The politics of urban trees: Tree planting is associated with gentrification in Portland, Oregon.

This study evaluated the hypothesis that urban-tree planting increases neighborhood gentrification in Portland, Oregon. We defined gentrification as an increase in the median sales price of single-family homes in a Census tract compared to other tracts in the city after accounting for differences in the housing stock such as house size and number of bathrooms. We used tree-planting data from the non-profit Friends of Trees, who have planted 57,985 yard and street trees in Portland (1990-2019). We estimated a mixed model of gentrification (30 years and 141 tracts) including random intercepts at the tract level and a first-order auto-regressive residual structure. Tract-level house prices and tree planting may be codetermined. Therefore, to address potential endogeneity of tree planting in statistical modeling, we lagged the number of trees planted by at least one year. We found that the number of trees planted in a tract was significantly associated with a higher tract-level median sales price, although it took at least six years for this relationship to emerge. Specifically, each tree was associated with a $131 (95% CI: $53-$210; p-value=0.001) increase in tract-level median sales price six years after planting. The magnitude of the association between the number of trees planted and median sales price generally increased as the time lag lengthened. After twelve years, each tree was associated with a $265 (95% CI: $151-$379; p-value<0.001) increase in tract-level median sales price. Tree planting was not merely a proxy for existing tree cover, as the percent of tract covered in tree canopy was independently associated with an increase in median sales price. Specifically, each 1-percentage point increase in tree-canopy cover was associated with a $882 (95% CI: $226-$1,538; p-value=0.008) increase in median sales price. In conclusion, tree planting is associated with neighborhood-level gentrification, although the magnitude of the association is modest.

An ergonomic study of arborist work activities.

Arborists work in high-risk environments, particularly when climbing trees, where a combination of grip strength and resistance to psychological stress are important attributes for safety. This study investigated the physical and cognitive activities of arborists combined with selected workload factors such as blood pressure, pulse, handgrip strength, and other anthropometric measurements, including manual dexterity and spatial awareness. The sample included 10 participants aged 17-48 years. Blood pressure was negatively correlated with handgrip strength after the activity had been performed. Different types of arborist activities led to various types of physiological feedback, as shown by the analysis of variance. According to our results, there is a difference between physical workloads, associated with activities such as tree felling, tree climbing, or chainsaw maintenance, and cognitive workloads, such as supervision or observation, in relation to blood pressure. Blood pressure was higher for activities that involved a cognitive workload. Before and after any activity, handgrip strength was positively associated with hand size. After any activity, greater changes in handgrip strength of the participant's right hand were associated with needing more time to successfully complete a peg test, which represents a greater cognitive burden. Our results suggest that arborists deal with physical activities such as tree felling, tree climbing, working with a chainsaw, and mental activities (supervising or observing) which were identified as two different groups correlated with hand grip strength, blood pressure, manual dexterity, and spatial awareness. In conclusion, the tree-climbing activity appeared to be the least stressful, and psychological stress appeared to have a greater impact on the health of observers and supervisors in the study group. This can be applied to other professions in many fields, including industries where workers face both physical and cognitive workloads.

Effects of four bolete species on ectomycorrhizae formation and development in Pinus thunbergii and Quercus acutissima.

BACKGROUND: Bolete cultivation is economically and ecologically valuable. Ectomycorrhizae are advantageous for plant development and productivity. This study investigated how boletes affect the formation of Pinus thunbergii and Quercus acutissima ectomycorrhizae using greenhouse-based mycorrhizal experiments, inoculating P. thunbergii and Q. acutissima with four species of boletes (Suillus bovinus, Suillus luteus, Suillus grevillei, and Retiboletus sinensis). RESULTS: Three months after inoculation, morphological and molecular analyses identified S. bovinus, S. luteus, S. grevillei and R. sinensis ectomycorrhizae formation on the roots of both tree species. The mycorrhizal infection rate ranged from 40 to 55%. The host plant species determined the mycorrhiza morphology, which was independent of the bolete species. Differences in plant growth, photosynthesis, and endogenous hormone secretion primarily correlated with the host plant species. Infection with all four bolete species significantly promoted the host plants' growth and photosynthesis rates; indole-3-acetic acid, zeatin, and gibberellic acid secretion increased, and the abscisic acid level significantly decreased. Indole-3-acetic acid was also detected in the fermentation broths of all bolete species. CONCLUSIONS: Inoculation with bolete and subsequent mycorrhizae formation significantly altered the morphology and hormone content in the host seedlings, indicating growth promotion. These findings have practical implications for culturing pine and oak tree species.

