Dense Crown Research Articles

Особливості поширення й екології ведмедя бурого (Ursus arctos) у Карпатському національному природному парку

The distribution and some ecological features of the brown bear (Ursus arctos) in the Carpathian National Nature Park (CNNP) during 2019–2023 are considered. The study is based on field observations and analysis of camera traps. The data was collected by the inspectors of the park's departments and employees of the scientific department. In particular, 157 cases of bear activity and presence were recorded, of which three cases were captured by camera traps. The results show that the brown bear prefers middle-aged spruce and fir plantations (38.7%). Bear tracks are also frequently found in middle-aged stands with dense crown closure (26.5 %), which may indicate the importance of dense forests for bears. Brown bears prefer old-growth spruce and fir stands, which account for 38.7 % of the total number of cases. This may be due to the fact that such forests provide sufficient food and shelter for bears. A smaller number of cases are occurrences in young and maturing stands. This may be due to the fact that such stands have not yet reached the optimal structure to meet the needs of bears. The lowest number of cases was found in pastures and hayfields. The maximum altitude at which a bear was recorded was 1696 m, and the minimum was 745 m. The highest number of observation was recorded at altitudes of 900–1000 m (31.2%), and the lowest at altitudes of 700-800 m (3.18%). According to the authors, this is due to the fact that there are no settlements at higher altitudes and the disturbance factor of animals is lower. The distribution and places of occurrence of this species in the Park over the past five years are analysed. The number of bears has increased in recent years. This is obviously due to a decrease in human impact (coronavirus restrictions, martial law and the absence of poaching). Currently, there are up to 20 individuals in the Park. The exact number of bears is difficult to determine due to double counting and lack of coordination between neighbouring forestry enterprises and protected areas. The data presented here are important for the development of conservation strategies for the brown bear, as they allow to identify the most favourable environments and plan measures for the protection and management of the Park's territory.

Phytoremediating the air down under: Evaluating airborne particulate matter accumulation by 12 plant species in Australia

AbstractAtmospheric particulate matter (PM) is the most inhaled hazardous air pollutant that can cause adverse health impacts. Plants can remove such contaminants and act as biological filters through phytoremediation. In this study, we screened 12 Australian native species (two deciduous trees, three evergreen shrubs, and seven evergreen trees) growing in three regions to determine their potential in accumulating leaf surface (SPM) and in‐wax PM (WPM). Among the screened species, Lagunaria patersonia (139.22 μg cm−2) was the most effective PM accumulator, followed by Ficus obliqua (131.02 μg cm−2). L. patersonia is an Australian native tree with a dense crown that can efficiently trap PM due to air turbulence between its leaves and branches; broad leaves with a rough texture enhance the plant's ability to trap PM. On the contrary, morphological characteristics like evergreen leaves with hairy appendages may act as an efficient trap for PM in F. obliqua. Due to smoother leaves, the least effective species were F. rubignosa and Eucalyptus saligna. In addition to leaf shape, leaf structures and micromorphology influence PM accumulation. For instance, Pittosporum undulatum accumulated more PM due to its wrinkled and folded leaf structures despite a significantly lower waxes layer. The findings highlight the importance of planting efficient PM accumulator species to shield vulnerable areas from pollution and decrease human exposure to pollutants. The sink capacity of these species can be used in urban tree planning to combat air pollution and improve air quality.

Urban greening with shrubs can supercharge invertebrate abundance and diversity

In urban areas, diverse and complex habitats for biodiversity are often lacking. This lack of diversity not only compromises essential ecological processes, such as pollination and nutrient cycling, but also diminishes the resilience of urban ecosystems to pests and diseases. To enhance urban biodiversity, a possible solution is to integrate shrubs alongside trees, thereby increasing the overall amount of vegetation, structural complexity and the associated resource diversity. Here, using a common garden experiment involving a variety of trees and shrubs planted alone and in combination, we evaluate how canopy-associated invertebrate assemblages are influenced by vegetation type. In particular, we test whether the presence of shrubs, alone or with trees, results in increased abundance and taxonomic richness of invertebrates, compared to trees on their own. We found that the overall abundance of invertebrates, and that of specific functional groups (e.g., herbivores, pollinators, detritivores), was higher on shrubs, compared to trees, and when trees and shrubs were planted in combination (relative to trees on their own). Our results suggest that planting shrub and tree species with wide and dense crowns can increase the associated abundance and taxonomic and functional group richness of invertebrate communities. Overall, our findings indicate that urban planning would benefit from incorporating shrubs alongside urban trees to maximise invertebrate abundance, diversity and function in urban landscapes.

