Edaphic Characteristics Research Articles

Invasive Nicotiana glauca shifts the soil microbial community composition and functioning of harsh and disturbed semiarid Mediterranean environments

Exotic invasive plants have been reported to alter the soil microbial community composition and function in order to facilitate their further invasion. These changes in the soil microbiome could be influenced also by the characteristics of the soil and sites. We hypothesised that (i) the invasion of Mediterranean semiarid ecosystems by the woody shrub Nicotiana glauca (tree tobacco) would promote a specific rhizosphere microbial community with particular functions and (ii) the rhizosphere microbial community associated with the invasive plant would be independent of the edaphic characteristics of the invaded site. We tested these hypotheses by comparing the rhizosphere microbial community of N. glauca with that of the native plant community at four sites covering a broad range of distinctive edaphic characteristics, including two human-disturbed environments and two naturally harsh Mediterranean environments (one saline and one gypsum soil). The soil microbial community composition was analysed using Illumina MiSeq sequencing and the rhizosphere microbial function was predicted by PICRUSt and FUNGuild. Our results suggest that the composition of the rhizosphere bacterial and fungal communities differed between N. glauca and the dominant native plant species and according to the soil characteristics. The metabolic functions of indicator taxa also differed between the invader and the dominant native plant species. In particular, the functions involved in the metabolism of carbon (C) and sulphur (S) compounds were overrepresented in the rhizosphere community of the invader. In conclusion, invasive N. glauca shifts the soil microbial community composition and its function related to C and S cycling in semiarid Mediterranean environments, including soils affected by salinity and gypsum.

Ecosystem (Dis)benefits Arising from Formal and Informal Land-Use in Manchester (UK); a Case Study of Urban Soil Characteristics Associated with Local Green Space Management

Urban soils are subject to anthropogenic influences and, reciprocally, provide benefits and disbenefits to human wellbeing; for example carbon storage, nutrient cycling and the regulation trace element and contaminant mobility. Collective stewardship of urban green commons provides contemporary examples of the diversity of uses and management of green space in cities and represents a growing movement in user participation in, and awareness of, the importance of urban ecological health. Exploring the range of social-ecological benefits exemplified in the urban environment has generally focused on above-ground processes, with few studies examining the potential for (dis)benefits arising from edaphic characteristics of collectively-managed spaces. An investigation into the influence of formal and informal green space management on carbon fluxes and heavy metal concentrations in urban soils was carried out in Manchester (UK) finding that carbon storage in soils of collectively managed urban green commons (7.15 ± 1.42 kg C m−2) was significantly greater than at formally managed sites (for example city parks: 5.08 ± 0.69 kg C m−2), though the latter exhibited reduced losses through CO2 emission. Variation in heavy metal concentrations and mobility were likewise observed, exemplified by the acidification of surface soils by leaf litter at orchard sites, and the resultant increase in the mobility of lead (Pb) and zinc (Zn). The results of this study indicate the importance of small-scale contemporary urban green space management on selected ecosystem services provided by the limited soil resource of cities. Thus, a greater consideration of the effects of horticultural and amenity activities with regards to soil quality/functionality is required to ensure available urban green commons retain or increase their ecological quality over time.

Landscape evolution across the Cretaceous/Paleogene boundary in southwestern North Dakota, U.S.A.

The Hell Creek Formation and overlying Fort Union Formation record a geologically rapid base-level rise that was approximately contemporaneous with the K/Pg extinction and deposition of Chicxulub-impact indicators. An outstanding question that remains is whether this base-level rise is attributable to: 1) a multi-thousand-year transgression adjacent to a relatively low-relief coastal plain, causing a rise in the water table; or 2) catastrophic flooding due to upland denudation, rapid channel accretion, and hydrologic reorganization resulting from wildfires/deforestation consequential of the impact. Herein we aim to address which of these hypotheses is most consistent with a paleolandscape reconstruction at Mud Buttes, a locality where the boundary clay (BC) is coincident with the Hell Creek-Fort Union contact. One hundred twenty-seven trenches were examined laterally across ∼2 km transect of K/Pg boundary. The uppermost Hell Creek is comprised of three pedotypes: Pale-Silt Inceptisol (PSI), Olive-Clay Vertisol (OCV), and Chocolate-Clay Vertisol (CCV), which range from moderately well-drained, to variable to poorly drained, to very poorly drained, respectively. All of the BC occurs superjacent to the CCV, despite this pedotype accounting for only ∼50% of the pre-event landscape. The edaphic features preserved in the CCV pedotype are not attributable to Paleogene overprinting, which indicates that hydromorphic conditions began prior to the impact. Furthermore, 46% of BC is overlain by lignite, despite lignite occurrence on 17% of the earliest Paleogene landscape. This reveals that the poorest-drained landscape positions of the latest Cretaceous persisted across the boundary. These relationships are most consistent with a non-catastrophic base-level rise.

Microbial Community Response to a Passive Salt Marsh Restoration

In response to current threats to salt marshes, there are increasing efforts to restore these vital coastal ecosystems and promote their resilience to global change drivers. Unfortunately, the economic cost associated with assessing the effectiveness of restoration is prohibitive and more information is needed about the trajectory and timing of restoration outcomes to improve restoration practices. Microbial communities provide essential salt marsh functions so assessing the degree to which microbial communities in restored marshes resemble reference marshes can serve as a proxy indicator for the potential return of microbial function. We studied a recently restored marsh located on Cape Cod, MA, USA, by examining shifts in the microbial community and sediment edaphic properties in three habitats of a degraded oligohaline marsh, both before and after restoration of tidal flooding and in comparison with three nearby S. alterniflora reference marshes that never had flow restrictions. We hypothesized that the microbial community would respond rapidly to the restoration and that over time these communities would be indistinguishable from reference marsh communities. We found that soil edaphic characteristics shifted along a trajectory of recovery toward the reference marshes, with increases in salinity and decreases in soil organic matter, percentage of carbon, and percentage of nitrogen. The microbial communities in all three habitats within the restored marsh were different from reference marshes, and both the prokaryotic and fungal communities within P. australis and Typha sp. habitats became more similar to reference marshes (similarities increasing from an average of 5 to 16% for prokaryotes and 3 to 10% for fungi) during the first 2 years after restoration. In that same time period, by contrast, there was no return of the native marsh vegetation. These results suggest that shifts in microbial community structure occur prior to shifts in marsh vegetation and may facilitate the successful revegetation of restored marshes. Understanding the recovery trajectory of marshes during restoration and the role that microbes play in promoting the long-term sustainability of these habitats is essential; these results suggest that microbial communities respond rapidly and in a positive direction to restoration efforts.

Modeling of eucalyptus productivity with artificial neural networks

Although it is easy to list the several factors that influence forest productivity, it is almost impossible to isolate or measure all biotic and abiotic components that influence crop growth and development on a field-scale. Artificial neural networks (ANN) have been widely used to model forest productivity, since habitual modeling is hampered by the inclusion of categorical variables as well as by the large number of independent variables and its complex relationships with the dependent variable. This study aimed to obtain ANN to estimate eucalyptus productivity as a function of environmental variables, genotype and silvicultural practices, and infer about those more important in forest productivity. It was used data from continuous forest inventory, climate, soil analysis and fertilization carried out on 507 eucalyptus stands, composed of different genotypes and spacing. Multiple-layer Perceptron networks were trained to estimate the mean annual increment of eucalyptus stands at six years of age (MAI6), testing different combinations of input variables, number of neurons in the hidden layer, training algorithms, data percentage in training and validation subsets, and activation functions. In the validation, it was obtained ANN with correlation between the estimated and observed MAI6 higher than 85 % and root mean square error less than 15 %. Despite data complexity, ANN made it possible to estimate MAI6 with good precision and to include easily numerous variables, even categorical. Genotype, spacing, edaphic characteristics (clay, organic matter and Cation exchange capacity- CEC), climatic characteristics (rainfall, temperature and water deficit) and fertilization were the predictive variables that most influenced eucalyptus productivity at the end of rotation.

Natural variation on whole-plant form in the wild is influenced by multivariate soil nutrient characteristics: natural selection acts on root traits.

