Proximity Of Trees Research Articles

Exploring Urban Greenery: A Case Study of Roadside Trees in Pokhara Metropolitan City

Roadside trees play a crucial role as important components of urban greenery, significantly enhancing the overall quality of cities and ultimately contributing to the quality of life for residents and visitors alike. This study examines the condition, maintenance, and proximity of roadside trees to electric wire corridors in Pokhara Metropolitan City, Nepal. This study employs field surveys, categorization based on tree attributes, and mapping techniques to analyze the distribution and characteristics of roadside trees. Out of approximately 1500 trees initially collected, 1435 were processed for further analysis. Trees were classified by species, height, condition, and the presence of fencing or resting structures (Chautaro), with proximity to electric wire corridors also assessed. Findings reveal a significant presence of trees in good condition, predominantly Dhupi, Kapur and Ashoka species, with a notable percentage requiring maintenance. A substantial number of trees were found in close proximity to electric wires, posing potential hazards. Mapping techniques facilitated visualizing the spatial distribution of trees, aiding in urban planning and management strategies. The study underscores the importance of sustainable urban greening practices and the need for proactive measures to address challenges related to tree maintenance and safety in urban environments like Pokhara Metropolitan City. This study emphasizes the pivotal role of roadside trees in enhancing the aesthetic appeal and quality of city life, positioning them as decisive factors in shaping urban environments and fostering a welcoming atmosphere for residents and visitors.

Beekeeping improves shea pollination and fruit set in West African agroforestry parklands

Abstract Shea (Vitellaria paradoxa C.F. Gaertn) is a fruit tree of domestic and industrial importance in arid and semi‐arid regions of Sub‐Saharan Africa. Fruit set is largely dependent on insect pollination but recent studies have revealed a pollen deficit. The introduction of managed bees into orchards is an effective approach for enhanced pollination services in temperate climates. However, there is limited information to guide the adoption of this practice in agroforestry parklands. This study investigated the effect of managed honey bee colonies (Apis mellifera) on fruit yield of shea in six parklands across three regions of Ghana. Tree proximity to the apiary had a detectable effect on fruit set within a 500 m range of the apiary. Proximity of shea trees to apiary was significantly related to number of immature fruit set but not number of mature fruits. Fruit weight and size were not significantly related to distance from apiary or pollination treatment. This implies that the introduction of beekeeping has the potential to address shea pollination deficit at least within a 500 m range of the apiary. Further studies are needed to determine the optimal hive density per acreage of shea parkland to maximise pollination services.

A Fast Adaptive Millimeter-Wave Radar Clustering Algorithm

This paper focuses on the intelligent recognition problem of radar detection targets. Aiming at the low accuracy and slow speed of millimeter-wave radar clustering point cloud information, a feature algorithm of millimeter-wave radar suitable for detecting targets is proposed. In the detection of targets by millimeter-wave radar, distance is the biggest factor affecting the number and degree of sparsity. A method that combines the feature information of the point cloud with the KD tree proximity search algorithm and the DBSCAN clustering algorithm is proposed, which can adapt to the problems of uneven target point cloud, small amount of data and slow clustering speed. The improved algorithm can use the KD tree to quickly find adjacent points and calculate the distance between adjacent points. The corresponding number of thresholds is set according to the distance where the target is located, and the radius of the target area reflected by the millimeter-wave radar plus the distance of the last threshold point is used as the neighborhood radius of the improved algorithm. Therefore, fast and adaptive parameter adjustment of the millimeter-wave radar can be realized. Simulation tests show that the improved clustering algorithm has better parameters. The accuracy of the improved algorithm is increased by 4.2%, and it also greatly improves the clustering speed.

