Variation In Species Composition Research Articles

Evaluating the influence of environmental factors on the early life history growth of chub mackerel (Scomber japonicus) using a growth and migration model

Chub mackerel is one of the most important fisheries target species worldwide. These fish have large fluctuations in biomass, the mechanism of which remains unclear. This study developed a bioenergetics individual-based model for chub mackerel distributed in the Northwest Pacific and evaluated the dominant environmental factors that affect their early life history. The parameters in the bioenergetics model were obtained or estimated from previous studies, and a migration model with a gradient area search algorithm was coupled. The growth rate of chub mackerel was calibrated to in situ growth data by adjusting the half-saturation constant of consumption (K). During 2002–2016, the growth and migration of chub mackerel were reproduced using the model with satellite-derived forcing. The migration routes and growth were tightly coupled: individuals located to the north of the Kuroshio axis experienced a better prey environment, showed a relatively higher growth rate, and entered a better prey field by self-selected swimming. Years with more high-growth individuals in the model corresponded to observed higher recruitment (R) and recruitment per spawner (RPS). These results support the hypothesis that a higher growth rate in the early stage results in higher recruitment, because individuals with higher growth can migrate into a better prey environment. A negative correlation was found between R and the distance of the Kuroshio axis from the Boso Peninsula, indicating that when the Kuroshio axis was located closer to the Boso Peninsula, the water temperature of the coastal area increased, resulting in an increase in coastal-dominant zooplankton species, which positively affected the growth of chub mackerel in the early life stage. In addition, interannual variations in prey zooplankton species composition and the relative position of the Kuroshio to the spawning grounds partially influenced the early growth of chub mackerel. The results demonstrate the complex mechanisms of ocean currents and prey fields controlling the recruitment of small pelagic species.

Comparing satellites and vegetation indices for cover crop biomass estimation

• Adequate biomass is required for cover crops to provide significant ecological benefits. • Satellite imagery predicted field level cover crop biomass accurately. • Satellite imagery more accurately estimated biomass than handheld sensors. • At least one vegetation index for each satellite system accurately predicted biomass. • NDVI was not the best predictor of cover crop biomass for any satellite. Cost-share programs based on measures of participation rather than performance are available to farmers who plant cover crops. However, cover crops only provide significant ecological benefits like reduced nutrient loss when adequate biomass is established. The purpose of this study was to determine whether satellite imagery can effectively estimate cover crop biomass in fields with diverse species composition, and whether increased spatial resolution and satellite imaging frequency can increase biomass estimation accuracy. Aboveground biomass samples of 1 m 2 were collected for 86 sites within 26 agricultural fields containing unique cover crop species composition to assess biomass production. In-field sensors were used to measure normalized difference vegetation index (NDVI) and groundcover percentage. Three satellites (Landsat-8 [30 m resolution], Sentinel-2 [10 m resolution], and PlanetScope [3 m resolution]) were used to calculate eight vegetation indices (VIs) for comparison with cover crop biomass. Multiple linear regression, correlation coefficients, and root mean square error (RMSE) were used to perform hierarchical clustering to rank VIs calculated from each satellite for biomass estimation accuracy. Satellites predicted cover crop biomass at the field level very accurately (r 2 up to 0.79), demonstrating the potential of large-scale biomass estimation at relatively low cost compared to in-field sampling. All satellite-VI pairs estimated biomass more accurately than the in-field sensors. Performance of VIs varied by satellite, but each satellite had at least one VI that performed very well for both site-level and field-averaged data. When using PlanetScope or Landsat-8 imagery, the perpendicular vegetation index provided the most accurate cover crop biomass estimation on a per-site basis and ratio vegetation index performed best using Sentinel-2 imagery. PlanetScope was the only satellite to provide useable imagery for every site due to increased revisit period; however, its increased spatial resolution did not increase estimation accuracy overall compared to Landsat-8 or Sentinel-2.

Similar fish species composition despite larger environmental heterogeneity during severe hypoxia in a coastal ecosystem.