Use of paraffin oils in agriculture and beyond: back to the future.

Paraffin (petroleum) oils have been used for many years for their insecticidal properties, but relatively little research had been conducted towards their introduction into the agricultural praxis, due to their potential phytotoxic effects. In the recent years, however, there has been an increased interest in petroleum-based pesticides due to their compatibility with integrated pest management (IPM) programs. Various improvements in the refinement methods have enhanced the manufacture of commercial products with many advantageous features over the original oil formulas. However, literature is still lacking of a general overview about the applicability of newly introduced commercial petroleum oils in agriculture and their compatibility with modern pest management practices. Therefore, the present work aims to depict the current status of petroleum oils in arboriculture and beyond, providing an in-depth analysis of their insecticidal properties with respect to the knowledge gained over the years about the factors responsible for the pesticidal efficacy and the phytotoxic activity of petroleum-derived oil insecticides. Moreover, commercial aspects of petroleum oil formulations and their toxicological profile to non-target organisms have also been addressed through the current legislation in EU and the USA.

Quantifying the stormwater runoff volume reduction benefits of urban street tree canopy.

Trees in the urban right-of-way areas have increasingly been considered part of a suite of green infrastructure practices used to manage stormwater runoff. A paired-catchment experimental design (with street tree removal as the treatment) was used to assess how street trees affect major hydrologic fluxes in a typical residential stormwater collection and conveyance network. The treatment consisted of removing 29 green ash (Fraxinus pennsylvanica) and two Norway maple (Acer platanoides) street trees from a medium-density residential area. Tree removal resulted in an estimated 198 m3 increase in surface runoff volume compared to the control catchment over the course of the study. This increase accounted for 4% of the total measured runoff after trees were removed. Despite significant changes to runoff volume (p ≤ 0.10), peak discharge was generally not affected by tree removal. On a per-tree basis, 66 L of rainfall per m2 of canopy was lost that would have otherwise been intercepted and stored. Runoff volume reduction benefit was estimated at 6376 L per tree. These values experimentally document per-capita retention services rendered by trees over a growing season with 42 storm events. These values are within the range reported by previous studies, which largely relied on simulation. This study provides catchment scale evidence that reducing stormwater runoff is one of many ecosystem services provided by street trees. This study quantifies these services, based on site conditions and a mix of deciduous species, and serves to improve our ability to account for this important yet otherwise poorly constrained hydrologic service. Engineers, city planners, urban foresters, and others involved with the management of urban stormwater can use this information to better understand tradeoffs involved in using green infrastructure to reduce urban runoff burden.

Talkin' About a Revolution. Changes and Continuities in Fruit Use in Southern France From Neolithic to Roman Times Using Archaeobotanical Data (ca. 5,800 BCE - 500 CE).

The use and socio-environmental importance of fruits dramatically changed after the emergence of arboriculture and fruit domestication in the eastern Mediterranean, between the 5th and the 3rd millennia BCE. Domesticated fruits together with cultivation techniques apparently reached the western Mediterranean via colonial activities during the 1st millennium BCE - early 1st millennium CE. However, the pace and chronology of this diffusion as well as the recompositions in diversity, to adapt to new socio-environmental conditions, remain poorly known. In this study we investigate archaeobotanical records in Southern France from the Neolithic to the end of the Roman empire (ca. 5,800 BCE - 500 CE) to assess changes in fruit use as well as the emergence, spread and evolution of fruit cultivation. We explore changes in native traditions faced with innovations brought by Mediterranean colonization and how domesticated fruit cultivation spread from the Mediterranean to more temperate areas. Archaeobotanical data from 577 assemblages were systematically analyzed distinguishing two datasets according to preservation of plant remains (charred vs. uncharred), as this impacts on the quantity and diversity of taxa. The 47 fruit taxa identified were organized in broad categories according to their status and origin: exotic, allochtonous cultivated, indigenous cultivated, wild native. We also analyzed diversity, quantity of fruits compared to the total of economic plants and spatio-temporal variations in the composition of fruit assemblages using correspondence factor analyses. Archaeobotanical data reflect variations and continuities in the diversity of species used through time and space. In the Mediterranean area, significant changes related to the arrival of new plants and development of fruit cultivation occurred mainly, first during the Iron Age (6th-5th c. BCE), then in the beginning of the Roman period. Large cities played a major role in this process. In agreement with archeological information, archaeobotanical data reveal the predominance of viticulture in both periods. However, arboriculture also included other fruit species that have been subject to less intensive and specialized cultivation practices. Most significantly, this study pinpoints the continuous contribution of native, supposedly wild fruits throughout the chronology. Despite the homogenizing Roman influence, results reveal clear differences between the Mediterranean and temperate regions.

