Neighbors in the Field

One of my favorite aspects of fieldwork happens to be the same component that makes ecological research so challenging: you are not working in a controlled environment. This means that you never know what--or whom you may run across on any given day.

Yesterday, my colleagues and I conducted a soil collection at a location designated for a new addition to our monitoring network. The purpose of this soil collection is to calibrate the instruments we will use in relation to the exact soil type at the site. Because soil type and texture influence how tightly water is held in the soil, readings by the same instruments can vary slightly depending on where in the ground the readings are taken. Calibrating the equipment to soil from your exact location helps to account for those differences when you later analyze the data.
Once the calibration is complete, the soil is returned to its original hole. It is especially important to return the samples to the hole in the correct order if soil type varied by depth. At one location where we collected soil yesterday, soil became progressively more sandy as we dug down, and the difference between the dark, soft soil near the surface and the light, sandy soil at 20 inches (50 cm) was quite striking!

During our soil collection we did not see much wildlife, but evidence of one particular neighbor in the field was quite evident, as we walked to and from our sites. Black bears (Usus americanus) are quite common in the Roaring Fork Valley, and we were not surprised that many of the aspens in the study area were marked with numerous gouges from bears, some of whom had clearly been climbing the trees. What did give us pause, however, was how very new many of the markings were--so new in places, that the raised wood was still light in color and splintery.  Additionally, we found multiple piles of fresh bear scat in a range of sizes. (It seems that service berries are good eating up there.) These clues that we may be working in an area favored by the large, furry locals offered an important reminder to remain alert at this, and other, sites.

We'll be back to these new site locations in a few weeks to install the climate and soil moisture stations, and we'll be sure to share any special signs or sightings of our neighbors.

On the Learning Trail

The Viewline Trail. Credit: AGCI

This time of year is a beautiful season for field work. We have been visiting our monitoring stations for their spring check-ups and updates, and we've been generating all kinds of questions about the natural world along the way!

Visting the Brush Creek station at the end of June, one of the first things I noticed was a small gang of ground squirrels basking in the dust of the pull-off from the road. I had suspected all winter that voles were the ones eating our wires, but it looks like there may have been competition in the rodent destruction department. So far, the new piping we buried in the spring has kept rodent visitors of all species out, though, and we're keeping our fingers crossed that this prevention method will continue to be successful.

Evening Primrose. Credit: AGCI

Coming down from the Sky Mountain station the following week, we spotted a mammal of a different kind. At the junction between the Ridgeline and Viewline trails, an ermine, also known as a short tailed weasel, paused to cast a glance our way. This ermine was sporting its summer color--a dusty tan.

Summer colors were in no shortage that day. The wildflowers were in vibrant bloom, and along the purple lupine edged trail, we stopped to take photos of some other wildflowers that neither of us recognized by name. One of our favorite discoveries was a white flower we later found to be evening primrose (Oenothera casepitosa). The distinctive nature of this white flower made it easy to identify in a search: its large petals were notably heart-shaped. Even more remarkable, however, was the manner in which the flower altered over the course of the day. In the morning, when we hiked up the trail, the flowers looked fresh and in full bloom, but by mid-day, when we hiked down, the flowers looked wilted and crumpled.

Tent caterpillar. Credit: AGCI

Even at the monitoring site itself we found a few moments to spare for curiosity. A furry caterpillar with a bright blue back and a row of white spots found its way on to a wrench. Research revealed it to be a forest tent caterpillar--and a potential threat to aspen trees. We delved further in our inquiry and asked the folks at Aspen Center for Environmental Studies about tent caterpillars. They reassured us that these insects are generally a threat to host plants only if other severe stressors already exist.