Landscape features drive insectivorous bat activity in Indian rice fields

ContextInsectivorous bats have been shown to control a number of agricultural insect pests. As bats exhibit species-specific responses to the surrounding landscape, tied closely to their morphology and foraging mode, the activity and distribution patterns of bats, and consequently the ecosystem services they provide, are influenced by the landscape characteristics.ObjectivesThis study aims to determine which features in the landscape surrounding rice fields influence the activity levels of insectivorous bats, and at what scales they are most influential.MethodsWe collected acoustic recordings to determine activity levels of seven bat sonotypes in rice fields surrounded by a variety of land-cover types in the Nagaon district of Assam, India. Using this, we determined the most important set of features in the surrounding landscape, and the scales at which had the strongest impact, for each sonotype.ResultsOur results suggest that tree cover variables are the most important predictors of bat activity in rice fields. Distance to nearest forest, area of forest within 1 km, distance to nearest forest edge, and landscape heterogeneity influenced all five of the analysed bat sonotypes. Also important were the amount of urban land within 1 km, which exerted a negative effect on the activity of one sonotype, and moonlight activity, which negatively influenced the activity levels of one sonotype.ConclusionOur results demonstrate that when flying over rice fields, bat activity is most influenced by presence and proximity of trees. Therefore, increasing tree cover in agricultural landscapes will increase bat activity and likely the level of pest control.

Root architecture, root biomass and nutrient cycling in a mixed‐species agroforestry system

AbstractUnderstanding root development in soil profiles of agroforestry systems is challenging. It is uncertain to what extent the proximity of cash crops, such as cocoa and coffee, to shade trees reduces nutrient concentrations in the topsoil and whether the cash crops continue to develop fine roots in the topsoil when they are planted in close proximity to shade trees. We aimed to investigate micro‐ and macro‐nutrient concentrations in the soil profile and understand root architecture using a novel DNA metabarcoding approach in an agroforestry system where cocoa and coffee were interplanted with a shade tree, canarium. Soil and root samples were collected from (1) cocoa‐only, (2) cocoa‐canarium, (3) canarium‐only positions in a cocoa plantation, (4) coffee‐only, (5) coffee‐canarium and (6) canarium‐only positions in a coffee plantation. Proximity of shade trees did not limit nutrient concentrations for cash crops. Topsoil concentrations of total N (TN: 0.59% and 0.69%), phosphorus (P: 7.28 and 6.65 mg/kg), potassium (K: 360 and 755 mg/kg) and calcium (Ca: 1865 and 1044 mg/kg) under cocoa and coffee trees, respectively, did not differ significantly from those under the corresponding canarium trees. Soil TN, K and Ca concentrations were well above minimum required concentrations under both cocoa and coffee. DNA metabarcoding showed that canarium trees occupied deeper rooting zones (30–80 cm soil depth) than cocoa and coffee trees (0–30 cm soil depth). DNA metabarcoding demonstrated greater root colonisation of the topsoil by cocoa and coffee than canarium, suggesting that canarium had the potential to extract nutrients from deeper soil layers. Soil Ca concentrations were associated with cocoa root biomass whereas soil NO3−‐N concentrations were associated with coffee root biomass. Our study highlighted the value of selecting suitable shade trees that maintain soil nutrient concentrations for cash crops. Furthermore, DNA metabarcoding can facilitate root distribution studies in complex agroforestry systems, thus providing insights into appropriate tree‐planting designs.

Stemflow infiltration hotspots near-tree stems along a soil depth gradient in a mixed oak–beech forest

In an upland forested micro-catchment during the growing season, we tested soil responses to precipitation events as well as soil water content (SWC). We asked ourselves if what is the difference of SWC response to precipitation events depending on the presence and proximity of a tree? The environmental heterogeneity of the small 7.5-ha headwater area was captured by soil probes at specific locations: (i) probe measurements of SWC at 10-, 30-, 60-, and 100-cm depths; (ii) resolution of near-tree (NT) and between-tree (BT) positions; and (iii) resolution of four slope classes. The results revealed significant differences between the hydrological responses of the soil. NT soils had faster infiltration but were also faster to dry out when compared to BT soils, which were less affected by the presence of trees. Water input threshold values, measured as the precipitation amount needed to cause a significant increase in SWC, were also significantly different, with NT positions always lower than BT positions. Total infiltration of the topmost NT and BT soil layers reached 185 and 156 mm during the study period, corresponding to 43% and 36% of the total 434 mm of precipitation, respectively. Infiltration into the deepest horizon was significantly higher in NT soils, where it reached 114 mm (26%) as opposed to 9 mm (2%) in BT soils, and was indicative of significant vertical hydraulic bypass flow in the proximity of trees. These observations contribute to better understanding the hydrological processes, their nonlinearity, and the expansion of conceptual hydrological models.

