News Article | April 25, 2017
Washington & Jefferson College (W&J) will continue its Arbor Day tradition of environmental excellence. For the fourth consecutive year, W&J has been honored with the Tree Campus USA® recognition by the Arbor Day Foundation for its commitment to effective urban forest management. The college was one of only 15 institutions in Pennsylvania, a state with more than 100 two- and four-year higher learning institutions, to receive this honor, part of a national program created in 2008. Currently there are 296 campuses across the United States with this recognition. In addition to the Tree Campus USA honor, the arboretum was awarded Level I Accreditation by The ArbNet Arboretum Accreditation Program and The Morton Arboretum last spring. “I’m excited to have earned this recognition four years in a row and look forward to subsequent years of this recognition. This includes more plantings on campus, more students getting involved, more of the community getting involved and enhancing the campus arboretum and the campus landscape,” said Associate Professor of Biology Jason Kilgore, Ph.D. Kilgore noted that it’s become increasingly more difficult to qualify for the designation over the past few years as the Arbor Day Foundation has raised its standards when examining Tree Campus USA submissions. “It’s become more selective, which is good, because it forces us to work harder to be bigger and better than we were before,” he said. In honor of the recognition, students in Kilgore’s Plant Diversity course will plant Quaking Aspen trees at the developing Rocky Mountain-themed grove near the W&J Admission House at 1 p.m. April 29. Kilgore and Grounds Supervisor Doston Kish chose the trees to fit the soil profile in the area. It will be the first themed grove on campus, according to Kilgore. Washington & Jefferson College achieved the title by meeting Tree Campus USA’s five standards, which include maintaining a tree advisory committee, a campus tree-care plan, dedicated annual expenditures for its campus tree program, an Arbor Day observance, and a student service-learning project. W&J has been recognized every year it has applied for the honor. Kilgore started W&J’s Campus Arboretum nine years ago after previously being involved with Michigan State University’s arboretum. Working with students, he created two databases identifying types of trees on campus and their location, with notes of what trees have been added and removed from the grounds. The Campus Arboretum now encompasses the entire 85 acres of urban campus and athletic facilities. All of the nearly 1,200 trees from 83 species are recorded and evaluated, with over 930 trees bearing metal tags with accession number and family, scientific, and common names. Particularly noteworthy trees include a mature American elm, a mature willow oak, and five mature osage-oranges from an historical property line separating the College from the former Washington Female Seminary. The Arboretum Advisory Committee, consisting of members of the faculty, staff, and the community, meets twice a year to make decisions about the arboretum’s presence on campus and what progress will be made.
Pearse I.S.,University of California at Davis |
Hipp A.L.,The Morton Arboretum
Evolution | Year: 2012
Plant defensive traits drive patterns of herbivory and herbivore diversity among plant species. Over the past 30 years, several prominent hypotheses have predicted the association of plant defenses with particular abiotic environments or geographic regions. We used a strongly supported phylogeny of oaks to test whether defensive traits of 56 oak species are associated with particular components of their climatic niche. Climate predicted both the chemical leaf defenses and the physical leaf defenses of oaks, whether analyzed separately or in combination. Oak leaf defenses were higher at lower latitudes, and this latitudinal gradient could be explained entirely by climate. Using phylogenetic regression methods, we found that plant defenses tended to be greater in oak species that occur in regions with low temperature seasonality, mild winters, and low minimum precipitation, and that plant defenses may track the abiotic environment slowly over macroevolutionary time. The pattern of association we observed between oak leaf traits and abiotic environments was consistent with a combination of a seasonality gradient, which may relate to different herbivore pressures, and the resource availability hypothesis, which posits that herbivores exert greater selection on plants in resource-limited abiotic environments. © 2012 The Author(s). Evolution © 2012 The Society for the Study of Evolution.
