Mason Heberling

Who needs leaves?
 
This red maple (Acer rubrum) specimen was collected on November 13, 1915 by former Carnegie Museum curator Otto Jennings on a rocky back north of Finleyville, Pennsylvania.
 
Something about herbarium specimens that are just branches, with no leaves or flowers.  But the flowers and leaves are there…well, sort of.  
 
Check out the nice buds on this specimen. Many deciduous tree species in temperate areas (like Pennsylvania) have “preformed” buds.  These buds are produced in the summer, packed with leave and/or flower tissue. You can see these buds swell during the winter in preparation for budburst.  Then when the conditions are right (like temperature and chilling time), the plant is ready to go! The cells don’t need to be made, and spring budburst is all about expansion.

It is fun to think of what is inside these buds.  There is a lot going on in there. Keep an eye on them on the trees in your neck of the woods. Many are rearing to go, riding out the winter.
 
Find this specimen and search for more here.

Well, that’s kinda weird!
These red maple (Acer rubrum) leaves were collected by Dorothy Pearth on November 6,  1959 at  Coles Summit in Huntingdon county, Pennsylvania. Dorothy Pearth (1914-1996) was a curator at the Carnegie Museum. She made two special notes on the label: “with exceptionally long petioles” and “many leaves with very long petioles.” (Petioles are the stalks that connects leaf to stem)
 
Herbarium data are often considered “biased.” All data collected haphazardly or by many different people across centuries with different intended purposes undoubtedly skew reality to some extent, depending on the research question.  It is rightfully something to consider when using specimens in research. Taxonomic bias (what species are collected), geographic bias (where specimens are collected – more often near roads, for example), temporal bias (high collection effort in some years), or collector bias (“that guy never collects grasses”) are just a few to consider. But just because “bias” may exist doesn’t mean it can’t be accounted for or the data are somehow useless.   Far from it!
 
In fact, bias can be a great thing! We want those “odd” specimens documented because they often tell us something important and new.  Maybe that specimen flowering in fall that normally flowers in summer is a sign of climate change.  Maybe that unfamiliar species is the first record of an introduced species that may  become invasive in the region.  Maybe that specimen that resembles species X, but has really huge leaves, is a new species  unknown to science!  Many undetermined specimens (that  is, those  that are identified to species)  are collected  for that very reason.  Many new species are first realized after someone  points out  that this specimen is “weird.” 
 
A recent paper in the American Journal of Botany (Pearson & Mast, 2019) surveyed collectors and search specimen records that include “outlier terms” – in other words, additional notes on the label written by the collector to point out something unusual about the specimen.  They found that this practice of pointing out outliers is an important route to detect early changes in the Anthropocene (the age of humanity).  Unusual specimens are important sentinels, bringing our attention to critical biological changes that may otherwise be overlooked in an era of rapid biological change.
 
Find this long-petioled red maple specimen online here: midatlanticherbaria.org/portal/collections/individual/index.php?occid=12233287&clid=0
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“Autumn is a second spring when every leaf is a flower” – Albert Camus
 
It’s peak fall color in southwestern Pennsylvania, depending on who you ask!  This beautiful specimen of red maple (Acer rubrum) was collected on November 2, 2007 by Loree Speedy near Virgin Run Lake in Fayette county. It is unclear to me what exactly the “red” in red maple refers to specifically, or perhaps many parts of the plant (flowers, leaves, petioles).  One thing is for sure – it can have beautiful bright red foliage in the fall.  Also once called “swamp maple,” this species is widespread across eastern North America.  Due to altered effects on fire, wildlife management, climate, and other environmental changes, red maple is said to have increased in abundance over the past century.
 
Red colors can be the most striking of all fall colors…but my opinion changes!  This specimen shows great variation within the leaf, with reds and greens.  Each leaf have a certain uniqueness to them.
 
Red coloration in fall leaves results from the production of red pigments called anthocyanins. The pigments serve as a protectant, a sunscreen of sorts. You may also see young or stressed leaves turn red at other times of the year for similar reasons.  Other pigments like carotenoids (oranges) and xanthophyll (yellows) are present throughout the growing season, serving as accessory pigments for photosynthesis.  As chlorophyll breaks down and nutrients resorbed, these colors have their chance to shine.  Anthocyanins, however, are actively produced in fall.
 
Fall leaf coloration is complex, and not easy to predict. Many hues exist, even within a leaf (as shown in this specimen). Every species has different coloration. And, coloration differs within species based on a variety of factors.  Each leaf is unique and although short, fall is a great time to celebrate the beauty and science of leaves.
 
All of the red maple specimens in the mid-atlantic region from the Carnegie Museum herbarium are now imaged and available online: http://midatlanticherbaria.org/portal/collections/list.php?db=328&hasimages=1&taxa=Acer+rubrum&usethes=1&taxontype=2 

Black maple (Acer saccharum ssp. nigrum) collected by Herbert W. Graham on January 15 , 1927 along Big Sewickley Creek, just outside of Pittsburgh.  Black maple is sometimes considered is own species (Acer nigrum), depending on who you ask.