Tree diversity effects on litter decomposition are mediated by litterfall and microbial processes

Forest ecosystems are critical for their carbon sequestration potential. Increasing tree diversity has been shown to enhance both forest productivity and litter decomposition. Litter diversity increases litter decomposability by increasing the diversity of substrates offered to decomposers. However, the relative importance of litter decomposability and decomposer community in mediating tree diversity effects on decomposition remains unknown. Moreover, tree diversity modulation of litterfall spatial distribution, and consequently litter decomposition, has rarely been tested. We studied tree diversity effects on leaf litter decomposition and its mediation by the amount of litterfall, litter species richness and decomposability, and soil microorganisms in a large‐scale tree diversity experiment in subtropical China. Furthermore, we examined how litter functional identity and diversity affect leaf litter decomposability. Finally, we tested how leaf functional traits, tree biomass, and forest spatial structure drive the litterfall spatial distribution. We found evidence that tree species richness increased litter decomposition by increasing litter species richness and the amount of litterfall. We showed that soil microorganisms in this subtropical forest perform 84–87% of litter decomposition. Moreover, changes in the amount of litterfall and microbial decomposition explained 19–37% of the decomposition variance. Additionally, up to 20% of the microbial decomposition variance was explained by litter decomposability, while litter decomposability itself was determined by litter functional identity, diversity, and species richness. Tree species richness increased litter species richness and the amount of litterfall (+200% from monoculture to eight‐species neighborhood). We further demonstrated that the amount of species‐specific litterfall increased with increasing tree proximity and biomass, and was modulated by leaf functional traits. These litterfall drivers increased the spatial heterogeneity of litter distribution, and thus litter decomposition. We highlighted multiple biomass‐ and diversity‐mediated effects of tree diversity on ecosystem properties driving forest nutrient cycling. We conclude that considering spatial variability in biotic properties will improve our mechanistic understanding of ecosystem functioning.

Interspecific facilitation of micronutrient uptake between cluster-root-bearing trees and non-cluster rooted-shrubs in a Banksia woodland

Background and aimsBelowground interspecific plant facilitation is supposed to play a key role in enabling species co-existence in hyperdiverse ecosystems in extremely nutrient-poor, semi-arid habitats, such as Banksia woodlands in southwestern-Australia. Manganese (Mn) is readily mobilised by Banksia cluster root activity in most soils and accumulates in mature leaves of native Australian plant species without significant remobilisation during leaf senescence. We hypothesised that neighbouring shrubs are facilitated in terms of Mn uptake depending on distance to surrounding cluster root-forming Banksia trees.MethodsWe mapped all Banksia trees and selected neighbouring shrubs within a study site in Western Australia. Soil samples were collected and analysed for physical properties and nutrient concentrations. To assesses the effect of Banksia tree proximity on leaf Mn concentrations [Mn] of non-cluster-rooted woody shrubs, samples of similarly aged leaves were taken. We used multiple linear models to test for factors affecting shrub leaf [Mn].ResultsNone of the assessed soil parameters showed a significant correlation with shrub leaf Mn concentrations. However, we observed a significant positive effect of very close Banksia trees (2 m) on leaf [Mn] in one of the understorey shrubs. We found additional effects of elevation and shrub size.ConclusionsLeaf micronutrient concentrations of understorey shrubs were enhanced when growing within 2 m of tall Banksia trees. Our model predictions also indicate that belowground facilitation of Mn uptake was shrub size-dependent. We discuss this result in the light of plant water relations and shrub root system architecture.

Влияние микроклиматических городских условий на рост Tilia cordata Mill. (на примере г. Уфы)

The biological state of plantings with contrasting microclimatic growing conditions within the city limits is influenced by the orientation of streets to the cardinal directions and the presence of high-rise buildings. The trunk diameters (d0,1 and d1,3) and the height of Tilia cordata Mill were measured (n = 1 476 trees on 12 trial areas) with different age range (within V-X classes), freely growing on twelve linear trial areas allocated within two districts of the Ufa city of the Republic of Bashkortostan. The comparison of the average values of biometric parameters of trees growing in areas with different microclimates was carried out using the Student's test (α=0.05). In the process of conducting research on sites with contrasting microclimatic conditions, it was revealed that the growth, development and productivity of green spaces in urban conditions is influenced by their location, microclimatic conditions and air temperature. The orientation of the streets to the cardinal directions and the presence of high-rise buildings - sunny or shady - are very important for the growth of the tree. On the shady side during the growing period there is more moisture and the air temperature is lower. Of great importance for the difference in the diameters of the trees of the objects under consideration is their age. In addition, the immediate proximity of trees to the carriageway of the main street of the city also has a serious impact on their condition. The data of this study allow them to be used in the organization of landscape care for urban plantings, including linden trees.