Environmental heterogeneity is one of the most influential factors that create compositional variation among local communities. Greater compositional variation is expected when an environmental gradient encompasses the most severe conditions where species sorting is more likely to operate. However, evidence for stronger species sorting at severer environment has typically been obtained for less mobile organisms and tests are scarce for those with higher dispersal ability that allows individuals to sensitively respond to environmental stress. Here, with the dynamics of fish communities in a Japanese bay revealed by environmental DNA metabarcoding analyses as a model case, we tested the hypothesis that larger environmental heterogeneity caused by severe seasonal hypoxia (lower concentration of oxygen in bottom waters in summer) leads to larger variation of species composition among communities. During summer, fish species richness was lower in the bottom layer, suggesting the severity of the hypoxic bottom water. In contrast to the prediction, we found that although the environmental parameters of bottom and surface water was clearly distinct in summer, fish species composition was more similar between the two layers. Our null model analysis suggested that the higher compositional similarity during hypoxia season was not a result of the sampling effect reflecting differences in the alpha or gamma diversity. Furthermore, a shift in the species occurrence from bottom to surface layers was observed during hypoxia season, which was consistent across species, suggesting that the severe condition in the bottom adversely affected fish species irrespective of their identity. These results suggest that larger environmental heterogeneity does not necessarily lead to higher compositional variation once the environmental gradient encompasses extremely severe conditions. This is most likely because individual organisms actively avoided the severity quasi‐neutrally, which induced mass effect‐like dispersal and lead to the mixing of species composition across habitats. By showing counter evidence against the prevailing view, we provide novel insights into how species sorting by environment acts in heterogeneous and severe conditions.

Riverine barrier hypothesis explains the structure of dung beetle communities in Brazilian Coastal Sand-dune forests

The Riverine Barrier Hypothesis (RBH) predicts that tropical rivers can be effective barriers to species dispersion, affecting different scales of biological organization, from genes to assemblages. We disentangled the latitudinal from the river presence effect to test the hypothesis that the Doce river mouth acted as a geographical, historical barrier for insects through North and South directions of the Brazilian coast, affecting the current community structure. We sampled dung beetle communities. In 16 Coastal Sand-dune Forest (“Restinga”) patches, across the Doce River Basin in the Brazilian coastline, nine through the South and seven through the North direction of the Doce River's mouth. We analyzed the relationship between the community composition and richness relative to the river (North and South regions) and latitude using linear modeling over a distance matrix (DistLM) approach. The latitude explained 17.74% of the total variation in dung beetle species composition, and the regional position relative to Doce River's mouth exhibited a significant effect (Pseudo F = 2.8479; p = 0.005) only after removing the latitudinal effect, here representing the habitat filtering. Both variables explained together with a total of 32.52% of the variability in dung beetles composition at coastal sand dune forests. The geographical position alone explained 48% of the richness difference between the North and South regions of the Doce River's mouth (Pseudo F = 16.534; p < 0.01). Meanwhile, the latitudinal position of the sites exhibited no significant relationship with species richness. Our findings highlight the role of Doce River as a biogeographical filter in the Doce river basin, while it represents the primary determinant of geographical segregation of the two key-species central to the dung beetle community structure.

When are mangrove crabs fat? Seasonal and sexual variation in the fatty acid composition of edible crab species Ucides cordatus from the Brazilian Amazon coast

Fatty acids play important role in several biological processes taking place in crustaceans, such as reproduction and molting. The aim of the current study is to evaluate the seasonal variation in fatty acid concentration and profile in crab species Ucides cordatus exploited in Brazilian mangroves. Eight samplings were performed throughout one year and 30 adult specimens - 15 males and 15 females - were selected - it totaled 240 individuals. Muscle and hepatopancreas were freeze-dried and had their fatty acid profiles analyzed through gas chromatography. Analysis of variance, principal component analysis and cluster analysis were carried out in order to find patterns among sample groups. Sixteen fatty acids were found in hepatopancreas; palmitic acid presented the highest concentration in male (22.25–33.72%) and female individuals (24.97–31.74%). On the other hand, five fatty acids were identified in muscle tissues - linoleic acid was the fatty acid recording the highest concentration in male (20.51–27.49%) and female individuals (21.62–28.05%). Based on multivariate analysis, fatty acid concentrations played major role in group formation. With respect to the hepatopancreas, reproduction and pre-ecdysis phases were more clearly distinguished for female than for male individuals. Higher fatty acid concentrations were found in the muscles of the pos-ecdysis group. Overall, fatty acid concentrations have shown different behaviors for both tissues and for both sexes - the main variations were observed during the breeding and intermolt phases.

