Average Annual Density Research Articles

First Abundance Estimates of Heaviside’s (Cephalorhynchus heavisidii) and Dusky (Lagenorhynchus obscurus) Dolphins Off Namibia Using a Novel Visual and Acoustic Line Transect Survey

Knowledge of a population’s abundance is of primary importance for conservation management. However, robust estimates of abundance are often difficult to obtain, especially for cetaceans which spend most of their lives submerged. Cetacean abundance is commonly estimated using aerial or vessel-based line transect surveys and distance sampling methods. During 2012–2014, the first line transect surveys to estimate cetacean abundance were conducted in Namibian waters. Surveys took place in the Namibian Islands’ Marine Protected Area (NIMPA), a large MPA located along the southern Namibian coastline. A combined visual and acoustic double-platform survey configuration was used to investigate the factors affecting detectability of the endemic Heaviside’s dolphin (Cephalorhynchus heavisidii) and dusky dolphin (Lagenorhynchus obscurus obscurus). The present analysis estimates the probability of detection on the transect line (g(0)) for these two species and generates density and abundance estimates which incorporate a correction for both animals missed on the transect line and attractive responsive movement. The average annual baseline density and abundance estimates for Heaviside’s dolphins in the NIMPA region during 2012–2014 were 0.08 individuals/km2 (CV = 28.6%, 95% CI = 0.04–0.15 individuals/km2) and 1594 individuals (CV = 28.6%, 95% CI =776–3275), respectively. The average annual baseline density and abundance estimates for dusky dolphins in the NIMPA region during 2012–2014 were 0.16 individuals/km2 (CV = 26.2%, 95% CI = 0.10–0.28 individuals/km2) and 3493 individuals (CV = 26.2%, 95% CI: 2015–6052), respectively. A discussion on the distribution of Heaviside’s and dusky dolphins is provided for this region where such information are urgently needed. Based on existing knowledge of the species and area, these estimates are regarded as reasonable. They indicate moderate sized populations of animals within the NIMPA and provide an important first baseline on which future estimates can build.

Community structure of macrozoobenthos and its relationship with environmental factors in Sanmen Bay, Zhejiang, China

To understand the status and dynamics of macrozoobenthos community in Sanmen Bay, we collected benthos samples by Agassiz trawl in November 2015, and February, May and August in 2016. The results showed that: 1) A total of 119 macrozoobenthos species were recorded, with main groups of fishes, crustaceans and molluscs, accounting for 79% of the total number of species. 2) The dominant species of macrozoobenthos throughout the year were Leptochela gracilis, Hyperacanthomysis longirostris and Amblychaeturichthys hexanema. The identity of dominant species changed significantly in different seasons. 3) The annual average biomass and density were 0.025 g·m-2 and 0.07 ind·m-2, respectively. 4) The Shannon's diversity index of macrozoobenthos in Sanmen Bay varied from 2.21 to 3.18, the Margalef's species richness index varied from 3.25 to 3.78, and the Pielou's evenness index varied from 0.53 to 0.79. Results from abundance-biomass curve analysis showed that the community was moderately disturbed in spring and winter, and slightly disturbed in summer and autumn. Results from Canonical correspondence analysis showed that water depth, temperature, salinity, and pH were the most important environmental factors affecting macrozoobenthos community.

Temporal variation in the population of bulbuls (Family Pycnonotidae) in lower montane forest, Northern Thailand

