Pleistocene survivors–Oaks

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.

Advertisements

Tags: , , ,

2 Responses to “Pleistocene survivors–Oaks”

  1. Mark Says:

    Mark, just looking over some of your older stuff. On walks this past winter (with record snows) I’ve found snow fleas on several ridges over 1400 feet. I hadn’t seen them for at least 10 years prior to that. I don’t know a lot of biogeographical info on them, and am wondering if you have ever studied them.
    Mark L.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s


%d bloggers like this: