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Earth Dr Reese Halter's Blog


Earth Dr Reese Halter next to ancient Douglas-fir near the Hoodoos

Most visitors to the northern Rocky Mountains have driven by the ethereal Hoodoos (sedimentary cliffs) of Banff National Park. You may have stopped and marveled at their formation, or driven to Johnson’s Lake and hiked the trail above the Hoodoos. Then you’ve also walked by the oldest Douglas-firs in the province of Alberta.

Some of these Douglas-firs have witnessed 300,000 sunrises; making them nearly eight centuries old. When the trees were beginning life in the 14th century – Black Death, otherwise known as bubonic plague, was ripping through Western Europe, leaving 25 million dead.

How do scientists determine the age of trees, especially when they’re centuries old? It’s done with the aid of a special core – called an incrementor – which carefully bores into trees extracting thin bands of wood. These bands contain growth patterns tracing the life histories of the trees. Each year, a tree’s life is recorded by one light and one dark band of growth. The lighter, less-dense band represents late spring and early summer tree growth (aptly called earlywood), while the dark, dense band results from late summer tree growth (called latewood). Tree scientists count (with the naked eye or microscope) either light or dark bands, but not both, and are accurately able to determine a tree’s age.

Yet the interesting aspect of these cores is that they relay other mysteries about trees and their environments. Trees are living museums and expert curators – called dendrochronologists – glean important climatological information that helps multi-disciplinary teams of biologic and earth scientists understand climatic conditions, past and present. If the summer has been wet bands for that year will be wide; if the summer has been dry bands will be thin, reporting a drought. Similarly, Rocky Mountain Douglas-firs on the Hoodoos are critically important because they hold crucial insights assisting teams of scientists in interpreting the extent of past and present climate changes.

The thin retractable cores can also tell of natural, lightning-induced fire frequency. Dark callous scars show evidence of past blazes. Some trees, like Douglas-fir, can tolerate surface fires (from just above the ground to 5 feet or 1.5 meters high). As it ages, Douglas-fir holds its branches high enough off the ground so that a fast surface fire cannot ignite its crown, providing natural protection against lethal crown fires. It also grows very thick bark (16 inches or 40 centimeters) which helps insulate the tree from the heat of surface fires.

The ancient Douglas-firs on the edge and above the Hoodoos are seven times older than the lodgepole pines, the provincial tree of Alberta, that grow behind them. Lodgepole pines have adapted to the natural occurrence of fire by growing cones with viable seeds which remain shut tight, held on the trees, for up to 20 years. The heat of the forest fire melts the resin around the cone scales and enables the cones to shed massive amounts of seed. Lodepole pine seedlings then quickly recolonize exposed soil. The fire frequency in the lodegpole pine forests of the Rocky Mountains occurs about every 50 years. If fire does not occur, lodgepole pine will live for about 125 years and then naturally die-out, because it cannot live in its own shade or it becomes infested with the voracious mountain pine beetles. Lodgepole pine depends upon fire for its very existence. If fire does not occur the montane lodgepole pine forest will be replaced by spruce and subalpine fir.

Douglas-fir has adapted to tolerate surface fires with its thick bark and uplifted crown. Moreover, the Douglas-fir above the Hoodoos have adapted to a specialized habitat that is considerably drier than the lodgepole pine forest behind them. Scientists believe that Douglas-firs have been able to survive for so long because dry conditions prevent fungus – which normally kills trees. Also, there are very few, if any, downed branches, to act as kindling and allow fire beneath these old trees. These are champion, thrifty Albertan trees!

In 2003 I had the honor of documenting the exact location of these magnificent creatures. In conjunction with Parks Canada and Banff National Park, we successfully undertook to protect these majestic trees from a controlled burn on the Fairholme Bench. The controlled burn carefully reintroduced fire, which had been deliberately suppressed for some 75 years. That promotes healthy new forests, animal habitat and it attempted to rid the insatiable mountain pine beetles (a harbinger of global warming) which had, in four years, infested about 7,000 mature lodgepole pines.

It is not difficult to recognize why the First Peoples revered the Hoodoos, not only is the landform remarkable – but so too are the towering trees.

Australia, Radio 1, National: Ockham’s Razor

Earth Dr Reese Halter is an award-winning broadcaster and distinguished conservation biologist. His latest book with Chris Maser is Life, The Wonder of it All

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Text © by Dr Reese Halter 2013. All rights reserved.


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