In the complex soil nutrient environments of wild populations of annual plants, in general, low nutrient availability restricts growth and alters root-shoot relationships. However, our knowledge of natural selection on roots in field settings is limited. We sought to determine whether selection acts directly on root traits and to identify which components of the soil environment were potential agents of selection. We studied wild native populations of Arabidopsis thaliana across 4 years, measuring aboveground and belowground traits and analyzing soil nutrients. Using multivariate methods, we examined patterns of natural selection and identified soil attributes that contributed to whole-plant form. In a common garden experiment at two field sites with contrasting soil texture, we examined patterns of selection on root and shoot traits. In wild populations, we uncovered selection for above- and belowground size and architectural traits. We detected variation through time and identified soil components that influenced fruit production. In the garden experiment, we detected a distinct positive selection for total root length at the site with greater water-holding capacity and negative selection for measures of root architecture at the field site with reduced nutrient availability and water holding capacity. Patterns of natural selection on belowground traits varied through time, across field sites and experimental gardens. Simultaneous investigations of above- and belowground traits reveal trait functional relationships on which natural selection can act, highlighting the influence of edaphic features on evolutionary processes in wild annual plant populations.

INFLUENCE OF SOIL COMPACTION LEVELS ON COWPEA PRODUCTION

Cowpea, a short-cycle legume with large production in the North and Northeast regions, has its productive potential limited by edaphic characteristics and degradation processes of soil physical quality, such as compaction. This process may interfere with plant development and productivity by restricting root system growth, aeration, water and nutrient availability. The objective of this work was to analyze the interference of different levels of compaction in the soil physical characteristics, root growth, development of the aerial part and productivity of cowpea. The experiment was conducted in a greenhouse following a completely randomized design with a control (control) and four levels of soil compaction, with four replications. Each experimental unit was composed of PVC tubes composed of a 0.05-m layer of gravel, cotton fabric and a 0.04-m layer of soil. The different levels of compaction were obtained using a proctor socket and a wooden base. Based on the value of penetration resistance (PR) of 1.00 MPa, soil reached the macroporosity considered as critical theresohold for soil aeration. Results indicate that the higher the PR of the soil, the lower the development of the root system and the aerial part. The productive aspects of cowpea presented better results in plants grown in soils with a level of resistance to penetration close to 0.8 MPa.

Metal Input in Lettuce Grown in Urban Agricultural Soils

Urban agriculture plays an important role in supplying produces to big cities; however, the quality of water used for irrigation can hinder this activity. Hence, the purpose of this study was to evaluate metal inputs, as well as their transfer and translocation factors, in lettuce (Lactuca sativa L.) crops cultivated in an urban plot. The research was conducted during the dry and rainy seasons. In the former, crops were irrigated with treated wastewater, whereas during the latter, crops were maintained just with rainwater. Composite samples for soils and plants were collected from the same plot during two crop cycles in 2013. Some edaphic variables were measured. Total metal concentration was determined, for both, soils and lettuce plants (leaves and roots). Water soluble and exchangeable soil metal fractions were also analyzed. A multivariate analysis of variance was performed to test for differences between seasons, among the variables analyzed. There were significant differences in edaphic characteristics between seasons. However, there was no difference in total metal content, except for Mn. Concentration of soluble metals was lower than exchangeable metal concentration, for both seasons. There was no correlation in total metal concentration between soils and plants. Transfer factor values were higher for Cd, Mn and Zn for the dry season, while for Cu, Fe and Pb were higher during the rainy season, as well as the translocation factors for all metals. Soil characteristics, together with transfer and translocation factors, showed temporal variations, leading to different metal concentrations in the edible lettuce tissues between the two analyzed crop cycles. The incorporation of metals is particular for each site, season and crop management type. Our results indicate that the metal concentration in lettuce tissues places no harm to human health. However, management strategies for urban agriculture must consider specific studies for each site.

Functional diversity turnover in the western Mediterranean saltmarshes: Effects of edaphic features and biotic processes on the plant functional structure