These types of learning experiences are one of the best parts of field work, in my opinion. They also help to inform the research we are conducting in an indirect way. The primary purpose of our monitoring sites is to shed light on the dynamics of soil moisture in a changing climate. In ecology, however, each component of the system interacts with the other components around it. The soil moisture helps determine which plants can grow in an area, and these plants in turn dictate the likely fauna of the region. The biotic and the abiotic factors of any ecosystem are intricately intertwined. As a consequence, keeping a weather eye open for changes in timing and presence of a natural event or species can prove helpful in creating a broad understanding of the ecosystem being studied. There is an even subtler benefit to this type of inquiry as well though. Curiosity is the driving force behind science, and by taking the time to ask questions and peer at flowers, two researchers at least are feeding the wonder that keeps them working in this field.

Muddy Waters Don't Always Mean the Blues

Meeting of Frying Pan and Roaring Fork Rivers after a heavy rain. Image Credit: John K., 2015

Rivers running red may sound ominous, but in the Roaring Fork Watershed it is a common spring phenomena. Heavy (or persistent) rains wash the red, iron-rich soil from steep areas of the slopes surrounding the Frying Pan into the swift-flowing waters of the river. This sediment laden water is carried downstream to Basalt where it joins the also high-flowing Roaring Fork River, creating a striking visual at the confluence.

That there has been a lot of erosion in the last few days is no surprise. Over the last week, all of our soil moisture stations showed over .95 inches of rain, with the Brush Creek station (near Snowmass Village) and Glassier Ranch station (near Basalt) showing as much as 1.39 inches in a single week. Between .8 and .9 inches of that rain fell in just 24 hours. To put that in scale, the Roaring Fork Valley receives only 16-19 inches  of precipitation on average per year. Last year, the most rain falling in a single 24 hour period was around .8 inches. Last year, such deluges did not occur until late summer.

In the arid state of Colorado, a good soaking is generally considered a good thing. What this heavy rain in early May means for water availability during the rest of the growing season is, like the Frying Pan, unclear. The rate at which soil dries depends on a number of related factors including air temperature, humidity, and plant water use. Consequently, weather conditions over the coming months will play a big role in how long this moisture sticks around in the soil. 

So far, this week's rain has raised soil moisture by the notable amount of between 7 and 10% at our sites at a 2 inch depth. Soil moisture at the 8 and 20 inch depths has only risen by between 1 and 2% so far, but as water from the shallow depths has time to percolate, these numbers may rise further.

As we continue to move toward summer, collection of data from the research sites will help to illuminate the relationship between precipitation, temperature, and soil moisture. In the meantime, the vegetation shows its response to the rain by making the valley look especially verdant and bright.

Data from the Smuggler Mountain Site from 4/30/15-05/07/15. It is important to note that the scales of water moisture are not consistent across the three graphs. As a result, although all lines visually appear to rise by similar amounts, the 2in depth is actually showing a much greater increase numerically. Image Credit: AGCI, using Hobolink data collection and graphs.

The Trouble with Voles

Meadow Vole, side view. Image Credit: Japanese Tea, Wikimedia Commons

These wee, furry beasties are cute enough to look at. Voles belong to the order Rodentia and are similar in appearance to a short-tailed version of their relative the mouse. Some species, including the prairie vole, mate for life. With an average length of 5-6 inches, they are just about the right size to fit in the palm of an adult's hand--not that handling a wild rodent is ever recommended. Five different species of vole can be found in the Roaring Fork Valley alone (Huggins, 2004). They feed on seeds; grasses; forbs; fungi; and, apparently, wires.

Thus we come to the trouble with voles. They are not friends to long-term monitoring, at least not to the sensors that gather data. We suspected a threat might be crouching on the horizon last August when we noticed numerous holes dotting the ground during a siting visit for one our soil moisture and climate monitoring stations. During the installation of the site, suspicions were confirmed when I saw a small, brown shape shoot from one hole to another. It was a vole.  I did not get a clear enough view to say which of the Roaring Fork's five species graced our site with its presence, but I did see enough to know that rodent presence in the area might be a challenge to our data collection.