Pinus sibirica Du Tour в условиях интродукции на примере Полярно-альпийского ботанического сада-института

The study has been conducted at the Polar-Alpine Botanical Garden-Institute, the northernmost botanical garden in Russia (67°38′ N). The aim of this work has been a comprehensive analysis of the condition of Siberian stone pine trees (Pinus sibirica Du Tour) during their introduction in the Arctic. The condition of 8 specimens of the species cultivated at the experimental plot in the town of Apatity has been examined. Their phenological development has been analyzed: the swelling and breaking of the vegetative buds, the end of the elongation and maturation of the needles, the beginning and end of growth of the annual shoots, the lignification of the shoots, the beginning and end of pollen dispersion. The degree of lignification of the annual shoot, the winter hardiness, the habit, the shootforming capacity, the height increment, the generative development and the reproduction in the plantation have also been assessed. The risk of a tree falling has been determined by considering its surroundings and exposure to wind. The root zones, the butts, the trunks, the crown bases, the boughs and the crowns have been examined for the presence of hollows, cracks, decomposition, fungal fruit bodies, damage, weak forks, dead branches, etc. The application of an approach combining the analysis of seasonal development, viability and risk of tree fall is promising for a comprehensive and objective assessment of the condition of Siberian stone pine trees by morphological and phenological characteristics during the introduction to the Arctic zone of the Russian Federation. The phenological rhythm of the studied trees corresponds to the environmental conditions during the introduction to the Polar-Alpine Botanical Garden-Institute named after N.A. Avrorin. Vegetation begins in late May. By the end of August the annual shoots lignify, which indicates the readiness of the plants for the winter period. The close timing of the onset of phenophases and their low variation may indicate a low dependence of the seasonal development of Siberian stone pine on weather conditions during the introduction to the central part of the Kola Peninsula. The trees are winter-hardy, retain the life form inherent to the species, have a high shoot-forming capacity and annual height increment. They reach the generative stage of development. For their propagation in the plantation, it is necessary to attract seed material from other regions. The trees are monocormic, unimucronate and bimucronate. They are characterized by dense crowns. Their apical and lateral shoots are developed. In rare cases, the increment of lateral shoots is reduced. The V-shaped forks have been noted on the stems and a hollow in the butt area has been found on one of the trees. An additional instrumental examination is needed to determine the effect of diseases or pathogens on the stability of the trees.

The impact of northern red oak (Quercus rubra; Fagaceae) on the forest phytodiversity in Ukraine

The impact of Quercus rubra on the plant diversity of native forests of Ukraine has been investigated. The plant communities of artificial plantations dominated by northern red oak have such general features as poor species composition, with projective coverage values of other species not exceeding 5%, and a simplified vertical structure of the tree layers. In natural forest plant communities with the participation of Q. rubra, there are no rare and typical nemoral dominant species, which results in disruption of consortial relations in ecosystems. Such changes are due to the biological and ecological peculiarities of this species, in particular, its dense crown, abundant biomass of leaves, which reduces lighting, and allelopathic properties; all those factors affect the physical and chemical characteristics of biotopes. Quercus rubra artificial plantations are more adaptive to changes of natural conditions and are able to withstand harsher winters and lack of precipitation. The ecological amplitude of this species is wide, and even with an increase in the average annual temperature by 3 °C most of the ecological indicators do not go beyond the optimum zone of the species, except for the soil moisture and thermal regime. The amplitudes of main indicators of ecological factors of temperate forests and Q. rubra artificial plantations overlap. The dominance of Q. rubra reduces the quality of ecosystem services of native forests. The high competitive advantages of Q. rubra are the reason for the impossibility of natural restoration of the typical broad-leaved or coniferous forests on those land plots where they were replaced by artificial plantations of northern red oak or its tree layers were formed as the results of the spontaneous distribution of this species. In the successions, the communities with the participation of northern red oak are potentially able to replace the native forest phytocoenoses.