Differentiation of natural scrub communities of the Cotoneastro-Amelanchieretum group in Central Europe.

Most of Central European rocky scrub communities formed by Cotoneaster integerrimus, Juniperus communis and Amelanchier ovalis are included in the association Cotoneastro-Amelanchieretum (= Junipero-Cotoneasteretum). However, this leads to the creation of syntaxon whose internal diversity is so great that it seems necessary to examine validity of its existence in the current form. This diversity entails species composition, habitat requirements and geographical distribution. Therefore, we posed the following objectives: i) to investigate the variability of species composition of the rocky scrub; (ii) to determine if there are ecological differences between the communities distinguished by species variability; (iii) to determine the geographical ranges of individual syntaxa. Altogether we analyzed 387 phytosociological relevés from Central Europe. Vegetation types of rocky scrubs were identified using the unsupervised K-means algorithm and detrended correspondence analysis. Mean Ellenberg’s indicator values were applied to identify the environmental gradients shaping the plant communities. Obtained results confirmed the validity of dividing this broadly defined syntaxon into six distinct vegetation units. In order to present the studied communities in a broader context, we included into our analyses other rocky scrub with the occurrence of Cotoneaster sp. and A. ovalis, which formed the remaining three clusters. The observed differences in species composition were further supported by significant differences in soil reaction, temperature and continentality between the syntaxa. Moreover, the distinguished communities differed among one another in geographical range. Our study provides a new typology of the selected type of natural rocky scrub vegetation in Central Europe which involves environmental aspects, hence better reflects community-habitat relationships. This study also indicates a need for further revision of the classification of other types of natural scrub communities. Such classification should be based on modern data analysis methods and should primarily focus on lower vegetation units at pan-European scale.

Weed Composition in Hungarian Phacelia (Phacelia tanacetifolia Benth.) Seed Production: Could Tine Harrow Take over Chemical Management?

Phacelia tanacetifolia, an excellent cover, green manure and honey crop is now widely cultivated throughout the world. One of its principal European seed production regions is north-western Hungary, where the recent withdrawal of a potent herbicide, linuron, created a new challenge for many growers. The goal of this study is to identify the main factors determining weed species composition in the phacelia fields of the region and to assess the efficiency of tine harrow and clopyralid herbicide in reducing weed abundance and biomass. We carried out a series of weed surveys across the study region following a two-level design: (i) we estimated the cover of all weed species in 205 fields (broad-scale survey, BS); and (ii) in 22 of these fields, we provided more precise biomass measurements (counting the individuals and measuring the dry weights of all weed species) in microplots samples (fine-scale survey; FS). To characterize the fields, 34 background variables were also collected for all of the studied fields. In both investigations, Chenopodium album was by far the most abundant weed. Within the BS, using a minimal adequate model containing 11 terms with significant net effects, 20.93% of the total variation in weed species data could be explained. The variation in species composition was determined by environmental factors (soil pH, clay and K; precipitation and temperature), non-chemical management variables (crop cover, preceding crop, irrigation and tillage system) and herbicides (linuron and clopyralid). Variation partitioning demonstrated the dominance of environmental and cultural components in shaping the weed species composition. Although the effect of mechanical treatments was most likely masked in the BS by the soil properties, our FS suggests that tine harrow could efficiently decrease the total number and biomass of weeds and can be a useful tool in the phacelia management of the future.