Salinity and soil moisture are considered main drivers of the plant zonation in Mediterranean saltmarshes. Therefore, both factors could have a remarkable effect on the plant functional structure of these habitats. The aim of this study was to identify the effects of abiotic and biotic factors on the plant functional structure of western Mediterranean saltmarshes. A total of 20 saltmarshes were assessed, and seven plant traits were considered. Community weighted mean and Rao index were used to measure the functional structure of the plant communities. Redundancy analysis was used to estimate the effects of soil variables on the community-weighted mean trait and functional diversity, and standardised effect size was used to assess the effect of biotic interactions. The functional traits showed a clear zonation along the salinity gradient in Mediterranean saltmarshes, mainly related to the electrical conductivity, and mainly gathered in trait syndromes. The succulent nanophanerophytes grew at the highest salinity zones. Salt excretors, both chamaephytes and mesophanerophytes, appeared in the intermediate and lowest salinity zones, respectively. Finally, geophytes with both selective cation root uptake and rhizome were mostly located in the lowest salinity zones. The abiotic factors strongly modulated the biotic interactions, and some convergence patterns were observed. The highest functional diversity was observed in the lowest salinity zones, a marked turnover. These findings indicate that multiple assembly processes determine the plant structure of Mediterranean saltmarshes, yet abiotic environmental filters strongly shape the local species assemblages and functional diversity turnover. Our results support that the whole salinity gradient should be protected to conserve the widest range of functional traits.

Estimation of oleoresin yield from Copaifera spp. in primary forest in meridional Amazon

The objectives of this research were to verify the relationships between the dendrometric and edaphic variables with the yield of oleoresin from Copaifera spp., and to adjust equations to predict yield from a primary forest. Thirty Copaifera spp. trees were selected to extract oleoresins over 24 hours, using a 1.91 cm (¾ inch) auger. In addition, data were collected on tree size and the edaphic characteristics of the topsoil around of each tree. Principal components analysis was used to verify the relationships between variables and a regression analysis was used to verify variables that may be best to predict oleoresin yield. After the principal components analysis, the only variable related to the oleoresin yield was the stem height, which had the best adjusted coefficient of determination (0.84) and relative standard error (13.11%). We found the yield of oleoresin from Copaifera spp. in primary a forest had a significant and positive correlation with the stem height, whereas no significant correlations were found between yield, or any other dendrometric or topsoil variables studied.

Organic matter priming by invasive plants depends on dominant mycorrhizal association

While it has long been held that invasive plants alter ecosystem processes, the magnitude and direction of these effects have rarely been quantified in situ. We measured the effects of an invasive C4 grass (Microstegium vimineum) on soil organic matter (SOM) decomposition in a deciduous forest in south-central Indiana, USA. The unique 13C signature of the C4 grass relative to the C3 trees allowed us to partition soil CO2 fluxes and estimate M. vimineum effects on decomposition. The magnitude and direction of priming effects hinged on the soil characteristics, which related to the mycorrhizal association of dominant trees. In forest plots dominated by ectomycorrhizal trees, with low nitrogen availability and most SOM in particulate (i.e., unprotected) forms, M. vimineum increased SOM decomposition by 58%. In contrast, in plots dominated by arbuscular mycorrhizal trees, characterized by high nitrogen availability and most SOM in mineral-associated (i.e., protected) forms, M. vimineum decreased decomposition by 14%. Collectively, our results demonstrate that invasive species can play a large role in altering ecosystem processes and suggest that the magnitude and direction of such effects depend on the dominant trees and edaphic characteristics of the stand.

Nonnative vegetation dynamics in the understory of a fragmented temperate forest1

Although the conditions that render forests likely to support nonnative plants are well documented, there are surprisingly few data on the long-term dynamics of nonnative invasive species in eastern temperate forests. We examined 11 years of compositional and structural change in a small (60 ha) forest preserve in Connecticut with abundant invasive plants, a diverse land use history, and varied edaphic characteristics. We quantified the extent to which vegetation composition changed at the species, life form, and community scales and then assessed the possible factors driving these changes. Fifty-four plots were sampled in 2004, 2009, and 2015; these plots spanned two major forest types, (a) Acer rubrum L.-Fraxinus americana L and (b) Quercus montana Willd.-Quercus coccinea Muenchh. Significant changes in composition occurred over time with a greater magnitude of change in the Acer-Fraxinus forest than in the Quercus forest at all scales of analysis. Large increases in the abundance of the invasive Microstegium vimineum (Trin.) A. Camus (+1760%), Berberis thunbergii DC. (+180%), and Rosa multiflora Thunb. ex Murr (+1790%), along with a surprisingly large decline in the dominant Alliaria petiolata (Bieb.) Cavara & Grande (–86%) occurred in the Acer-Fraxinus forest. Native shrub and herb life forms growing alongside these invasive species remained unchanged or increased in abundance. Soil moisture predicted change in abundance of R. multiflora and B. thunbergii. Our results suggest that A. petiolata may be less persistent over time than previously believed and underscore the difficulties of generalizing about invasive species dynamics and relationships with native plants.