The Thermal Effect of Various Local Park Settings: A Simulation-Based Case Study of Sunshine Coast, Australia

Local parks are widely used to mitigate urban heat islands. However, the increase of dry weather periods in subtropical climates has caused natural grass failure, leading some city councils to replace it with artificial grass. Therefore, this study investigates various local park settings to assess the performance of different ground covers (i.e., irrigated and non-irrigated natural grass, bare soil, and artificial grass) and the influence that tree proximity has on them, as well as the total thermal performance of the investigated local parks. This study finds that non-irrigated parks could harm park users’ health due to the high concentration of mean radiant temperature (MRT) around trees. Although the surface temperature of the artificial grass was higher (2.60 °C) than that of asphalt during periods of peak temperature, the parks using artificial grass performed better at reducing air temperature and enhancing thermal comfort than the ones with dry grass or bare soil, where both tree proximity and soil water content played significant roles. However, artificial grass negatively affected night cooling, resulting in a poorer daily performance. This study discusses the influence of various park settings on air temperature, MRT, thermal comfort, surface temperature, soil temperature, and water content. In addition, various recommendations and settings are offered to direct decision makers and future studies.

Faidherbia albida trees form a natural buffer against millet water stress in agroforestry parklands in Senegal

Description of the subject. In central-west Senegal, agroforestry parklands dominated by Faidherbia albida trees might protect the millet crop against drought and increase agricultural production. Only few studies examined the water relations between the trees and the crop in farmers’ field conditions. Objectives. Our aim was to explore the effect of F. albida trees on millet water potential and the implications for millet yield in F. albida parklands. Method. Sixty-eight F. albida plots scattered in five villages were selected in the 2019 rainy season. In each plot, a pair of millet subplots, “close-to-tree subplot” and “open subplot”, was monitored. We measured millet predawn and midday leaf water potential (Ψp, Ψm), top soil bulk density, water content and temperature, and grain and straw yields at harvest. Results. Pairwise comparisons of Ψp and Ψm of millet indicated better and more stable water status and lower soil temperature and bulk density in close-to-tree subplots. Soil water was sometimes lower in close-to-tree subplots, perhaps because the higher crop biomass in this location resulted in higher water loss through crop transpiration. Tree effects on millet grain and straw yield were positive or null. Correlations between millet yield and Ψp, Ψm measured around flowering were weak. Conclusions. Given their common positive effects on millet water status and yield, F. albida trees could play a key role in promoting sustainable agriculture under the changing climate conditions. Millet yield increase due to the tree proximity was likely due to changes induced by the tree on multiple environmental resources. The interactions of micro-pedoclimatic conditions, livestock and tree management (e.g. density, pruning intensity) on the tree effects should be the focus of future studies.

Environment and density-dependency explain the fine-scale aggregation of tree recruits before and after thinning in a mixed forest of Southern Europe.

Thinning in forest management primarily reduces the density of trees and alters the patchiness and spatial complexity of environmental factors and individual interactions between plant recruits. At fine spatial scales, little is known about the relative weight of ecological processes affecting tree regeneration before and after thinning events. Here we studied the density and aggregation of tree recruits in fully-mapped plots located in mixed forests in Northern Iberian Peninsula (Southern Europe) for over four years, which comprises one year before and three years after a thinning event. We applied spatial point-pattern analyses to examine (a) the aggregation of recruits, and their association with trees and (b) the relative effect of both environmental (i.e., the patchiness of the local environment) and density-dependent factors (i.e., the aggregation of trees and/or recruits) to predict the density, aggregation, and survival of recruits. We found, in thinning plots, that recruits were less dense, their aggregation pattern was more heterogeneous, were distributed randomly in respect of trees and their survival was almost unaffected by the tree proximity. By contrast, recruits in control plots were denser, were only aggregated at distances lower than 1.0 m, were closer to trees, and such closer distance to trees affected negatively in their survival. Independently of the treatment, the aggregation of recruits was chiefly determined by the density-dependent factors at less than 1.0 m and environmental factors at distances beyond that proximity. Overall, our results suggest that thinning affected the aggregation of recruits at two spatial scales: (a) by favoring the tree-recruit and recruit-recruit facilitation at less than 1.0 m and (b) by modifying spatial heterogeneity of the environment at distances beyond that proximity.

