A Wetland of Black and Green

DSC_0145This blog entry is about my visit to Rossow Prairie in Webster County, and the apparent aftermath of a fire there.

“But Paul,” you say. “Isn’t this blog about wetlands? Why discuss fire??” Because, fire CAN be important in wetlands! Most famously, the amazing wetland landscape of south Florida known as the everglades, or the northern peat bogs, have regular fires…and the biota of those wetlands (including humans) have had to adapt to the effects. The Association of State Wetland Managers has a nice review.

Unlike the landscape-level wetlands like the Everglades or the vast northern peatlands, Rossow is a small slough wetland in a larger tallgrass prairie landscape. The prairie is, of course, a fire-dominated (fire-dependent!) biome. Iowa’s prairies always burned, and the wetlands within them—marsh, slough, fen, whatever—would have certainly burned, too.  But how does a prairie fire compare to a wetland fire?

DSC_0151
Last year’s blackend stems and recent, green growth

The similarities are actually quite striking. Prairies and these wetlands are both dominated by tall, herbaceous plants, especially grass-like “graminoids” and are dominated by perennials whose roots (or underground stems) would send up new shoots after a fire. The soil is unlikely to burn hot—usually only the very surface burns. Seeds in the soil can germinate in the open, sunny ground after the burn. The soil gets a boost of available nutrients: chemicals previously locked up in plant tissues are now released into the soil through the ash.

Plants have less competition after a burn…fires opens up the space, knocking back the dominant species (at least for a while, perhaps). Wetland managers concerned about weedy plants may use fire as a tool for weed control. Woody plants for example can be invasive in these habitats, but fire is hard on them especially (their active growth tissues are vulnerable to heat damage). So, “woody encroachment” may be lessened after fire.

 

 

The fire in this wetland is a “spill-over” from a fire set intentionally by the land managers in the adjacent uplands. Matt from the County Conservation Board mentioned their use of so-called “prescribed burns” as a tool in the prairie, for some of the same effects I just described for wetlands; and the fire moved into the wetland, potentially giving those very benefits to our slough. Cattails (Typha) in particular tend to dominate a shallow-water wetland such as this, and perhaps other species will fare better after this fire.

Time will tell. The site is undergoing improvements to the water-control structure; such infrastructure is vital to managing a system, but must be maintained or repaired from time-to-time. But for now, I saw a more open marsh, and it is verdant in the extreme. Hard-stem Bulrushes (Schoenoplectus acutus), sedges (Carex) and wildflowers like (possibly, Swamp) Milkweed (Asclepias incarnata??) were starting to come up and were a vibrant green. Birds such as Marsh wrens (Cistothorus palustris), Red-winged Blackbirds (Agelaius phoeniceus), and Common Yellowthroats (Geothlypis trichas) flitted about and scolded me as I sloshed about. A local resident who chatted with me as I was leaving, mentioned that he enjoyed the variety of waterfowl he has observed at the site.

 

 

If I return to this site, will I see more of these species, or perhaps others? How would the biota recover from this type of disturbance? How would the fire effects be different in this late, cold, wet spring in this part of Iowa? So many “burning” questions! Feel free to leave your thoughts in the comments. Thanks for visiting…

 

Author: Paul Weihe

Associate Professor of Biology at Central College, traditional author (Textbook of Limnology, Cole & Weihe, 5th ed.; Waveland Press), and now...blogger!

2 thoughts on “A Wetland of Black and Green”

  1. Even though the deliberate use of prescribed fire in wetlands is relatively recent in Iowa, after many decades of general fire suppression, we now have significant experience and information. I hope that information is being passed along as experienced land managers retire, which is happening more and more.

    I’ve heard a few talks and seen presentations indicating that in some other parts of the country, including the tallgrass biome south of Iowa , some land managers have found that summer fires are more effective against invading woodies, in general, than spring, fall, or winter fires. Of course summer fires would have impacts on other biota. We are seeing a lot of woody invasion in Iowa prairie/wetland complexes, however, and maybe summer fire is an option that should be considered(?) Is it already being tried?

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    1. I haven’t heard of fire use being commonly used in Iowa…or elsewhere, actually. Fire would be most common in fall perhaps and the high water in spring to “drown” unwanted plants. But perhaps others could chime in too??

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