Abstract. Ponpituk Y, Siri S, Safoowong M, Suksavate W, Marod D, Duengkae P. 2020. Temporal variation in the population of bulbuls (Family Pycnonotidae) in lower montane forest, Northern Thailand. Biodiversitas 21: 3644-3649. Temporal variations in the population of bulbuls (Family Pycnonotidae) were studied over the course of four years in a 16-ha lower montane permanent plot, Northern Thailand. This study aimed to determine the relationship of the temporal variation of forest gaps with the population size of the bulbul, which plays a crucial role in seed dispersal and insect control in tropical forest ecosystems. This long-term monitoring study in a permanent plot was conducted monthly from January 2016 through October 2019. Data were collected using the mist-netting method for the capture-recapture protocol with individual bird banding. A total of 33,120 traps hour for 46 months,180 traps hour per day and 720 traps hour per month were recorded. The banding of a total of 94 individual bulbuls resulted in their classification into 5 species, consisting of Puff-throated Bulbul (Alophoixus pallidus), Mountain Bulbul (Ixos mcclellandii), Black-crested Bulbul (Pycnonotus flaviventris), Ashy Bulbul (Hemixos flavala) and Flavescent Bulbul (Iole virescens). The annual average density of bulbul for four years tended to decrease, but the difference was not significant. The highest average population occurred in 2016 and the lowest in 2018 with the changes being attributable to forest gap. Over time, monthly detection of bulbuls decreased gradually under closed canopy conditions, while in forest gaps, bird detection remained constant. As gap conditions so did detection probabilities. Our findings suggest that natural forest gaps can play an essential role as a temporal inhibitor to the rapid bird population decrease in the lower montane forest. This study will be useful for bird conservation and in balancing ecosystems for sustainability and providing interest in conservation initiatives requiring spatially explicit estimates of density.

Young urban households in Shanghai, China: Characteristics of energy use and attitudes

Current domestic energy saving policies are mainly focused on building fabrics and domestic appliances, with less attention to address occupants’ energy use behaviour and their attitudes towards potential policies. This study aims to address the gap in understanding domestic energy use through a survey in Shanghai, which focuses on the characteristics of energy use in urban households, the demographics of high energy consumers, and attitudes towards energy saving and smart meters. The survey results reveal a great variety within the target group of urban young households, with the average annual power density value of 10.9 kW h/m2/occupancy, between 2.0 to 35.7 kW h/m2/occupancy, varying by a factor of about 17.8. Intensive energy use results from stricter comfort standards and longer heating and cooling periods. For the targeted high energy consumers, real-time electricity pricing is suggested as an effective policy instrument. The respondents are more likely to agree with policy instruments of fiscal incentives and communication, rather than consumption or price control. The overall research results could be used by policy-makers in the design of energy saving policies relating to smart meters and contribute to the development of a more sustainable city in China.

The Proximal Drivers of Large Fires: A Pyrogeographic Study

Variations in global patterns of burning and fire regimes are relatively well measured, however the degree of influence of the complex suite of biophysical and human drivers of fire remains controversial and incompletely understood. Such an understanding is required in order to support current fire management and to predict the future trajectory of global fire patterns in response to changes in these determinants. In this study we explore and compare the effects of four fundamental controls on fire, namely the production of biomass, its drying, the influence of weather on the spread of fire and sources of ignition. Our study area is southern Australia, where fire is currently limited by either fuel production or fuel dryness. As in most fire-prone environments, the majority of annual burned area is due to a relatively small number of large fires. We train and test an Artificial Neural Network’s ability to predict spatial patterns in the probability of large fires (> 1,250 ha) in forests and grasslands as a function of proxies of the four major controls on fire activity. Fuel load is represented by predicted forested biomass and remotely sensed grass biomass, drying is represented by fraction of the time monthly potential evapotranspiration exceeds precipitation, weather is represented by the frequency of severe fire weather conditions and ignitions are represented by the average annual density of reported ignitions. The response of fire to these drivers is often non-linear. Our results suggest that fuel management will have limited capacity to alter future fire occurrence unless it yields landscape-scale changes in fuel amount, and that shifts between, rather than within, vegetation community types may be more important. We also find that increased frequency of severe fire weather could increase the likelihood of large fires in forests but decrease it in grasslands. These results have the potential to support long-term strategic planning and risk assessment by fire management agencies.

Assessing rainfall erosivity and erosivity density over a western Himalayan catchment, India

The present study aims to assess rainfall erosivity and erosivty density both in space and time over the Suketi River catchment of western Himalayan region in India during 1971–2015. The data used comprises of daily rainfall measurements at three rain gauge stations, which are sparsely distributed over the catchment. Rainfall erosivity was assessed by employing Wischmeier and Smith algorithms, whereas erosivity density was estimated by applying Kinnell’s algorithm. The spatial distribution of both algorithms was analyzed through Kriging method based on geographical information system. The obtained results indicate remarkable year-to-year, seasonal and monthly variations in average annual rainfall erosivity and erosivity density. Apart from this, individual cases of high and very high rainfall erosivity and erosivity density were noticed. The long-term average annual rainfall erosivity and erosivity density revealed a general decreasing trend. This decreasing trend in rainfall erosivity was found to be statistically significant at 0.05 significance level, whereas it was found to be non-significant for erosivity density. The highest values of both indices were observed in the month of July followed by August and June particularly in northern parts. These results indicate that July month followed by August and June are the most susceptible months for soil erosion over the Suketi River catchment with lower reaches (northern) being the most vulnerable one. Finally, results of this study will be valuable for farmers, agronomists and regional planners in chalking out best management practices for reducing water erosion in vulnerable areas of the catchment.