Determinants of bryophyte assemblages in traditionally managed grasslands of the Carpathian Mts

Questions Although bryophytes play an important role in grassland ecosystems, environmental factors that drive bryophyte assemblages were rarely studied, especially in low-intensity traditional grasslands. Therefore, using fine-scale data on bryophyte assemblages in traditionally managed secondary grasslands, we studied the relative importance of several sets of environmental drivers (related to topography, soil properties, landscape, and management) of: (i) taxonomic and functional compositions; and (ii) cover and species richness of bryophyte communities. Location Central and Eastern Europe, Carpathian Mountains, 15 sites with preserved traditional management practices distributed in Romania (six sites), Ukraine (four), Slovakia (two), Austria (one), Hungary (one) and Poland (one). Methods Fine-scale data on soil, topography, and vegetation structure as well as on bryophyte assemblages (taxonomic and functional composition, cover, species richness) were collected in 10-m2 plots. We used stratified random sampling to select six 10-m2 plots of traditionally managed grasslands in each of the 15 sites (n = 90). Climatic and landscape variables were extracted from online databases and available maps. Detailed data on present and historical land use were obtained from parcel owners. To assess the effect of drivers on bryophyte taxonomic and functional composition we applied canonical correspondence analysis (CCA) and redundancy analysis (RDA), respectively; for bryophyte species richness and bryophyte cover we used GLMMs. Forward stepwise variable selection procedure was used to find best set of drivers for each of the analyses. Results Topographic (microrelief and solar radiation) and soil-related factors (cover of stones and rocks, soil depth, moisture), as well as the cover of the herb layer and bare soil were the strongest drivers of bryophyte taxonomic composition. Among the management- and landscape-related variables only mean size of grassland parcels within 1-km2 plot surroundings and grazing by horse were included in the CCA model explaining in total 25.9% of variation in species composition. Bryophyte functional composition was explained by a similar set of variables (RDA explained 27.3% of variation in functional composition) including additionally cover of gravel and burning. Solar radiation (negative effect) and management stability (positive effect) were the strongest drivers of bryophyte cover. Management stability had the strongest effect (positive) on bryophyte species richness, followed by grassland age (negative) and microrelief (positive). Conclusions Taxonomic and functional composition of bryophyte assemblages as well as bryophyte cover in traditional grasslands were determined mainly by variables related to moisture and light availability. Management-related factors seem to be at least as equally important as abiotic factors for bryophyte species richness and cover. Our results suggest that for maintaining bryophyte-rich grasslands one should also consider stability of grassland management, that is, temporal continuity and regularity of management practices applied.

Rock‐climbing shifts cliff‐face vegetation community composition based on site characteristics

AbstractQuestionsWhat are the effects of rock‐climbing on diversity, abundance and composition of cliff‐face vegetation along environmental gradients? Does site variability influence cliff vegetation more than the presence of climbing?LocationLinville Gorge Wilderness Area, NC, USA.MethodsWe compared species richness, Shannon’s diversity, abundance and species composition of lichens, bryophytes and vascular plants within 334 plots, each 1 m2. We compared climbed plots with unclimbed plots using Non‐metric Multidimensional (Distance) Scaling ordination, means comparison and regression analysis.ResultsEighty‐five species were observed within 334 m2 of cliff‐face plots, including one North Carolina state (Canoparmelia alabamensis) and 21 Burke County collection records. Climbing altered cliff plant communities: unclimbed cliffs supported more diverse and different species than did climbed cliffs. However, site was more important than was climbing in differentiating cliff community composition. Variation in species composition was driven mostly by variation in cliff aspect and surface heterogeneity. Cliffs with the highest surface heterogeneity had the highest species richness, diversity and abundance of all three vegetation types (lichens, bryophytes and vascular plants). Unclimbed areas had similar richness, diversity and abundance compared with easy climbing routes, whereas harder climbing routes supported lower species richness and abundance of all vegetation types.ConclusionsDifferences in cliff‐face vegetation in Linville Gorge were due more to site variability than to climbing impact. Therefore, management of climbing areas and decisions for future route development should be site‐specific and include a thorough biological survey.

