Posts Tagged ‘oaks’

Foxglove: Another Pleistocene Survivor

July 23, 2010

Poison lurks around the corner.  A half acre stand of yellow foxglove grows on land two lots down from my house where an abandoned trailer sits behind hundred year old laurel oaks.  The trailer was owned by a bachelor  before he died of a heart attack on a trip to Vegas a few years ago.  Yellow foxglove (Digitalis grandiflora) is poisonous to people and animals, including both carnivores and herbivores.   Ingestion causes loss of appetite, nausea, and a dangerously lowered heart rate that can cause death.  Drug-makers manufacture medicine from this plant, and it’s used to control the irregular hearbeats suffered by patients in congestive heart failure.

Up close views of foxglove plants.

Part of a stand of foxglove.

Foxglove was probably a common plant during the Pleistocene.  It thrives in open oak glades and prefers disturbed and burned over areas.  An old pine tree in my yard exhibits evidence of a light brush fire in my neighborhood, perhaps 30-40 years ago before houses were built here.  Foxglove also grows well in acidic soils as does low bush blueberry which grows within this patch as an associate and also likes burned over areas.

Lowbush blueberry plant growing in association with foxglove.  Both like burned over areas with acidic soil.

During the Pleistocene light brush fires, frequent in both arid and rainy climate phases, shaped the environment along with the large herds of herbivores which consumed and destroyed many succulent plants but avoided poisonous foxglove.  Foxglove would have grown with grass, which can survive grazing because their taproots remain safe underground, and blueberry which also can resprout from suckers.  All three are tough plants, surviving on this lot, despite sandy acidic soils and extreme drought and heat.  Many a Pleistocene landscape would have been dominated by these three.

Foxglove should please flower gardeners–with no maintenance, this patch in the abovementioned lot has been continuously blooming for three months, since May.

Foxglove does require the presence of oak trees, and they are restricted to forest edges and open woodlands.  They are parasitic feeders; their roots latch on to the roots of oaks and that’s how they absorb nutrients.  False foxgloves, members of the figwort family, are close relatives of the true foxgloves, and they too are parasitic feeders.  In my opinion, though the flowers are similar to those of true foxgloves, the leaves are not.

Eolian sand dunes, formed throughout the southeast during Ice Age droughts when windborne river sand accumulated, were another ideal habitat for foxglove which could grow with scrub oaks and grass on these sparsely vegetated areas.

Pleistocene survivors–Oaks

March 8, 2010

The purpose of this blog is to promote my newly published book–Georgia Before People: Land of the saber-tooths, mastodons, vampire bats, and other strange creatures.

I just approved my book for distribution. Within the next 6-8 weeks it will be available from http://www.amazon.com, and will show up in book search databases. It’s already available for purchase at http://stores.lulu.com/GeorgiaBeforePeople

I will use this blog to highlight some points that I didn’t cover completely in my book, or to discuss new findings that didn’t make it into my book.

Pleistocene survivors

Think about this: Every animal and plant that you see today is a Pleistocene survivor. All extant species lived during the Ice Age, otherwise they wouldn’t be here today. Oak trees are among the most abundant living species found in temperate North America today. Pollen studies from Georgia and other southeastern sites show that oak trees were fairly common here during the Ice Age as well. Oak consistently makes up about 12% of pollen samples at various Pleistocene sites in Georgia. Though pollen studies have some drawbacks (which I discuss in my book) when estimating actual tree populations, this means that about 1 in every 8 trees in the Pleistocene forests of Georgia were oaks. Like today, they shared the landscape with southern pines and hickory, but unlike today, Pleistocene forests in Georgia also consisted of northern species of pines and spruce trees as well, at least in the north and central parts of the state. A more equable climate with cooler summers and mild winters allowed more species of trees (as well as small animals) to co-exist than do in today’s Georgia.

Oaks require a great deal of sunshine to germinate and do well. This means that in Pleistocene Georgia, there were plenty of sunny locations for oak trees to sprout up on. This implies an open woodland kind of forest rather than the closed canopy woods that began to dominate in the Holocene. Fire, drought, ice storms, wind, and megafauna browsing and trampling are the factors that kept Pleistocene landscapes more open.

Man is the reason oaks continue to thrive in today’s environment. Men cut down trees, clear the land for agriculture, than abandon it, thus allowing oaks to return.

I visited protected areas in the Appalachian mountains of North Carolina last summer where there has been little lumbering for the past 100 years. Surprisingly, the forests here have few oaks. The dominant trees are maple, tulip, beech, white pine, and hemlock. These trees shade out oaks. This makes me think that the Great Smoky Mountains National Park has less wildlife than it should because the habitats are undisturbed. Oak is an important mast tree–the acorns providing an important food source for all kinds of wildlife. After the blight wiped out the chestnuts, oaks became even more important, but without lumbering or fire to open the landscape, the supply of acorns is declining, and accordingly, the wildlife in this park is a pitiful remnant of what it should be. Park officials probably wouldn’t agree with me when I say some of it should be lumbered for the purposes of diversifying habitat.

One more thing to consider about oaks in Georgia. I’ve studied the range map of the bur oak–this is a tree that likes rocky calcareous soils and thrives in the cross timber region of midwestern North America where prairie meets woods. A very small scattered population exists in northern Alabama and Mississippi, but none have been found in Georgia. It’s possible that during the Pleistocene, bur oaks were more widespread and may have occurred in state. Unfortunately, plant macrofossil sites in Georgia are so rare we’ll never be able to confirm my suspicion.

Next up: A discussion of Pleistocene eagles.