Monday, November 20, 2017

Quercity—Thoughts on Oaks

Coast live oaks, Quercus agrifolia, in the California Coast Range.

Free time has been scarce lately, so I’m offering a short post on oaks, inspired by “Querc-y Characters” at the Lady Bird Johnson Wildflower Center website.

I have a fondness for the Wildflower Center that surfaces at the least provocation, for I once talked plants with Lady Bird! It was 40 years ago, when I was botanist and sole employee of the Wyoming Natural Diversity Database. Jane Sullivan, wife of the governor, invited a small group of botanically-inclined ladies to gather for tea with Mrs. Johnson in Jackson Hole, at the base of the Grand Tetons. Conversation was awkward at first, but Lady Bird had done her homework, and as we introduced ourselves, she responded with what she had heard or read about our work. Soon we were happily discussing plants. Afternoon tea is not my idea of fun in the Tetons—I prefer hiking. But I really enjoyed my time with Lady Bird. She was so gracious and down-to-earth, a wonderful mix.

Now to the oaks …
Bur oak leaves, Dugout Gulch Botanical Area in the Black Hills.
In Wyoming, we have two oaks, both at the edge of their range here. Bur oak, Quercus macrocarpa, is a tree of the eastern and midwestern US that reaches its westernmost extent in northeastern Wyoming, mainly in the Black Hills. Gambel oak, Quercus gambelli, is common in Colorado and the southwestern US, but in Wyoming it grows only in the Sierra Madre, near Colorado. I was going to add “northernmost extent” but when I checked the NRCS PLANTS Database distribution map, I discovered that Gambel oak has been reported from South Dakota! However, there’s no county recorded, and the Forest Service FEIS treatment doesn't mention South Dakota. This would be a major disjunction, and news to me. But it’s an oak matter for another time.
Gambel oak; source.
In a way, we’re lucky we have just two oaks in Wyoming. I worked several winters in southeast Arizona, and struggled with the oak situation there. Apparently it’s even worse in Texas … or better, if you're not obligated to come up with identifications. Texas has more oak species than any other state in the US. Amy McCullough has put together an elegant straightforward guide to four of the common ones in Central Texas: Querc-y Characters, illustrated by Samantha N. Peters. Besides being a work of art, it shows clearly the characters and challenges in oak identification.
If you’re a hardcore oak fan, or looking for a botanical adventure, check out Quercus in the Flora of North America (FNA). There are 90 oak species in North America according to taxonomist Kevin Nixon, who prepared the FNA treatment. The exact number is debatable because oaks hybridize readily. “An astounding number of hybrid combinations have been reported in the literature, and many of these have been given species names, either before or after their hybrid status was known. … Hybridization in most cases results in solitary unusual trees or scattered clusters of intermediate individuals.” Oh dear!!

Even if you’re not up for a Querc-y Mega-Challenge, you might find Nixon’s introduction interesting—a revealing glimpse into the tortured world of oak taxonomists.
“A representative selection of mature sun leaves” is required for oak identification. Shade leaves won’t do. These are leaves of the coast live oak—sun above, shade below.


Monday, November 13, 2017

Boxelder—pest, pleaser, or provider?


Yesterday I went to check on “my” boxelder, the one I’m following. I’m limited to weekend visits, as weekdays belong to the Gustav A. Larson Company, which rents warehouse space next to the tree. Before I show you what I found, have a look at the road construction project en route, now almost a year ahead of schedule! It has been fascinating to watch.
This machine is laying down a bikepath as I write!

