Gradients Of Environmental Factors Research Articles

Height-diameter model of broad-leaved mixed forest based on species classification in Maoershan, Northeast China.

The complex stand structure and high species diversity of natural forests pose great challenges for analyzing stand growth and formulating reasonable plans for forest management. The height-diameter relationship is of great significance for predicting stand growth and formulating forest management measures. Based on survey data of 48 broad-leaved mixed forest plots in Maoershan, we classified 23 tree species into four groups based on species structure, growth characteristics and bionomics. We established a generalized model including stand, tree competition, species mixing and species diversity variables by reparameterization method, and a two-level mixed effect model of plot and tree species group. We tested the prediction ability of the model by leave-one-out cross-validation method. The results showed that the Ratkowsky (1990) model was the optimal basic model. The introduction of dominant height, basal area of trees larger than the object tree, basal area proportion of each species, and Shannon index could better explain the height-diameter relationship of broad-leaved mixed forest in Maoershan. The introduction of the mixed effect model of plot and tree species group could significantly improve the prediction accuracy of the model, with a Ra2 of 0.83. Under the same gradient of environmental factors, intolerant tree species exhibited higher tree heights than shade-tolerant tree species. In this study, we used the constructed tree height-diameter model to analyze the effects of species mixing and tree functional traits on tree height, which provided a theoretical basis for accurately predicting height of different tree species and analyzing the growth relationships in broadleaved mixed forests.

Climatic water availability modifies tree functional diversity effects on soil organic carbon storage in European forests.

Forest stand and environmental factors influence soil organic carbon (SOC) storage, but little is known about their relative impacts in different soil layers. Moreover, how environmental factors modulate the impact of stand factors, particularly species mixing, on SOC storage, is largely unexplored. In this study, conducted in 21 forest triplets (two monocultures of different species and their mixture on the same site) distributed in Europe, we tested the hypothesis that stand factors (functional identity and diversity) have stronger effects on topsoil (FF + 0-10cm) C storage than environmental factors (climatic water availability, clay + silt content, oxalate-extractable Al-Alox) but that the opposite occurs in the subsoil (10-40cm). We also tested the hypothesis that functional diversity improves SOC storage under high climatic water availability, clay + silt contents, and Alox. We characterized functional identity as the basal area proportion of broadleaved species (beech and/or oak), and functional diversity as the product of broadleaved and conifer (pine) proportions. The results show that functional identity was the main driver of topsoil C storage, while climatic water availability had the largest control on subsoil C storage. Functional diversity decreased topsoil C storage under increasing climatic water availability, but the opposite was observed in the subsoil. Functional diversity effects on topsoil C increased with increasing clay + silt content, while its effects on subsoil C were negative at increasing Alox content. This suggests that functional diversity effect on SOC storage changes along gradients in environmental factors and the direction of effects depends on soil depth.

Mosses of the Western Part of the Chukchi Highlands. 2. Number of Species and Cover on Gradients of Environmental Factors

Based on geobotanical studies conducted in the summer of 1989 in the western part of the Chukchi Highlands, it was found that the number of moss species varies depending on the altitude, slope exposure and angle. Taking into account samples of different volumes for different parameters, the following dependencies were revealed: the largest number of species (35) was noted in the altutude range of 250–300 m, the smallest (14) – for the altutudes above 400 m; the slopes of the northern exposure are characterized by the largest number of species (22), the south-eastern and north-western ones – by the smallest number (18); a decreasing tendency in the number of species manifests itself with an increase in the slope angle: on gentle slopes (up to 5°) there are 37 species, while on steep ones (more than 25°) their number decreases to 23. Based on the position of the species optimum on the scale of soil moisture, 7 groups of species were distinguished: xerotopes, mesoxerotopes, xeromesotopes, mesotopes, hygromesotopes, mesohygrotopes, hygrotopes. The total percent cover value of mosses varies differently on the slopes of different exposures (on gravelly-fine-stony substrates): on the northern slopes it increases to an altitude of 400 m, then decreases sharply; on the south-western slopes it only increases to an altitude of 450 m, on all the other slopes it monotonously decreases from an altitude of 230–250 m to 370–600 m. At different altitude levels, the maximum of the total percent cover value of mosses is also related to the slope exposure: in the lower altitude range, it is confined to the south-eastern slopes, in the medium altitudes, it shifts to the north-eastern slopes, and in the uppermost range to the south-western ones. With an increase in the slope steepness, the total percent cover value of mosses decreases on the slopes of all exposures, with the greatest intensity being on the eastern slopes.