Escudero M.,Pablo De Olavide University |
Hipp A.L.,The Morton Arboretum |
Hansen T.F.,University of Oslo |
Voje K.L.,University of Oslo |
Luceno M.,Pablo De Olavide University
New Phytologist | Year: 2012
Changes in chromosome number as a result of fission and fusion in holocentrics have direct and immediate effects on the recombination rate. We investigate the support for the classic hypothesis that environmental stability selects for increased recombination rates. • We employed a phylogenetic and cytogenetic data set from one of the most diverse angiosperm genera in the world, which has the largest nonpolyploid chromosome radiation (Carex, Cyperaceae; 2n=12-124; 2100 spp.). We evaluated alternative Ornstein-Uhlenbeck models of chromosome number adaptation to the environment in an information-theoretic framework. • We found moderate support for a positive influence of lateral inflorescence unit size on chromosome number, which may be selected in a stable environment in which resources for reproductive investment are larger. We found weak support for a positive influence on chromosome number of water-saturated soils and among-month temperature constancy, which would be expected to be negatively select for pioneering species. Chromosome number showed a strong phylogenetic signal. • We argue that our finding of small but significant effects of life history and ecology is compatible with our original hypothesis regarding selection of optima in recombination rates: low recombination rate is optimal when inmediate fitness is required. By contrast, high recombination rate is optimal when stable environments allow for evolutionary innovation. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.
Morgenroth J.,University of Canterbury |
Buchan G.,Lincoln University at Christchurch |
Scharenbroch B.C.,The Morton Arboretum
Ecological Engineering | Year: 2013
Impermeable pavements cover a considerable land area in cities. Their effect on the hydrological cycle is clear; as a barrier in the soil-atmosphere continuum they minimise rainfall infiltration and evaporation. Porous pavements are beginning to replace impermeable alternatives because of perceived hydrologic benefits. The impact of porous pavements on soil moisture and chemistry as they relate to urban vegetation was investigated in Christchurch, New Zealand. An experiment was established comprising 25 plots evenly distributed amongst controls (no pavement, exposed soil) and four different pavement treatments: a factorial combination of pavement type (porous, impervious) and pavement profile design (including or excluding a greywacke gravel base). Results indicate that pavements altered soil pH from moderately acidic (pH = 5.75) to more neutral levels (pH = 6.3). The effect on pH was greater beneath porous pavements, and also when a gravel base was included. Concentration of soil Al, Fe, and Mg decreased, while Na increased beneath pavements. Soil moisture was consistently higher beneath pavements than control plots, except following periods of heavy rainfall where high soil moisture muted all treatment effects. Throughout most of the study period, soil moisture content was lower beneath pavement profiles designed with the gravel base, presumably due to the gravel acting as a capillary break to a distillation process, whereby soil moisture migrates upwards to the soil surface. In early autumn, when soil moisture content was lowest for all treatments, precipitation recharged soil moisture in control plots and beneath porous pavements. But impervious pavements prevented infiltration resulting in significantly lower soil moisture content beneath these pavements. Pavements can alter soil moisture and chemical characteristics, but the effects differ depending on pavement porosity and profile design. Implications of the results pertain to stress physiology of urban vegetation, in particular drought stress avoidance. © 2012 Elsevier B.V.
Pryor M.,University of Hong Kong |
Watson G.,The Morton Arboretum
Arboricultural Journal | Year: 2016
Replicated research on transplanting mature trees (trunk diameter >750 mm) is not practical. Instead, we must apply the knowledge we have gained from studying smaller trees to maximise success at this larger scale. This article summarises our understanding of tree biology and horticulture contributing to the successful transplanting of trees, e.g. root loss and regrowth, water stress, carbohydrate status, root ball size, preparatory root and canopy pruning, timing of operations. The specific detail of the transplanting operations undertaken on four mature trees in Hong Kong in the last 15 years is then evaluated to examine the extent to which the arboricultural factors may have contributed to the outcome of each operation. © 2016 Taylor & Francis and Arboricultural Association.