Who doesn't love a good herbarium specimen of sticks collected in winter?  We have quite a few specimens collected in Pennsylvania during winter when the species is leafless.  It is unclear exactly why they were collected in every instance, but it was likely for reference material to help with species identification in winter.  The downside is that specimens without leaves and/or reproductive structures can be difficult to definitively identify.  But what specimen is "perfect" anyway?

​We don’t always think of trees when we think spring wildflowers. But trees can have flowers too.  Many trees flower in early spring, before leafing out. Many of these flowers are small and inconspicuous, and wind pollinated. This specimen of sugar maple (Acer saccharum) was collected in April 1898 in Olena, Ohio. This specimen was collected by Otto Jennings, one of the first botany curators at the Carnegie Museum.  But this specimen is especially cool because it was one of his first collections, collected in his hometown, years before he became curator.
 
Jennings (1877-1964) was born on a farm in Olena, Ohio.  He collected this species in Olena when he was 21 years old, the year he started as a student at the Ohio State University.  Jennings started his 60-year tenure at the Carnegie Museum six years later, in 1904. He made many contributions throughout his career, serving as the Curator of Botany, Director of Education, and eventually Director of the Carnegie Museum of Natural History.  He also was Professor of Head of the Department of Biological Sciences at the University of Pittsburgh, having advised many students.  His legacy remains to this day for his influence on the museum, botany, conservation, and environmental education.

Spring leaf out is a bit “behind” in Pittsburgh this year.  Well, for Norway maple in Schenley Park compared to 1948.  Plant leaf out and flowering times is variable for many species each year due to differences in spring temperatures. This Norway maple specimen was collected by Botany curator Otto Jennings.  Norway maple (Acer platanoides) is commonly planted across our region, common as a street tree or park plantings.  Norway maple is invasive in Pennsylvania, spreading into natural habitats. Its leaves superficially resemble the well known sugar maple but has a different leaf shape. Norway maple has even been put on the Canadian 20 dollar bill instead of the native sugar maple (http://www.cbc.ca/news/canada/ottawa/canada-s-new-20-bill-at-centre-of-maple-leaf-flap-1.1343767). A good way to tell it is Norway maple is that exudes a white latex from the leaf when picked.

Keep an eye out for Norway maple over the next week!  That light yellow/green you see at the tips of trees (especially along highways) in early spring is not tree leaves, but flowers. And many of these trees in urban areas around Pittsburgh are Norway maple.  Many trees flower early in the spring, before they leaf out.  Many tree species are primarily wind pollinated, so flowering before most species leaf out facilitates pollen to blow around with fewer obstructions.
 
In a long-term project initiated last year, we are recollecting specimens on the same calendar date and in the same location as historic specimens in the herbarium.  These recollections will grow the herbarium with future use in mind – permitting comparisons across time, such as changes in leaf out dates, flowering, and genetic works.  Long term studies (and herbarium specimens) are important to understand the effects of climate change and other human activities because of yearly variation.  Check back for more on this project!
 
Image below: Norway maple buds today on a tree in Schenley Park, Pittsburgh (Apr 4, 2018).  It is not quite ready to go. Note the buds are swollen but are not yet burst.  Compare this to the specimen collected in 1948, in full flower and early stages of leaf expansion.

​Over 90 years old and still beautiful color!  This red maple specimen was collected on October 23, 1926 by Otto Jennings during a field trip of the Botanical Society of Western PA to Chestnut Ridge in the beautiful Laurel Highlands of Pennsylvania.  Red maple (Acer rubrum) is one of the most common trees in eastern North America.  You can find it from southern Canada down to Florida and Minnesota down to eastern Texas. And it is renowned for its beautiful scarlet red foliage in autumn.  Happy fall!  

Both of these specimens were collected on May 17 in Highland Park– but 50 years apart. John Bright collected the specimen on the left in 1952.  Fifty years later to the day, Bonnie Isaac unknowingly recollected the same species in the same location! 
 
If you look closely, you’ll notice the 1952 specimen did not yet produce seed by mid-May, while the 2002 specimen has already started developing the characteristic maple-like seeds.  Due to increasing spring temperatures in recent decades, many plants tend to flower earlier, as shown through herbarium specimens. Botanists at the museum are studying the impacts of human-caused environmental changes over the past century by following in the footsteps of past collectors.  We are revisiting field sites on the same day to compare modern day plants to specimens collected over 100 years ago.
 
Sycamore maple (Acer pseudoplatanus) is a common forest tree in Europe, where they simply call it “sycamore” but should not be confused with our native and introduced sycamores.  Sycamore maple has been intentionally introduced across temperate regions, including the US and New Zealand.  It has since become invasive, meaning it actively spreads across the landscape and can cause ecological damage. It is less common than other invasive maples (such as Norway maple) in this region, but is invasive in several sites in the Pittsburgh area.