Climate-sensitive tree height-diameter models for mixed forests in Northeastern China

Models based on height-diameter (H-D) are helpful for estimating forest biomass and carbon storage on a large scale. Climate change has an impact on allometric height-diameter growth. H-D models explaining climatic effects are still inadequate due to the complexity of mixed forests. This paper developed climate-sensitive mixed-effects models for 14 tree species based on 316 natural mixed forest plots in Northeastern China and compared the response of tree height growth to environmental gradients for multiple species. The results showed that the species heterogeneity leads to the differences in scaling exponents in varying degrees. The analysis revealed that incorporating mean annual temperature (MAT), mean annual precipitation (MAP), dominant tree height (HT), basal area of the larger trees (BAL), and Shannon diversity index significantly enhanced the predictive ability of the model. By exploring the tree height change patterns of each tree species under different gradients of environmental factors, we found that increases in temperature, precipitation, site quality, and competition intensity positively affected height growth in mixed forests. In contrast, increases in species diversity inhibited height growth. The degree to which environmental factors regulate the H-D allometric growth of trees in mixed forests is related to species specificity. This paper provides theoretical support for tree height estimates of major tree species in mixed forests under global climate change by introducing environmental factors to improve the H-D model of 14 tree species.

Soil erosion gradient and quantitative attribution in southwest China based on karst development degree

The heterogeneity of the geographical environment determines the complexity of soil erosion patterns. Determining the effects of changing gradients and combinations of environmental factors on soil erosion is the key to combating soil erosion. In this study, based on the division of the karst development degree, the revised universal soil loss equation model was optimised based on the rocky desertification factor to determine the effect of the different gradients of environmental factors on soil erosion. The geographical detector method was used to identify the dominant and interactive factors of soil erosion under different karst development degrees. The gradient attribution shows that: soil erosion is influenced by the type of bedrock assemblage and the form of the assemblage. Soil erosion is strongest at 1400–1800 m above altitude. Grassland in karst areas is prone to soil erosion and the effect of vegetation coverage on soil erosion has a critical value of 0.6–0.7. Interaction analysis shows that the interaction between land use and slope plays a dominant role in the spatial differentiation of soil erosion, but has significantly higher explanatory power (q)in sub-karst and non-karst areas than in pure-karst areas. Combined with slope and rainfall, soil erosion is obviously intensified, and the pure-karst and sub-karst areas are higher than the non-karst areas. The significant interaction between lithology and slope is a typical feature of karst areas. The findings of this study have crucial theoretical significance for the site-specific control of soil erosion in areas with different karst development degrees.

Plant communities of the park “Gurzufsky” on gradients of environmental factors

The article provides a comprehensive assessment of the habitat capacity and packing density, which characterizes the position of plantings on the gradients of environmental factors, indicating mainly the stability of the adapted composition of the majority of the cultural phytocenosis of the park "Gurzufsky". The sections reflecting the most characteristic ecological conditions of the park territory are highlighted. Graphs of the position of plantings on the gradients of environmental factors by allotments are given. Three zones are identified depending on environmental conditions and groups of plants are proposed that can realize their capabilities on the gradients of environmental factors.

Phytoindication approach to assessing factors determining the habitat preferences of red deer (Cervus elaphus)

