 µg/kg body weight) and taurine (50 and 100 mg/kg body weight) in rats. Locomotor incompetence, motor deficits, and anxiogenic-like behavior induced by AgNPs were significantly alleviated by both doses of taurine. Taurine administration enhanced exploratory behavior typified by increased track plot densities with diminished heat maps intensity in AgNPs-treated rats. Biochemical data indicated that the reduction in cerebral and cerebellar acetylcholinesterase activity, antioxidant enzyme activities, and glutathione level by AgNPs treatment were markedly upturned by both doses of taurine. The significant abatement in cerebral and cerebellar oxidative stress indices namely reactive oxygen and nitrogen species, hydrogen peroxide, and lipid peroxidation was evident in rats cotreated with AgNPs and taurine. Further, taurine administration abated nitric oxide and tumor necrosis factor-alpha levels cum myeloperoxidase and caspase-3 activities in AgNPs-treated rats. Amelioration of AgNPs-induced neurotoxicity by taurine was confirmed by histochemical staining and histomorphometry. In conclusion, taurine via attenuation of oxido-inflammatory stress and caspase-3 activation protected against neurotoxicity induced by AgNPs in rats.

Making religious buildings more accessible: The case of mosques in Abu Dhabi’s and Dubai’s neighborhoods

More than a house of worship, religious buildings have a critical and authoritative role in the social and political life of people. Yet, such places of divine and spirit have received limited attention in transportation and urban planning research. This research evaluates accessibility to one kind of religious institution: mosques. The article studies the ease of access to mosques at walkable distances of 400 m and 800 m radii in twelve selected neighborhoods in Abu Dhabi and Dubai. Analysis uses the gravity metric under two network scenarios: streets only, and the combined network of streets and alleys. Gravity values demonstrate three types of accessibility to mosques: plots without access, plots with minimum access to one mosque, and plots with choice access to more than one mosque. Findings show neighborhoods have experienced an erratic decrease in accessibility to mosques. In both cities, percentages of plots with an overall accessibility to mosques, (sum of both minimum and choice), were higher in the pre- and-early-suburban phases. With the inclusion of alleyways, the overall accessibility percentages increased in many cases. The study reveals that good pedestrian accessibility results from an effective interplay between street design, plot densities, network intersection density, strategic placement of alleys, and mosques’ ratio and spatial distribution.

Neurobehavioral and biochemical responses to artemisinin-based drug and aflatoxin B1 co-exposure in rats.

Populations in malaria endemic areas are frequently exposed to mycotoxin-contaminated diets. The possible toxicological outcome of co-exposure to dietary aflatoxin B1 (AFB1) and artemisinin-based combination therapy warrants investigation to ascertain amplification or attenuation of cellular injury. Here, we investigated the neurobehavioral and biochemical responses associated with co-exposure to anti-malarial drug coartem, an artemether-lumefantrine combination (5mg/kg body weight, twice a day and 3days per week) and AFB1 (35 and 70µg/kg body weight) in rats. Motor deficits, locomotor incompetence, and anxiogenic-like behavior induced by low AFB1 dose were significantly (p < 0.05) assuaged by coartem but failed to rescue these behavioral abnormalities in high AFB1-dosed group. Coartem administration did not alter exploratory deficits typified by reduced track plot densities and greater heat map intensity in high AFB1-dosed animals. Furthermore, the reduction in cerebral and cerebellar acetylcholinesterase activity, anti-oxidant enzyme activities, and glutathione and thiol levels were markedly assuaged by coartem administration in low AFB1 group but not in high AFB1-dosed animals. The significant attenuation of cerebral and cerebellar oxidative stress indices namely reactive oxygen and nitrogen species, xanthine oxidase activity, and lipid peroxidation by coartem administration was evident in low AFB1 group but not high AFB1 dose. Although coartem administration abated nitric oxide level, activities of myeloperoxidase, caspase-9, and caspase-3 in animals exposed to both doses of AFB1, these indices were significantly higher than the control. Coartem administration ameliorated histopathological and mophometrical changes due to low AFB1 exposure but not in high AFB1 exposure. In conclusion, contrary to AFB1 alone, behavioral and biochemical responses were not altered in animals singly exposed to coartem. Co-exposure to coartem and AFB1 elicited no additional risk but partially lessened neurotoxicity associated with AFB1 exposure.

