Charismatic Megaflora: What do Old Trees Look Like?
Charismatic megaflora? What kind of a tree might that be? As with many things, one person’s charismatic megaflora is another person’s tree. For myself, a tree that would draw and hold my attention as a younger person/student is very different than my current definition of a charismatic tree. My earlier self was typically drawn to the large eastern white pines that inhabit the Pack Forest in the southeastern Adirondacks or the massive eastern white pines at Cranberry Lake, N.Y. When I was getting introduced to the world according to dendrophiles, these trees triggered emotions similar to those in a Sierra Club calendar where they literally towered over any nearby object. In the northeastern U.S., these large white pines are about as good as they get. They are big. They are stupendous. They make us look up. They make us wonder about times long ago. They convey a sense of great age.
You know, like this scene:
I do not have pictures of those eastern white pine, but this white oak has a similar kind of charisma for eastern trees:
Now, however, after searching many forests for the oldest trees to obtain the longest possible, tree-ring based records of environmental history, my definition of charismatic megaflora has changed. Significantly (p < 0.0001). Ah, these large trees are beauts, but if you want to truly wonder about time, don’t miss the old tree hiding right in front of your eyes.
What do old trees look like?
When I was cutting my teeth in tree-ring analysis, I was mostly involved in projects studying conifers. Notably, I was able to core the old’ish, large loblolly pines of the Congaree National Park in South Carolina. Soon after, I had a job in the wonderful longleaf pine ecosystems of the Deep South. At the time, there were few guides to what old trees looked like, though two papers were published on the subject prior to my time among the longleaf pines – here and here [be sure to check out the beautiful line drawings of old trees by Richard Guyette in that second link]. So, my first intuition was a natural one: seek out the large trees to find the oldest trees. Prior to Hurricane Hugo, the Congaree had 22 state champion trees and 7 national champion trees. It is a kind of heaven. However, most of the trees that have been cored in the Congaree [as far as I know] top out at 250-300 years. That is old for a person. But, for a tree being sought out by a dendrochronologist, honestly, that is kind of middling.
Soon after settling into the longleaf pine forest, I started paying closer attention to what old trees really looked like. I studied the papers linked above and got advice from seasoned foresters, like Leon Neel, and my supervisors. Thus began my study of old trees. Sometimes we found them. Sometimes we were stumped.
The main characteristics for old conifers are discussed in this report on ponderosa pine by Laurie Huckaby. The image on page 17 in Huckaby’s paper pretty much sums up what you are looking for: a spiked top, a flattened crown (or loss of apical dominance), smooth bark (balding is a potential sign of age in trees, too!), and a small living crown. A few, large, twisting branches in the canopy (as opposed to a crown with many smaller branches), a characteristic related to a small living crown, can be added as a useful characteristic. You can also add lower stem taper as an important characteristic. In this case, if the diameter at the base of the stem is not too much larger than at the base of the live crown, you likely have an old conifer, except when you do not.
I’ll never forget the time a buddy and I had a couple of free hours to cruise a 22,000 acre landscape of longleaf pine. We decided to try to find the oldest tree in the landscape. Suddenly, we spotted Ye Olde Longleaf Pine. It was flat-topped, had a spiked crown, was of decent diameter, and, most excitedly for us, was perched on a sandy ridge. We had learned by then that trees growing in poor-quality sites can be slow growing and thus older than expected if of decent diameter. We sprinted to that tree! We rapidly cored that tree!! We hit the pith of that tree!!! It was 55 years old….wha? The marker ring for southwest Georgia, a thin latewood band in 1954, was only a few rings from the pith (the center of the tree). Oh yeah, we were stunned. It wouldn’t be the last time I would be fooled. Trees are cunning.
Since that time I have focused more on broadleaf or hardwood species like oak, tulip-poplar, hickory, and Magnolia. I applied many of the characteristics above when looking for old broadleaf trees. For the most part, it works. Balding bark is an important characteristic, although you have to know your species. Do not get fooled by the natural balding of cucumbertree (cucumber Magnolia). They can have bald patches at young ages. In fact, it is one of the better identifying characteristics of this species. Also, balding on the side of a tree next to a hiking trail can also be a false sign of age (you know, they can bald from the loving they get from those two-legged mammals with tendencies toward dendrophilia). Narrow stem taper in broadleaf species generally works: It can take a long time to get a good amount of wood 50-80 feet above the ground. A small amount of live crown, especially when combined with a decent-sized diameter, indicates an older hardwood tree. A few large, heavy, twisty branches are good characteristics, too.