The Impact of Tree Planting on Infiltration Dependent on Tree Proximity and Maturity at a Clay Site in Warwickshire, England

Urbanisation and the replacement of previously vegetated areas with impermeable surfaces reduces the lag times of overland flow and increases peak flows to receiving watercourses; the magnitude of this will increase as a result of climate change. Tree planting is gaining momentum as a potential method of natural flood management (NFM) due to its ability to break up soil and increase infiltration and water storage. In this study, a 2.2 km2 clay-textured area in Warwickshire, England, planted with trees every year from 2006 to 2012 was sampled to investigate how infiltration varies dependent on season and tree proximity and maturity. Infiltration data was collected from 10 and 200 cm away from selected sample trees from November 2019 to August 2021 using a Mini Disk infiltrometer (MDI). The results show that mean infiltration is higher at the 10 cm proximity compared with the 200 cm proximity by 75.87% in winter and 25.19% in summer. Further to this, mean 10 cm infiltration is 192% higher in summer compared with winter, and mean 200 cm infiltration is 310% higher in summer compared with winter. There is little evidence to suggest a relationship between infiltration and tree maturity at the study site.

Facilitation differentially affects competitive responses of aspen and subalpine fir through stages of stand development

AbstractSpatial interactions between trees influence forest community succession. The objective of this study was to investigate how shifts in forest composition and proximity between tree species affect stand development over time in mixed forest systems. At six locations across the Fishlake National Forest, Utah, USA, in stands where facilitation has been documented previously, tree‐ring samples were collected from aspen and subalpine fir trees. Basal area increment was calculated to characterize the effects of the proximity of overstory trees on multidecadal growth responses of aspen and subalpine fir in aspen‐dominant and mixed aspen–conifer stands. Subalpine fir seedlings were established next to aspen (within 10 cm) when aspen was between 15 and 120 years old with a mean age of 60 years. Aspen and subalpine fir growth rates were reduced with increasing conifer abundance. Aspen trees growing next to a proximate subalpine fir tree had slower growth rates over time than aspen trees growing independently. Growth rates of subalpine fir in aspen‐dominated stands were similar when growing independently or near aspen trees. However, subalpine fir in conifer‐dominated stands maintained higher growth rates when growing next to an aspen tree than when growing independently. The data suggest that as stand competition increases with conifer abundance, the proximity of overstory trees increases competitive exclusion of aspen while having a beneficial growth effect on subalpine fir. These results underscore the importance of maintaining natural fire regimes in forest systems that keep competitive interactions in balance.

최대 엔트로피 모델을 활용한 경주시의 소나무재선충병 위험지역 분포 예측

This study predicted the distribution of risk areas for pine wilt disease (PWD) based on machine learning by using 15 environmental variables. The maximum entropy model was employed for the study and AUC (area under the curve) was used to evaluate the model. The study area is Gyeongju, and the study period is 2018-2020. In the study area, the core distribution area of trees infected with PWD expanded 2.5 times and 4.7 times in 2019 and 2020 compared to 2018, respectively. The AUC of the spatial estimation for PWD was at least 0.86 in each year. The most important variable in the model was the proximity of infected trees in the previous year. The topography, proximity to roads and wooden buildings, and the average temperature in May were also important variables. It means that human activities and the environment of its vectors play an important role in the spatial distribution of PWD. Furthermore, the results of the study suggest that the establishment and sharing of the distribution data for infected trees are important for policies and research for the prevention of PWD.