Escudero M.,The Morton Arboretum |
Escudero M.,Pablo De Olavide University |
Hipp A.L.,The Morton Arboretum |
Waterway M.J.,McGill University |
Valente L.M.,Imperial College London
Molecular Phylogenetics and Evolution | Year: 2012
The sedge family (Cyperaceae: Poales; ca. 5600 spp.) is a hyperdiverse cosmopolitan group with centres of species diversity in Africa, Australia, eastern Asia, North America, and the Neotropics. Carex, with ca. 40% of the species in the family, is one of the most species-rich angiosperm genera and the most diverse in temperate regions of the Northern Hemisphere, making it atypical among plants in that it inverts the latitudinal gradient of species richness. Moreover, Carex exhibits high rates of chromosome rearrangement via fission, fusion, and translocation, which distinguishes it from the rest of the Cyperaceae. Here, we use a phylogenetic framework to examine how the onset of contemporary temperate climates and the processes of chromosome evolution have influenced the diversification dynamics of Carex. We provide estimates of diversification rates and map chromosome transitions across the evolutionary history of the main four clades of Carex. We demonstrate that Carex underwent a shift in diversification rates sometime between the Late Eocene and the Oligocene, during a global cooling period, which fits with a transition in diploid chromosome number. We suggest that adaptive radiation to novel temperate climates, aided by a shift in the mode of chromosome evolution, may explain the large-scale radiation of Carex and its latitudinal pattern of species richness. © 2012 Elsevier Inc.
Scharenbroch B.C.,The Morton Arboretum
HortScience | Year: 2013
Aerated compost teas (ACTs) are applied to soils with the intent of improving microbial properties and nutrient availability and stimulating plant growth. Anecdotal accounts of ACT for these purposes far outnumber controlled, replicated, and peerviewed experiments that have examined the impacts of ACT on soil properties and plant growth responses. This research assessed the impacts of four rates of ACT compared with water on containerized Acer saccharum and Quercus macrocarpa saplings growing in loam, compacted loam, and sandy soils. No significant differences were found comparing water with ACT applied at rates of 2, 4, and 40 kL ACT/ha for any of the six tree responses and 21 soil responses. Microbial biomass nitrogen (N) and potassium (K) increased, and available N decreased, in soils treated with ACT at 400 kL·ha-1 compared with water. Shoot, root, total biomass, and the root/shoot ratio were significantly greater for Quercus macrocarpa trees growing in compact loam with the 400 kL ACT/ha treatment compared with water, but significant differences were not detected for this application rate compared with water in the other soil types and in no instances with Acer saccharum saplings. These results provide some support for claims of ACT being able to increase soil microbial biomass and K, but provide minimal support for ACT being able to increase tree growth across multiple species in a variety of soil types. An application rate of 400 kL ACT/ha may be attainable for trees in containers with limited soil volumes, but this application rate is likely cost-prohibitive, and not practical, in the landscape. At this application rate, ≈1000 L of ACT would be required to treat a typical, and relatively small, critical root zone of 25 m2.
Scharenbroch B.C.,The Morton Arboretum |
Nix B.,Chicago State University |
Jacobs K.A.,Chicago State University |
Bowles M.L.,The Morton Arboretum
Geoderma | Year: 2012
For the last 23years, low-severity prescribed fire has been used to decrease shade and fire tolerant tree species, increase oak (Quercus spp.), and increase herbaceous plant diversity in the East Woods of The Morton Arboretum, Lisle, Illinois, USA. The impacts of these fires on the belowground ecosystem have yet to be measured. Soil (0 to 10cm) and litter samples were collected 12, 19, and 24months following the most recent fire on 40 plots in burned and un-burned control areas. Soil physical, chemical, and biological properties were measured and compared with vegetation composition and structure from these same plots. Compared to un-burned controls, burn plots had greater canopy openness, greater herbaceous richness, and a lower spring/summer herbaceous ratio. Burned plots had higher soil moisture content, pH, electrical conductivity, Ca 2+, Mg 2+, K +, Na +, NO 3 -, total N, particulate organic matter (POM), total organic C, and potential N mineralization. Soil microbial biomass and respiration, texture, color, aggregate stability, and hydrophobicity were not different in burned compared to un-burned plots. Indices of litter and soil invertebrate diversity were also not affected by prescribed fire. Three stepwise least squares models predicted woody richness, herbaceous richness, and spring/summer herbs with aspect, litter invertebrate richness, and soil factors (pH, potential N mineralization, C/N ratio, Mg 2+, Bray P, and soil invertebrate Simpson index). These results confirm others showing prescribed fire to increase soil nutrient availability. Forest structural changes with fire appear correlated with soil nutrient availability. Decreased soil C, nutrient retention, invertebrate diversity, or increased hydrophobicity and the presence of exotic plants is often observed with high-severity fire; but, these negative impacts do not appear to be present with these long-term, low-severity fires. © 2012 Elsevier B.V.