One somewhat common characteristic of old broadleaf trees that I have run into, not in the papers above, is a sinuous trunk. Others have discussed a spiral grain as an important characteristic of older trees. It works well for post oak. But this trait, the sinuous stem, is an important clue of age in dense forests, no matter if they have been cut or are uncut. Sinuous trees remind me of the first time I saw a rat snake climbing a tree in the Congaree: While rigid, its body is twisted from side-to-side. In case you haven’t had been lucky enough to see a snake climb a large tree, I just found a video of a black rat snake climbing a tulip-poplar: [youtube]http://www.youtube.com/watch?v=U8MEwIEyS5E&feature=youtu.be[/youtube]
At any rate, here is an example of a particularly sinuous tree:
I’ve not investigated why this trait seems to be somewhat common to old hardwood trees (there are papers on sinuosity). I like to think (hypothesize) that each twist is a record of decadal-scale phototropism. Individual plants track or move with the sun as it moves through the sky. Sunflowers are a classic example, though cartoon broccoli are apparently capable of the same thing. In dense forests like the Eastern Deciduous Forest, one of the most important elements that seedlings and saplings need for survival is sunlight. To go with this, the most dominant natural disturbance regime in dense forests like the Eastern Deciduous Forest is gap dynamics. Gap dynamics can be generalized by the mortality of 1-2% of the forest (a handful of trees) in a given area each year. Thus, if you are a seedling or sapling sitting below towering trees during a relatively stable period of time, you would yearn for some light. And, if a neighbor tree died, you would run to the sunlight streaming to your level of the forest like we ran to that 55-year-old longleaf pine.
Except, you are a tree. You cannot run. While trees are awesome, one drawback to their life strategy is that they are a bit sedentary. When Trouble comes to your neighborhood, there is little hiding. Thus, one reason trees are so awesome is how they persist despite it all.
So, what do you do if you are an understory tree and a small gap has created a fleck of light in your general vicinity? You reach for it, almost literally. Your solar panels “detect” the higher light levels, intercept more light, and grow in that general direction. If you are successful in that pursuit, you then gain more energy and stretch more in that direction. This becomes a positive feedback loop: As you gain more energy, you can grow more. As you grow more in that direction, your mass will “move” in that direction. And, in opposition, “trailing” or more heavily-shaded branches and leaves might lose out as you “move” toward the more resource-rich area of the forest.
There are many quotes used above because this is not moving in the same way or at the same time scales as animals move. So, as you imagine that, think of something moving slower than molasses in January 1777 (not January-March 2012).
And, here is another problem for you: At the time scale of forests, most gaps created annually are small and ephemeral. So, as you spend 2-3 years or so moving toward the light, your towering neighbors, with greater resources as acquired through a larger canopy and root system, will fill these gaps with their lateral branches. You are blocked again. So, you must wait again for another pocket of light. Perhaps it is in another direction? Perhaps you have to grow in another direction? If so, then one could imagine how these sinuous stems are found in older trees in dense forests. Mind you, this a rather simple hypothesis. There are other factors that likely play a role in the sinuous architecture of trees. It is a place to start. However, I certainly saw potential examples of this in an old-growth forest in Manchuria. Check out this ash:
Or, how about this black walnut in Mammoth Caves National Park:
One more thought on what old trees look like: Size does not always imply age. If I didn’t hint about it enough above, let’s be clear: Big broadleaf trees can be old, but they might not be old. Some of the oldest trees I’ve cored in the eastern U.S. are of middling size. Most folks might walk by them while hunting for large trees. Not me. For me, they are the charismatic megaflora in dense forests. There are more details in the paper here. Contact me if you would like a copy.
So, as you go out to enjoy the current “heat wave” in eastern North America, have a little different look at the forest. Can you find my definition of a charistmatic megaflora? Can you spot the old trees hiding in front of your eyes?