Trees with a Denser Crown have Lower Water Consumption than Trees with a Sparser Crown

Trees with a Denser Crown have Lower Water Consumption than Trees with a Sparser Crown

A Simulation Study of the Impact of Urban Street Greening on the Thermal Comfort in Street Canyons on Hot and Cold Days

The urban heat island effect has become a widely concerning issue worldwide. Many researchers have made great efforts to improve the summer thermal comfort of urban street canyons by optimizing street greening. Relatively less research has focused on how to improve the thermal comfort of street canyons by optimizing street greening during cold days. Many researchers have proposed strategies to improve the summer thermal comfort of street canyons using road greening. This may have a significant negative impact on the winter thermal comfort of street canyons due to the lack of consideration of the impact on hot and cold days simultaneously, especially when the road green space is mainly composed of evergreen tree species. We aimed to explore the impacts of urban street greening on thermal comfort on hot and cold days at the same time. We used Zhutang West Road in Changsha, China, as an example and built six different models to explore the impacts of the street vegetation types, number of street trees, tree heights, crown widths, and Leaf Area Index on the thermal comfort of the street canyon. In addition, we also considered the impact of different building features and wind directions on the thermal comfort of the street canyon. We employed ENVI-met (version 5.5.1) to simulate different urban street greening models. The results show that the model with a high tree canopy density, tall trees, large and dense crowns, and sufficient building shade has good thermal comfort on hot days (the average physiological equivalent temperature (PET) is 31.1 °C for the study period) and bad thermal comfort on cold days (the PET is 13.3 °C) when it is compared with the other models (the average PETs are 36.2 °C, 31.5 °C, 41.5 °C, 36.2 °C, and 35.5 °C, respectively, on hot days and for other models). In addition, the model with a very large number of short hedges has a positive impact on thermal comfort during hot days (the PET is 31.1 °C). The PET value of another comparable model which does not have hedges is 31.5 °C. Even if the model with a small building area has good ventilation, the small building shade area in the model has a more obvious impact and the model has relatively good thermal comfort during cold days (the PET is 14.2 °C) when it is compared to models with bigger building areas (the PET is 13.9 °C). In summer, when the wind is parallel to the direction of the street canyon, the wind speed in the street canyon is high and the model has relatively good thermal comfort (the PET is 35.5 °C) compared with another model which has different wind direction and lower wind speed at the street canyon (the PET is 36.2 °C). In winter, when the wind is perpendicular to the direction of the street canyon, buildings and trees have a strong windproof effect and this is beneficial to the improvement of thermal comfort (the PET is 15.3 °C for this model and 13.9 °C for another comparable model). This research lays a solid foundation and encourages people to think about the impact of building and tree composition and configuration on the thermal comfort of street canyons during hot and cold days simultaneously.

Economically optimised target state of uneven-aged forest management for main forest types in Slovakia

Abstract The study presented a bioeconomic modelling approach for an uneven-aged mixed forest management planning. Regression models for transition (increment), and ingrowth (regeneration) used the National Forest Inventory (NFI) of Slovakia and regional inventory data. Mortality was based on salvage logging records. Models were specific for five tree species within three forest types (FT) (oak with hornbeam and beech, beech, mixed fir-beech-spruce). Net timber prices were calculated with regard to stem quality. Tree growth depended on crown characteristics. The regression models were adjusted to three main geobiotope (GBT) sites per FT. Forest growth was simulated with the density-dependent stand-level matrix transition model. Financial optimisation of harvest was sensitive to an interest rate. Long-time optimisation stabilised in a steady state equilibrium characterised by a stable diameter distribution. Target diameters were specific for site and tree species, and were highest for fir, a dense crown, a good stem quality, and a lower interest rate. Standing timber volume varied from 150 m3 ha–1 (oak forests, 2% interest rate) to 400 m3 ha–1 (beech and fir-beech-spruce forests, 0.5% interest rate). Harvested volume varied from 38 to 93 m3 ha–1 per 10 years, stand basal area (ba) varied from 19 to 36 m2 ha–1 depending on the site, timber price, and interest rate. The discussion pointed out that the relative low volume of the oak FT resulted from the light-demanding characteristics of oak. The mean of oak mosaic structures was lower compared to the high level of more storeys present in the single tree selection structures in beech and mixed fir-beech-spruce forests.

