Botany Blogs

These blogs are written about and by our Section of Botany researchers. The herbarium at the museum which contains approximately 3,000 type specimens--specimens that define an entire plants' species. These type specimens only represent about 0.6 % of the collection.

Mason Heberling, head of the section, regularly shares herbarium specimens that have been "Collected on this day" in history.

February 2, 2021 by Erin Southerland

Free and Open Sharing of Biodiversity Data Promises New Era of Research

Analysis of more than 4,000 studies published over the past 15 years makes case for ongoing development of the next generation of research

Contributions of amateur citizen scientists and natural history museums emphasized

Miami mist (*Phacelia purshii*) observed in Upper Burrell Township, PA, USA by J. Mason Heberling. Photo via iNaturalist (CC BY 4.0)

Herbarium specimen of Miami mist (*Phacelia purshii*) collected from Upper Burrell Township, PA, USA by J. Mason Heberling.

Carnegie Museum of Natural History (CMNH) announces a study published in Proceedings of the National Academy of Sciences (PNAS) providing comprehensive analysis and review of more than 4,000 peer-reviewed studies published between 2003 and 2019 that make use of data mediated by the Global Biodiversity Information Facility (GBIF), the world’s largest biodiversity data network. The study, written in coordination with GBIF by Mason Heberling, CMNH Curator of Botany, and Scott Weingart, Program Director of Digital Humanities at Carnegie Mellon University, provides an evidence base for the ongoing development of the next generation of biodiversity-related research.

While the accessibility of global biodiversity information has surged in the past 20 years—thanks to widespread funding initiatives for museum specimen digitization and the emergence of large-scale public participation in community science with applications like iNaturalist and programs like the City Nature Challenge—scientific impacts of consolidated biodiversity data networks had not yet been quantified. The authors conclude the global aggregation of these diverse data sources empowers research at scales otherwise not possible, “launching biodiversity sciences into a new era.”

“The possibilities of a sustainable future urgently depend on this integration of biodiversity data,” says Heberling. “The good news is biodiversity science has made great strides towards data access, thanks to a community ranging from research universities, to natural history museum collections, to amateur citizen scientists making observations on day hikes. Though far from over, the impact to date has been profound, resulting in more than two peer-reviewed studies published per day, cutting across taxonomic, disciplinary, geographical, and socio-economic boundaries.”

By analyzing the research uses of the GBIF’s biodiversity data network, the authors report on the emerging roles of open-access data aggregation in the development of increasingly diverse, global research. These results indicate a new biodiversity science landscape centered on big data integration, informing ongoing strategic initiatives of biodiversity data aggregation across diverse fields, including environmental sciences and policy, evolutionary biology, conservation, and human health.

Coordinated through its Secretariat in Copenhagen, the GBIF network of participating countries and organizations provides data-holding institutions around the world with common standards and open-source tools that enable them to share information about where and when species have been recorded.

Cited by more than 200 studies, Carnegie Museum of Natural History has made nearly a million specimen records publicly available through GBIF to date. This number is actively growing, as the digitization of more than 20 million museum objects continues.

December 29, 2020 by wpengine

Milkweed Observations

Opportunities to capture dramatically different seasonal pictures of the same subject come with the territory of our temperate region. Next year, consider challenging yourself to document how a flower bed or prominent deciduous tree transforms seasonally in response to changing light, temperature, and moisture.

The picture above, taken on the first day of winter, records the deteriorated condition of the common milkweed plant (Asclepias syriaca) I began observing during the first week of summer. The image might easily be termed an end point, but for documentation images that preceded it.

Here, on a bright early November day, the burst seed pod offered dozens of matchhead-sized brown seeds, each attached to sparkling down-like filaments to the wind. With this picture as reference, the empty winter solstice pod implies continuance as much as conclusion.

My observations began in late June, several days after the summer solstice, and just before the milkweed plant bloomed. My resolution for future observations is to begin them far earlier in the growing season, and to learn more about the insect fauna associated with the plant.

Monarch butterflies (Danaus plexippus), a species currently experiencing alarming population declines, are the most well-known insects associated with milkweed. This one pictured above visited the plant’s lavender blossoms on July 25.

Monarch butterfly caterpillars, such as the one photographed eating this leaf on August 19, are dependent on milkweed for nourishment and the predator protection they gain from the plant’s toxins.

milkweed tussock moth caterpillar on milkweed

A lesser known milkweed dependent insect is the milkweed tussock moth (Euchaetes egle). A caterpillar of the species was photographed on the plant in mid-August.