The actions of key agents in facilitating rural super-gentrification: Evidence from the English countryside

Whilst the process of gentrification in rural spaces is widely recognised, there has been less focus to date on the emergence of rural super-gentrification - defined as the displacement of the wealthy from rural communities by the super-wealthy. Of the limited work which has been conducted on super-gentrification, this has focused on the nature and outcomes of displacement taking place in different rural settings without considering the actions of key agents, such as planners and estate agents. Consequently, this paper explores the role of gentrifying agents - namely planners and estate agents - in shaping processes of rural super-gentrification in the English countryside. The paper highlights how restrictive planning regimes, including constraints on higher plot densities, contribute to ‘rural exclusivity’ and rural super-gentrification. Within such contexts, the promotional and steering strategies of estate agents - based upon incomers perceived economic and cultural capital - also facilitate rural super-gentrification. In such a way, the paper advances existing consumption-side theories of gentrification by highlighting desires by super-wealthy incomers for consuming rural village locations with local services, a slower pace of life and a ‘sense of community’. In addition, the importance of privacy and seclusion, urban proximity and connectivity and access to educational circuits by incomers also shape the promotional and steering strategies of estate agents. Consequently, the paper highlights how more localised ‘micro-geographies’ of rural super-gentrification are of relevance to rural areas in comparison to urban contexts, where super-gentrification is argued to be a neighbourhood-level phenomenon.

Streets, density, and the superblock: neighborhood planning units and street connectivity in Abu Dhabi

ABSTRACT This article studies the efficiency of street networks of Neighborhood Planning Units. Pedestrian Route Directness quantified the NPUs’ efficiency. The sample includes ten Abu Dhabi NPUs built during two periods: pre-1990 and post-1990. Two scenarios are assessed. First, as-built streets are evaluated based on the PRD test. Second, PRD values of NPUs with different plot densities are compared. Results show that plot density does not affect efficiency. A good network design produces high efficiency regardless of its plot density. The effects of streets on efficiency were further revealed by Betweenness. Combining PRD and Betweenness yields important principles of network design. This method can be applied to assess the connectivity of streets in different contexts. Future research should focus on: How do alleys contribute to the efficiency of NPUs? How do street configurations influence the behavior of movement? And how should NPUs be evaluated as local street systems with global implications?

Urban tree composition, diversity and structural characteristics in North-western Nigeria

Urban trees composition and diversity are gaining more relevance for academic, urban planning and sustainability purposes. Despite their free ecosystem services, little is documented on urban trees especially in developing countries such as Nigeria. This study assessed the composition, diversity, structural characteristics and provenance of trees in two cities of North-western Nigeria. Landsat images for 2015 were used to classify each city into five broad land cover classes to facilitate stratified sampling. Data on tree species, height, Diameter at Breast Height (DBH) and provenance was collected from a total of 373 plots of 30 × 30 m dimension. A total of 1558 trees belonging to 56 species in 46 genera and 22 families were assessed with generally more categories of native than exotic species but higher populations of exotic stems. Azadirachta indica and Mangifera indica were the most dominant species in both cities while Meliaceae, Anacardiaceae, Fabaceae, Moraceae and Combretaceae were the dominant families. Lower diversity (H’ = 1.8), lower evenness (J = 0.53) and lower mean density (42.4 trees/ha) were recorded in Sokoto compared to Zaria (H’ = 3.30, J = 0.84 and density = 50.48 trees/ha). A one-way ANOVA revealed significant difference in these parameters across the land cover types within the cities except mean height which was not significantly different in Sokoto. An independent samples t-test also revealed significantly different mean height, diameter and Basal Area (BA) but similar plot densities between the cities. Urban tree composition, diversity and structural characteristics vary significantly between these two cities in North-western Nigeria and though exotic species have fewer categories, their stems are gradually dominating the cities. This may cause alterations in tree species composition and diversity and possibly, biotic homogenization. This calls for expanded tree planting with more emphasis on the native species.

