School can be fun. Tomorrow, I’ll be heading up into the mountains outside of Boulder for my first official in-the-field lab. I’ll be the first to admit, I’m more of a research and writing person than an experimental and field work sort of person. Since I hope to make a career out of science writing, I’m particularly eager to get this sort of hands on experience. So, what will I be doing in the mountains, exactly? I’ll be looking at ponderosa pine trees (Pinus ponderosa). Well, not just looking at them, but measuring them (height and width at breast height), taking core samples, and noting competition with other trees growing in the area.
This class--Introduction to Ecology--will probably end up being one of my most memorable educational experiences. The professor has a fascinating research background, which I’m sure to describe in future posts, plus the class includes a lab, which turns out to be about half field work. By the time my Tuesday or Thursday afternoon rolls around, I hardly want to leave... the science is just too cool. So, since I’m so excited about this first lab, I thought I’d take you, my readers, along. In the next few posts, I’ll describe what we’re doing, why we’re doing it, and how it turns out, with pictures and graphs to highlight the process (and the fun!) It’s probable that I’ll run into some of the pine beetle devastation along the way, so I may have pictures of that as well. For now, I’m including a few botanical illustrations of the ponderosa cones... they make such lovely fractal patterns:
So, to begin, why am I about to become so intimate with ponderosa pines? Specifically, the goal is to examine the primary factors limiting growth of the pines. Colorado is in sort of a strategic location for ecology, due to the Rocky Mountains running smack dab through the middle of the state. The elevation divides up the ecosystems nicely: down on the plains where I live, you’ll find lots of grasses and yucca shrubs, and virtually no naturally occurring trees, save along the creek beds. When I go to class in Boulder, I’m entering the fringes of a different ecosystem called the lower montane, but known more familiarly as the foothills. A variety of trees grow there, including pinyon and lodgepole pines, as well as oaks and alders. Just above is the actual montane region, where we’ll find most of our ponderosa pines, mingled with Douglas fir. Above that, the ponderosa/Douglas fir mix gives way to spruce and other varieties of fir... until about 11,000 feet or so. There, the trees disappear altogether; mostly only lichens and wildflowers can grow in the harsh alpine ecosystem which tops the Rockies.
Below, you'll find a map which shows how Colorado’s topography divides its ecosystems:
The boundaries of these different "life zones" (to quote C. Hart Merriam, via my lab book) are, of course, fuzzier than they appear on the map. Usually, one species doesn’t abruptly end where another begins. So, ponderosa pines may be found outside of the typical boundaries, even if they aren’t the dominant flora. So, this is why we’re about to hike up a mountain in the snow and stab at pine trees... to figure out what seems to keep the pines where they are.
We’re going to be wrestling with a few hypotheses. Elevation obviously has something to do with it, but which aspect? Precipitation increases with altitude, which would cause the trees to be bigger and stronger the higher you go. On the other hand, the growing season shrinks rapidly with a rise in elevation, giving trees at lower elevations a better chance for growth than those above. Meanwhile, there are, naturally, other trees around... could a competing stand of trees keep the growth of a tree in check? That’s what we hope to discover--which has the greatest effect?
That basically sums up the purpose of our experiment and the hypotheses and predictions involved. (If you’d like to know my guess, I think the length of the growing season will show to have the largest impact... but I could be wrong.) After we return, I’ll try to share some photos of our work, and explain the methods we use. The following week, we’re scheduled to compile and compare all of our data, so you’ll have to wait until then to find out how the experiment actually turns out.
Botanical illustrations via Trees.Stanford.edu, map via the Natural Diversity Information Source.
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We did a somewhat simpler experiment in introductroy biology lab. There are two groves of pine trees planted by the campus library. We went out and measured DBH on the trees (16 in each grove). Used Mann-Whitney-U to test the null hypothesis that the two groves were the same age. Turns out cannot reject the null hypothesis. This upset the students a little, so we showed them the aerial photo of the library with the two groves just planted. Made the point that statistical tests do not always detect differences, particularly if there aren't any.
Since your "expedition" is over, maybe my input from personal observation won't skew your answer to this question: "That's what we hope to discover--which has the greatest effect?".
I live in a Pinon-Ponderosa forest. But north slopes will occasionally have Spruce stands (and an occasionally hardy fir). The answer is: moisture. North slopes retain snow longer, dry out less, and drain to ravines where the spruce live in my neighborhood. Ponderosas need more moisture than Pinons; 15" is a critical point. Or rock underlayments which retain water giving them even footing for survival.
And I regret your going into the woods in the winter. Visit them in summer and smell the Ponderosas. Seriously. Especially when they are stressed; the spice smell is great. And each is slightly different. Some are so odoriferous, they can be smelled feet away!
Oh, yeah. I hope your field trip went well!