Interactions of Microhabitat and Time Control Grassland Bacterial and Fungal Composition

Dryland grasslands are vast and globally important and, as in all terrestrial ecosystems, soil microbial communities play fundamental roles in regulating dryland ecosystem function. A typical characteristic of drylands is the spatial mosaic of vascular plant cover surrounded by interspace soils, where biological soil crusts (biocrusts)—a complex community of organisms including bacteria, fungi, algae, mosses, and lichens—are common. The implications of this heterogeneity, where plants and biocrust cover co-occur, are often explored in the context of soil fertility and hydrology, but rarely has the impact of these multiple microhabitat types been simultaneously explored to determine the influence on bacterial and fungal communities, key biological players in these ecosystems. Further, our understanding of the temporal dynamics of bacterial and fungal communities in grasslands, and of how these dynamics depend on the microhabitat within the ecosystem, is notably poor. Here we used a temporally and spatially explicit approach to assess bacterial and fungal communities in a grassland on the Colorado Plateau, and to link variation in these communities to edaphic characteristics. We found that microhabitat (e.g., vascular plant rhizosphere, biocrust, and below biocrust)was the strongest driver of differences in bacterial and fungal community richness, diversity, and composition. Microhabitat type also significantly mediated the impact of temporal change in shaping community composition. Taken together, 29% of the variation in bacterial community composition could be explained by microhabitat, date, and microhabitat-by-date interactions, while only 11% of the variation in fungal community composition could be explained by the same factors, suggesting important differences in community assembly processes. Soil microbial communities dictate myriad critical ecosystem functions, thus understanding the factors that control their compostition is crucial to considering and forecasting how terrestrial ecosystems work. Overall, this case study provides insights for future studies on the spatial and temporal dynamics of bacterial and fungal communities in dryland grasslands.

Changes in soil properties rather than functional gene abundance control carbon and nitrogen mineralization rates during long-term natural revegetation

Agricultural abandonment has been taken as one of the most widely used strategies for ecological restoration. Abandoned croplands expanded worldwide since the middle of the twentieth century and will increase considerably in the future. Whether agricultural abandonment alters the abundances of soil carbon (C) and nitrogen (N) mineralization genes, and whether these functional genes are linked to alterations in C and N mineralization rates remain unknown. We took advantage of a well-established chronosequence of nature restoration sites on abandoned croplands which represent a century of vegetation succession in China’s Qinling Mountains, to determine soil C and N mineralization rates, and their relationships with vegetation succession, edaphic characteristics, soil microbial communities, and functional genes based on GeoChip 5.0. We found that soil C and N mineralization rates, microbial biomass and composition, and the number and abundances of functional genes were significantly affected by vegetation succession following agricultural abandonment. Soil C and N mineralization rates increased by sixfold and threefold, respectively, along the cropland to forest successional gradient. The NO3-N, NH4-N and soil available phosphorus (P) concentrations were important factors associated with the C and N mineralization genes. The shifts in edaphic environments (i.e., soil moisture, cation exchange capacity, and C/P ratio), vegetation-derived substrates (i.e., soil organic C and N), and soil microbial composition (i.e., Fungi/Bacteria ratio, amounts of Gram-negative bacteria, Actinomycetes, and arbuscular mycorrhizal fungi), rather than the abundances of functional genes involved in mineralization processes, controlled soil C and N mineralization rates along the long-term vegetation successional gradient. Abandoning cropland for natural succession could facilitate the recuperation of soil C and N processes and alter soil microbial composition and functional genes. The abundances of microbial functional genes are less important than previously expected in regulating soil C and N mineralization rates.

Exploring environmental determinants of Fusarium wilt occurrence on banana in South Central Mindanao, Philippines

Summary This study used Maximum Entropy (MaxEnt) to explore potential environmental determinants of Fusarium wilt occurrence on banana in south-central part of the Philippines. Different variables representing topographic, bioclimatic, and edaphic features of an area were tested against data of Fusarium wilt occurrence. Based on the results, precipitation during the driest month, precipitation during the wettest month, precipitation of the warmest quarter, slope, and elevation were the most important variables for predicting the probability of Fusarium wilt occurrence on banana. Results also suggest that among the variables tested, precipitation had the major contribution to the occurrence of Fusarium wilt.

Forest ecological heterogeneity determines contrasting relationships between crown defoliation and tree diversity

Tree diversity is found to enhance ecosystem functions in forests and increase the resistance and resilience of trees subjected to environmental stress, including climate change. This effect, however, can be different depending on tree species assemblages and ecological contexts. The pan-European programme for monitoring forest health (ICP Forests) considers crown defoliation as an indicator of tree vitality. Only a few studies have analysed the role of tree diversity in crown defoliation, with contrasting results. This paper analyses the relationships between defoliation and forest diversity in a country (Italy) characterised by heterogeneous bioclimatic and edaphic characteristics (from Mediterranean to Alpine) and with a wide range of forest tree species and functional groups. National-scale results show that defoliation increased in more diverse forest stands. This result can be explained by the fact that the tree mixtures reflect varying ecological conditions in heterogeneous environments. The most relevant factors that explain tree defoliation at the national level, investigated through random forest analysis, were the geographic position, tree species identity and forest stand age and structure. Cluster analysis was applied to identify homogeneous groups of plots based on their ecological and vegetation features. Four clusters were selected. Within each homogeneous cluster, the crown defoliation of the tree species showed different and contrasting patterns, changing their relationships with diversity over time. A beneficial role of diversity on defoliation (i.e. decrease of defoliation) has been observed in Quercus ilex, growing in Mediterranean conditions, and Picea abies in Alpine areas after dry periods. In the latter species, drought led to a greater increase in defoliation in monospecific than in mixed stands, suggesting the stabilising role of tree diversity.

Hierarchical drivers of soil microbial community structure variability in \u201cMonte Perdido\u201d Massif (Central Pyrenees)

Microbial activity is highly dependent on climatic factors (moisture and temperature) and edaphic characteristics in temperate ecosystems. Moreover, soil microbial community composition in high mountain areas is less known when compared to plant communities. In this study we investigated the soil microbial community from a functional perspective using PLFA (phospholipid fatty acid) methods in the four aspects of four summits (2,242 – 3,012 m above sea level) in the Spanish Central Pyrenees. Soil organic carbon (C), microbial biomass and nutrient dynamics (N{H}_{4}^{+} + N{O}_{3}^{-}, N mineralization and nitrification potential) were also determined. Microbial biomass C was highest in the lowermost summit and decreased by approximately 50, 14 and 12% with increasing altitude. In each summit soil N{H}_{4}^{+} and N{O}_{3}^{-} concentrations differed significantly among summits and aspects. Soil nitrification potential varied significantly between the factors summit and aspects, e.g., southerly vs. northerly, easterly vs. westerly aspects. Gram negative bacteria and Actinobacteria functional groups dominated the microbial community, with almost 40% of the total PLFA. Non-metric multidimensional scale (NMS) analysis showed that most of the PLFA functional groups were present in all summits and aspects, although with specific biomarkers. A high abundance of biomarkers 16:1ω9c and 16:0 2OH (gram negative bacteria) were obtained in the lowermost summit, while the biomarkers 16.1ω7cDMA (anaerobes) and 19:3ω6c (Eukaryote) were only found in the uppermost summit. Linear mixed model (lmm) analysis was used with summit as fixed effect and aspect as random effect. In general, our results demonstrate a fundamental role for environment, principally moisture, temperature and organic matter in explaining the pattern observed for soil PLFA biomarkers. Under a global change scenario, we need to shed light on the relationships between soil microbial functional groups and soil nutrient-related variables in order to identify the associated patterns of decomposition rates and soil processes driven by microbial communities in mountain areas. The results could thus be used in global predictive models on climate change impact on C or N cycles in these environments.