Proximity and abundance of mother trees affects recruitment patterns in a long‐term tropical forest restoration study

Remnant trees and forest fragments in agricultural landscapes can be important sources of propagules to facilitate forest recovery. However, many studies simply quantify forest cover in the surrounding landscape as a percentage, with little attention given to species composition, and subsequently fail to detect an effect on recruitment patterns. We assessed the relative importance of the spatial distribution and life‐history traits of 77 tree species on recruitment patterns at a landscape scale in a well‐replicated long‐term restoration study in southern Costa Rica. We censused and mapped potential mother trees in a 100‐m buffer surrounding eight replicate restoration plots and quantified respective tree recruits within each plot. We assessed how mother tree abundance, species life‐history characteristics (seed size, dispersal mode), tree size (DBH, height) and distance to restoration plot affected recruitment at coarse (plot: 50 × 50 m) and fine (quadrat: 3 × 3 m) spatial scales. The presence of a mother tree within 100 m of a restoration plot resulted in a 10‐fold increase in potential mean recruitment. Mother tree abundance was also an important driver of recruit density, and particularly so for large‐seeded (≥ 5 mm) zoochorous species with a fivefold increase in recruit density across the observed mother tree abundance range. An interaction between mother tree abundance and proximity demonstrated that the effect of mother tree abundance on recruit density was important but waned with increasing distance from restoration plots. At the fine spatial scale, proximity was uniformly important; height and DBH of the closest potential mother tree also affected recruit abundance but responses differed by seed size. Results highlight the importance of remnant vegetation composition to the recovery of adjacent degraded habitats, underscoring the outsized role nearby remnant forest and isolated trees can play for the persistence of localized biodiversity.

Pollen limitation and xenia effects in a cultivated mass-flowering tree, Macadamia integrifolia (Proteaceae).

Pollen limitation is most prevalent among bee-pollinated plants, self-incompatible plants and tropical plants. However, we have very little understanding of the extent to which pollen limitation affects fruit set in mass-flowering trees despite tree crops accounting for at least 600 million tons of the 9200 million tons of annual global food production. We determined the extent of pollen limitation in a bee-pollinated, partially self-incompatible, subtropical tree by hand cross-pollinating the majority of flowers on mass-flowering macadamia (Macadamia integrifolia) trees that produce about 200 000-400 000 flowers. We measured tree yield and kernel quality and estimated final fruit set. We genotyped individual kernels by MassARRAY to determine levels of outcrossing in orchards and assess paternity effects on nut quality. Macadamia trees were pollen-limited. Supplementary cross-pollination increased nut-in-shell yield, kernel yield and fruit set by as much as 97, 109 and 92 %, respectively. The extent of pollen limitation depended upon the proximity of experimental trees to trees of another cultivar because macadamia trees were highly outcrossing. Between 84 and 100 % of fruit arose from cross-pollination, even at 200 m (25 rows) from orchard blocks of another cultivar. Large variations in nut-in-shell mass, kernel mass, kernel recovery and kernel oil concentration were related to differences in fruit paternity, including between self-pollinated and cross-pollinated fruit, thus demonstrating pollen-parent effects on fruit quality (i.e. xenia). This study is the first to demonstrate pollen limitation in a mass-flowering tree. Improved pollination led to increased kernel yield of 0.31-0.59 tons ha-1, which equates currently to higher farm-gate income of approximately $US3720-$US7080 ha-1. The heavy reliance of macadamia flowers on cross-pollination and the strong xenia effects on kernel mass demonstrate the high value that pollination services can provide to food production.

Bird-window collisions: Mitigation efficacy and risk factors across two years.

BackgroundResearch on bird-window collision mitigation is needed to prevent up to a billion bird fatalities yearly in the U.S. At the University of Utah campus (Salt Lake City, Utah, USA), past research documented collisions, especially for Cedar Waxwings (Bombycilla cedrorum) drawn to fruiting ornamental pears in winter. Mirrored windows, which have a metallic coating that turns window exteriors into mirrors, had frequent collisions, which were mitigated when Feather Friendly®bird deterrent markers were applied. Bird-friendly windows–ORNILUX®ultraviolet (UV) and fritted windows–also reduced collisions when data were collected across fall and winter. Extending this prior research, we evaluated additional mitigation and tested the replicability of effects for pear trees, mirrored windows, and bird-friendly windows across two years.MethodsUsing published data from eight buildings monitored for collisions in year 1 (Fall and Winter, 2019–2020), we added another year of monitoring, Fall and Winter, 2020–2021. Between years, Feather Friendly®mitigation markers were added to collision-prone areas of two buildings, including both mirrored and transparent windows.ResultsThe two buildings that received new Feather Friendly®mitigation had significantly fewer collisions post-mitigation. Control areas also had nonsignificant decline in collisions. The interaction of area (mitigation vs. control) by time (year 1 vs. 2) was significant, based on generalized estimating equations (GEE). The total yearly collisions across all eight buildings declined from 39 to 23. A second GEE analysis of all 8 buildings showed that mirrored windows, pear trees, and bird-friendly windows were each significant when analyzed separately. The best-fit model showed more collisions for mirrored windows and fewer collisions for bird-friendly windows. We found pear tree proximity to be related to more collisions in winter than fall. In addition, pear trees showed reduced collisions from year 1 to 2, consistent with new mitigation for two of three buildings near pear trees.DiscussionFeather Friendly® markers can mitigate collisions with transparent windows, not only mirrored windows, compared to unmitigated areas over 2 years. Results also underscore the dangers of pear tree proximity and mirrored windows and the efficacy of bird-friendly windows. Thus, bird collisions can be prevented by window mitigation, permanent bird-friendly windows, and landscape designs that avoid creating ecological traps.