Now on to the tree. First, its habitat ...
The boxelder grows in a corner formed by north- and east-facing warehouse walls. The sun has moved far enough south now that it's shaded most (maybe all) of the time. Since last month, it has dropped most of its leaves; just a few dead ones hang on. Another difference: this visit was snow-free. In fact, we’ve been snow-free for almost a week, and it has warmed up enough to feel like fall again. I took advantage of the nice day to examine the boxelder more closely.
Bark.
Dead leaves: petioles stay on longer than blades. Note opposite branching.
Oppositely arranged buds.
Sucker shoots up against the wall.
Urban habitat wouldn’t be complete without trash. I predict trash composition will change from month to month thanks to our wind. This time I found an inspiring message :-)

Following a tree provides the opportunity to learn about that species. My first stop along the knowledge pathway was the Biodiversity Heritage Library (BHL), “a consortium of natural history and botanical libraries that cooperate to digitize the legacy literature of biodiversity held in their collections and to make that literature available for open access ...” It’s my go-to place for interesting, fun, and often surprising information about plants. I like the emphasis on early pioneering botany, especially accounts by the explorers themselves.

A BHL search on Acer negundo returned 3843 hits. I sorted by date, browsed at the extremes, and found two interesting and contrasting accounts of the boxelder.

In 2013, Euardo Franceschi and Silvia Boccanelli reported that “spontaneous little forests” (núcleos boscosos espontáneos) of boxelder trees have developed in native Pampean grasslands in J. F. Villarino Park (Santa Fe, Argentina). Boxelder is a non-native and invasive pest species in Argentina, as well as in central Europe, China and Australia. In the Villarino grasslands, it’s clearly thriving. The researchers found overstories often to 40 ft in height (12 m), with boxelder common enough to be a dominant. Seedlings and small saplings were common in the understory, suggesting boxelder is there to stay in the absence of aggressive eradication.



François André Michaux, 1851; source.
At the other end of the BHL time line, I found boxelder in the The North American sylva, or A description of the forest trees of the United States, Canada and Nova Scotia by the pioneering French botanist and explorer François André Michaux (1770-1855). He made several trips to North America to botanize, beginning in 1785. In 1806, following detention in the Bermudas after being captured by the British, Michaux spent three years studying and collecting North American trees. After returning to France, he compiled his monumental work on the North American sylva—three volumes published 1818-1819. It was later translated by Augustus L. Hillhouse; this is the version I found at the BHL.

Below, “Box Elder or Ash leaved Maple” Plate XLVI. Courtesy Linda Hall Library Digital Collections. LHLDC was a great discovery. It provides online access to “significant rare and fragile materials” with free downloads.
Michaux explained that Ash leaved Maple was “a perfectly appropriate denomination,” but that general usage forced him use Box Elder, “though absolutely insignificant of any characteristic property of the tree.” Ash leaved Maple is perfectly appropriate because Acer negundo is indeed a maple, and the leaves are pinnately compound, looking a lot like those of ash trees. As is true for all maples, boxelder leaves are opposite on the stems. “The barren and fertile flowers [male and female] are borne on different trees” (i.e., dioecious).

Michaux found boxelder to be uncommon east of the Alleghenies, but “west of the mountains, on the contrary, it is extremely multiplied,” and abundant on floodplains. Especially interesting was his account of the reception the boxelder received in Europe post-introduction. Apparently humans jump-started its European invasion:
“Subsequently, it has spread into Germany and England, where it is in great request for adorning pleasure grounds, on account of the rapidity of its growth, and the beauty of its foliage, whose bright green forms an agreeable contrast with the surrounding trees.”
There are other reasons to like boxelders. Some botanists note that invasive species like boxelders provide ecosystem services in urban environments. Being an admirer of underdogs and the under-appreciated, I suspect I will become a fan of this tree.

Check out this month's tree-following news, kindly hosted by The Squirrelbasket. And consider joining us ... it's fun!


Sources

Franceschi, E., and Boccanelli, S. 2013.  Floristic-structural analysis of spontaneous little forests in the J. F. Villarino park (Santa Fe, Argentina). Bol. Soc. Argent. Bot. 48: 301-314. https://www.biodiversitylibrary.org/part/112675

Michaux, FA. (translated by Hillhouse, AL). The North American sylva, or A description of the forest trees of the United States, Canada and Nova Scotia ... https://www.biodiversitylibrary.org/bibliography/42243#/summary