Right from installation, any exposed wire at the site was wrapped in reflective tape, a common method for deterring rodents. After the one sensor became damaged at the start of winter, I secured the remaining sensors in an additional 5 five layers of the aluminum tape.  The resulting bundle was as wide around as the pvc pipe used to protect the wires stretching from the tower to their monitoring location location. This measure was only sufficient until the end of winter. Last week, we made a repair visit to the site and found a pile of small rolls of aluminum tape  that had been plucked from the wires and flung about a 2-foot diameter radius in little, chewed-upon balls. In addition to removing the protective tape from the exposed section of wire, the voles had pulled a greater length of wire out of the PVC pipe to access further surfaces for chewing. The wires themselves had been completely chewed through. It was both distressing and impressive.

Science loves nothing like a challenge, however, and we were game for this one. Having preemptively armed ourselves with piping elbows, lengths of unused pipe, duct tape, and reflective tape, we removed the damaged soil sensors and replaced them with new equipment--now protected by an elaborate system of piping that descends underground to a depth of over 6 inches. 

By the end of the afternoon, storm clouds were beginning to scud in, bringing with them a biting wind. But before the rain and chill drove us out, we were able to burry new sensors (now successfully gathering data) and collect the damaged sensors for later repair. Previous splicing experience will soon be put to the test as we attempt to salvage our vole-ravaged wires.

Stringing the wires from the hole to the logger tower. Image Credit: AGCI, 2015

Sometimes research looks like a calm lab technician in a white coat surrounded by spotless beakers, sometimes it looks like someone intent on a computer screen running data through a newly designed modeling system, and sometimes it looks like a person lying on her stomach in the soil and spikey grass, taping wires with muddy fingers. All of these scenarios represent the earnest endeavor to better understand how this world works and the ways it may be changing over time. The one scenario we hope science does not look like any time soon is a charming little rodent with its mouth full of wire.

Reference:

Huggins, Jain Lindsey. 2004. Wild at Heart. WHO Press. Basalt, CO.

2015 Year of the Soil!

Soil profile at Brush Creek. Image Credit: AGCI, 2014

It's official, this year is the year to dig your hands into the dirt!

The Food and Agriculture Organization (FAO) of the United Nations has officially declared 2015 the "International Year of Soils." The humble earth beneath our feet is receiving this recognition for a variety of reasons. Soil is the foundation of all plant life on Earth (literally!) from the foods we eat, to the flowers we admire, or the forests that become timber to build tools or homes.

Soil plays a critical role in non-living systems as well. It filters and stores ground water, it interacts with the atmosphere and it can play a role in the warming (or cooling) of microclimates.

While all soils serve a similar purpose within their ecosystems, soil is incredibly diverse. Soil comes in a variety of colors, textures, and chemical compositions. Different soils also have their own individual arrays of bacteria.

Here within the Roaring Fork Valley, some of this diversity is evident even from a distance. Traveling from Glenwood Springs to Aspen, the soil undergoes a visible change from the bright red, iron-rich soil near Glenwood to the more muted brown tones of the soil up near Aspen.

These soils differ on a less-visible level as well.  Among the four study sites that currently comprise the Roaring Fork Soil Moisture Network, there are clear differences in soil texture and composition.

At Smuggler Mountain, the soil is a slightly acidic, loose loam (a mix of sand, silt, and clay) with less than 1% organic matter. It's low in nitrogen, but high in phosphorus.

At Sky Mountain, by contrast, the soil is also a loam, but it is less acidic and more densely packed. The organic matter is much higher--around 11%, and it has more nitrogen available than phosphorus.

The Brush Creek site, a meadow, is very different from the two forested sites. It's classified as clay and is nearer to neutral pH than the other two sites. Its organic matter content is around 7% and its nitrogen and phosphorus availability are close to one another.

Glassier, which is something of a wetland in the summer, is a sandy loam, and near the surface, it is near neutral for pH and has a high phosphorus availability and 33% organic matter.

The differences in the soils is both driven by and drives the type of plants that live in these areas. For example, at Smuggler Mountain, the low nitrogen availability may limit what types of plants are able to establish and succeed in the area. Meanwhile, the fact that the dominant vegetation in the area are conifers likely contributes to the acidic nature of the soil. (Needles from conifers tend to lead to acidic soils when the decompose.)