Influence of sample selection method and estimation technique on sample size requirements for wall-to-wall estimation of volume using airborne LiDAR

Light detection and ranging (LiDAR) is commonly used to predict forest inventory attributes of interest across large regions. Most studies utilize model-derived estimators whose performances are affected by training data, and give less attention to using design-derived estimators. The influence of sample design and estimation method is an important consideration for determining sample sizes or calibration plot densities; however, this has not been systematically explored, particularly in mixed-species forests. In this study, 10 sample selection methods (four equal probability and six variable probability selection methods) and six estimation techniques (two model-derived and four sample-derived estimators) across a range of sample sizes are evaluated using LiDAR-derived predictions of volume per ha. Results show that the use of variable probability selection methods combined with sample-derived estimation techniques are more efficient than using model-derived estimates. Estimation technique had a greater effect on sample efficiency than did selection method, though specific combinations were more efficient than others. For example, random forest imputation was the most efficient at the lowest sample sizes (n < 50); however, significant biases were obtained when used with variable probability selection methods. The required plot densities across the combinations of selection methods and estimation techniques used in this study ranged from one plot per 15.7–32.6 ha. Use of a variable probability selection method based on attributes derived directly from LiDAR point clouds coupled with a ratio or regression estimator was a very efficient LiDAR-assisted sampling design that should be considered more in the future.

Long-term tree inventory data from mountain forest plots in France.

We present repeated tree measurement data from 63 permanent plots in mountain forests in France. Plot elevations range from 800 (lower limit of the montane belt) to 1942m above sea level (subalpine belt). Forests mainly consist of pure or mixed stands dominated by European beech (Fagus sylvatica), Silver fir (Abies alba), and Norway spruce (Picea abies), in association with various broadleaved species at low elevation and with Arolla pine (Pinus cembra) at high elevation. The plot network includes 23 plots in stands that have not been managed for the last 40years (at least) and 40 plots in plots managed according to an uneven-aged system with single-tree or small-group selection cutting. Plot sizes range from 0.2 to 1.9ha. Plots were installed from 1994 to 2004 and remeasured two to five times during the 1994-2015 period. During the first census (installation), living trees more than 7.5cm in dbh were identified, their diameter at breast height (dbh) was measured and their social status (strata) noted. Trees were spatially located, either with x, y, and z coordinates (40 plots) or within 0.25-ha square subplots (23 plots). In addition, in a subset of plots (58 plots), tree heights and tree crown dimensions were measured on a subset of trees and dead standing trees and stumps were included in the census. Remeasurements after installation include live tree diameters (including recruited trees), tree status (living, damaged, dead, stump), and for a subset of trees, height. At the time of establishment of the plots, plot densities range from 181 to 1328 stems/ha and plot basal areas range from 13.6 to 81.3m2 /ha.

Quinone-Based Flow Battery with Increased Open Circuit Voltage

Quinone-based flow batteries exhibit rapid redox kinetics, contain no electrocatalyst and use very inexpensive redox active materials [1]. Consequently, they appear to be very attractive candidates for inexpensive, large-scale electrical energy storage. We compare the performance of several substituted quinone/hydroquinone redox couples in an aqueous flow battery. We show that various substitutional groups can alter the electrochemical properties of the quinone, which in turn affects the performance of the flow battery. One substituted quinone at the negative electrode, when combined with Br2/HBr at the positive electrode, exhibits an open circuit voltage exceeding 1.0 V and a peak galvanic power density exceeding 0.24 W/cm2when fully charged.Fig. 1. Polarization plot (a) and galvanic power densities (b) of a substituted quinone-bromine flow battery at various states of charge (SOC). The electrodes are Toray carbon paper with no electrocatalyst. The membrane is Nafion 212. The negative side is 0.5 M substituted quinone in 1 M sulfuric acid. The positive electrode is 1.5 M hydrobromic acid, 0.25 M bromine.

