Rhododendron Conservation and Collections

Ornamental Plant Breeding

The late David Leach was obsessed with elepidote rhododendrons and dedicated his life to breeding and studying them. He gifted the station to Holden Arboretum in 1986 with the condition that we continue his breeding project. Most of the research conducted at the station throughout its history has focused on new plant development.

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Ornamental Plant Breeding

Rhododendron Conservation and Collections

Rhododendron Collection Curation

Rhododendrons have a storied history, both locally and across the world, and they have thrilled gardeners for centuries. The genus contains roughly one thousand wild-occurring species, and man-made selections number in the tens of thousands. How do we decide which rhododendrons to include in our plant collection?

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Rhododendron Collection Curation

Evolutionary Ecology

The perks of genome size in a rapidly changing world

Polyploidy, or whole genome duplication of an organism or cell, exists in all eukaryotes. Not only does polyploidy exist in fungi, insects, fish, amphibians, reptiles, and humans (e.g. cancer cells), but also occurs frequently in plants. Essentially, all flowering plants are ancient polyploids or bear a polyploid ancestry. Around 15% of the speciation events can be linked to polyploidy. For contemporary plant species, around 1/4 to 1/3 are polyploids (i.e. with >2 sets of chromosomes). Thus, polyploidy is considered as one of the most important drivers of plant biodiversity on Earth.

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The perks of genome size in a rapidly changing world

Evolutionary Ecology

Pollinators mediate microbiome assembly in flowers

Microbiomes can profoundly influence plant fitness in natural and agricultural settings. Relative to rhizosphere (root) and phyllosphere (leaf), the anthosphere (floral) microbiome is least well studied but has the most direct impact on plant reproductive success. Our understanding of what governs microbiome assembly in flowers – a highly dynamic niche – has advanced only recently.

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Pollinators mediate microbiome assembly in flowers

Evolutionary Ecology

Harnessing microbiomes for disease resistance

Plants are associated with numerous microorganisms in the wild. Some of these microorganisms are beneficial but others, such as pathogens, can be harmful to plants. Thus, maintaining a healthy microbiome is key to plant health. For wild apples (crabapples, Malus), we have observed that some crabapple cultivars/species are more disease resistant than others at the National Crabapple Evaluation Project (NCEP) plot at the Holden Arboretum.

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Harnessing microbiomes for disease resistance

Evolutionary Ecology

Emerging threats of nanoparticles to plants and microbiomes

Engineered nanomaterials released from industrial, agricultural, biomedical, and domestic applications are emerging environmental threats to the terrestrial and aquatic ecosystems in the Anthropocene. While nanoparticles are known to influence plant survival, growth, and reproduction, little is known whether and how the effects of nanoparticles on plants are mediated by plant-associated microbiomes.

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Emerging threats of nanoparticles to plants and microbiomes

Community Ecology

Working Woods

We are exploring best practices in forest management in northeast Ohio, and beyond. Since 2018, scientists and conservation staff at the Holden Arboretum have partnered with area scientists and land management professionals to develop the Working Woods, a 67-acre forest management demonstration.

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Working Woods

Community Ecology

Global Warming Shifts Plant Phenology

We are exploring how spring phenologies are shifting with the changing climate in the Holden Arboretum’s Bole Woods. In this citizen science project, volunteers have been monitoring spring leaf out in the forest canopy in relation to the emergence and flowering of spring ephemeral wildflowers in the forest understory since 2018. We use these data to understand how the shifting climate is driving changes in the timing of these events, and how mismatched shifts between the canopy and understory may change the forest wildflower community.

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Global Warming Shifts Plant Phenology

Community Ecology

Community Assembly in a Warmer World

When a plant community develops anew (community assembly) the order in which species arrive can shape what that community will ultimately look like. In general, arriving early can be beneficial, but who arrives first and how helpful that is can be driven by both the climate, and the origin of the species (whether it is native or not). My lab is currently working to understand how nonnative species and warming temperatures interact to shape community assembly dynamics in our natural areas.

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Community Assembly in a Warmer World

Plant Physiological Ecology

How do you stop a green glacier?