Soil is an important determinant in the type of ecological communities you find, no matter where you go on Earth--and the relationship is reciprocal. So what does the soil like where you live? 2015 is the year to find out!

Digging in at Brush Creek. Image Credit: AGCI, 2014

Goodbye Field Season, Hello Data Analysis

A newly installed station. Image credit: AGCI, 2014.

It's been a busy summer here on the soil moisture front! Since March, two new soil monitoring sites were scouted and tested, and two new stations are now on the ground, courtesy of Pitkin County Parks and Open Space!

Both of the new stations differ slightly from the two previous stations. The existing stations, at Smuggler Mountain and Sky Mountain, are sited in relatively undisturbed natural areas. The two new stations, by contrast, are both sitting on heavily disturbed land--land that has been altered from its natural state by prolonged human activities. The Glassier site overlooks the Roaring Fork River from a riparian zone on a former ranch, and the much of the surrounding property will still be used for agricultural purposes in the future.  The Brush Creek site is in a high mountain meadow formerly used for grazing. The Brush Creek meadow is currently dominated by an invasive species of brome grass that was commonly planted by early ranchers in the Roaring Fork Valley because it is good for grazing.

Observations of site hole. Image credit: AGCI, 2014.

The property at Brush Creek is currently owned by Pitkin County Parks and Open Space and is under consideration for some form of restoration to a more native species composition. The soil monitoring station at this site, therefore, has a few extra sensors installed: there are soil moisture probes located at 2in, 8in, and 20in depths both immediately below the tower, and 50 feet away. The intention is that one location will serve as a control and the other location will serve as a variable site once restoration begins. In this way, we will be able to observe what impact a change in dominant plant species may have upon soil moisture.

Another new addition this summer is the variable of soil temperature. Soil temperature probes have been included at both of the two new stations, added to the station at Smuggled Mountain, and will be soon added to Sky Mountain site as well.

Installing a soil monitoring and weather station is a multi-step process.

The first step is site selection. Ideally, the ground should be relatively level, soil moisture of the exact site should be comparable to other soil moisture readings taken nearby, and it needs to be high enough above any local rivers or creeks that high spring flows won't flood the area.

Conducting a perc test. Image credit: AGCI, 2014.

The second step is to conduct a percolation test and collect several gallons on soil samples.

Then, the soil samples have to be dried and sifted to remove large stones or clods. The dried soil is used to calibrate the soil moisture sensors to make certain that they are functioning properly before we put them into the ground.

Once the equipment has been tested, it's time for an installation! The tower must be erected and the sensors attached or inserted into the ground. After everything is grounded, attached, and plugged in comes the tense moment of checking the online database to make sure that everything is operating properly.

After the installation is complete, that doesn't mean that site visits are done. Equipment has to be checked periodically, and site visits can help build background information about any changes that are occurring at the site in terms of plant composition.

There's still work to be done back in the office as well! The months where it is too snowy and the ground too frozen for us to do site installs or updates are "data season" back in the office. This indoor time is used to look for interesting relationships in our data and to conduct background investigations on soil moisture research being conducted elsewhere.

If you want to take a look at some of our existing data yourself, visit the iRON's Downloadable Data page.

Thinking About Thaws

I can hardly believe that the end of March is upon us already. That being said, I feel ready for spring weather.  March in Colorado often feels like a temperature toss-up, with some of us ready for spring to look like this:

Pansies. Image Credit: Amy Rice

Although in the mountains, spring more often looks like this:

Snow near Glenwood, March 2011. Image Credit: ECO

As ready as I am to thaw out my own chilly limbs, however, an early spring thaw isn't always a good thing in nature. Timing of thaws and snowmelt have impacts that last throughout the entire summer, long after the last of the snow has vanished. Some animals, like the wolverine, produce their young at the end of winter and need a lingering snowpack to insulate their dens and keep their young warm until air temperatures rise. Snow depth and date of snowmelt have broad impacts too, though, spanning the entire watershed.