Conifer reinvasion of montane meadows following experimental tree removal and prescribed burning

Tree invasion of mountain grasslands and meadows, pervasive throughout western North America, has become a management concern. Restoration of these systems requires tree removal and possibly prescribed burning; however, subsequent reinvasion by trees may compromise these efforts. In this study, we assess patterns of tree seedling establishment 8years after tree removal (with and without burning) from 1-ha experimental plots in conifer-invaded meadows in the Oregon Cascades. We quantify variation in the timing, spatial distribution, and density of establishment of species with differing seral roles; compare effects of burning; and explore relationships with distance to and characteristics of adjacent, residual forests. Seedlings established continuously after tree removal, dominated by late-seral Abies grandis (cumulative plot densities of 116–460/ha). Early-seral Pinus contorta and Pseudotsuga menziesii were much less abundant (0–25 and 1–52/ha, respectively). Frequency (percentage of 5×5m subplots) and density of seedlings did not differ between treatments (burned vs. unburned), nor did seedling growth rates (inferred from height-age relationships). Seedling spatial distributions and relationships with distance to adjacent forest varied both within and among plots. On average, however, seedlings were concentrated along edges. In the 5-m outer band of subplots, frequency averaged 37% and density, 682/ha, compared to 18% and 140/ha in the remaining cores of the plots. Density of Abies was significantly greater along more shaded southern edges (north-facing) than along more exposed northern edges (south-facing), but it declined steeply with distance from edge, especially for southern edges. Plot-level density of Abies seedlings was also correlated with basal area of Abies in the adjacent forest (but not with tree density or summed height). Strong relationships of seedlings with distance, exposure, and characteristics of adjacent forests suggest that conifer reinvasion can be minimized by targeting tree removal to maximize distances to residual trees. However, absence of a treatment effect suggests that burning—critical for reducing woody residues—does not increase the probability of seedling establishment, particularly in systems in which late-seral species are the principal colonists.

Comparison of remote sensing and ground-based methods for determining residue burn pile wood volumes and biomass

Following forest harvest, residues left on site are often piled and burned. Quantification of residue piles is required in many jurisdictions to estimate billable waste, harvest efficiency, smoke emissions, C budgets, and available bioenergy biomass. Piled residues and harvested wood were measured on four blocks of a second-growth Douglas-fir forest in coastal British Columbia. Pile wood volumes were determined by two ground-based methods (a Waste and Residue Survey (WRS) and a geometric equation (EEP) used for smoke emissions) and by two geospatial methods using orthophotography (GIS) and LiDAR. Eight sample piles were disassembled to determine plot densities (PD) and packing ratios (PR). Plot density did not differ between the WRS and GIS method. Packing ratios of the EEP were 50% of that of the LiDAR method. LiDAR pile bulk volume and PR were negatively correlated. Choice of LiDAR digital elevation model had no significant effect on pile bulk volumes. The WRS method underestimated pile areas by 50% and the EEP method overestimated pile bulk volumes by two times. Pile wood volumes from the WRS method (20.0 m3·ha−1 (SE 2.8)) were 30%–50% of those for all other methods (46.1–60.4 m3·ha−1). The EEP method overestimated wood volume if nonspecific PRs were used. The residues to harvest ratio for the WRS method (3.3% (SE 0.45)) was lower than for all other methods (7.5%–9.6%). Total pile wood biomass from LiDAR was 25.4 t dry mass·ha−1 (SE 5.9). Ground-based methods are still required to determine PD or PR. Since their estimation depends on the method used to determine pile area or bulk volume, and may vary with pile size and type, they remain the major source of uncertainty in determining pile wood volumes. However, use of remote sensing techniques to determine the area or bulk volume of all piles in a cutblock can improve estimates of pile wood volumes and biomass.