Vertical Extrapolation of Wind Speeds Under a Neutral Atmosphere and Evaluation of the Wind Energy Potential on Different Sites in Guinea

This study has been focused on the vertical profile determination of the winds under a neutral atmosphere in order to assess of the wind power density at three sites in Guinea. The power law has been used as an extrapolation model for wind speed. The Weibull function has been used to estimate the wind power density. The satellite data at 10 m above the ground recorded during the period from January 2001 to December 2015 on the sites of Conakry, Mamou and N’zérékoré sites were used. The results indicate that the Conakry site is the windiest of the three study sites with an average speed estimated at 2.83 m.s^-1 at 10 m and 4.23 m.s^-1 at 100 m above the ground. The form parameter k of Weibull varies from 1 to 1.8 and the scale parameter c from 1.5 to 6 m.s^-1 and are both increasing functions of altitude. Finally, the quantities of energy obtained at the three sites reveal that only the Conakry site could be suitable for the installation of small wind turbines for the wind energy production. The average annual density is estimated at 45.77 W.m^-2 at 10 m; 85.62 W.m^-2 at 50 m and 113.31 W.m^-2 at 100 m. On the Mamou and N’zérékoré sites, the pumping water from multi-blade wind turbines could be considered.

Numerical Study of the Power Range of Wind Devices Adapted to the Wind Potential of the Coastal Region of Cameroon

Profitable exploitation of wind energy requires a good estimation of the wind's potential. This preliminary study phase represents a key factor in the implementation of a wind project. In this perspective, this article assesses the wind energetic potential of the coastal region of Cameroon and offers a range of suitable wind turbines. The wind analysis is carried out using a Weibull model with two parameters, the form factor k and the scale factor C. The determination of the Weibull’s parameters is then carried out by the Maximum Likelihood Method (MLM), using measured wind data from the meteorological station of the multinational company COTCO-Cameroon for the period of 2009 to 2019.The study reveals that the average annual wind speed varied between 2.64 m/s in 2009 and 4.36 m/s in 2019 at 10 m from ground level. By contrast, the annual average power density varies between 35.9 W/m 2 to 195.3 W/m 2 , respectively from 10m to 100m from ground level. The range of wind turbines retained is that of small wind turbines, whose powers are included between 1kW to 100 kW, with starting speeds and nominal speeds respectively in the intervals (1.5-3m/s) and (10-12 m/s).

Spatial variation of ecological environment quality and its influencing factors in Poyang Lake area, Jiangxi, China

Based on Landsat 8 OLI/TIRS remote sensing image data, indices including NDVI, WET, NDSI and LST were selected from the aspects of greenness, humidity, dryness and heat respectively, and remote sensing ecological index (RSEI) was constructed by principal component analysis to analyze the spatial distribution of ecological environment quality in Poyang Lake area in 2014. The spatial heterogeneity and its influencing factors of the original remote sensing ecological index (RSEI0) were quantitatively analyzed using spatial autocorrelation, semi-variance function, maximum information coefficient, and factor detection. The results showed that ecological environment quality of Poyang Lake area was generally at a moderate level in 2014 and that the overall spatial distribution pattern from southwest to northeast gradually improved. The exploratory spatial data analysis showed that RSEI0 had strong spatial clustering and spatial heterogeneity under the sampling of 2 km grid element. The nugget effect value of RSEI0 was 25.8%, which belonged to medium spatial variability and was mainly affected by structural factors. The results of maximum information coefficient and factor detection analysis showed that slope had the strongest positive correlation with RSEI0. Slope, elevation, curvature, annual average rainfall, annual average temperature, proportion of garden forest area, proportion of cultivated land area, proportion of construction land area, annual average population density and annual average GDP significantly affected RSEI0, but with different magnitude of influences. Among them, the slope independent explanatory power was 57.1%, which was the main factor affecting spatial variation of RSEI0 in Poyang Lake area. Our results could provide reference for the protection and management of ecological environment in the Poyang Lake area.