Effects of farmland consolidation in southern China on wild bee species composition, nesting location and body size variations

Abstract Traditional smallholding‐dominated agricultural landscapes in Southern China are increasingly homogenized and consolidated, resulting in large mono‐cropped fields and impoverished pollinator communities. The exact impact of this farmland consolidation on composition and functional traits of wild bee communities remains poorly understood. We studied these communities and functional traits in oilseed rape fields embedded in 18 agricultural landscapes located in Jiangxi Province, China, with 11 sites representing traditional (pre‐consolidation) and the remaining 7 sites consolidated agricultural landscapes. The composition of wild bee assemblages was not differentiated into consolidated and traditional farmland communities. The mean body size of wild bee species similarly did not shows significant differences between consolidated and traditional farmland. The mean intraspecific body size for a dominant species, Lasioglossum proximatum, was larger in consolidated than traditional farmland, while individuals of co‐dominant Eucera floralia showed no such differentiation. In consolidated farmland, the proportion of semi‐natural habitat was positively linked to the abundance‐based average interspecific body size of wild bee species. For abundance‐based calculations, the proportion of aboveground nesting bee species was lower in consolidated landscapes than in traditional ones. Our study suggests that farmland consolidation might affect intraspecific composition, particularly in abundant small‐bodied species. Above‐ground nesting bees may require specific management interventions in consolidated agricultural landscapes to promote their persistence, which could take the form of semi‐natural habitat patches introduced to fields that can also benefit the pollinator community more widely.

PRELIMINARY STUDY ON SPECIES COMPOSITION OF ZOOBENTHOS ON COASTAL INTERTIDAL AREA IN HAI PHONG AND CAT BA

Study on zoobenthos species composition on coastal intertidal area in Hai Phong province was conducted from 11-12/2020. The results showed that total of 152 species, of 116 genus, 71 families, 26 order belonging to 10 classes (Polychaeta, Merostomata, Thecostraca, Malacostraca, Scaphopoda, Bivalvia, Gastropoda, Cephalopoda, Holothuroidea, and Actinopteri) and 5 phyla (Annelida, Arthropoda, Mollusca, Echinodermata and Chordata). In which, Bivalve had the most species (8 orders, 22 families, 44 genera, 56 species accounting for 36.84%), followed by gastropod (with 6 orders, 25 families, 38 genera, 53 species, accounting for 34.87%), and the third was Malacostraca (3 orders, 14 families, 24 genera and 33 species, accounting for 21.71%). Other groups only 1or 2 species. From the results showed that the coastal area of Hai Phong has a relatively diverse species composition, the main composition is Bivalvia, Gastropoda and Malacostraca accounting for about 95.4% of the total number of identified species. The biodiversity level in the coastal area of Hai Phong was medium with biodiversity index (H') about 2.39.

Stable Carbon and Nitrogen Isotope Composition in Suspended Particulate Matter Reflects Seasonal Dynamics of Phytoplankton Assemblages in the Gulf of Riga, Baltic Sea

The ratio of stable carbon and nitrogen isotopes in the suspended particulate matter has been widely used to study processes occurring in the marine ecosystem. At the same time, the signals provided by isotope ratios in coastal ecosystems can be difficult to interpret, due to several, often contradictory processes taking place simultaneously. In this study, we hypothesized that the carbon and nitrogen isotopic variation is predominantly affected by seasonally occurring phytoplankton species succession in the Gulf of Riga, Baltic Sea. Cyclical seasonal patterns were observed for carbon and nitrogen isotopic compositions of both SPM and phytoplankton data. Enrichment of heavy isotopes in the Gulf of Riga took place during spring phytoplankton bloom (from on average between + 7.1 and + 8.8 ‰, and between − 23.7 and − 21.9 ‰ for δ15N and δ13C, respectively) and pooled at significantly lower values (from + 3.1 to + 5.1 ‰ and from − 28.7 to − 25.1 ‰ for δ15N and δ13C, respectively) for the rest of the year. At the same time, the spatial gradient of isotope ratios was sporadic and inconclusive. The results showed that terrestrial and anthropogenic input to particulate matter is negligible from spring to autumn. Multivariate analysis revealed that the observed seasonal variability was indeed driven by variation in phytoplankton species composition. The diatoms, dinoflagellates, and the ciliate Mesodinium rubrum facilitated enrichment of 15N and 13C in spring. In contrast, atmospheric nitrogen fixation by cyanobacteria and the assimilation of their released nutrients by other organisms resulted in lower δ15N values during summer. This variability requires careful considerations for conducting food web studies in temperate coastal and estuarine environments during high phytoplankton biomass periods.