Applying Plant Hydraulic Physiology Methods to Investigate Desiccation During Prolonged Cold Storage of Horticultural Trees.

Plant nursery production systems are a multi-billion-dollar, international, and horticultural industry that depends on storing and shipping live plants. The storage environment represents potentially desiccating and even fatal conditions for dormant, bareroot, and deciduous horticulture crops, like orchard trees, forestry trees, ornamental trees, and grapevines. When tree mortality is considered within a plant hydraulic framework, plants experiencing water stress are thought to ultimately die from hydraulic failure or carbon starvation. We hypothesized that the hydraulic framework can be applied to stored crops to determine if hydraulic failure or carbon starvation could be attributed to mortality. We used deciduous trees as model species because they are important horticultural crops and provide a diversity of hydraulic strategies. We selected cultivars from six genera: Acer, Amelanchier, Gleditsia, Gymnocladus, Malus, and Quercus. For each cultivar, we measured stem hydraulic conductance and vulnerability to embolism. On a weekly basis for 14 weeks (March-June), we removed trees of each cultivar from cold storage (1-2°C). Each week and for each cultivar, we measured stem water potential and water content (n = 7) and planted trees to track survival and growth (n = 10). At three times during this period, we also measured non-structural carbohydrates. Our results showed that for four cultivars (Acer, Amelanchier, Malus, and Quercus), the stem water potentials measured in trees removed from storage did not exceed stem P 50, the water potential at which 50% of stem hydraulic conductivity is lost. This suggests that the water transport system remains intact during storage. For two cultivars (Gleditsia and Gymnocladus), the water potential measured on trees out of storage exceeded stem P 50, yet planted trees from all weeks survived and grew. In the 14 weeks, there were no significant changes or directional trends in stem water potential, water content, or NSC for most cultivars, with a few exceptions. Overall, the results show that the trees did not experience detrimental water relations or carbon starvation thresholds. Our results suggest that many young deciduous trees are resilient to conditions caused by prolonged dormancy and validate the current storage methods. This experiment provides an example of how a mechanistically based understanding of physiological responses can inform cold storage regimes in nursery tree production.

Origins of the Apple: The Role of Megafaunal Mutualism in the Domestication of Malus and Rosaceous Trees.

The apple (Malus domestica [Suckow] Borkh.) is one of the most economically and culturally significant fruits in the world today, and it is grown in all temperate zones. With over a thousand landraces recognized, the modern apple provides a unique case study for understanding plant evolution under human cultivation. Recent genomic and archaeobotanical studies have illuminated parts of the process of domestication in the Rosaceae family. Interestingly, these data seem to suggest that rosaceous arboreal crops did not follow the same pathway toward domestication as other domesticated, especially annual, plants. Unlike in cereal crops, tree domestication appears to have been rapid and driven by hybridization. Apple domestication also calls into question the concept of centers of domestication and human intentionality. Studies of arboreal domestication also illustrate the importance of fully understanding the seed dispersal processes in the wild progenitors when studying crop origins. Large fruits in Rosaceae evolved as a seed-dispersal adaptation recruiting megafaunal mammals of the late Miocene. Genetic studies illustrate that the increase in fruit size and changes in morphology during evolution in the wild resulted from hybridization events and were selected for by large seed dispersers. Humans over the past three millennia have fixed larger-fruiting hybrids through grafting and cloning. Ultimately, the process of evolution under human cultivation parallels the natural evolution of larger fruits in the clade as an adaptive strategy, which resulted in mutualism with large mammalian seed dispersers (disperser recruitment).

