Rim Country Land Blog

From our February Newsletter. For photos, check out “winter burrows” set on http://www.flickr.com/photos/rclimontana.

Prairie Soils in Winter

Winter is a tricky time for hiking on the prairie; it seems like the soil is either covered in snow and ice or the surface has melted into a sloppy prairie gumbo. Voles and pocket gophers and any number of other species in the subnivean zone make the ground even more treacherous, the ground uneven and pock-marked as a result of their digging. But these activities, both of weather and of animal species, are an important part of prairie ecology, especially when it comes to aerating the soil.

As for weather, you may remember learning in school about erosion of rocks caused by physical weathering. (For those who don’t, physical weathering is the action of physical forces, i.e. pressure, on rocks over time, which leads to erosion, i.e. the breakdown of bigger rocks into smaller rocks). Moisture is a big component of this erosion, as water seeps into cracks in rocks and then expands when it freezes, widening the crack and eventually breaking the rock. This same freeze-thaw cycle breaks up soils, as well, breaking them apart to making space for pockets of air and water that are needed for plants to grow. In fact, this freeze-thaw impact is one of the primary ways soils are aerated.

The small mammals that burrow into the soil are a more visible disturbance in the winter soil. When the snow starts to melt, as it does multiple times in a single winter, you can see the remains of these “vole highways” and pocket gopher casts. The small mammals take advantage of the insulating snow above and dig tunnels at the edge between the soil and the snow, which is often warmer than either the air above or the ground below. When the snow melts, these trails act as low points and collect water. Pocket gopher casts are clearly a way for soil to be churned up. They burrow underground for food and pack the dug-up soil into snow tunnels. When the snow melts, a negative of the tunnels remains in the form of dirt.

Especially on overgrazed rangelands, these actions are important to breaking up soil compaction and helping in the return of native plant species.

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I took a walk this week to both test out the baby backpack (success!) and celebrate the sunshine and above zero temperatures. The prairie dogs were out doing the same, at least the latter, and I got to watch one of them doing the “jump-yip” motion/call before they all started to run and bark and crouch in the entrances to their burrows as they usually do when a human approaches. In the town itself was plenty of evidence of other species taking advantage of the shelter of old burrows, plenty of small mammal tracks leading to the older holes. Snow covered the entrances of these almost completely but for a hole just large enough for a mouse or vole.

I walked across the town to check a gully where for the previous two Februaries I have seen a pair of owls. While there were no owls in sight, there was plenty of evidence. Thick white drips of scat like dried plaster coated and hung from the underbrush beneath two old, gnarled Ponderosa, perfect for perching. An oddly-colored stick turned out to be a piece of broken bone, maybe 1.5 inches long and split lengthwise, a bit of red left in the exposed cavity. At the second perching tree, burned at the roots but still green on top, the scat was splattered across rocks. And here were a few cough pellets! I stuck them in my coat pocket for later dissection but was surprised at how big they were and also how fragile and lightweight. I also readied myself for smart comments from the husband about always bringing home pockets full of animal scat All of this could also be from a hawk, and I’ll have to learn more about the differences, but at the moment I’m going to stick with owl.

It seems that once something catches you and you begin to look, the whole world opens up and every broken branch and shadow in the snow starts to speak to you. Such was the case with the owl sign, as all of the sudden I was seeing patches of hair stuck among juniper branches, pine boughs whittled to sharp points by a wandering porcupine, sumac bushes bashed apart by frustrated buck mule deer in rut (I can just imagine the scene: an amorous young buck is in the mood for a challenge, any challenge, and spies a suspicious-looking shrub. Predictable, bar-room dialogue ensues–”what are you looking at, shrub? Hah, you’re not even half the size of that chokecherry over there. And it’s no wonder they call you ‘skunkbush’ with the way you smell. Take that! And so on…) And the tracks, of course, everywhere: deer, voles, elk, magpie, coyote. The underside of a sandstone slab had tracks of another kind, those of minerals left behind by seeping water and the minerals collected on the way, a green cast to the white salts.

owl urine splattered on underbrush

precipitate salt on the sandstone

A good February walk, returning just as the sun and the temperature began to drop.

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