Spatial and temporal variations of phytoplankton composition and biomass in Lake Bunyonyi, South-Western Uganda.

The purpose of this study was to examine the spatial and temporal variations of phytoplankton species composition and biomass in Lake Bunyonyi, South-Western Uganda. Samples were collected monthly from nine fixed stations in the lake from October 2019 to September 2020. Based on the morphological characterization, 52 different species of phytoplankton were recorded. These were dominated by cyanobacteria (21 species) and chlorophytes (15 species) followed by diatoms (10 species), euglenophytes (4 species), dinoflagellates (2 species), and cryptophytes (1 species). The biomass (Chl-a concentration) ranged from 0.019 ± 0.009mg/L at Heissesero station to 0.045 ± 0.013mg/L obtained at Nyombe station. On a temporal basis, the highest mean Chl-a concentration of 0.044 ± 0.03mg/L was recorded in March 2020while the least concentration of 0.015 ± 0.011mg/L was obtained in September 2020. Significant differences existed in the Chl-a concentration values between stations and across sampling months. Chl-a concentration was significantly positively correlated with dissolved oxygen (DO), turbidity but negatively correlated with temperature. The Shannon-Wiener index and evenness put it clear that the distribution of phytoplankton species in the lake is inequitable. Besides, 94.2% of the phytoplankton species revealed had never been reported by the previous studies in the study area. The dominance of species cyanobacteria (such as Microcystis spp., Cylindrospermopsis raciborskii, Anabaenopsis sp., and Anabaena sp.) presents potential future challenges to water quality management. Therefore, the establishment of a strong and committed committee dubbed "Lake Bunyonyi Water Management Committee" to oversee the activities and avert potential water quality challenges is strongly recommended. The existence of some toxic phytoplankton species calls for regular monitoring and careful use of the lake and its food products.

Riparian health conditions of headwater streams in Southwestern Nigeria

ABSTRACT River health assessments and threat analysis on the riparian corridors in Sub-Saharan Africa have received little or no attention, therefore this study assessed the healthiness of riparian corridors using the Rapid Appraisal of Riparian Condition (RARC) indices within a river catchment. The biogeography of the riparian corridor, factors responsible for the modification of riparian vegetation, and causes of riparian disturbance were examined. Twelve study sites were randomly selected from where reaches were identified. The riparian corridor extents were delimited from the bank of the river to the uppermost point within reaches. Species diversity indices were computed while bank height, width, and average depth were measured. Also, cross-sectional area and river discharge were derived along each riparian zone using standard measurement techniques. The ecological values and threat severity along each riparian zone were assessed following the RARC model. The ecological values and disturbance level revealed r as −0.7(p < 0.05). The variation in species composition along the river orders suggests that the first-order streams have the highest number of taxa. The level of ecological destruction is fairly low in the first-order streams and increases as order increases. This study concludes that higher-order rivers have low diversity, low ecological values, and consequently, relatively poor health, especially when under severe anthropogenic pressure.

Species misidentification affects biodiversity metrics: Dealing with this issue using the new R package naturaList

Biodiversity databases are increasingly available and have fostered accelerated advances in many disciplines within ecology and evolution. However, the quality of the evidence generated depends critically on the quality of the input data, and species misidentifications are present in virtually any occurrence dataset. Yet, the lack of automatized tools makes the assessment of the quality of species identification in big datasets time-consuming, which often induces researchers to assume that all species are reliably identified. In this study, we address this issue by evaluating how species misidentification can impact our ability to capture ecological patterns, and by presenting an R package, called naturaList, designed to classify species occurrence data according to identification reliability. naturaList allows the classification of species occurrences up to six confidence levels, in which the highest level is assigned to records identified by specialists. We obtained a list of specialists by using the species occurrence dataset itself, based on the identifier names within it, and by entering an independent list, obtained by contacting experts. Further, we evaluate the effects of filtering out occurrence records not identified by specialists on the estimations of species niche and diversity patterns. We used the tribe Myrteae (Myrtaceae) as a study model, which is a species-rich group in Central and South America and with challenging taxonomy. We found a significant change in species niche in 13% of species when using only occurrences identified by specialists. We found changes in patterns of alpha diversity in four genera and changes in beta diversity in all genera analyzed. We show how the uncertainty in species identification in occurrence datasets affects conclusions on macroecological patterns by generating bias or noise in different aspects of macroecological patterns (niche, alpha, and beta diversity). Therefore, to guarantee reliability in species identification in big data sets we recommend the use of automated tools such as the naturaList package, especially when analyzing variation in species composition. This study also represents a step forward to increasing the quality of large-scale studies that rely on species occurrence data.