Between domestication and civilization: the role of agriculture and arboriculture in the emergence of the first urban societies.

The transition to urbanism has long focused on annual staple crops (cereals and legumes), perhaps at the expense of understanding other changes within agricultural practices that occurred between the end of the initial domestication period and urbanisation. This paper examines the domestication and role of fruit tree crops within urbanisation in both Western Asia and China, using a combination of evidence for morphological change and a database that documents both the earliest occurrence of tree fruit crops and their spread beyond their wild range. In Western Asia the domestication of perennial fruit crops likely occurs between 6500 bc and 3500 bc, although it accompanies a shift in location from that of the earliest domestications within the Fertile Crescent to Mesopotamia, where the earliest urban societies arose. For China, fruit-tree domestication dates between ca 4000 and 2500 bc, commencing after millet domestication and rice domestication in Northern and Southern China, respectively, but within the period that led up to the urban societies that characterised the Longshan period in the Yellow River basin and the Liangzhu Culture in the Lower Yangtze. These results place the domestication of major fruit trees between the end of the domestication of staple annual crops and the rise of urbanism. On this basis it is argued that arboriculture played a fundamental role within the re-organisation of existing land use, shifting the emphasis from short-term returns of cereal crops into longer term investment in the developing agricultural landscape in both Western and East Asia. In this respect perennial tree crops can be placed alongside craft specialisation, such as metallurgy and textiles, in the formation of urban centres and the shaping the organisational administration that accompanied the rise of urbanism.

Long and attenuated: comparative trends in the domestication of tree fruits.

This paper asks whether we can identify a recurrent domestication syndrome for tree crops (fruits, nuts) and track archaeologically the evolution of domestication of fruits from woody perennials. While archaeobotany has made major contributions to documenting the domestication process in cereals and other annual grains, long-lived perennials have received less comparative attention. Drawing on examples from across Eurasia, comparisons suggest a tendency for the larger domesticated fruits to contain seeds that are proportionally longer, thinner and with more pointed (acute to attenuated) apices. Therefore, although changes in flavour, such as increased sweetness, are not recoverable, seed metrics and shape provide an archaeological basis for tracking domestication episodes in fruits from woody perennials. Where available, metrical data suggest length increases, as well as size diversification over time, with examples drawn from the Jomon of Japan (Castanea crenata), Neolithic China (Prunus persica) and the later Neolithic of the Near East (Olea europaea, Phoenix dactylifera) to estimate rates of change. More limited data allow us to also compare Mesoamerica avocado (Persea americana) and western Pacific Canarium sp. nuts and Spondias sp. fruits. Data from modern Indian jujube (Ziziphus mauritiana) are also considered in relation to seed length:width trends in relation to fruit contents (flesh proportion, sugar content). Despite the long generation time in tree fruits, rates of change in their seeds are generally comparable to rates of phenotypic evolution in annual grain crops, suggesting that gradual evolution via unconscious selection played a key role in initial processes of tree domestication, and that this had begun in the later Neolithic once annual crops had been domesticated, in both west and east Asia.

Compliance with the ANSI Z133.1 - 2006 safety standard among arborists in New England.

INTRODUCTION: Arboriculture is hazardous work. A consensus safety standard exists, but little is known about compliance with it. This study aimed to determine whether accreditation and certification are associated with safety practices and to identify specific safety practices adhered to most and least. METHOD: Sixty-three tree care companies in southern New England were directly observed on job sites. Adherence to the American National Standards for Arboricultural Operations (ANSI Z133.1 - 2006) was compared across companies that were accredited, non-accredited with certified arborists on staff, and non-accredited without certified arborists on staff. RESULTS: Companies with accreditation or certified arborists demonstrated greater safety compliance than those without. However, low compliance was found across all company types for personal protective equipment (PPE) use, chain saw safety, and chipper safety. CONCLUSIONS: Greater attention to PPE, chain saw, and chipper practices is warranted across the industry. Safety in non-accredited companies without certified arborists especially needs improvement. PRACTICAL APPLICATION: Only partial compliance was found among accredited companies and companies with certified arborists. Intervention strategies are needed for all company types for the use of PPE and safer use of chain saws and chippers.