Species Sensitivity Distribution Estimation from Uncertain (QSAR-based) Effects Data

In environmental risk assessment, Species Sensitivity Distributions (SSDs) can be applied to estimate a PNEC (Predicted No-Effect Concentration) for a chemical substance, when sufficient data on species toxicities are available. The European Chemicals Agency (ECHA) recommendation is 10 biological species. The question addressed in this paper, is whether QSAR-predicted toxicities can be included in SSD based PNEC estimates, and whether any modifications need to be made to account for the uncertainty in the QSAR-model estimates. This problem is addressed from a probabilistic modelling point of view. From classical analysis of variation (ANOVA), we review how the error-in-data SSD problem is similar to separation into between-group and within-group variance. ECHA guidance suggests averaging similar endpoint data for a species, which is consistent with group means, as in ANOVA. This exercise reveals that error-in data reduces the estimation of the between species variation, i.e. the SSD variance, rather than enlarging it. A Bayesian analysis permits the assessment of the uncertainty of the SSD mean and variance parameters for given values of mean species toxicity error. This requires a hierarchical model. Prototyping this model for an artificial five-species data set seems to suggest that the influence of data error is relatively minor. Moreover, when neglecting this data error, a slightly conservative estimate of the SSD results. Hence, we suggest including (model-predicted) data as model point estimates and handling the SSD as usual. The Bayesian simulation of the error-in-data SSD leads to predictive distributions, being an average of posterior spaghetti plot densities or cumulative distributions. We derive new predictive extrapolation constants with several improvements over previous median uncertainty log10HC5 estimates, in that they are easily calculable from spreadsheet Student-t functions and based on a more realistic uniform prior for the SSD standard deviation. Other advantages are that they are single-number extrapolation constants and they are more sensitive to small sample size.

Grazing Exclusion Effect on Soil and Vegetation Properties in Imam Kandi Rangelands, Iran

Most of the rangeland of Urmia in Iran is degraded and will require considerable reclamation to achieve a desirable state. The aim of this study was to evaluate the effects of 14 years of grazing exclusion on vegetation and soil properties in Imam Kandi rangelands. Sampling in both grazing exclosure and grazed areas were conducted using a systematic randomized sampling method. Six 100-m long transects were randomly located in each area and ten 1 × 1 m sampling plots were located along each transect. Within each plot, species presence, canopy cover, species yield, and plant densities were measured. Soil cores were taken in the center of each vegetation sampling plot at 0–30 cm and 30–60 cm depths. Organic matter, nitrogen content, the amounts of phosphorus and potassium, electrical conductivity (ECe), pH, the percentage of CaCO3, and soil texture were determined for each sample. Results indicate differences in plant canopy cover, species composition, and yield between the grazing exclosure and the control site. All plant growth forms at the exclusion site differed from those at the grazed site. Biomass of perennial grasses, perennial forbs and annual forbs was greater at the exclusion site than at the grazed site, and biomass of annual grasses and shrubs at the control site was greater than at the exclusion site. Overall grazing exclosure site improved the vegetation composition and soil quality parameters ECe, pH, organic matter, nitrogen, phosphorus, and potassium content relative to the grazed site.