Global estimations of wind energy potential considering seasonal air density changes

The literature typically considers constant annual average air density when computing the wind energy potential of a given location. In this work, the recent reanalysis ERA5 is used to obtain global seasonal estimates of wind energy production that include seasonally varying air density. Thus, errors due to the use of a constant air density are quantified. First, seasonal air density changes are studied at the global scale. Then, wind power density errors due to seasonal air density changes are computed. Finally, winter and summer energy production errors due to neglecting the changes in air density are computed by implementing the power curve of the National Renewable Energy Laboratorys 5 MW turbine. Results show relevant deviations for three variables (air density, wind power density, and energy production), mainly in the middle-high latitudes (Hudson Bay, Siberia, Patagonia, Australia, etc.). Locations with variations from −6% to 6% are identified from summers to winters in the Northern Hemisphere. Additionally, simulations with the aeroelastic code FAST for the studied turbine show that instantaneous power production can be affected by greater than 20% below the rated wind speed if a day with realistically high or low air density values is compared for the same turbulent wind speed.

The Use of Littoral Benthic Macroinvertebrates of the Martín Garcia Island Nature Reserve as Indicators of Water Quality

At Martín García Island—a Natural Reserve located at the confluence of the Paraná and Uruguay rivers—we used benthic-macroinvertebrate biotic indices to elucidate the structure and community parameters of the littoral benthos and their response to environmental variables and to evaluate the island's coastal water quality. Seasonal campaigns were carried out (March/1995-March/1996) at eight sites of the island's littoral sites, selected according to the substrate characteristics (fine sands, sandy-silty, reedbed, and silty with great hydrophyte development). From the sites with a soft substrate, triplicate samples were extracted using a 225-cm2 Ekman manual dredge. The relative abundances of 71 taxa were measured: Nematoda, Turbelaria, Oligochaeta (23 sps.), Mollusca (21 sps.), Crustacea (11 sps.), Insecta (12 families), and Tardigrada. Macroinvertebrate density: 15-58,800 ind.m-2. Analysis of variance revealed significant differences between the average annual macroinvertebrate-population densities among the five sites (F: 3.059; p<0.05). Site 7 exhibited the highest density at 38,700±19,000 ind.m-2 Community parameters: diversity (H'; 0.77-2.16 bits); equitability (J; 0.16-1.02), and species richness (S; 3-29). Canonical-correspondence analysis indicated the environmental variables experiencing the greatest fluctuation to be: dissolved-oxygen concentration, pH, temperature, and conductivity. The results of this analysis suggest that macroinvertebrate-species distribution involves the physicochemical conditions of the water. Of the correlation between species and environmental variables, 95.5% were distributed on the canonical-correspondence ordering diagram's Axis 1. Functional feeding groups: In all sites and seasons, the gathering collectors predominated, followed by the scrapers, filtering collectors, shredders, and predators. Macroinvertebrate Index of Pampean-Rivers: values generally ranged from weak to weak-to-very-weak to zero pollution, but there was a high degree of pollution (2.4 and 1.5) in the spring of 1995.

Technical and economic analysis of wind energy potential in Uzbekistan

Uzbekistan is the most populated country in Central Asia with a population of about 32 million people. Unfortunately, the country's electricity generation is highly dependent on fossil fuels and the electricity generation infrastructures in the country are relatively old and obsolescence. The energy security of the country could be significantly improved by investing in environmental-friendly energy sources in order to reduce its dependence on the natural gas in the future. The present study aims to assess the wind energy potential of Uzbekistan for the very first time. The hourly wind speed data of 17 different sites (10 m height) in a typical meteorological year are collected and utilized. The collected data are fitted in the widely utilized statistical two-parameter Weibull distribution function. Several performance metric indicators of annual power density, energy production, capacity factor and levelized cost of energy (LCOE) are used to assess the technical and economic feasibility of the systems. In addition, the study assesses and compares 15 different commercially available wind turbines to infer the best option for implementation in the country. The results show that the average annual wind speed, power density and energy production are in the range between 0.61 and 3.98 m/s, 1.74–88.55 W/m2, and 15.27–775.72 kWh/m2, respectively at a height of 10 m above the ground. It is observed that Nukus, Kungrad, Ak Bajtal, and Buhara are the best sites for wind energy development in Uzbekistan. The study is expected to aid policymakers, designers and investors in decision-making regarding the development and deployment of wind energy technology as a future power source in the country.