The diet of the large milkweed bug (Oncopeltus fasciatus) includes seeds, so the presence of seed pods does not necessarily guarantee a bountiful crop the next growing season. The insect pictured above visited the plant on August 21.

Patrick McShea works in the Education and Visitor Experience department of Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

Collected on this Day in 1934

Has your Charlie Brown tree lost its needles yet?

dried specimen of larch on an herbarium sheet

Not all needled-leaved trees are evergreen! Yes, there are deciduous species in the Pine family (Pinaceae). That is, unlike most needle-leaved trees that retain their leaves all year long (evergreen), there are several conifer species that shed their leaves each year for the winter. Perhaps most famous are a group of species called larches.

No, this needle-free specimen of twigs and a cone wasn’t collected by Charlie Brown on Christmas Eve. Rather, this humble yet festive specimen of European larch (Larix decidua) was collected by J.F. Lewis on December 24, 1934. Native to the mountains of central Europe, this species was planted in a cemetery in Northumberland county (central Pennsylvania). It is highly likely the tree is still there – many decades later – as European larches can live for many hundreds of years (perhaps even a thousand years!).

The herbarium at California University of Pennsylvania is named for the person who collected this specimen – John Franklin Lewis.

European larch recently made the big time news too, featured in a new study published in the scientific journal Science. The researchers used leaf out and leaf fall data collected from across Europe since the late 1940s for four tree species (including European larch). Surprisingly they found that trees may drop their leaves much earlier than expected with ongoing climate change. In other words, as spring temperatures warm, deciduous trees produce leaves earlier in the spring, but this also causes trees to drop their leaves earlier in the fall. This means that climate change may not result in longer growing seasons, as has been previously predicted. You can read more about this study here.

Find this Charlie Brown larch specimen (and more) here.

Check back for more! Botanists at the Carnegie Museum of Natural History share digital specimens from the herbarium on dates they were collected. They are in the midst of a three-year project to digitize nearly 190,000 plant specimens collected in the region, making images and other data publicly available online. This effort is part of the Mid-Atlantic Megalopolis Project (mamdigitization.org), a network of thirteen herbaria spanning the densely populated urban corridor from Washington, D.C. to New York City to achieve a greater understanding of our urban areas, including the unique industrial and environmental history of the greater Pittsburgh region. This project is made possible by the National Science Foundation under grant no. 1801022.

Mason Heberling is Assistant Curator of Botany at Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

Collected on this Day 105 years ago

So long, leaves.

Autumn has fallen.

specimen of red maple on herbarium sheet

This specimen of red maple (Acer rubrum) was collected on November 13, 1915 by Otto Jennings near Finleyville, Pennsylvania (about 30 miles south of Pittsburgh). Jennings was an influential botany curator (and biology professor at University of Pittsburgh and director of Carnegie Museum, among many other roles through his many decades career at the museum).

Just imagine how beautifully red these leaves must have been. And you’ll have to imagine because this specimen is just twigs!

But upon closer look, the twigs have a lot to admire. As with other deciduous trees in Pennsylvania, the buds are primed and ready. In spring (as early as March for red maple!), these buds will swell and flowers will emerge. Leaves will follow.

But first, we wait it out through winter.

Pay attention to tree buds this winter. They have a lot to say.

Find this red maple specimen here (along with 512 others!).

Mason Heberling is Assistant Curator of Botany at Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

Why Do Leaves Change Color?

*Image by 👀 Mabel Amber, who will one day from Pixabay*.

This fall seemed to sneak up on me as time has been simultaneously moving at a rapid pace and in slow motion. As someone once told me when I became a parent, “the days are long, but the years are short,” and this global pandemic brings those words even closer to home. Nevertheless, I took the time to slow down and bask in the beauty of the changing fall leaves this October. For me, nature is truly restorative, and there aren’t many things more beautiful than driving through the mountains of Western Pennsylvania during peak color change.

But, why do leaves change their color?

During the warmer months in Pennsylvania, trees take advantage of the increasing amount of light and good weather available from longer and warmer days. Using their leaves, trees absorb energy from sunlight, breathe in carbon dioxide, drink up water to produce their own food sources – sugar and starch. This process is only possible through chlorophyll housed in the leaf cells – giving leaves their vibrant green coloration.

Leaves also contain other color pigments ranging from yellow to orange – these pigments are often masked by great amounts of green coloring. But in the fall, the tree begins to prepare for shorter days and colder weather, and the leaves stop their food-making process. To prepare for the upcoming winter, the chlorophyll begins to break down, causing the green color to disappear. This change allows the ever-present yellow, orange, and red pigments to become visible. While chlorophyll breaks down, other chemical changes in the leaves can occur, creating an additional ray of colors through the development of red anthocyanin pigments. The yellow and orange pigments mixed with the red anthocyanin pigments give rise to the reddish and purplish fall colors of trees, such as dogwoods and sumacs.