Eastern Red Cedar (Juniperus virginiana) is a conifer species native to the Eastern United States, where this attractive tree has long-been a popular choice for landscaping. But out West in the Great Plains, Red Cedar is known as the “Green Glacier”, because this slow-growing species is invading once-productive grasslands. Ranchers face substantial economic costs in removing Eastern Red Cedar from grazing lands, and it reduces grassland biodiversity through competition with native grassland species. But how do you stop a “Green Glacier”?

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How do you stop a green glacier?

Plant Physiological Ecology

Physiology of urban and rural trees in NE Ohio

As urban areas expand, native forest fragments are becoming surrounded by pavement and cement, exposing them to higher temperatures, elevated CO2, higher light availability and pollution. We rely on urban forests to provide carbon storage, recreation, and pollution mitigation, but urban forests are often overlooked as an important ecological system.

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Physiology of urban and rural trees in NE Ohio

Plant Physiological Ecology

Local adaptation to climate in Rhododendron minus

Plant species are distinct types which we recognize by their unique leaf and flower traits, but how do different species evolve? One way this can occur is when populations of a widespread species become adapted to the local climate where they are growing, thus preventing seedlings from establishing outside of their home climate and isolating populations from each other.

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Local adaptation to climate in Rhododendron minus

Plant Physiological Ecology

Leaf and Flower Heat Tolerance of cold hardy Rhododendron species

While Rhododendron are well-adapted to cold climates, owing to changes in climate, heat stress is becoming a major factor limiting Rhododendron production. The way plants allocate resources, i.e. the economics of carbon and water use, determines their ability to survive stressful events like frost or heatwaves, as well as the timing, quality, and longevity of growth and reproduction. We will determine species leaf and floral resource allocation, their temperature tolerance, as well as the timing of leaf and flower growth and how this relates to seed production.

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Leaf and Flower Heat Tolerance of cold hardy Rhododendron species

Soil and Microbial Ecology

Soil Ecology of Urban Environments

Urbanization has a substantial impact on natural ecosystems where only certain plant or animal species can thrive in areas that have high amounts of development and chemical pollution from human activities. Whether urbanization has this same effect on organisms belowground is currently unknown. But belowground organisms, such as mycorrhizal fungi that form beneficial relationships with plants and assist plants in acquiring nutrients, are necessary for proper plant growth and survival.

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Soil Ecology of Urban Environments

Soil and Microbial Ecology

Forest Pathogens and Tree Health

When given the proper environmental conditions and susceptible hosts, pathogens can do significant damage to forests. Forest pathogens are usually microscopic and include fungi, bacteria, viruses, and invertebrates. Because they are typically microscope, pathogens associate not just with the host organism such as the tree or plant species they affect, but with other microscopic organisms that live on plant surfaces. These microorganisms that live on leaves, roots or in soil make up the forest microbiome, and can include bacteria, fungi, and other microorganisms that associate with these habita

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Forest Pathogens and Tree Health

Community Ecology, Soil and Microbial Ecology

Ecological Integrity of Forests

Global change phenomena are imminent and substantial threats to biodiversity. Such threats include invasive species, global warming, land use history, and predator decline and are often induced or exacerbated by humans. To date, most studies on how these phenomena influence ecosystems have focused on aboveground communities. We know far less about how global change phenomena influence belowground organisms. To investigate this question, scientists at HF&G have studied how agricultural land use history, invasive species, and deer herbivory have altered soil fungi and bacteria. Current research

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Ecological Integrity of Forests

Soil and Microbial Ecology

Diversity of Soil Fungi and Microbes

Holden is conducting research into the effects of soil physical and chemical properties on the diversity and function of soil microbes in these forests.

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Diversity of Soil Fungi and Microbes

Soil and Microbial Ecology

Acidic Precipitation and Forest Health

Holden scientists received a grant from the National Science Foundation to look at how forests and soils respond to changes in acidity and soil phosphorus availability. They are manipulating soil pH and fertility in a long-term study of Ohio forests using crushed limestone (lime) and phosphorus fert

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Acidic Precipitation and Forest Health

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