The origin and persistence of alpine vernal ponds in mineral soils

AbstractLittle is known of the processes that create and maintain vernal ponds in mineral soils in alpine environments. On the Central Plateau, Tasmania, we tested the hypotheses that vernal pond complexes on mineral soils formed in response to the underlying topography of a glacio‐fluvial plain; relate to present day topography; resulted from past damming by organic accumulation; are moulded by wind. The underlying topography did not relate to the surface ponds, nor were they on steeper slopes than adjacent areas without ponds. The morphology of the ponds and the morphological and edaphic characteristics of the pond complexes and adjacent areas are consistent with an origin by organic material damming. The strongest winds orientate most ponds, rather than the aspect of the slope. Sediments were preferentially caught on sticky traps to the northeast of the ponds, away from fierce prevailing southwesterly winds. Temperature measurements and fortnightly observation showed non‐concordant patterns of variation in water levels in the ponds. We deduce that the complexes of vernal ponds may have formed in previous moister conditions more favourable to organic matter accumulation, possibly in the early Holocene, and are maintained by a faster rate of accumulation of mineral and organic particles in the tussock grassland adjacent to the ponds than in the ponds themselves. © 2019 John Wiley & Sons, Ltd.

Establishing sustainable roadside vegetation communities of high botanical and aesthetic value: the basic concept statement and experimental justification

The basic principles for the development of a new greening system for the region of Belarus aimed at creation and restoration of sustainable roadside plant communities of high botanical and aesthetic value are formulated on the basis of the use of conservation, restoration and “incorporation” methods of flowering native plant species, characteristic of a particular region. The statements of the concept are developed and recommended for roadways and highways in the Republic of Belarus and tested on the model site between the city of Myadel and the resort village of Naroch of Highway P28. Roadside vegetation management practices in other countries as well as our research has shown that along the investigated roads there is a high adaptive potential of native flora; by changing the mowing regime, sustainable plant communities can be established while enhancing the aesthetics and expressiveness of key elements of the landscape of the roadsides. The implementation of the strategy for each geobotanical region depends on the development of an assortment of native plant species that can be used for the greening of roadside areas. This should be done by taking into account their geobotanical and edaphic features, creation of a seed bank for grass mixtures, the formation of natural genetic reserves (field banks) of meadow flora to conserve the local and overall ecosystem and genetic balance. For examples, the atlas of plants “Roadside flowers” developed for the National Park “Narochansky” is recommended for use in roadsides (verges) greening within the boundaries of the Oshmyany– Minsk geobotanical district. To expand the use of gained positive experience on increasing the biodiversity of roadside ecosystems and reducing the cost of their maintenance, it is desirable to implement this strategy for the entire road network of Belarus, which will require adjustment in technologies for managing roadside ecosystems, based on priorities of conservation, restoration and formation of native plant communities, including meadows and wetlands.

Seedling Survival at Timberline Is Critical to Conifer Mountain Forest Elevation and Extent

Conifer mountain forests influence a large portion of the World’s human population by providing a host of critical economic, sociological, and ecosystem services. Although the causes of the elevational, transitional boundaries of these forests (i.e. upper and lower timberlines) have been questioned for over a century, these investigations have focused predominately on the growth limitations of saplings or mature trees at the upper alpine boundary. Yet, the elevational movement of timberlines is dependent initially on new seedling establishment in favorable microsites that appear to be generated by ecological facilitation. Recent evidence suggests that this facilitation is critical during the initial 1-2 years of growth when survival may be less than a few percent, only cotyledons are present, and survival occurs only in favorable microsites created by inanimate objects (e.g. boulders, dead stems), microtopography, or already established vegetation. Dramatic changes in tree form (e.g. krummholz mats) across the timberline ecotone also plays an important role in generating microsite facilitation. These favorable, facilitated microsites have been characterized broadly as experiencing low sky exposure during summer (day and night) and leeward wind exposure during winter that generates protective snow cover, all of which are needed for new seedling survival. Thus, determining the specific microclimate and edaphic characteristics of favorable microsites, and their frequency at timberline, will provide a more mechanistic understanding and greater predictability of the future elevation and extent of conifer mountain forests. In addition, although the ecophysiological advantages of a needle-like leaf morphology is well established for adult conifer trees, the advantage of this phylogenetically unique trait in emergent seedlings has not been thoroughly evaluated. Understanding seedling ecophysiology and the functional morphology that contributes to survival, plus the nature and frequency of favorable microsites at timberline, will enable more reliable estimates of future elevational shifts in conifer mountain forests. This approach could also lead to the development of a valuable and sensitive tool for forest managers interested in evaluating future changes in these forests under increased large-scale infestation and drought mortality, as well as for current scenarios of predicted climate change.