Diary of an Urban Watershed, Week 4 by Tracy S. Feldman Blog post week 4 (21 July 2014): It's the little things At Glennstone Preserve this weekend, I (and others with me) spent time looking for small things. We found lots of them. These little living things took the form of ants, tiny spiders, tiny iridescent green Dolichopodid flies, but also many different tree diseases (shown on the side panel) caused by tiny agents of disease (fungi, bacteria, and viruses), and perhaps even some “imaginary friends”—well, sort of. During this past weekend’s activity , we looked on a small patch of ground for as many species as we could find. I remember doing something similar during my 5th grade camping trip, and I loved it. Before then, I had never been asked to make a list of interesting things I saw, or to look at the biodiversity of a defined area (albeit, a small one). Since then, I have never stopped making lists of species I see in the different places I go, or documenting them with photographs. I love making lists, because I love when biodiversity is made apparent to me. Certainly, this exercise isn’t new. Biologists have been assessing biodiversity in small “quadrats” (square area of some standardized size) in studies for probably at least a century. Recently, this kind of technique made the news when David Liittschwager (a portrait photographer) decided to photograph all of the living things, that he could detect, that lived in or passed through a one-foot cube during a 24-hour period. He compared as vastly different landscapes as tropical rainforests, streams, gardens, and cornfields. The results are stunning—biodiversity, beautifully laid out in portrait form. Yet he found that in a cornfield in Iowa, there were only 8 living things: four insect species, one mite, one spider, one fungus, and, well, corn. Many ecologists are concerned with “homogenization” of our landscapes. We plant large monocultures (single species, or even single genetic types) in agriculture and forestry, plant lawns with primarily a single species, etc. If you are lucky, and do not take great care to homogenize it, your lawn can actually be a pretty diverse place. We found many species on the lawn by the retention pond at Glennstone Preserve—at least, we found about double that found in the Iowa corn field, looking at a smaller area. The middle of the small prairie clearing we measured wasn’t so much more diverse per area, but the species were mostly all different. On average, in the prairie patch, we probably found fewer species introduced by humans (intentionally or accidentally) from other places. Many introduced species are interspersed with the native species at the Preserve, and some, like the “Tree of Heaven” or “Japanese honeysuckle” are particularly invasive, covering large areas. Some introduced species threaten populations of native species, or if the introduced species are predators, they may decimate populations. One forest example involves introduced wooly adelgids (aphid relatives from Asia) that infect and kill hemlock trees, including those in the North Carolina mountains and at Hemlock Bluffs Nature Preserve in Cary. Some invasive/introduced species in Glennstone Preserve are featured in the photos below. Certainly, we did not detect all of the species in our respective patches of ground. We missed fungi, slime molds, worms, and insects in the soil, and we missed bacteria and viruses everywhere. Diseases are everywhere, and at least some type of disease infects each type of organism known. Plants may become infected by many diseases at once, but may tolerate them to a degree— Bitty Roy and her colleagues found that plants in the great basin did not seem to suffer from their many diseases in terms of reproductive output or survival. But it depends upon the disease. Like “war of the worlds” in reverse, many mainly introduced diseases have severely altered our forests. American chestnuts (killed by a fungus called chestnut blight) used to dominate forests in Eastern North America, and American elms (killed by Dutch elm disease) were much more common than they are today. Diseases have irreversibly changed the character of our forests. Even crazier, many of these diseases are carried by insects whose young eat dead trees. Thus, these insects, usually specific to the disease, are in a mutualism with the tree pathogens. The insects carry spores around with them and inject spores into trees with their eggs, then their babies feast on the dead tree that results from the infection. The American chestnut is still not far from extinction, as infected trees cannot reproduce. As Rob Dunn warns, any extinction (local or global) can carry with it many other species on which those extinct organisms depend. What’s more, climate warming may also cause pests and diseases to become more prevalent. Over these past weeks, I have seen evidence of diseases in the forest at Glennstone, in the form of spots on tree leaves, etc. (see photos on the side bar). There are many, and they are diverse. I hope the trees are tolerating them, and that they are not silently killing the forest… Meanwhile, managers at Glennstone are working to rid the Preserve of particularly nasty invasive species, which is a huge, never-ending job. Managers in other locations work to contain some diseases (and insects that carry them). We cannot afford to “leave our forests alone”, as humans continually contribute many factors, often unwittingly, that change our forests. This weekend at Glennstone, I tried to notice the little things. But I also found myself speculating about what the forest might have looked like a century or two ago, or even further back than that. I wondered if any of the species I’ve come to know from other places I’ve been (some like “friends”) would have lived here then. I wondered how the forests have changed, which native species have disappeared already, and which new ones (even native species) have arrived. Life always brings something new, and forces us to say goodbye to other things. I know I do not want the sorts of goodbyes brought on by extinctions. Yet some kinds of goodbyes in life come in the form of new opportunities. In particular, I’ll be moving on to other things this summer, so for now, I am signing off. Thank you for reading my blog posts. Selected References: cornstalks everywhere but nothing else not even a bee Forests Under Siege: Nonnative Insects Are Threatening Our Trees High disease incidence and apparent disease tolerance in a North American Great Basin plant community Three American tragedies: chestnut blight, butternut canker, and Dutch elm disease Rob Dunn Warns of Co-extinction of Hundreds of Thousands of Species Urban Warming Drives Insect Pest Abundance on Street Trees Links: Diary of an Urban Watershed: introductory blog post Sounds of Silence Interdependence Day Seeing the trees for the forest blog index page Tracy S. Feldman's page

Natural history photos by Tracy S. Feldman.

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Last updated July 2014
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