IMPACT OF FOREST SHELTER BELTS ON THE DEVELOPMENT OF SPRING WHEAT IN THE NEAR-EDGE ZONE OF CROPS

The system of shelterbelt forests is a long-lasting ecological framework of an agrarian territory. Their main function is to prevent the degradation of arable soils, improve the microclimate of fields, and preserve the stability and biological diversity of landscape. However, the presence of forest belts complicates field cultivation, and along their borders zones (strips) of depression in crop development could formed, reducing the productivity of lands. This impedes field-protective afforestation, and, consequently, the solution of the problem of reliable protection of land resources. The aim of the work is to establish the causes and regularities of formation of depressive zones in agrocenoses, and to determine the possibility and methods of suppressing their development. The research has been conducted for 8 years in the experimental-production system of 30 to 53-year old 2 to 4-row forest belts of Betula pendula ROTH, Pinus silvestris L., Ulmus laevis PALL. and other species on the automorphic chestnut soil of the Kulunda steppe (the Altai territory) by the generally accepted methods. It was found that the depressive zone in agrocenoses is the least wide for relatively sparse forest belts of birch and pine, and also for forest belts with marginal rows of xerophytic shrubs (3-7 m in total on windward and leeward sides), and the largest (up to 25-30 m) for elm and poplar (Populus laurifolia LEDEB.), i. e. for plantations of hydrophylous tall species with dense crowns. It is 1-3 m wider on the leeward side of forest belts, where more snow is deposited in winter and soil moisture is better in spring. The increase in height and density of stands, influencing the length and intensity of day-time soil shading, stimulates the expansion of the zone. Crop depression is more pronounced in wet years. The increased amount of atmospheric precipitation during the cold season, as well as at the beginning of the growing season and during the reaping season till the onset of stable cold weather also contributes to it. The development of depressive zones is suppressed by abundant precipitation during the period of active growth of field crops. Thus, the formation of depressive zone in agrocenoses of shelterbelt forests depends on many factors. Under arid conditions, the most effective factors are the need for soil moisture and moisture availability for the stand. The most active expansion of the tree root system in the field and the suppression of crops occur in wet years and during the periods with high soil moisture in the absence or weakened competition of field crops. To reduce damage to their productivity, it is necessary to implement a set of coordinated organizational, silvicultural and agrotechnological measures aimed at increasing moisture availability and limiting the expansion of tree root system of forest belts in the field.

Study on selection of woody plants to create sustainable green spaces in sparsely forested rural areas

For sustainable development of rural areas in low forested regions it is necessary to create additional areas of artificial plantations from the adapted gene pool of woody plants. The existing artificial plantations were created more than 70 years ago, so they do not effectively fulfill their ameliorative functions. The aim of the research is the selection of woody plants to form landscaping spaces of recreational type in sparsely forested regions. Bioecological studies of 18 tree species of the families Rosaceae, Oleaceae, Fabaceae, Fagaceae, Cornaceae, Caprifoliaceae, Corylaceae, Anacardiaceae, Rhamnáceae in dendrological collections of the Federal Research Centre of Agroecology RAS were carried out from July to October 2021 under field conditions. Conventional methods for evaluating crown structure on microclimatic parameters and ornamental value were applied. Original data were obtained by non-invasive method (Dualex Scientific device), which showed species-specificity of quantitative indicators of photopigments, their lability as an indicator of resistance to high temperatures was given. Dynamics of pigment indices in leaves showed that interspecific variation of the index is higher than intraspecific variation. The adapted assortment of trees and shrubs for arid regions has been identified. It is established that trees (Quercus robur) and shrubs with dense crowns (Ligustrum vulgare, Syringa vulgaris, Rosa rugose, etc.) reduce air temperature more effectively (by 2.2-4.3°C) than woody species with openwork crowns (species of genera Gleditsia and Robinia). It is shown that changing the composition of phytodiversity will increase the quality class of plantations. Quercus robur, Robinia pseudoacacia, Rhus typhina, Cotinus coggygria, species of Gleditsia and Amelanchier are recommended for creation of artificial plantations in the research region.