Spheres of Influence: Host Tree Proximity and Soil Chemistry Shape rRNA, but Not DNA, Communities of Symbiotic and Free-Living Soil Fungi in a Mixed Hardwood-Conifer Forest

Host and symbiont diversity are inextricably linked across partnerships and ecosystems, with degree of partner reliance governing the strength of this correlation. In many forest soils, symbiotic ectomycorrhizal fungi coexist and compete with free-living saprotrophic fungi, with the outcomes of these interactions shaping resource availability and competitive outcomes for the trees aboveground. Traditional approaches to characterizing these communities rely on DNA sequencing of a ribosomal precursor RNA gene (the internal transcribed spacer region), but directly sequencing the precursor rRNA may provide a more functionally relevant perspective on the potentially active fungal communities. Here, we map ectomycorrhizal and saprotrophic soil fungal communities through a mixed hardwood-conifer forest to assess how above- and belowground diversity linkages compare across these differently adapted guilds. Using highly spatially resolved transects (sampled every 2 m) and well-mapped stands of varying host tree diversity, we sought to understand the relative influence of symbiosis versus environment in predicting fungal diversity measures. Canopy species in this forest included two oaks (Quercus agrifoliaandQuercus douglasii) and one pine (Pinus sabiniana). At the scale of our study, spatial turnover in rRNA-based communities was much more predictable from measurable environmental attributes than DNA-based communities. And while turnover of ectomycorrhizal fungi and saprotrophs were predictable by the presence and abundance of different canopy species, they both responded strongly to soil nutrient characteristics, namely pH and nitrogen availability, highlighting the niche overlap of these coexisting guilds and the strong influence of aboveground plants on belowground fungal communities.

Variations in urban forest allergy potential among cities and land uses

Tree pollen with allergenic potential in cities triggers nasal, skin, eye, and asthmatic allergic reactions in humans. Pollen is one of the most common allergy-causing inhaled substances. Tree species composition, cultivar selection and the proximity of certain trees to humans can influence allergic responses. Data from 53 cities or states from various parts of the world were used to assess the magnitude and differences in an allergy index (AI) among the sampled locations and among land uses within cities. Index values for species ranged from one (most allergy-free species) to 10 (highest allergy potential). The average index score among the cities and states was 6.3, with values ranging from 4.2 (Halifax, Nova Scotia) to 8.3 (Austin, Texas). On average, forest/open space areas had a slightly higher average index score (6.4) than commercial/industrial/transportation (6.2) and residential areas (6.1). About 2/3 of the analyzed cities had higher index scores in forest/open space than in residential areas. Forest/open space areas contributed over 40 percent of total leaf area and may influence allergenicity in cities. Cities developed within areas with naturally occurring Pinaceae (pine, spruce, fir, cedar, Douglas fir, larch) forests and/or have more Pinaceae species tended to have the lowest pollen index scores. Most leaf area tended to come from trees in index class 8. While pollen production is essential for natural regeneration and potential seed/food production, limiting tree species with high allergenic potential in areas near people can help reduce tree-related allergies. Through better understanding and quantification of urban forest allergenicity, managers can create sustainable local-scale landscapes that limit pollen exposure to humans, but also provide numerous ecosystem services and values to residents.