Do fires save water?
By Carol Flaherty, MSU News Service
|"Marlow has come to suspect that fires also are necessary for the health of streams and riparian areas."|
Beautiful moments become associated with the places in which they occur. So we love the grove where we first noticed the spicy smell of fall leaves. We have a special fondness for the hillsides we hiked during our first years of exploration. We feel comforted by the look of favorite places and don't want them to change by fires, floods or other acts of nature.
But allowing our favorite spot to change -- perhaps to be "ugly" in a classical sense for a few years -- may be necessary for its long-term health, says Clayton Marlow, professor of range sciences at Montana State University and a researcher of stream-side or "riparian" ecology.
"What we as a society have to do is to learn to live with the ebbs and flows of nature," says Marlow. "Change is the rule. If anything is unnatural, it's trying to freeze nature at one moment."
Just as people have come to value fire for its ability to regenerate different stages of vegetation, Marlow has come to suspect that fires also are necessary for the health of streams and riparian areas.
He has begun to think that in addition to the rhythms of forest and fire that have been talked about so much since the Yellowstone Park fire of 1988, there also is a rhythm of forest, fire and creek, where lack of fire leads to too many trees that then may decrease nearby stream flows.
Marlow says his idea that fires are essential for stream flow cycles started with a puzzle and a U.S. Forest Service research report. "We've been trying to improve the health of riparian areas long enough now that we should be seeing results, but they're only recovering to a point, and it's been perplexing me. Why can't we make more advances?
We've greatly reduced logging and cattle, and still don't see the rebound of riparian areas as we had hoped."
The Forest Service report was one he was reading a few years ago. He said he noticed that as conifers encroached and timber stands increased, the data showed that stream flows decreased.
"I wondered if we could be costing people their livelihoods in the timber and livestock industries and actually be doing harm to riparian areas we were trying to help. Maybe periodic fires aren't just needed for vegetative renewal but are also needed for refilling stream and groundwater flows."
To find out, Marlow enlisted several people: Blair Stringham, an MSU Agricultural Operations Technology teacher who has designed monitoring equipment, Kevin Ettinger and Dave Patcheretti in the Whitehall Bureau of Land Management and Mitch Maycox and Jennifer Walker in BLM's Central Montana Fire Zone office. He also has guided two graduate students toward research related to the question. Chris Wood from Las Cruces, New Mexico and Travis Miller of Burns, Ore. have two years of studies related to the effects of up- land fires on valley creeks and wildlife movements. Wood is looking at the movement of wildlife through burned areas in the Missouri Breaks area of Fergus County. Miller is assessing five different methods of monitoring stream ecosystems using a proposed controlled burn site northeast of Whitehall.
"It's hard for creeks to flow in Montana," says Marlow. He explains that creeks have to overcome at least three major obstacles in order to have a continuous flow of water. One obstacle is Montana's cracked and tormented bedrock. It often takes creeks for a dive underground. The second is the most obvious: our arid environment limits how much water is available to recharge creeks and ground water. The third circumstance is the topic of Marlow's current research. Early results suggest that increasing numbers of conifers like juniper and ponderosa pine are soaking up more than their traditional share of moisture.
"Basically, what we think is supposed to happen is that conifer seeds and ultimately seedlings move downhill over time. Fires chase the conifers back to the rocks, the streams recharge, and the whole process starts again. Perhaps we need the fires to get enough water to keep the streams flowing," says Marlow.
But how can we tell for sure the effect of geology, limited precipitation and increasing conifers? It will be hard to tease those influences apart, but Marlow and his team have made a start. In the Whitehall area, they have selected two drainages that are similar, though the geology isn't known in detail. The Pony and Hay drainages feed Whitetail Creek. Their complex geology includes sandstone from an ancient lake, fractured granite and many feet of ash from volcanoes, uplift of the land and several periods of erosion by wind and water.
The research team has laid out stream flow monitoring sites on Whitetail Creek and hopes the public and federal authorities will allow a controlled burn next spring of what is mainly juniper on the hillside above. If so, they should be able to see whether the reduction in juniper increases the water in the creek below. The proposed burn areas have been carefully selected to form a pattern that saves sagebrush for grouse and browse for larger wildlife.
Marlow says the comparison of the effects of fire in both Fergus and Jefferson counties should be a good start on the issue. So far, two of the four selectively burned Missouri Breaks drainages have higher groundwater levels than other unburned counter parts, even though the area continues in drought.
Such controlled burns, carefully leaving patches of vegetation, don't seem to be a problem for elk and mule deer, says Wood, who has monitored the wildlife movements in the Fergus County burn area. "The burn is very small compared to the overall site available to wildlife," says Wood. "It created a nice mosaic of scorched areas, heavily burned areas and unburned areas. So far, based on pellet droppings, there doesn't seem to be any kind of preference or avoidance of scorched, burned or unburned areas, but that may change next year when the forbs become more abundant in the second year after the burn."
Wood says hunters often prefer burned to unburned areas, because the post-fire flush of new forbs and grasses attract deer and elk. The proposal to selectively burn parts of the upper hillsides of the Whitetail drainage northwest of Whitehall still needs to be reviewed by the BLM and public hearings are expected on the proposal this winter.
Marlow thinks that recharge in only two of the four Fergus County burn sites may indicate that either the stream beds simply need more time to recharge or differences in the local bedrock limit groundwater responses.
If conifer encroachment is reducing water recharge, it would be important in much of While we usually hear about deforestation in the Amazon and logging in the northwest United States, studies have documented increasing conifers cover in many areas, including Montana. One USDA compared photos from 1918 to the present, and another such study used military photographs taken on a 1870s expedition led by George Armstrong Custer to photographs taken about a hundred years later. These photo comparisons show increasing conifer populations. Conifers use considerably more water than deciduous shrubs and forbs, says Marlow, because they are physiologically active for longer periods. While all plants give off moisture they grow, deciduous shrubs and forbs generally "transpire" this moisture during a short spring/ summer growing season. In contrast, conifers give off moisture nine months a year, roughly from through early November, says Marlow.
Conifers are beautiful, as are babbling brooks, fields of grass, arrowleaf balsam and other of Montana rangelands. If Marlow is right, it may that we simply must take our time and see a our favorites on one excursion, and others a few later.
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