Graphical Application to Assist Students Understand the Basic Concepts in Acid–Base Titrations

During the 1960s, Edgar Dale published the concept that learners are likely to retain more information if they see and hear information rather than just listen. Therefore, many educational applications have been created for students to learn theoretical concepts through visuals and in an interactive manner. Microsoft (MS) Excel has been used in many of these applications due to ease of use and widespread applicability. The main objective of this research is to introduce an MS Excel application to study the theoretical concepts associated with acid–base titrations. This application allows the user to select the type of titration, Ka/Kb values where applicable, concentrations of the reagents, titration volume, commonly used indicators, and follow the variation in the titration curve. With the use of the application, students can clearly visualize the change in pH during the titration, buffer region, and the effect of reagent concentrations and Ka/Kb values on the titration curves. It further allows the user to determine the end point of the titration via a first derivative plot, observe the variation in fractional composition of the reactive species with pH, and identify the indicator best suited for the titration. The application was proven successful when used to teach the concepts of acid–base titrations to a group of high school students.

Composition, abundance and distribution of rodent species in Alemsaga Priority State Forest and farmlands, northwestern Ethiopia

AbstractThe aim of this study was to investigate species composition, relative abundance, habitat preference and seasonal variations of rodents in Alemsaga Priority State Forest and the nearby farmlands. A total of 1311 individual rodents were captured in six permanent grids and line transects, comprising of nine species, namely Lophuromys simensis, Arvicanthis abyssinicus, Desmomys harringtoni, Mastomys natalensis, Stenocephalemys albipes, Rattus rattus, Arvicanthis dembeensis, Mus musculus and Acomys cahrinus. Hystrix cristata and Tachyoryctes splendens were also recorded but not captured in trapes. About 44.4% of captured species are endemic to Ethiopia. Lophuromys simensis was captured from all habitats, while Acomys cahrinus was recorded only in Carissa land. The highest abundance of rodents was recorded in crop fields and the lowest in Carissa land. The overall trap success was 14.76%. Statistical variation was observed between individual rodent species among different habitats. Highest rodent populations were recorded during the wet season. Females comprised more individuals than males. Adults outnumbered sub‐adults and juveniles. Vegetation composition, altitudinal variations and human disturbance were the major factors affecting the distribution of rodents in the area. Attention should be given by the local administrators to conserve the area.

The danger and indeterminacy of forfeiting perching space of bryophytes from climate shift: a case study for 115 species in China.

