Hubbard Fellowship Blog – The Sky is My Mountain

This post was written by Eric Chien, one of our Hubbard Fellows.  Eric comes from Minnesota and brings great energy to our prairie stewardship work.  He’s also very bright, and an engaging writer, as you’ll see in this and other posts.

The sky is my mountain. I recently heard Jeff Walk from Illinois Nature Conservancy articulate this notion of prairie geography. If westerners are defined by their mountains, those of us from the Midwest and Great Plains are defined by our skies. Prairies are open horizons. Even on the most heavily plowed landscapes, the ghosts of prairies loom as long as the land stretches toward an expansive sky.

Sky

Flat land compensates the viewer with tremendous skies.

All landscapes affect the prejudices about comfort and beauty of those born to them. I know someone who moved to Minnesota from the West for a job and was gone within the week, overcome by the flatness of the land. That might be a little dramatic, but I can understand the uneasiness. For me claustrophobia and paranoia rises in deeply wooded landscapes that lack the promise of a lake or field offering a glimpse beyond the trees. I think we all have that affinity for particular aesthetics to some degree, and because of that I think we can all empathize with the plight of prairie wildlife.

Unlike humans, most prairie wildlife lacks the flexibility to adapt to the uneasiness brought on by changes in their natal landscapes. Prairie chickens may be the most well known of the prairie wildlife terrorized when the land loses the sky, but they are almost certainly not the only ones. One needs only to watch the predatory efficacy of hawks and owls from their perches high atop the crowns of trees to understand why the development of tall vertical structure results in the extirpation of prairie species. There are more trees than ever closing off the sky, threatening to fundamentally alter the ecology, composition, and aesthetics of our prairies.

Historical records from the mid-late 1800’s in Nebraska’s Lower Platte River Valley (to the east of our Platte River Prairies) suggest trees occurred as widely scattered individuals and small clusters; a far cry from the ubiquitous shelterbelts and heavily wooded groves that cloak what almost certainly was formerly prairie. Trees and the changes they have already wrought and continue to promise are why most of our field season at the Platte River Prairies has played out to the whine of chainsaws.

The small row of trees on the horizon may seem insignificant, but the removal of those trees would visually reconnect three chunks of prairie; potentially having pronounced effects on grassland bird nesting occurrences and brood rearing success. Photo by Eric Chien.

The small row of trees on the horizon may seem insignificant, but the removal of those trees would visually reconnect three chunks of prairie; potentially having pronounced effects on grassland bird nesting occurrences and brood rearing success. Photo by Eric Chien.

 

I am haunted by trees. Back on June 8th, Katherine and I picked up chainsaws and walked into a grove of cottonwoods along a creek bottom. On September 23rd, another 10ft tall Siberian elm twirled to the ground. In between, we spent hundreds of more hours felling, bucking, and stacking trees. Always to the backdrop of more deep green tree lines on the near horizon; a reminder of how far trees have come, and how far prairie stewards have to go.

Katharine Hogan (Hubbard Fellow) wields a chainsaw

Katharine Hogan (Hubbard Fellow), technician Calla Olson, and I spent several days extracting a row of large twisting mulberry trees from between two stretches of fence. Photo by Eric Chien

Looking down the fence line of this tree removal project illustrates the process. Sawyers fell, limb, and buck trees, while a tractor follows behind and piles material into burn piles within the interior of the prairie. Photo by Eric Chien

Looking down the fence line of this tree removal project illustrates the process. Sawyers fell, limb, and buck trees, while a tractor follows behind and piles material into burn piles within the interior of the prairie. Photo by Eric Chien

The most time intensive portion of tree removal, and thus limiting factor, is the organization and removal of downed tree material. Left on the ground, mature trees rarely burn up well in prescribed fires, and the skeletons impede maneuvering within the area during future management actions. Photo by Eric Chien

The most time intensive portion of tree removal, and thus limiting factor, is the organization and removal of downed tree material. Left on the ground, mature trees rarely burn up well in prescribed fires, and the skeletons impede maneuvering within the area during future management actions. Photo by Eric Chien

Despite the specter of an advancing forest, I love tree cutting. I like to think of tree control on the prairie as the big game hunting version of plant management. Removing mature trees demands thorough planning, and constant attention to one’s surroundings.  To date, I am not aware of an incidence of death by reed canary grass. Put that focus factor together with the fact that there are few prairie management activities with as immediately noticeable impact as the removal of dramatic woody encroachment, and it is a task ready made for those of us brain dead from spraying, and still cultivating patience for observing the effects of our work. Walking through a completed tree removal, or thinning, noting the full sunlight, and the unrestrained wind, gives me the same feeling as looking at a maturing prairie restoration. I think in many ways it is an equally profound change in the land; a taking back of the sky, and a return of a prairie.

Prairie Word of the Day – Habitat Heterogeneity

Do you know what time it is?  It’s time for another PRAIRIE WORD OF THE DAY!

Today’s Prairie Word of the Day (fine, it’s actually two words) is:

Habitat Heterogeneity

Heterogeneity is really just a longer word for Diversity, which is another way of saying “lots of different things”.  So why use the word “heterogeneity” instead of just saying “lots of different things”?  Well, for one thing, using big words makes a person sound smart, and when you’re a prairie ecologist and no one really understands what it is you do for a living, it’s good to at least sound smart.