Local offspring density and sex ratio affect sex allocation in the great tit

The expected fitness gain for offspring of a given sex may depend on local population sex ratio and density. Knowing the influence of such social factors on brood sex ratios may contribute considerably to the understanding of sex allocation in higher vertebrates. For 3 consecutive years, we manipulated sex ratios and densities of juvenile great tits (Parus major) within forest plots and investigated how next year’s brood sex ratios were affected. For yearling female breeders, we considered the treatment of the plot of fledging and settlement and for experienced female breeders the treatment of the breeding plot. Experienced females produced more female offspring at increased plot densities and more males at reduced densities. Yearling female’s brood sex ratio was not affected by the density treatment but was positively related to the natural density in the plot of fledging. The plot sex ratio treatment affected sex allocation differently for yearling and experienced females. Yearling females produced more females when fledged from male-biased plots and more males when fledged from female-biased plots. Experienced females produced more females in control plots and unbiased brood sex ratios in male- and female-biased plots. Our results show that experimental changes in local sex ratio and density generate social or environmental cues that are used in sex allocation. We cannot show that sex allocation was adaptive. However, natural and experimental plot density and experimental plot sex ratio related differently to sex allocation for yearling and experienced females, which suggest that several sex allocation scenarios might act simultaneously. Key words: frequency dependence, local competition, sex-biased dispersal, social environment, Trivers and Willard hypothesis.[Behav Ecol]

Fruit yield, essential oil concentration and composition of three anise cultivars (Pimpinella anisum L.) in relation to sowing date, sowing rate and locations

Three field experiments were conducted to evaluate the effect of sowing date and plant density on phenology, fruit yield and essential oil quality of three anise cultivars (Pimpinella anisum L.) at two different ecological conditions Gross-Gerau and Giessen, Germany. The experiments were designed as RCBD under factorial plot arrangement with two factors: cultivars in main plot and plant densities in sub plots realized in two sowing dates. Results showed that aniseed sown on April 1st had higher fruit yield in comparison with two weeks delayed sowing. Delayed sowing induced strong effects on yield contributing parameters such as branches/plant, umbels/plant, fruits/plant and 1000-fruit weight which were all reduced. The highest fruit yield was related to lower plant densities of 39plantsm−2 (Giessen) and 200 and 374plantsm−2 (Gross-Gerau). Higher plant density reduced branches/plant, umbel/plant, fruits/plant and 1000-fruit weight and led to lower fruit yield. The essential oil concentration of anise fruits was not affected by different levels of plant densities. A higher concentration of essential oil was synthesized in delayed sowing date in Gross-Gerau 2009 as compared to earlier sown anise plants. The essential oil concentration of anise showed no remarkable variation regarding sowing date and plant density. Cv. Hild Samen synthesized a significant higher concentration of estragol and trans-anethole. From all tested cultivars cv. Hild Samen was characterized by lowest fruit yield as well as lowest essential oil concentration. For successful cultivation, aniseed should be sown as soon as possible in April with a plant density of 50–200plants/m2 considering soil conditions.

Impact of a spruce budworm outbreak in balsam fir and subsequent stand development over a 40-year period

Nine 0.04-ha plots were established in 1956 (age 35 years) in a balsam fir (Abies balsamea [L.] Mill.) stand in northwestern New Brunswick, Canada to determine the impact of an uncontrolled spruce budworm (Choristoneura fumiferana [Clem.]) outbreak on stand development. The plots were measured annually from 1956 to 1961 and at five-year intervals from 1965 to 1995. Moderate to severe defoliation occurred from 1951 to 1957 and again in 1975 to 1977, 1981, and 1986 to 1988. Budworm-caused mortality from 1956 to 1961 (age 35 to 40 years) varied considerably among plots, reducing volume by 35 to 113 m3/ha (34%-84%), and resulting in a wide range of post-outbreak plot densities. Plots were grouped into three post-budworm outbreak (1965, age 45 years) basal area classes, of ≤ 20 m2/ha, 21 to 27 m2/ha, and ≥ 28 m2/ha, to examine stand recovery. Recovery of volume up to age 60 years ranged from 72 to 132 m3/ha, in the lowest to highest basal area classes, respectively. From age 60 to 75 years, five plots declined in volume due to the onset of stand break-up and four plots increased in volume. By age 60 years, survivor growth was greatest in the high basal area plots, ranging from 6.2 to 9.0 m3/ha/yr in seven plots, versus 2.6 to 3.2 m3/ha/yr in two low basal area plots. From age 60 to 75 years, survivor growth averaged only 2.8 to 5.2 m3/ha/yr, and the stand exhibited major decline, with 63%, 74%, and 78% mortality of fir ≤ 15 cm DBH in the low to high basal area plots, respectively. Budworm-caused "thinning" in the 1950s largely determined subsequent stand development and the rate of stand break-up 25 to 35 years later. The timing and rate of natural stand decline was strongly influenced by post-outbreak stand density. Key words: budworm-caused mortality, stand structure, stand development, growth, mortality, stand density