Post-release ecology of rehabilitated Hoffmann’s two-toed sloths in Panamá

The field of wildlife rescue and rehabilitation continues to grow as human expansion increases the rate of deforestation in Latin America. Sloths (Bradypus spp. and Choloepus spp.) are often admitted to rescue centers throughout Latin America due to their poor dispersal abilities and vulnerability to anthropogenic impacts. Although post-release monitoring is fundamental to measuring the success of wildlife rescue programs, few studies have assessed the outcomes of releasing hand-reared sloths back into the wild. We studied the ecology of rehabilitated and relocated Hoffmann’s two-toed sloths (Choloepus hoffmanni) in central Panamá during 2019- 2020. Eleven two-toed sloths rescued from the wild were hand-reared in captivity for 727±193 days and then radiomarked, placed in an outdoor 500 m2 soft-release enclosure for 3 months, and released in a nearby national park. While in the softrelease enclosure, two-toed sloths spent 80.0% of their time resting and became active and more alert in the evening (p=0.01). Upon release into the wild, two-toed sloths traveled a mean linear distance of 82.3±21.6 m and a mean distance of 25.6±9.5 m between successive radiolocations. The mean home range size was 2.92±1.19 ha, with females occupying larger areas than males. Two-toed sloths used trees with a smaller dbh than available (p≤0.001; p≤0.015) and selected trees with dense crowns and ≥50% lianas. Eight mortalities were recorded, with predation and natural causes being the main causes of mortality. Monthly survival was 0.72±0.14 and did not differ (p≤0.30) between males (1.00±0.00) and females (0.44±0.22). Rehabilitated two-toed sloths exhibited behavioral and space use patterns similar to wild two-toed sloths, with the exception of having lower survival rates following release in the wild. Our study provides information that can be useful in evaluating the efficacy of sloth rescue and rehabilitation programs throughout Latin America.

Diversity in the morphology of clones of witches’ broom in Siberian stone pine

Mutational witches’ broom (WB) is a fragment of a tree crown with abnormally dense branching and slow shoot growth compared with those of a normal crown. All WBs have thicker and denser crown compared to the normal crown part of their parental tree, but the crown density differs significantly among WBs. There are both relatively loose WBs, whose crown density differ from normal crown part not very strong, and WBs with a very dense crown. The aim of this study was to conduct a comparative analysis of morphological traits in Pinus sibirica WB clones with different crown densities and to determine which traits contribute most to their differences. The object of the study was clones from 11 mutational WB with different crown density. The density of WB was considered low if it exceeded the density of a normal crown by less than 2 times, medium - by 2-3 times, high - by more than 3 times. Morphological characteristics of crown and shoots were measured in 12-year-old clones. It was found that the higher the WB clone crown density the smaller and less elongated its crown shape, as well as less crown continuity. The basis of this phenotype formation was primarily the shorter length of annual shoots, the reduced level of apical dominance compared to other clone groups, and advanced branching. An additional factor that increased crown density was the significantly shorter internodes compared to the other clone groups. The needle length did not contribute to the differences in crown density of the clones.

Actual sky visibility under shading by trees with different crown densities

Introduction. The development of green infrastructure is an important task in urban planning strategies to reduce urban heat island effect and improve urban ecosystem. The aim of this study is to determine the actual visibility of the skyline when shaded by trees of different crown densities. The scientific novelty is that for the first time a study of the actual sky visibility with trees shading as complex heterogeneous systems has been conducted to assess the effect of mitigating of urban heat island. The practical significance lies in the establishment of the actual visibility of the firmament under the shading of trees with different crown density, which enables the correction of simulation models to analyze the parameters of the microclimate of the urban environment under given climatic conditions.
 
 Materials and methods. Various approaches to determining the sky visibility are considered. Direct measurements were made by photographing with a special fisheye lens and a smartphone. The research was carried out in a temperate continental climate (according to the international climate classification Köppen — type Dfa). Several tree species most commonly found in landscaping under the climate conditions in question and having different crown densities were selected: elm, oak, maple and poplar. For each, several samples were selected as required for data averaging. A total of 27 samples were studied.
 
 Results. A diagram of measured averaged values of the sky visibility factor was plotted, taking into account shading by trees with different crown densities in different periods of the year. To protect trees with dense spreading crowns from the direct solar radiation in the summer daytime, it is better to use trees with dense spreading crowns to intensify the radiant heat exchange of the urban surface with the sky at night — trees with less dense crowns. In case of the need to soften the urban heat island during the day, hybrid solutions are the most effective.
 
 Conclusions. The actual assessment of the sky visibility, made by the authors taking into account shading by trees, allows us to make corrections in simulation models to analyze the parameters of the microclimate of the urban environment under the given climatic conditions. The results of the study make it possible to select the type of tree providing the required shading and urban heat island’s mitigation effect.

Forest conversion into pasture selects dung beetle traits at different biological scales depending on species pool composition.