The study examined the possibility of using the phytoindication technique to describe habitat preferences of red deer in a relatively homogeneous area. Two alternative hypotheses were tested. Hypothesis 1 suggests that the relationship between red deer and vegetation is due to a trophic factor, so preferences for individual plant species cause vegetation to influence the distribution of animal numbers. Hypothesis 2 suggests that environmental factors influence vegetation, structuring and determining the productive level of the community as a whole. Therefore, environmental factors, rather than individual plant species, cause vegetation-animal interactions. The research was conducted on Biryuchiy Island Spit, where the Azov-Sivash National Nature Park is located. The geobotanical surveys were performed in three types of ecosystems: sandy steppe (vegetation class Festucetea vaginatae), saline meadows (vegetation class Festuco–Puccinellietea), and artificial forest plantation (vegetation class Robinietea). 250 releves were recorded according to the Brown-Blanquet approach. The number of fecal pellets and the number of groups of pellets of red deer was recorded together with geobotanical surveys in the same sample plots. The pellet groups counted in the field were converted to deer densities in specific vegetation classes taking into account the number of pellet groups on the site and the decay rate of the fecal pellets. The vegetation types were distinguished by the number of deer fecal pellets per unit area. The highest number of fecal pellets was found for the plant class Festucetea vaginatae, somewhat fewer fecal pellets were in the plant class Robinietea, and the lowest number was in the plant class Festuco-Puccinellietea. A geometric distribution model is adequate for explaining the experimental data on the number of fecal pellets. A total of 59 species of flowering plants were found. Based on the species composition and projective cover of species, the ecological regimes of ecotopes were identified by phytoindication. The correspondence analysis of the vegetation revealed two ordination axes. The ordination axis 1 (CA1) was able to explain 11.3% of community inertia, and the ordination axis 2 (CA2) was able to explain 5.2% of community inertia. The maximum excretory activity of animals was recorded for the central part of the ordination space, indicating the presence of an optimum zone in the gradient of environmental factors that structure plant communities. The forward selection procedure allowed the Nutrients Availability variable to be selected as the most important variable to explain variation in the plant community structure. The number of deer fecal pellets exhibited different patterns of response in the Nutrients Availability gradient. The response within the plant class Festucetea vaginatae could best be explained by Model III from the list of HOF-models. The response of the excretory activity of deer within the class Festuco-Puccinellietea could best be fitted by the model IV, which represents a symmetric Gaussian curve. The response of excretory activity in the Robinietea vegetation class was asymmetrical bimodal. The ecological properties of the red deer ecological niche in both the drier and less mineralized part of the range of ecological conditions and the wetter and more mineralized part should be assessed in the context of the prospects for future studies.

Variability in macrozoobenthic assemblages along a gradient of environmental conditions in the stream water of karst caves (Lower Shakuranskaya Cave, western Caucasus)

The fauna of the stream water in the Lower Shakuranskaya Cave in central Abkhazia, western Caucasus, was studied. This cave has a large inlet and an extended entrance ecotone area of approximately 60 m, which makes it a convenient area for studying macrozoobenthic assemblages across a gradient of environmental factors. The cave has 13 species of stygobionts, 10 species of stygophiles and 18 species of stygoxenes. The number of species and the abundance and biomass of stygobionts per station were the highest near the boundary of the photic zone, at a distance of 50–60 m from the entrance to the cave, and gradually decreased toward both the remote parts of the cavity and the cave exit. The most abundant stygobionts were gastropod mollusks of the Hydrobiidae family, and Xiphocaridinella shrimp comprised the main part of the biomass. It has been shown that the main environmental factors determining the distribution of macrozoobenthos are luminosity and distance from the entrance to a cave. According to the differences in their reactions to these environmental factors, several groups of species were identified. In addition, three main assemblages of macrozoobenthic species were described: (1) an assemblage of epigean species near the cave entrance area; (2) stygobionts in remote parts of the cave outside the photic zone; and (3) a mixed assemblage in the cave ecotone, where a faint light penetrates. The specific details related to the faunal structure in the ecotone of the cave are discussed, as well as active and passive methods by which stygoxenes invade underground cavities.

Who lives in a pine tree well? Community Associations Salvio tomentosae-Pinetum pallasianae Korzh. 1984 on gradients of environmental factors

Goal. To analyze the current state of the Crimean pine forest communities and give a forecast of possible changes in the trend of global climatic changes. Materials and methods. The object of research is phytocenosis (nomenclature description of the association), described in the Yalta Amphitheater at an altitude of 1000 m above sea level. The packing density of species on gradients of environmental factors was calculated using the original Pover program. Unified information on the distribution of plant species along gradients of factor conditions and resource factors (illumination-shading, thermal mode, cryo mode, humidification, moisture variability, substrate acidity, salt regime (anionic composition), carbonate content, nitrogen content, particle size distribution (mechanical) composition (porosity) of the substrate) was obtained from the Ecodata database. Results. The community will become most vulnerable when the cenotic factor “lighting-shading” changes with a significant decrease in the amount of light entering the day surface. Succession rearrangements of phytocenoses can cause an increase in the average July temperature by 2.4 degrees, exceeding the tolerance level for a given phytocenosis. Other environmental factors and resource factors have a significant margin of safety.