Each species of tree shows off their own fall color. All these colors are due to the mixing of varying amounts of the chlorophyll residue and other pigments in the leaf during the fall season. This winter preparation creates a nature show like no other.

Another aspect of the leaves changing colors is that those leaves will eventually drop to the ground. Most of the broad-leaved trees in Pennsylvania shed their leaves in the fall (some trees retain their dead leaves until new growth starts in the spring). So, what should you do with your leaves in the fall? According to the U.S. Environmental Protection Agency, leaves and other yard debris account for more than 13% of the nation’s solid waste—33 million tons a year. In typical landfills, there isn’t enough oxygen to decompose the yard waste, causing the development and release of the greenhouse gas methane.

So, what do I do? LEAF IT! (get it?). Leave your leaves where they fall in the fall – or at least, find a nice place in your yard to pile the leaves. Leaf litter can act as both a fertilizer returning the nutrients back into the ground, and as a weed suppressant by acting as a ground cover. Leaf litter is also a vital habitat for much of our favorite wildlife. Many critters – from insects to mammals and everything in between – rely on leaf litter for food, shelter, and nesting material. Many of our favorite moth and butterfly caterpillars overwinter in fallen leaves before emerging in spring! So, if you want free mulch and fertilizer, to create wildlife habitat, and have more free time – LEAF IT!

Heather Hulton VanTassel is Assistant Director of Science and Research at Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

Collected on This Day 98 Years Ago

Chestnuts (used to be) on Chestnut Ridge

And across the entire state of Pennsylvania.

American chestnut (Castanea dentata) was once a very common tree, native from Maine to Mississippi. In the heart of the Appalachians, the historical range covered the entire state of Pennsylvania. I say “historical” and “once a very common tree” because it is no longer. You may occasionally stumble upon an American chestnut tree, especially small trees and saplings persisting as sprouts from the large trees that graced our landscape a century ago. Older trees, with mature fruits, are quite rare.

In fact, some estimates suggest American chestnut accounted for one in four trees in some forests! So, what happened? In the early 1900s, a disease caused by a pathogenic fungus (Cryphonectria parasitica) was accidentally introduced with imported Asian trees. It was first recorded in New York City in 1904. In a matter of decades, American chestnut was nearly decimated by this disease known as Chestnut blight.

The Carnegie Museum of Natural History herbarium captures this change in our forests.

American chestnut specimen on herbarium sheet

This specimen of American chestnut was collected by influential Carnegie Museum curator Otto Jennings on October 21, 1922 on a field trip of the Botanical Society of Western Pennsylvania to Chestnut Ridge, near Derry Township, Pennsylvania. Chestnut Ridge is a ridge of the Allegheny Mountains, presumably named for its (once) many American chestnuts.

This specimen is from the fruit collection of the herbarium. These specimens are different than the “standard” pressed flat specimens on paper. Instead, they are stored to maintain their three-dimensional structure.

Note the note made by Jennings on the label on this specimen: “Trees from ¼ to all killed by blight.”

The case of the American chestnut is an interesting one. It served important cultural and ecological roles; some even calling it a “keystone” species. There is no doubt that the functional extinction of American chestnut ricocheted through the ecosystem, causing long-term biological changes. Many of these changes we may not know. Yet, at the same time, despite the species importance, our forests continue. Presumably other species have filled the functional and physical space of American chestnut.

Disease and pest outbreaks in Pennsylvania’s forests continue. Many of our critical tree species are likely to decline in coming years and decades. Some iconic species have already declined or are at risk. These include our ash species (mortality caused by introduced Emerald Ash Borer), American beech (Beech leaf disease, Beech bark disease caused by an introduced scale insect), and eastern hemlock (mortality caused by introduced sap sucking bug, the hemlock woolly adelgid)…to name only a few threats.

What will Penn’s woods look like in another 100 years?

Our collections document the past and present to inform our decisions for the future.

Find this American chestnut specimen here (along with 268 others!): https://midatlanticherbaria.org/portal/collections/list.php?db=328&includecult=1&taxa=Castanea+dentata&usethes=1&taxontype=2

Free and Open Sharing of Biodiversity Data Promises New Era of Research

Analysis of more than 4,000 studies published over the past 15 years makes case for ongoing development of the next generation of research

Contributions of amateur citizen scientists and natural history museums emphasized

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