More importantly, there’s a nice alliterative (another big word!) feel to the phrase Habitat Heterogeneity, which happens to be one of the most important phrases in prairie ecology.  In fact, I would argue that the foremost objective of any prairie manager should be to create habitat heterogeneity within the prairie(s) they manage.

Habitat heterogeneity simply means diversity or variety in habitat types.  Habitat homogeneity is the opposite – a lot of habitat that is all the same.

Every organism in a prairie has its own unique habitat requirements, so the number of different habitat types in a particular prairie is correlated with number of species that can live there.   Let’s use prairie birds as an example.  Birds such as upland sandpipers like to nest in large patches of relatively short-stature grassland.  Around here, a big hay meadow is great habitat for them, especially if it was cut fairly late in the previous year and is still short in stature when the subsequent breeding season starts.  On the other hand, Henslow’s sparrows want to nest in prairie habitats with relatively tall and dense vegetation.  It would be highly unusual to find Henslow’s sparrows and upland sandpipers nesting in the same patch of prairie because their habitat preferences are very different.  So, if you want both species in your prairie, you have to provide both short and tall/dense habitat.  Other birds have their own unique habitat requirements, including nearly bare ground (e.g., horned lark), relatively short, but with abundant thatch (grasshopper sparrow), tall with lots of tall/weedy wildflowers (dickcissels), tall and nearly impenetrably dense vegetation (sedge wrens), and many others.  Only if your prairie provides all those different habitat conditions will you attract all those different bird species.

Dickcissels prefer

Dickcissels prefer habitat with lots of tall wildflowers or weeds.  They often weave their nest into the stems of a tall clump of vegetation.

The same diversity of habitat preferences exists in other groups of prairie species as well.  Among small mammals, for example, voles tend to prefer habitats with abundant thatch, while pocket mice are more often found where bare ground is abundant – and there are many others.  Insects and other invertebrates have the same kind of diversity in habitat preferences

Scale is important.  While a bird, mammal, or insect might have a broad preference for a certain kind of habitat structure, it is likely to need some heterogeneity within that habitat too.  A mouse, for example, might prefer patches of prairie with fairly sparse vegetation, but it is likely to need a few clumps of vegetation dense enough to hide in when predators are near.  Insects and reptiles are ectothermic (cold blooded) and need to regulate temperature, so while a snake might like to hide in tall dense so it can bite your ankle as you walk by (I’M KIDDING!), it also needs some places to bask in the sun.  All of this means that habitat heterogeneity is important any many different scales.  Heterogeneity at a fairly large scale (acres) helps provide places for many different animals to live in a prairie, but heterogeneity within the home range or territory of each animal (square meters, or even centimeters) can be important too.

Some habitat heterogeneity occurs simply because soil texture, nutrients, and moisture, along with topography all vary across a landscape.  A prairie is likely to have areas of more productive soils where vegetation grows tall and thick, and less productive soils where vegetation is more sparse, for example.  In addition, water will pool in some areas of a prairie more than others because of topography, altering the habitat for both plants and animals.  However, despite this “naturally occurring” heterogeneity, it’s still important for prairie managers to look for ways to provide more.

This landscape at The Nature Conservancy's Broken Kettle Grasslands in northwest Iowa shows the kind of natural heterogeneity that occurs in many landscapes.

This landscape at The Nature Conservancy’s Broken Kettle Grasslands in northwest Iowa shows the kind of natural heterogeneity that occurs in many landscapes.  Topography, soil variability, and other factors create a diverse set of conditions for plant growth and habitat structure.  Land management can add to that heterogeneity and improve it even more.

Prescribed fire and haying/mowing do a great job of altering habitat structure at a fairly large scale (acres).  By applying those treatments in different parts of a large prairie each year (and varying the timing of each from year to year), a manager can create a shifting mosaic of habitat patches that supports a wide diversity of animals.  However, both fire and mowing are pretty non-selective – most or all of the vegetation within a burned or mowed area gets the same treatment.  Leaving unmowed patches of grass here and there and varying the height of the mower as it moves across the site can help leave more heterogeneity behind.  Designing prescribed fires so that not all vegetation burns (e.g., mowing around some patches ahead of time, burning on days with lower temperatures or higher humidity, etc.) can also help with habitat heterogeneity – though those kinds of fire might also be less effective at killing trees or accomplishing other objectives.

In prairies where livestock grazing (cattle or bison, for example) is feasible, it is much easier to create small scale heterogeneity because grazers pick and choose which plants, and how much of each plant, to eat at any one time.  By controlling grazing intensity, and varying it across both time and space, managers can create prairie patches that are ungrazed, almost completely grazed, and in various stages of partial grazing – with a mixture of tall vegetation and nearly bare ground.  The uneven application of “fertilizer” from the rear ends of grazers contributes even more to habitat heterogeneity by temporarily altering soil productivity in lots of little spots across the prairie.

These cattle at Konza Prairie in Kansas

These cattle at Konza Prairie in Kansas have created a nice example of small scale habitat heterogeneity by grazing many of the grasses short while leaving leadplant, purple prairie clover, and other wildflowers ungrazed.

Whether it’s fire, mowing, grazing, herbicides or various combinations of those, creating habitat heterogeneity may the most important job of a prairie manager.  We still have a lot to learn about how the scale and configuration of habitat patches affect wildlife and insect populations.  What we do know, however, is that the prairies thrive when they have a lot of different types of habitat.  …When they have habitat heterogeneity.

And that, folks, is your Prairie Word of the Day.