Effect of Control Plot Density, Control Plot Arrangement, and Assumption of Random or Fixed Effects on Nonreplicated Experiments for Germplasm Screening Using Spatial Models

Early generation selection experiments typically involve several hundred to thousands of lines. Various systematic and statistical techniques have been developed to increase effectiveness and efficiencies in such experiments, including the development and application of spatial statistical models. In this study, mixed model equations were used to provide least squares means (LSMEANs) and best linear unbiased predictors (BLUPs) and compare selection effectiveness and efficiencies to observed (Y) and true values in simulated experiments varying in size (10 × 10, 20 × 20 and 30 × 30 grids), control plots densities (0, 5, 10, 20, and 50%), control plot arrangements (high, medium, and low A‐optimality), and spatial range of influence (short and long). Results were similar for all grid sizes. In experiments in which the simulated land areas were highly variable (short range), none of the predictors, Y, LSMEAN, or BLUP, were very effective in identifying the true superior genotypes. When the simulated land areas were less variable (long range), use of BLUPs consistently resulted in the highest proportion of true top ranking genotypes identified across all control plot densities, while using the observed values consistently resulted in identification of the lowest proportion of the true top ranking genotypes. Effectiveness of LSMEANs was dependent on control plot density and arrangements. Use of BLUPs for early generation germplasm screening experiments should result in a high effectiveness in selecting truly superior germplasm and high efficiency because of the ability to account for spatial variability with the use of few or no control plots.

Biotic resistance to invader establishment of a southern Appalachian plant community is determined by environmental conditions

Summary Tests of the relationship between resident plant species richness and habitat invasibility have yielded variable results. I investigated the roles of experimental manipulation of understorey species richness and overstorey characteristics in resistance to invader establishment in a floodplain forest in south‐western Virginia, USA. I manipulated resident species richness in experimental plots along a flooding gradient, keeping plot densities at their original levels, and quantified the overstorey characteristics of each plot. After manipulating the communities, I transplanted 10 randomly chosen invaders from widespread native and non‐native forest species into the experimental plots. Success of an invasion was measured by survival and growth of the invader. Native and non‐native invader establishment trends were influenced by different aspects of the biotic community and these relationships depended on the site of invasion. The most significant influence on non‐native invader survival in this system of streamside and upper terrace plots was the overstorey composition. Non‐native species survival in the flooded plots after 2 years was significantly positively related to proximity to larger trees. However, light levels did not fully explain the overstorey effect and were unrelated to native survivorship. The effects of understorey richness on survivorship depended on the origin of the invaders and the sites they were transplanted into. Additionally, native species growth was significantly affected by understorey plot richness. The direction and strength of interactions with both the overstorey (for non‐native invaders) and understorey richness (for natives and non‐natives) changed with the site of invasion and associated environmental conditions. Rather than supporting the hypothesis of biotic resistance to non‐native invasion, my results suggest that native invaders experienced increased competition with the native understorey plants in the more benign upland habitat and facilitation in the stressful riparian zone.

Deviation of the level populations of iron atoms and ions from the boltzmann distribution in an inductively coupled plasma. Part 1. Spatial and power dependences

The deviation from the Boltzmann distribution was studied for the excitation of iron atoms and ions in an inductively coupled plasma supported by a Meddings–Anderson–Kaiser torch. Its spatial and power dependences are discussed in conjunction with such properties as curvature of the Boltzmann plot, tangential temperature and relative number densities of the iron atoms and ions.