The conversion of forests into open areas has large effects on the diversity and structure of native communities. The intensity of these effects may vary between regions, depending on the existence of native species adapted to open habitats in the regional pool or the time since habitat change.We assess the differences in species richness and functional diversity of dung beetle communities (Coleoptera: Scarabaeinae) between native forests and novel pasturelands of the Atlantic Forest and the Cerrado, two biomes with contrasting histories of human occupation in Brazil. We conducted standardized surveys in seven forest fragments and adjacent pastures in each region and measured 14 traits in individuals collected in each type of habitat at each particular site. We calculated functional richness, functional evenness, functional divergence, and community-weighted mean of traits for each area, and analyzed individual variation through nested variance decomposition and Trait Statistics.Communities were richer and more numerous at the Cerrado. We did not find any consistent relationship between functional diversity and forest conversion beyond the changes in species diversity. Although landscape changes were more recent at the Cerrado, the colonization of the new habitat by native species already adapted to open habitats lessens the functional loss in this biome. This indicates that habitat change's effects on trait diversity depend on the regional species pool rather than on time since land conversion.Forest conversion effects were primarily due to internal filtering. The effects of external filtering only appear at the intraspecific variance level, with contrasting differences between the Cerrado, where traits related to relocation behavior and size are selected, and the Atlantic Forest, where selection operates for traits related to relocation behavior and flight. These results evidence the importance of considering individual variance to address the responses of dung beetle communities to forest conversion.

Analysis of Changes in Mangrove Land Cover in West Langsa District, Langsa

This study aims to analyze changes in land cover and mangrove crown density in Langsa Barat District for the period 2000-2020. The method used in this study is the maximum likelihood classification (MLC) to determine changes in mangrove land cover while determining mangrove density using the NDVI equation. Based on the results of the analysis of changes in mangrove land cover there was an increase and decrease in area. In 2000 the area of ​​mangrove land was 1,039.17 ha, then increased in area in 2005 amounted to 1.325,59 ha (27.56%). In 2010, the mangrove area decreased by 1.145,22 ha (15.75%). In 2015, the mangrove area increased to 1,357.10 ha (18.50%), and finally, in 2020 there was an increase in the mangrove area to 2.027.05 ha (49.37%). While the analysis of mangrove crown density using NDVI value from 2000 to 2020, the highest crown density value was in 2020 with the category of the dense crown density of 1,509.40 ha (74.46%), while the medium crown density value was recorded in 2020 namely 517.49 ha (25.53%). Meanwhile, the lowest sparse category canopy density value was recorded in 2020 with an area of ​​0.17 ha (0.01%).

Environmental magnetic signatures in mangrove ecosystems in northern Persian Gulf: Implication for pollution assessment in marine environment

Magnetic properties of root, bark, and leaf of mangrove (Avicenna marina) and sediment were determined for pollution assessment at three locations in the northern coast of the Persian Gulf. The study revealed that the sources of the particles deposited on leaf surfaces can be discriminated via saturation isothermal remanent magnetization (SIRM) values and heavy metal. However, different factors including wind direction, size of the magnetic particles and crown density, play a role using SIRM for biomonitoring of atmospheric particulate matter. For leaves, the significant correlations between SIRM and leaf elemental contents indicated that the deposited particles on their surface mainly have geogenic sources. The magnetic analyses revealed that leaves are more suitable than bark for monitoring atmospheric pollution using mangrove trees due to the effect of different factors including dense crown of trees, washing of tree trunk by sea waves, and elements translocation from roots and sediments. Instead, the positive and significant correlation between the SIRM values for sediments and mangrove roots, and no or negative correlation between sediments and roots with barks and leaves indicates that the magnetic properties of the sediments and mangrove roots are suitable indicators of pollution in aquatic environment.

Experimental investigation on the erosion-deposition characteristics around isolated plants of different shapes in a wind tunnel

• Plant shape has an important effect on the patterns of erosion and deposition. • The erosion and deposition areas around plant usually increase with blowing time. • Tree model has a larger erosion area than slender plant under similar frontal area. • Tree with short trunk and dense crown is better for sparse plant erosion control. Accurate description of the characteristics of erosion and deposition around single model plants of different shapes is important to evaluate the protective role of plants in wind erosion control. The variation of bed topography with time was measured in a wind tunnel for two flexible models and two rigid tree-like models. The bed surface height close to the plant decreases forming a deep well, while in the lee, a deposition area generally appears whose shape is affected by plant type. The local wind erosion rate on both sides usually decreases with time, and the deposition area in the lee with the local erosion rate less than zero gradually moves downwind with time while disappears for the tree-like plant model with a long trunk and a large crown. Under similar frontal areas of plants, both the erosion and deposition areas around the tree-like plant with a short trunk and conical crown, and the flexible plant with a large upper part and a small lower part are generally larger than that around the slender flexible plant. The rigid tree-like plant with a short trunk and a dense conical crown is better for erosion control due to the smallest net erosion rate and the erosion area similar to the deposition area, while the other plant models have larger net erosion rate and much larger erosion area.