Differential Leaf Age-Dependent Thermal Plasticity in the Keystone Seagrass Posidonia oceanica.

Introduction: Gene-expression patterns and their upstream regulatory mechanisms (e.g. epigenetic) are known to modulate plant acclimatability and thus tolerance to heat stress. Within species, thermal plasticity (i.e. temperature-sensitive phenotypic plasticity) and differential thermo-tolerance are recognized among different genotypes, development stages, organs or tissues. Leaf age and lifespan have been demonstrated to strongly affect photosynthetic thermo-tolerance in terrestrial species, whereas there is no information available for marine plants. Materials and Methods: Here, we investigated how an intense warming event affects molecular and photo-physiological functions in the large-sized seagrass Posidonia oceanica, at fine spatial resolution. Plants were exposed for one week at 34°C in a controlled-mesocosm system. Subsequent variations in the expression of 12 target genes and global DNA methylation level were evaluated in three leaf-age sections (i.e. basal, medium and high) established along the longitudinal axis of youngest, young and fully mature leaves of the shoot. Targeted genes were involved in photosynthesis, chlorophyll biosynthesis, energy dissipation mechanisms, stress response and programmed cell death. Molecular analyses paralleled the assessment of pigment content and photosynthetic performance of the same leaf segments, as well as of plant growth inhibition under acute warming. Results: Our data revealed, for the first time, the presence of variable leaf age-dependent stress-induced epigenetic and gene-expression changes in seagrasses, underlying photo-physiological and growth responses to heat stress. An investment in protective responses and growth arrest was observed in immature tissues; while mature leaf sections displayed a higher ability to offset gene down-regulation, possibly through the involvement of DNA methylation changes, although heat-induced damages were visible at photo-physiological level. Discussion: Overall, mature and young leaf tissues exhibited different strategies to withstand heat stress and thus a variable thermal plasticity. This should be taken in consideration when addressing seagrass response to warming and other stressors, especially in large-sized species, where sharp age differences are present within and among leaves, and other gradients of environmental factors (e.g. light) could be at play. Molecular and physiological evaluations conducted only on adult leaf tissues, as common practice in seagrass research, could give inadequate estimates of the overall plant state, and should not be considered as a proxy for the whole shoot.

Damage to artificial seedlings across a disturbed Afromontane forest landscape

AbstractSeedling mortality is an important demographic bottleneck for forest regeneration, yet the factors influencing recruitment are often poorly characterized across space and time. In African highlands, where extensive patches of previously disturbed forests remain in persistent shrub‐dominated states, patterns of damage to seedlings have not been examined in detail. We used artificial seedlings to determine how (non‐herbivory‐related) damage varies across a fragmented forest landscape in the Bwindi Impenetrable National Park, Uganda. A total of 848 artificial seedlings were established in 106 plots, each with 8 seedlings, across a gradient of environmental factors, including habitat type, topographic position, distance to water, and distance to human activity. We divided damage into that due to vertebrates, plant debris, and unknown agents. From our 16,960 monthly stem assessments, 1,289 damage events were recorded. The mean “seedling” damage per year (± 1 SE) was 59.5 ± 2.3%. Damage was significantly more frequent in sites dominated by short herbs (66.1 ± 3.0) than in sites dominated by shrubs (60.1 ± 2.6) and ferns (47.9 ± 2.7). The mean percentage of damage by each class of agents was 45.8 ± 2.1% for vertebrates, 21.4 ± 2.1% for plant debris, and 3.8 ± 0.6% for unknown agents. These rates surpass those reported in other montane forests, likely reflecting the density of large vertebrates in our site. Our results indicate that most damage to artificial seedlings arises from larger vertebrates but that most spatial variation in this damage reflects the impacts of falling plant debris. These damage processes appear sufficient to constrain the regeneration of tree species in areas where forest cover is patchy and fragmented.

Characterization of a nifH-Harboring Bacterial Community in the Soil-Limited Gotjawal Forest.