Assessment of Wind Power Potential and Economic Analysis at Hyderabad in Pakistan: Powering to Local Communities Using Wind Power

Wind power is the fastest growing and environmentally sustainable source of energy among all available renewable energy resources. The primary objective of this paper is to analyze the wind characteristics and power potential at Hyderabad, Southeastern province in Pakistan. Two years of wind speed data measured at 10 m above ground level (AGL) have been considered in this study. The annually, monthly, and seasonal variations in wind speed were analyzed, and minimum, maximum, and average values of recorded wind speeds are presented in this paper. Weibull and Rayleigh distribution functions have been applied to analyze the wind characteristics and evaluate the wind power potential of the proposed site. The Weibull shape k and scale c parameters have been estimated using the Weibull function. The higher values of k showed that the wind speed is steady at the site. The average wind speed was found above 6 m/s throughout the year. The most probable wind speed (Vmp) and maximum carrying energy (VmaxE) wind speed were also calculated using Weibull parameters. Root mean square error (RMSE), the coefficient of determination (R2), and mean bias error (MBE) were computed to ensure the good fit of Weibull distribution function. The annual average wind power and energy densities were estimated at more than 255 W/m2 and 2245 kWh/m2, respectively. The power density calculated by Weibull and Rayleigh functions was compared with that calculated by using measured wind data. The energy output and capacity factor of different commercially available wind turbines (WTs), i.e., power ratings from 0.33 to 2.75 MW, have been calculated. The cost of energy was estimated and ranged from $19.27 to $32.80 per MWh. Wind power potential and economic analysis of the collected data reveals that the site is suitable for developing wind power generation projects to power the local communities.

Vertical Profile of Wind Speed in the Atmospheric Boundary Layer and Assessment of Wind Resource on the Bobo Dioulasso Site in Burkina Faso

This study investigates both the characteristics of the vertical wind profile at the Bobo Dioulasso site located in the Sudanian climate zone in Burkina Faso during a day and night convective wind cycle and the estimation and variability of the wind resource. Wind data at 10 m above ground level and satellite data at 50 m altitude in the atmospheric boundary layer were used for the period going from January 2006 to December 2016. Based on Monin-Obukhov theory, the logarithmic law and the power law made it possible to characterize the wind profile. On the study site, the atmosphere is generally unstable from 10:00 to 18:00 and stable during the other periods of the day. Wind extrapolation models were tested on our study site. Fitting equations proposed are always in agreement with the data, contrary to other models assessed. Based on these equations, the profile of a day and night cycle wind cycle was established by extrapolation of wind data measured at 10 m above the ground. Lastly, the model of the power law based on the stability was used to generate data on wind speed from 20 m to 50 m based on data from 10 m above the ground. Weibull function was used to characterize wind speed rate distribution and to calculate wind energy potential. The average annual power density on the site is estimated at 53.13 W/m2 at 20 m and at 84.05 W/m2 at 50 m, or 36.78% increase. Considering these results, the Bobo-Dioulasso site could be appropriate to build small and medium-size turbines to supply the rural communities of the Bobo Dioulasso region with electricity.

Parameter Characterization of High Latitude Geomagnetic Storms in 2010

Geomagnetic storm is a kind of severe disturbance that lasts for more than ten hours to several tens of hours in the entire Earth’s magnetosphere. This paper uses the NRLMSISE-00 model to calculate the temperature and density data. According to the surveyed medium magnetic storm events, the characteristics of daily average density and temperature in the occurrence of magnetic storms in 2010 were studied. At the same time, high latitude meridians were taken as research objects. Divide the temperature and density characteristics at different heights. Results showed that the annual trend of density is the same for different heights, and there is an average of the average density every day on the six medium magnetic storm mountains. For the average daily temperature, each medium magnetic storm event corresponds to a temperature peak. The peak temperature on April 5 was the highest temperature throughout the year, consistent with the annual average density distribution. Due to the intensity of the magnetic storm, the temperature of a large area of bright areas rose sharply on April 12, which is also the highest in the year. At 18:00 on May 2, it was the peak time of the moderate magnetic storm event caused by CIR, but May 3 was the date of the peak temperature. This peak delay is reasonable.