Photonic crystal fiber supporting 394 orbital angular momentum modes with flat dispersion, low nonlinear coefficient, and high mode quality

A photonic crystal fiber (PCF) with an SSK2 dense crown glass ring is designed and analyzed. After optimization of the radius of the central air hole and thickness of the annular region, 394 orbital angular momentum (OAM) modes in the range of 1.48 to 1.62 μm can be transmitted stably. The effective refractive index, effective index difference, dispersion, effective mode area, nonlinear coefficient, numerical aperture (NA), mode quality, and confinement loss are analyzed numerically by the finite element method. The results show that the effective index difference of all the OAM modes is greater than 1 × 10 − 4 and they can propagate stably in the PCF. Besides, the fiber shows flat dispersion with a minimum variation of 8.55 ps / ( km · nm ) , very small nonlinear coefficient of less than 0.232 W − 1 · km − 1, as well as high mode quality bigger than 94.57%. This high-performance PCF has immense application potential in optical fiber communication.

Complementary effects of tree species on canopy rainfall partitioning: New insights for ecological restoration in Andean ecosystems

Vegetation affects local water balance partitioning via effects on incoming precipitation, local radiation balance and soil hydrological properties. The extent of these effects is related to plant functional traits, such that forest composition plays an important role in its hydrological function. Therefore, the selection of species in forest restoration processes is key to recovering ecological (including hydrological) function. However, most restoration projects often do not include functional criteria for species selection, and even less frequently they include ecohydrological functions, although many projects are intended to recover hydrological regulation. We explored the association between plant functional traits and ecohydrological function, indicated by precipitation partitioning in the canopy into stemflow and throughfall, in an 8-year watershed restoration project in the Central Andes of Colombia. We monitored stemflow and throughfall (both mean and variability) on planted individuals from ten native tree species for almost two years and measured functional traits that describe tree crowns and are associated with rainfall partitioning. We found that stemflow and throughfall behavior is generally inverse and differ among species, with the highest variability in mean stemflow and coefficient of variation of throughfall. Furthermore, our results show that stemflow and throughfall are significantly associated with tree crown functional traits (R2 = 0.74 for crown area and R2 = 0.62 for crown density × volume). Besides, the studied species are organized in a variation space of ecohydrological processes and crown functional traits (first two principal components from PCA explain 71.7% of data variability). They are organized from wider/less dense crowns in Alnus acuminata to smaller/denser crowns in Quercus humboldtii, which significantly influenced the temporal variability of stemflow and throughfall, respectively. Other species are located intermittently along this variation space. From a multivariate perspective, our species were differentiated into four discrete groups based on similar functional traits and, therefore, with similar effects on ecohydrological processes. This suggests a complementary effect of different species on the ecosystem hydrological functions, thus highlighting the importance of considering diversity on ecosystem management and ecological restoration for the recovery of ecosystem integrity.

Spectral properties of CsPbX3 (X=Br, I) perovskite nanocrystals in borogermanate glass-ceramics

Pure CsPbBr3 and CsPbI3 perovskite nanocrystals are nucleated in the borogermanate glass. Nanocrystals precipitation in glass are controlled via isothermal treatment at temperatures above Tg by adjusting the temperature and duration starting from 15 min. X-ray diffraction data and optical measurements have confirmed the formation of 5–8 nm sized CsPbBr3 nanocrystals and 6–15 nm sized CsPbI3 nanocrystals. Wherein, the photoluminescence of lead cesium bromide perovskite is tuned in the 490–530 nm range, and the luminescence of iodide perovskite is changed in the 640–740 nm range. The maximum luminescence quantum yield of pure CsPbI3 perovskites is 19%. Water, climate and acid resistance tests show borogermanate glasses with perovskite nanocrystals are compatible with commercial dense crowns.