I want to start by acknowledging the irony in this post. As someone who has spent a lot of time killing trees in prairies and urging others to do the same, it’s pretty funny that this post is all about the positive aspects of having a big tree in a prairie wetland. In my defense, I’ve never said there shouldn’t be ANY trees in prairies, and I’m writing this particular post as a photographer, not an ecologist. Matt H and other tree lovers – this one’s for you.
I was out on the edge of one of our restored wetlands last week as the sun was coming up. The wind was calm, the weather was cool, and I was hoping for some nice close-up photos of flowers and insects. Most photographers know that first light is a great time for photography because the sunlight is soft and warm as the sun pops over the horizon. Often, a little haze or thin cloud cover near the horizon can extend that period of nice diffused light as the sun rises higher. Last week, however, there was no haze or cloud cover to help out, and I only had about 10 minutes between the time the sun breached the horizon and the point at which the light was too bright to make good photos.
Fortunately, (I can’t believe I’m saying this) there was a big cottonwood tree nearby and I had the opportunity to use a little trick I’ve found useful for extending my time window for close-up photography. Essentially, I just followed the shadow of the tree as the sun rose into the sky. I didn’t take pictures in the shade, exactly, but neither did I take pictures in the sun. I used the very edge of the shadow.
Here’s my elegant diagram of how to use the diffused light at edge of a tree’s shadow during the first hour or so after sunrise. As the sun rises, the tree’s shadow shortens, but in the soft edge of the shadow, the light is beautifully diffused and perfect for close-up photos. I find a composition just inside the edge of the tree’s shadow and then wait to snap the shutter until the rising sun’s light just starts to pop through the upper leaves of the tree. Then I move closer to the tree, find another subject, and start the process again.
The boundary of the shadow created by a big tree is not a hard edge. Instead, there is a narrow zone of diffused light between complete shade and bright sunlight. That narrow zone creates some nice opportunities for photography. Essentially, I just follow the shadow as it moves across the ground. I find potential photo compositions inside the shadow and then take the picture as the edge of the shadow passes by. I have to work quickly because the shadow moves right along, but I usually have enough time to get several shots of each subject in nice light.
Here are some photos from from last week’s tree-diffused light.
I had time to take 4 or 5 quick shots of this great lobelia (Lobelia siphilitica) before the shadow moved away completely and the light got too bright. The Nature Conservancy’s Platte River Prairies, Nebraska.
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Several species of beggarticks (Bidens) grow along the edge of wetlands along the Platte River.
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Field mint (Mentha arvensis) is another wetland edge plant. Plants in the mint family usually have a pronounced square stem.
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This damselfly was the only one I successfully photographed – out of more than a dozen I stalked. I crept slowly up to it with my tripod while it was still in the shade of the tree and then got my photo as the shadow’s edge came across it.
Interestingly, our staff has had several discussions over the years about whether or not we should cut down the big cottonwood I used as a photo diffuser last week. There are some good ecological arguments for taking it out. For example, large trees act as perches for predatory birds and can affect the way other birds use nearby habitat. Migratory sandhill cranes (a focus of our wetland management) tend not to roost near trees, and many breeding bird species avoid nesting near them as well. In addition, trees often act as gateways for invasive plants because they create a different microclimate that favors some invasives (especially cool-season grasses) and because they attract perching birds that drop seeds of other invasives.
Good ecological arguments can be made for keeping the tree too – including some that are similar to the arguments against it. It’s kind of nice to have a big tree for eagles and other large predatory birds to hang around in because predators are important players in the ecosystem. Orioles, red-headed woodpeckers, kestrels, and many other bird species – including some of conservation concern – nest in big cottonwoods. Also, the plants that grow beneath cottonwoods are not all invasives, and include some nice native species such as Jerusalem artichoke, Virginia wild rye, and many others.
To be honest, the biggest factor that has swayed our discussions about the tree is its size. No one has really felt like tackling the job of cutting it down, so the arguments to keep it have gained the upper hand.
I guess that’ll be ok…
The Prairie Ecologist 
Fun post, Chris. I am admittedly conflicted by cottonwood in prairie. I have childhood memories of lying under a cottonwood and staring up into a sky that defines blue, with the lovely near-transluscent yet intensely yellow triangled leaves juxtaposed against that exultant background. As a child I thought that nothing could, or ever would, be more beautiful. Now, as an adult, I marvel almost as much at the subtle colors and swells of a bluestem stem, or at sideoats grama’s imitation of wash-hanging-on-a-line. And of course, intellectually I understand all the arguments against cottonwood in prairie. Yet, I still feel a terrible guilty pang each time I cut one from the bank of our tiny pond. It’s as if adulthood is destroying childhood. Now that’s perfectly silly, isn’t it?