Spatiotemporal shifts in distribution of a recolonizing black bear population

AbstractFollowing one of the most successful relocations of a large carnivore species, American black bears (Ursus americanus; hereafter bears) have expanded from Arkansas to the Ozark Highlands of southern Missouri, USA, where they were potentially extirpated in the early 1900s. Our first objective was to estimate spatial and temporal shifts in probability of bear presence to understand the population distribution in Missouri. Our second objective was to assess which factors might influence any detected shifts. We used public sightings of bears to develop statewide spatial distribution models for early (1991–2003) and late (2004–2015) bear presence probability in Missouri using maximum entropy modeling and determine the rate and direction of population expansion. We evaluated the effects of environmental variables (e.g., land cover, roads) on bear presence probability and predicted the total area of three levels of bear presence probabilities. The average annual density of bear sightings increased temporally by about 3.4/1000 km2 in Missouri. The Ozark Highlands ecoregion contained the highest average annual density of sightings during both time periods. The bear presence probability increased spatially about 29 km in a north–northwest direction between the two time periods and the distribution became more dispersed over time. Our results corroborate prior findings suggesting bear presence is greatest in forests and rural areas. However, the increased importance of cultivated crops over time combined with the consistently positive relationship with roads indicates little negative effects from anthropogenic features on the bear presence probability in Missouri.

Spatial–Temporal Distribution Characteristics of PM2.5 in China in 2016

Air pollution in China, mainly caused by PM2.5, has become worse in recent years. Large-scale studies on spatial–temporal distribution characteristics of PM2.5 in China have been carried out. Little research was focused on nationwide China, and most previous studies have paid little attention to western China. Based on the observed PM2.5 concentration sample data in 2016 from 1445 air monitoring sites in 367 cities, our research reveals the spatial–temporal variations of PM2.5 concentrations and the possible impacting factors in China using spatial statistical and regression models. The results show that (1) PM2.5 concentrations varied hourly, daily, monthly, and seasonally. The hourly averaged values have two peaks and two valleys every day; the daily and monthly averaged values show U-shaped patterns; and the seasonal averaged values are high in winter but low in summer, with spring and autumn somewhere in between. (2) The Huanyong Line is the E–W dividing boundary between high and low pollution values in China; the Yangtze River and the second ladder dividing line in the east and west of Hu Huanyong Line are the respective S–N dividing boundaries. (3) The concentration of PM2.5 shows a significant clustering pattern in Xinjiang and the North China Plain, as the centers of the dual core of the “hot spots”. The “cold spots” consist of the southeast coastal areas, Tibet, and several other cities with good air quality. The warm temperate zones and subtropical regions are places for hot spots and cold spots, whose rankings and locations are both very sensitive to temperature. (4) China’s air quality is good in the first half of the year and becomes worse in the second half. The spatial distribution of PM2.5 concentrations mainly follows a NE–SW direction, and the air quality in North China is significantly worse than that in the south. (5) The regression relation and spatial variability of PM2.5 pattern and its impacting factors are discussed from both global and local dimensions. Overall, if the aridity index, average annual temperature, industrial GDP, and road network density increased by 1%, PM2.5 concentrations would increase by 66.9, 35.7, 29.1, and 17.4%, respectively. From a local perspective, the positive and negative influences of each impacting factor exist, and the influence differs in different geographical locations.