Identifying the danger and expressing the indeterminacy of forfeiting perching space of species induced by rapid climate warming is crucial for biodiversity risk management under future changes in climate conditions. The scenarios of climate shift named the representative concentration pathways, the categorizing technique with regard to fuzzy-set, and Monte Carlo scheme was employed to survey the indeterminacy and the danger of forfeiting perching space caused by climate warming for 115 bryophytes in China. For the deterministic scenarios of climate shift, the richness of 115 bryophytes improved in several areas in north-eastern China, while it dropped in some areas in southern, eastern, south-eastern, and central China. In addition, for the deterministic scheme of altering climatic state, the count for bryophytes with the proportion of contracting the present areal range as less than 20%, 20-40%, 40-60%, 60-80%, and over 80% was belike 34-38, 19-38, 24-35, 9-19, and 4-9, separately; the count of bryophytes with the ratio of the occupying entire areal range as over 80%, 60-80%, and less than 20% was roughly 97-109, 4-14, and 2-8, separately. For the scenarios of randomly change in climate state, the number of bryophytes with a various proportion of forfeiting the present perching space dropped with enhancing the possibility; with the likelihood beyond 0.6, the count of bryophytes with forfeiting present perching space as less than 20%, 20-40%, 40-60%, 60-80% and high than 80% of the present areal range was approximately 7-14, 2-10, 0-7, 2-9, and 13-20, separately; the number of bryophytes with the ratio of occupying the whole areal range as less than 20%, 20-40%, 40-60%, 60-80%, and over 80% was more or less 1-3, 0-3, 1-5, 1-3, and 38-44, separately. Roughly 48 bryophytes would face the risk of extinction from climate warming, including endemic and non-endemic species. Forfeiting perching space induced by climate warming would cause variations in species composition and the disappearance of some ecological functions associated with these bryophytes. The inconstancy of forfeiting areal range caused by climate warming should be incorporated into the policy-making of conservation bryophytes for adaptation of climate warming.

Riverscape View of Fish Assemblages, Habitat, and Stream Temperatures during Summer Low Flows in the Chehalis River, Washington

The Chehalis River is a coastal river in southwestern Washington State where decision makers are considering options to reduce flood damage and improve freshwater habitats. This study focused on the mainstem river above and below the location of a potential dam, one of the flood-reduction options being considered. Our objectives were to describe spatial patterns of fish species, physical habitat, and stream temperature, and identify associations between fish species and the physical environment at two spatial scales. Data were collected in spatially continuous reaches following a “riverscape” approach, and patterns in the data were described using three different ordination techniques. Most of the variation in fish species composition occurred at the sub-basin scale (entire study area), with additional but minor patterns at the reach (1-km) scale. At the sub-basin scale, fish species composition was organized in an upstream (salmonid) to downstream (cyprinid) replacement pattern and was best explained by the combination of river location, habitat, and temperature. At the reach scale, physical habitat and stream temperature differentiated juvenile trout versus coho salmon in the salmonid-dominated upstream extent of our study area, and dace versus shiner in the cyprinid-dominated downstream extent. We conclude that salmon and steelhead are particularly vulnerable to habitat loss upstream of the proposed dam because they disproportionately use this area as summer rearing habitat. Protection and restoration of headwater areas, such as our study area in the Chehalis River, will be critical to support salmonid populations into the future.

Mapping Forest Aboveground Biomass Using Multisource Remotely Sensed Data

The majority of the aboveground biomass on the Earth’s land surface is stored in forests. Thus, forest biomass plays a critical role in the global carbon cycle. Yet accurate estimate of forest aboveground biomass (FAGB) remains elusive. This study proposed a new conceptual model to map FAGB using remotely sensed data from multiple sensors. The conceptual model, which provides guidance for selecting remotely sensed data, is based on the principle of estimating FAGB on the ground using allometry, which needs species, diameter at breast height (DBH), and tree height as inputs. Based on the conceptual model, we used multiseasonal Landsat images to provide information about species composition for the forests in the study area, LiDAR data for canopy height, and the image texture and image texture ratio at two spatial resolutions for tree crown size, which is related to DBH. Moreover, we added RaDAR data to provide canopy volume information to the model. All the data layers were fed to a Random Forest (RF) regression model. The study was carried out in eastern North Carolina. We used biomass from the USFS Forest Inventory and Analysis plots to train and test the model performance. The best model achieved an R2 of 0.625 with a root mean squared error (RMSE) of 18.8 Mg/ha (47.6%) with the “out-of-bag” samples at 30 × 30 m spatial resolution. The top five most important variables include the 95th, 85th, 75th, and 50th percentile heights of the LiDAR points and their standard deviations of 85th heights. Numerous features from multiseasonal Sentinel-1 C-Band SAR, multiseasonal Landsat 8 imagery along with image texture features from very high-resolution imagery were selected. But the importance of the height metrics dwarfed all other variables. More tests of the conceptual model in places with a broader range of biomass and more diverse species composition are needed to evaluate the importance of other input variables.