Using a high-throughput metagenomic approach, we evaluated nifH-harboring bacterial communities and their assembly in the Gotjawal forest, which was naturally formed on basalt rocks with thin layer of soil. Significant differences in soil properties and community structure were observed in comparison with similar communities in various habitats, including other lava-formed forests (on Jeju Island and in Hawaii) and in regions with high humidity (Florida) or low temperatures (Alaska). nifH-harboring bacterial communities were found to assemble along gradients of environmental factors, particularly cation-exchange capacity. Unlike in other regions, in the Gotjawal forest, Paenibacillus and Clostridium, which belong to the phylum Firmicutes, were present in significantly higher proportion than in other regions. Network analysis suggested that much fewer co-occurrence relationships occurred in the Gotjawal forest than in other lava-formed forests. Our results indicate that the unique nifH-harboring bacterial community and its assembly in the Gotjawal forest are due to its distinctive soil properties, which has implications for microbial interactions and functional potentials.

Exploring environmental predictors of aquatic macrophytes in water‐dependent Natura 2000 sites of high conservation value: Results from a long‐term study of macrophytes in Greek lakes

Abstract Aquatic macrophytes play a key role in lake dynamics, but human activities and eutrophication have resulted in macrophyte loss in many lakes throughout Europe. In this study, the relationships between aquatic macrophytes and gradients of environmental factors were explored using an extensive set of data collected from 13 lakes of the Greek mainland that are part of the European network Natura 2000. The main objectives were to assess the importance of key abiotic predictors and estimate possible environmental thresholds of macrophyte richness, diversity, and abundance using boosted regression trees (BRTs), as well as to explore further the distribution of dominant macrophyte taxa along environmental gradients. The results reveal conductivity as a significant predictor of macrophyte total cover and diversity. In addition, orthophosphate and nitrate nitrogen appear to play an important role for several macrophyte species and assemblages, reflecting a major effect of eutrophication on the distribution of taxa. The majority of macrophyte assemblages were found in waters characterized by high nutrient content, although their distribution extends along a wide range of phosphorus and nitrogen concentration. In contrast, charophyte species show the optimum of their distribution in clear, oligotrophic waters. This integrated study can be used for ranking environmental factors that influence macrophyte distribution in the lakes of Greece and for identifying taxa or macrophyte assemblages that can be used as effective indicators of changes in the abiotic environment. In addition, the results can contribute to the conservation of freshwater habitats in the protected areas studied. In particular, measures that aim to improve water quality are expected also to restore oligotrophic habitats that are characterized by benthic charophyte vegetation. Overall, the links between macrophyte assemblages and abiotic factors are critically important in improving freshwater biodiversity management and environmental policies in east Mediterranean lakes.

Scale‐dependency of the environmental influence on fish β‐diversity: Implications for ecoregionalization and conservation

AbstractAimTo determine the ecoregions (spatial marine areas with similar environmental and physical conditions associated with relatively homogeneous fish assemblages) for shallow reef fish assemblages based on predictive models of beta diversity (β‐diversity) that account for both large‐scale environmental factors and local habitat characteristics. We assessed the influence of a spatial scale to rank the importance of these factors.LocationNew Caledonian (south‐west Pacific Ocean, 17–24° S, 158–172° W) Exclusive Economic Zone, Coral Sea Marine Park.TaxonFish.MethodsFish and habitat data that were collected at 13 sites around New Caledonia using unbaited rotating underwater video (285 sampling stations) were analysed. Gradient forest modelling was used to predict the fish β‐diversity along the gradients of environmental factors. Ecoregions were obtained by applying clustering methods to gradient forest predictions.ResultsThe gradient forest models of β‐diversity retained 59 species (total: 206 fish species) with R² > 0, including 19 fish species with R² from 0.03% to 69%. For these 19 species, the models explained up to 26% of the variance. At a large scale, β‐diversity was significantly explained by nutrient concentrations, sea surface salinity and temperature. Among the eight ecoregions that were delineated based on the β‐diversity predictions, three regions corresponded to remote sites under oceanic influence where human pressures are low and the surface nutrient concentrations are high. On the local scale, the benthic habitat explained β‐diversity better than the physical and chemical parameters, particularly in the areas subject to anthropogenic pressures.Main conclusionsOn the local scale, the respective importance of environmental factors (physical and chemical parameters versus benthic habitat) differed according to ecosystem health. Our findings suggest that nutrient enrichment due to avifauna may have a positive effect on fish β‐diversity when an ecosystem is healthy. The ecoregions reflect fish species composition in relation to a large set of environmental parameters.