What? No picture of the tree that helped you out?
Just my two cents…Keep The Tree!
Nice to see you show a little love for the trees.
I have ambivalent feelings toward cottonwoods. There is often a good sized tree on our local hill prairies. Stewards frequently tell me they want these cottonwoods removed. The Stewards cite the fact that “Cottonwoods do not belong here.” However, it seems the tree disagrees. An ecologist saw one of these trees and said “How did we miss that one?” It has always seemed ironic to me that someone whose responsibility is to conserve nature laments the fact they had not successfully eradicated every last individual of a native species.
When I see these tough old cottonwoods up on the hill prairies I am often reminded of Henry Cowles and his beloved dunes. I do not believe Mr. Cowles considered the cottonwood to be an invader. Instead, I think he saw the cottonwood as a stage in succession.
In contrast to the above thoughts, in a different situation I loathe the cottonwood. I am helping to restore a wetland locally. Although this wetland was formerly in agriculture, a number of species characteristic of wet prairie have sparsely appeared. The County Forest Preserves have been burning this unit in the spring. However, during spring the wetland has consistently been too wet to burn. Without fire the unburned-wet areas have quickly filled with an uncountable number of cottonwood saplings. These cottonwood saplings have shaded out the wetland species I have worked so hard to grow and plant for restoration of this wetland.
I should not blame the cottonwood for just doing what it does. I project my expectations onto nature and when it does not follow them I am disappointed. My frustration is directed at myself as much as this pioneering tree. I feel I should have foreseen that the cottonwoods would take over this area. I feel this way even though such a prediction would have been impossible to make when I decide to put effort into this wetland. I may have been able to predict the invasion of the cottonwood and its response to a burn. However, I know better than to think I can predict whether or not my county will do its part.
Reblogged this on Lyrebird Communications and commented:
A great post on how to use natural features to enhance photography. I think it is probably especially relevant for trying to photograph grassland and grassy woodland flora as we enter Spring in the Southern Hemisphere…
Trees… I am so torn about them on my property. We have 9 acres surrounded by crop land. The yard area has trees of varying types. We enjoy all the birds that nest in them, but we’re trying to keep trees to a minimum in the pasture area. Our bane is mulberry, which sprout up along the fences. Because our little “prairie” is small and the surrounding habitat is muddled, do we keep those trees up for birds here that normally wouldn’t be, or do we cut them down?
No, I am not really seeking your opinion so much, other than just sharing what we are dealing with here.
I have found the trees to be useful in photography, especially when that bird across the road is right in the sun. I am able to get in the shade of the tree to get a better photo. Or to help with lighting when photographing the flowers and their visitors.
Those are tough choices. One way you might look at things is to think about what your piece of ground can best contribute to the habitat needs in the area. If you have the only grassland in the surrounding landscape, keeping it free of trees to maximize its size and value to grassland birds and other wildlife/insects might be very valuable. If the rest of the landscape has abundant small patches of trees (in amongst the cropland) allowing a few more on your place might not add much relative value. That said, it’s your land, so if you like the trees, keep them! Good luck… : )
As usual your pictures are delightful. As for trees, I am concerned about the number of migrating birds that need trees along the Platte and trees along the Platte. My understanding is the many of these birds are very loyal to their particular woods as they migrate, returning year after year to the same spot. And also that these spots are filled and that some of these tropical migrants themselves are struggling. For these reasons, I am glad you saved the cottonwood, but I would love to know your thoughts on these arguments.
Ann
Ann – as you know, it’s a complicated subject. I don’t have the answers – just some perspective. Researchers studying on neotropical migratory birds (along the Missouri River) are catching the same species of birds (in similar numbers) in farmstead woodlots as they are in riparian forests. That might mean that those birds are more plastic in their habitat use needs than we might think. When I was in grad school, my fellow student was finding that the same breeding birds were found in small wooded areas on the Platte as in large wooded islands (with only a few exceptions) and that breeding success was similar between the two habitat types as well. More importantly, habitat management is all about objectives, and trying to balance the needs of species that use open habitats vs wooded habitats is a constant challenge. Along the Central Platte River, I think we’ve struck a pretty good balance between wooded and open wetland areas, though advocates for individual species that rely on each habitat type (as well as others, such as shrub-nesting birds) can sure argue that they are under-represented. Trying to manage a greatly altered river for all the species (not just birds) that rely on it is always going to be full of tradeoffs. We’ll do the best we can, I guess. I hope everyone keeps sharing ideas and – most importantly – listening to the ideas of others.