Investigation of Lightning Flash Locations in Isolated Convection Using LMA Observations

AbstractUsing Lightning Mapping Arrays (LMAs), lightning flash locations in three dimensions have been investigated using multiple methods. Approximately 500,000 flashes were analyzed to reveal the variability of lightning initiation and propagation within convective storms. These flashes were produced by over 4,000 isolated convective storms during one warm season across diverse weather regimes in northern Alabama, Washington, D.C., central Oklahoma, and northeastern Colorado. Lightning locations are analyzed within the context of radar reflectivities and examined for vertical variability. Results show that storms in Colorado preferentially produced flashes at lower altitudes and in regions of higher reflectivity compared to the other regions. The regional differences in flash altitudes are largely attributed to the prevalence of anomalous polarity storms (middle‐ or low‐level dominant positive charge) in Colorado, as anomalous storms produced a majority of flashes at lower altitudes compared to storms with normal polarity charge structures (middle‐level negative charge). Conversely, anomalous storms are exceedingly rare in the other regions of study. The differences in flash altitudes are coincident with discrepancies between annual average densities estimated by satellite observations and LMA. Specifically, large differences in annual average flash density estimates exist in northeastern Colorado, which are not present in the other regions, suggesting that the lower altitude flashes in Colorado may be more difficult to detect by satellites.

Beaver Habitat Selection for 24 Yr Since Reintroduction North of Yellowstone National Park

Beavers (Castor canadensis) disappeared from drainages north of Yellowstone National Park in the mid-1900s because of trapping, a potential tularemia outbreak, and willow (Salix spp.) stand degradation by ungulates. Beavers were reintroduced in 1986 after a 40–yr absence with inventories of active-beaver structures completed each fall after reintroduction for 24 consecutive yr. We used this inventory to evaluate the expansion of beaver populations in a riparian environment recovering from past overuse by ungulates. Specifically, we investigated the density of active-beaver colonies and dams, the change in willow cover, and habitats associated with beaver expansion since reintroduction. Successful establishment and expansion of beavers indicate that sufficient resources were available to the population despite the suboptimal condition of riparian vegetation. Carrying capacity on third-order streams was reached approximately 14 yr after reintroduction (2000) with an average annual density of 1.33 (95th percentile = 1.23−1.44 active colonies/stream km) between 2000 and 2010. The average annual density of beaver dams during this time was 2.37 (2.04−2.71 active dams/stream km). Despite the beaver population being at carrying capacity in meadows since 2000, willow cover increased by 16% between 1981 and 2011. We speculate that beaver activities, together with reduced ungulate browsing from predation and habitat loss, combined to increase willow cover. Willow cover and height were positively associated with colony longevity, but numerous other influencing variables included secondary channels, sinuosity, stream depth, and sandbar width. Our results provide evidence that beaver reintroduction can be successful in riparian areas where willow stand condition is less than optimal and that beavers might ultimately improve willow condition. We suggest that reducing ungulate use of overgrazed riparian environments will facilitate the reestablishment of beaver populations. We also provide managers with habitats that should be identified in an environment targeted for reintroduction.

Adoption and Effect of Vetiver Grass (Vetiveria zizanioides) on soil Erosion in Somodo Watershed, South-Western Ethiopia

Soil erosion is an important cause of land degradation and consequent to soil fertility which reduces land productivity and production. This problem aggravates in developing countries like Ethiopia. To minimize this challenge, soil and water conservation with proper design is the first choice. The aim of this study was to assess the adoption and effect of Vetiver grass on soil erosion in Somodo watershed. Community mobilization was used to implement Vetiver grass on farm lands as bund stabilization and grass strip. Accordingly, more than 45 km (20%) of the watershed was covered by Vetiver grass on soil bund as bund stabilizing measure. The hedge was fully established within two years and formed averagely 36 cm raised terrace. The result of the study showed that within two years period about 36 cm soil was accumulated above the hedgerow. From mean annual soil deposition and average bulk density of the watershed, the mean annual soil loss was recorded 20.88 ton ha﹣1·year﹣1 in the absence of Vetiver hedge row as erosion barrier. In addition, field slope was reduced on average by 2.5% due to soil accumulated above Vetiver hedgerow. And phosphorus availability was found higher on the above hedgerow than below the hedge row while, exchangeable acidity was found less above the hedgerow than below the Vetiver hedgerow in the watershed which implies soil fertility improvement. The study recommends Vetiver hedgerow as an immediate mitigation measure for soil erosion on hill slopes and farm lands which can be implemented through community mobilization. Further study on how the Vetiver hedgerow improves phosphorus availability and decreases exchangeable acidity is also highly recommended.