Killing me slowly: Harsh environment extends plant maximum life span

Life span (the age of death for individuals that survived the establishment phase) is a key trait in plant life history. Despite its importance for understanding plant–environment relationships, there are still numerous substantial knowledge gaps about variation in plant maximum life spans and the ecological processes underlying these patterns.Based on plant age data obtained by means of herbochronology, we analysed patterns of intraspecific plant maximum life span variation in three perennial species (Campanula scheuchzeri, Helianthemun nummularium and Lotus corniculatus) along environmental gradients of mean annual temperature, soil depth and soil nutrients. This variation was compared with predictions from the ‘death-by-starvation hypothesis’ proposed by Hans Molisch in 1938, an unjustly forgotten ‘extrinsic’ theory on plant life span variation.Our study suggests that plant age variation within populations responds sensitively to growing conditions. The most important finding is that mean annual temperature or environmental conditions related to it seems to be a driving factor for intraspecific variation in plant maximum life span in all species studied. Despite large within-population variation, individuals of C. scheuchzeri, L. corniculatus and H. nummularium generally had a longer life span under colder climates (uplands in our case). In addition, soil depth (as a proxy for habitat susceptibility to drought) was found to have a significant positive effect on the age values in the case of C. scheuchzeri.These findings, therefore, are in line with Molisch’s “death-by-starvation hypothesis”: extended maximum life span results from reduced production of sink tissues and slow vegetative growth. We conclude that the analysis of plant life span adjustments along gradients of environmental factors can considerably contribute to our understanding of how plants may cope with changing environmental conditions, e.g., due to global change.

Cell compartmentation of ultraviolet‐absorbing compounds: An underexplored tool related to bryophyte ecology, phylogeny and evolution

Abstract Excessive exposure to ultraviolet (UV) radiation can be harmful to photosynthetic organisms, that most frequently respond with the accumulation of protective UV‐absorbing compounds (UVACs). UVACs location in different cell compartments can influence their preferential protective role as antioxidants and/or UV screens. However, the phylogenetic, ecological and evolutionary implications of UVACs compartmentation has been little studied, particularly in bryophytes. We analysed UVACs in the methanol‐soluble and ‐insoluble fractions (SUVACs and IUVACs respectively) in extracts of 87 bryophytes belonging to their three evolutionary lineages: 22 liverworts, 64 mosses and one hornwort. Assuming that the cell wall‐bound IUVACs are more effective UV screens than the mainly vacuolar SUVACs, thus conferring a higher UV tolerance, we evaluated whether UVACs levels and compartmentation were related to: (1) the bryophyte phylogeny down to the Order level; and (2) the bryophyte ecological attributes, including sun exposure and Ellenberg indicator values (numerical system classifying species' habitat along gradients of environmental factors). A similar phylogenetic and ecological analysis was conducted on the sclerophylly index (the ratio between the dry mass and the surface area of the bryophyte shoot). Mosses showed lower SUVACs but higher IUVACs and total UVACs, together with higher IUVAC/SUVAC ratios, than liverworts. Thus, mosses would better tolerate UV radiation than liverworts, which matches well with their general ecological preferences. As bryophytes were the earliest diverging land plants, we could infer that the different UVACs compartmentation between mosses and liverworts could have influenced their ecological segregation upon plant land colonization. UVACs compartmentation also differed between the two major moss lineages (acrocarpous and pleurocarpous), while the anatomically peculiar Sphagnales were the best characterized Order. There were not solid relationships between UVACs and the ecological attributes considered. Hence, UVACs might be mainly constitutive in bryophytes, depending more on the species phylogeny than on the habitat occupied in nature. Liverworts were less sclerophyllous than mosses, and, as in tracheophytes, water restrictions and high sun exposures increased sclerophylly. In conclusion, UVACs compartmentation represents an ecophysiological trait useful to understand the bryophyte ecophylogeny, because different compartmentation modalities seem to imply different UV adaptations and tolerance. A plain language summary is available for this article.

Mcp, aer, cheB, and cheV contribute to the regulation of Vibrio alginolyticus (ND-01) adhesion under gradients of environmental factors.