Chung K.-S.,The Morton Arboretum |
Weber J.A.,The Morton Arboretum |
Hipp A.L.,The Morton Arboretum
American Journal of Botany | Year: 2011
Premise of the study: High intraspecific cytogenetic variation in the sedge genus Carex (Cyperaceae) is hypothesized to be due to the "diffuse" or non-localized centromeres, which facilitate chromosome fission and fusion. If chromosome number changes are dominated by fission and fusion, then chromosome evolution will result primarily in changes in the potential for recombination among populations. Chromosome duplications, on the other hand, entail consequent opportunities for divergent evolution of paralogs. In this study, we evaluate whether genome size and chromosome number covary within species. Methods: We used flow cytometry to estimate genome sizes in Carex scoparia var. scoparia, sampling 99 plants (23 populations) in the Chicago region, and we used meiotic chromosome observations to document chromosome numbers and chromosome pairing relations. Key results: Chromosome numbers range from 2 n = 62 to 2 n = 68, and nuclear DNA 1C content from 0.342 to 0.361 pg DNA. Regressions of DNA content on chromosome number are nonsignificant for data analyzed by individual or population, and a regression model that excludes slope is favored over a model in which chromosome number predicts genome size. Conclusions: Chromosome rearrangements within cytogenetically variable Carex species are more likely a consequence of fission and fusion than of duplication and deletion. Moreover, neither genome size nor chromosome number is spatially autocorrelated, which suggests the potential for rapid chromosome evolution by fission and fusion at a relatively fine geographic scale (< 350 km). These findings have important implications for ecological restoration and speciation within the largest angiosperm genus of the temperate zone. © 2011 Botanical Society of America.
Scharenbroch B.C.,The Morton Arboretum |
Johnston D.P.,University of Illinois at Chicago
Urban Ecosystems | Year: 2011
Designed soils are used in specialized urban areas, such as under sidewalks or on roof-tops. These substrates have coarse light-weight aggregates to meet load-bearing specifications with soil in voids for rooting medium. A full-factorial microcosm approach was used to study Lumbricus terrrestris (two adult worms added and no-worms added), compaction (bulk density of 1.95 and 1.48 g cm-3), and litter (litter and no-litter additions) in a designed soil. Earthworm biomass, soil physical, chemical, and biological properties, anion leaching and surface C efflux was measured on days 0, 7, 14, 21, 28, 72, 112, and 140. Earthworms decreased bulk density in compacted soil, but did not impact density of un-compacted soil. Earthworm biomass increased days 7 to 14, but declined from days 28 to 140, likely as result of the abrasiveness of the aggregate component and relatively shallow depth of the soil (25 cm). During the period of increasing earthworm biomass, surface C efflux, microbial biomass N, soil Ca2+ and NH4+ increased with earthworms. During the period of declining earthworm biomass, surface C efflux, microbial biomass N, soil Ca2+ and NO3-, and leachate NO3- increased, and soil pH decreased with earthworms. While alive and dying, Lumbricus terrestris stimulated microbial activity and biomass and nutrient availability, but an apparent shift to nitrification was observed as earthworm biomass declined. The results show Lumbricus terrestris to improve designed soil properties for plants, but the improvements may be short-lived due to the inability of these earthworms to survive in the designed soil. © 2010 Springer Science+Business Media, LLC.