Snow offers a form of water storage. It also keeps the ground underneath from drying out early in the spring. Once the snow melts completely in the spring, water begins evaporating from the ground as temperatures rise, and soil begins drying.  A deep snowpack saturating the soil in early spring creates an important moisture base to provide plants with water until the next heavy summer rain event. If you look at the graph below, showing rain events and soil moisture at three depths for the 2013 growing season, you can see that rain events--even big ones--rarely soak into the ground enough to have a large impact on soil at the 20 inch depth. This means that for the deeper soil layer, the amount of snow that soaks into the ground in the spring may determine moisture availability for the entire season. How saturated the soil becomes in spring also determines the base moisture amount for the 2 and 8 inch depths, although a heavy rain mid-season can help replenish soil moisture moisture at the shallower depths.

Soil Moisture at 3 depths and temperature for the 2013 growing season. Image Credit: AGCI.

Because snowmelt plays such an important role in soil saturation, the snow water equivalent (how much water you get if you melt the snow) on April 1st is sometimes used as an indicator for how much water will be available later in the year. If the snow melts rapidly or there is not much snow, then it may run off early or evaporate rather than soaking deep into the ground. This can have impacts for the entire water table, and thus for water availability in our streams and rivers.

Below is a graph showing the snow water equivalent on April 1st for an Independence Pass SNOTEL site in Colorado. The graph was created by AGCI for the City of Aspen using data from the National Resources Conservation Service. There has not been a strong trend in snow water equivalent since 1981.

Snow Water Equivalent on April 1st on Independence Pass in Colorado. Created using data available through NRCS.

Snowmelt date and snow depth also influence the risk levels for the fire season. The earlier the soil dries out, the sooner the fire season begins. Drier soil means less water available to plants. It also means warmer ground temperatures because when soil is dry, is is less buffered against temperature change, so it heats more quickly if the air temperature is high. This past winter we were up above 100% snowpack. With the combination of cold temperatures and deeper snowpack, the soil has thawed later than it did last year when the winter was dry.

The two graphs below show data from our Sky Mountain soil moisture station for this year and last year. You can see that soil moisture at the 2 inch depth thawed over a week later in 2014 than it did in 2013 (March 9th vs. March 1st, respectively). The thaw is visible as a sudden spike in soil moisture. The 8 and 20 inch depths that later in the season. Last year, the 20 inch depth began thawing around April 1st. As of April 1st this year, the 20 inch thaw has yet to happen. These graphs also reveal that the soil is starting out the spring with a higher moisture content this year than last year.

Soil Moisture data from Sky Mountain, Colorado. Image Credit: AGCI

In addition to the amount of snow we get each year, timing of runoff (the time of year when river flows are the highest) impacts human activities. Low snowpack, warmer temperatures, or a combination of both can lead to earlier than usual date of peak runoff. Farmers, hydro-electric plants, even municipal users also have ebbs and flows in the timing of when they use the most water, so timing of peak flow can be important to farmers, city planners, and others.

Changes in snowmelt timing also impact phenology: the timing of events in the natural world. Ecological impacts of earlier snowmelt are still being investigated by scientists. Warming average air temperatures across the globe (and here in the Roaring Fork Valley) may lead to snowpack melting sooner in the season. Once the insulating layer of snow is gone, and thaw begins, some plants to begin grow, even if the date is earlier than it has been in previous years. Of flowering plants that have been studied in the mountains, some begin growing and blooming earlier in the season as a response to early snowmelt. Others sprout from the ground earlier, but still bloom around the same time. Some flowers don't even begin growing early at all. 

The timing of plant bloom, seeding, and growth is important to the survival of animals that eat them and, indirectly, the carnivores that eat those herbivores. As a result, a shift in timing the timing can have ecological impacts that move from plants all the way up the food chain.

Snow may be an inanimate object, but its role in providing insulation and soil moisture have widespread consequences for the plants and animals living in this valley.