Adhesion is a key virulence factor of pathogens and can be affected by the environment. Our previously research with RNA‐seq indicated that mcp, aer, cheB, and cheV might play roles in the regulation of adhesion in Vibrio alginolyticus (ND‐01). In order to determine whether and how environmental factors affect adhesion through these genes, gene silencing was performed followed by quantitative real‐time PCR (qRT‐PCR), RNAi, transmission electron microscopy, and adhesion, capillary, and motility assays to verify how these genes influence adhesion. Silencing these genes led to deficiencies in adhesion, chemotaxis, flagellar assembly, and motility. The expression levels of cheA, cheW, and cheY, which are important genes closely related to the functions of mcp, aer, cheV, and cheB, were significantly downregulated in all of the RNAi groups. The expression of mcp, aer, cheV, and cheB under different gradients of temperature, pH, and salinity and after starvation for various durations was also detected, which showed that these genes were sensitive to certain environmental stresses, particularly pH and starvation. Our results indicated that mcp, aer, cheB, and cheV: (1) are necessary for ND‐01 adhesion; (2) play key roles in the bacterial chemotaxis pathway by controlling the expression of downstream genes; (3) might affect adhesion by impacting motility, though motility is not the only route through which adhesion is affected; and (4) contribute to the regulation of ND‐01 adhesion in natural environments with different temperatures, pH levels, and salinities as well as after various starvation periods.

Spatial dynamics of species richness of phytoplankton of Lake Balkhash in the gradient of abiotic factors

Abstract The spatial distribution of species richness of phytoplankton was studied along the Balkhash Lake water area during the summer of 2004. With statistically weak connections of phytoplankton with environmental parameters, three-dimensional graphs revealed a complex character of its spatial variability in the gradient of environmental factors. Macrophytes had a stimulating effect on the species richness of planktonic algae. We found a correlation between species richness of Cyanobacteria, Chrysophyta, Euglenophyta and Dinophyta and the ionic composition of water. The important role of temperature was traced. Species richness of algal communities increased with increasing temperature in the gradient of nutrients and correlated with the abundance of macrophytes.

The development of the protistan species-maximum concept for the critical salinity zone

Until recently, the general biodiversity concepts have suggested common patterns of species richness dynamics for both small planktonic and large benthic organisms in the gradients of environmental factors, including salinity, which is the major abiotic characteristic that influences the diversity of flora and fauna in coastal marine ecosystems. Recent studies discovered an extremely species-rich aquatic microworld and resulted in proposing new concepts and shifting the paradigms in biodiversity studies, including those on planktonic unicellular eukaryotes such as protists. As a result, Remane’s species-minimum concept has been revisited and the range of its application updated. This paper provides a review of the studies dedicated to establishing, developing, and analyzing the novel protistan species-maximum concept for the critical salinity zone (5–8‰), or the horohalinicum. The obtained new data contribute to the formation of the modern views on aquatic ecosystem dynamics, biodiversity conservation, and effective ecological management aimed at maintaining the environmental balance and the rational use of marine biological resources.

Correlates of cave-roosting bat diversity as an effective tool to identify priority caves

Cave ecosystems are subterranean biodiversity hotspots, but limited knowledge of the distribution of diversity among caves hampers their conservation. Surveys of surrogate taxa (e.g., keystone species) can identify hotspots of biodiversity when knowledge about an ecosystem is lacking. Bats are keystone species in cave ecosystems because their guano is the primary energy source supporting diverse assemblages of cave-dependent wildlife. However, directly measuring bat diversity is time-consuming and requires expert knowledge; instead, we suggest the use of correlates of bat diversity that can be derived from readily accessible data (e.g., land-use maps) and straightforward methods not requiring expert knowledge (e.g., cave surveys, interviews) as a foundation for prioritizing caves. To identify easily measurable correlates of bat diversity, we compared assemblage composition and species abundances of 21 bat species captured in 56 caves on Bohol Island, Philippines, along gradients in environmental factors and human disturbance. Model- and distance-based methods indicated that surface-level disturbance (i.e., percent non-forested habitat, degree of urbanization and road development) along with cave complexity (i.e., available roosting area, structural heterogeneity, number of entrances and temperature range) were the most influential factors governing cave-roosting bat assemblages, thus representing correlates of bat diversity. Prioritization schemes based on these correlates select combinations of caves with greater species richness than both random selection and selection of caves based on observed richness from intensive bat surveys. The use of easy-to-measure environmental and disturbance correlates of bat diversity is an effective tool to prioritize caves to protect cave-roosting bats and the cave-dependent wildlife they support.