Category Archives: Prairie Insects

The Problem with “Calendar Prairies”

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I think I first heard the term “calendar prairie” from my friend Bill Whitney of Prairie Plains Resource Institute.  He was talking about the mental image many people have of prairies that comes from seeing photographs of grasslands full of big showy flowers in books, posters, and calendars.  The term, and its implications for prairie management, has stuck with me over the years. 

 
 
 

An example of a "Calendar Prairie" photo. The Henry C. Greene Prairie at the University of Wisconsin-Madison Arboretum.

 

Unrealistic Expectations

There are a couple of dangers associated with people holding a mental image of what a prairie is supposed to look like.  The first is that it’s easy for people to have unrealistic expectations for prairies.  I’m a photographer, so I know firsthand that flowery photos don’t always represent an accurate picture of the prairie in which the photos were taken.  Photographers are often drawn to the biggest patches of showy flowers, and by creative use of perspective they can make those patches look even showier than they look in real life.  The result is usually a beautiful photograph that someone familiar with the prairie might not recognize.  To be clear, I’m not saying this kind of photography is a bad; on the contrary, attractive photographs have been extremely important for building the public’s interest in prairies. 

However, photos dominated by big showy flowers have the potential to be counterproductive as well.  For example, I worry that someone whose only vision a prairie comes from a “calendar prairie” image will be disappointed when they first see a prairie in person.  Regardless of how wonderful that real-life prairie is, it’s unlikely to live up to the photograph(s) that person has seen.  If that happens, it’s possible that a possible prairie enthusiast might instead feel duped and decide that prairies aren’t their thing after all.

For people that are already prairie enthusiasts, or perhaps prairie owners/managers, calendar prairies can become an unfair standard by which they measure the prairies they’re familiar with.  I’ve been in some astonishingly showy tallgrass prairies, where photos full of big flowers are easy to take just by pulling out a camera and shooting randomly.  However, not all prairies look like that – nor should they – and the ones that do don’t usually look like that all season long.  There are numerous conditions (including topography, soil moisture, soil texture, management history, etc.) that determine the appearance of a prairie’s plant community.  Using a calendar prairie image as the standard by which all prairies is judged is obviously naïve – much like a young woman using a movie star as the standard by which she judges her own identity.  The value of a prairie can be judged in many ways, including by its habitat value for a wide range of animal and insect species, many of which do not rely on big showy flowers.  In fact, the biggest value of an individual prairie is its very individuality – its unique combination of species composition and habitat attributes makes a unique contribution to the larger prairie conservation mission.  (Read my earlier post on this topic.)

This is not to say that all prairies are perfect the way they are.  Most (all?) prairies can be improved, but goals for improvement should be based on increasing the value of those prairies for biological diversity – not on making them look more like a photograph.

Effects on Management

The second danger of a calendar prairie image is that it can affect the way a prairie is managed.  Prairie managers sometimes form a mental picture of what they want their prairie to look like.  Sometimes that picture is based on an unrealistic idea of what prairies should look like.  Other times, it’s based on a fond memory of what their prairie looked in a previous season.  Either way, the problem occurs when that manager tries to make the prairie look like that mental picture all the time.  Rather than managing the prairie in response to threats such as invasive species, or in ways that allow different plant and animal species to gain an advantage each year, the prairie gets the exact same management treatments every year.

A summer fire on The Nature Conservancy's Platte River Prairies. We've seen very interesting and positive responses from summer fires, with and without grazing. For example, I've been managing this prairie for more than 10 years and have only seen wind flower (Anemone caroliniana) twice - both times it was growing in the portion of the prairie that had been burned the previous summer.

 

When a prairie gets the same management each year (e.g. early spring fire or summer haying) some plants, animals, and insects that are favored by that management and others are not – year after year.  Eventually, those species that are put at a disadvantage each year can disappear from the prairie.  Sometimes the strategy seems successful to the manager because the plant community appears the same each year; they always see the same big showy flowers blooming, for example.  However, other plant species may be slowly fading away.  More importantly, many animals and insects that have specific requirements for habitat structure will have a difficult time surviving in a prairie that provides only a single habitat structure type across the entire prairie each year.  Even those animals and insects that thrive may become more at risk from predation because the number of predators and their focus on particular prey species can both grow when their food source is consistently available in the same place and abundance each year.

 In a large contiguous grassland landscape, individual parcels of land that are managed the same way every year may not be a big deal – as long as there is variety among parcels.  If the Brown prairie is managed with annual late-spring fire, the adjacent Smith prairie is managed with annual summer haying, and nearby prairies are managed with other strategies, the conglomeration may retain good biological diversity, even if each individual tract of land contains a relatively narrow set of species.  However, when neighbors manage in similar ways, or when isolated prairies are managed in ways that decrease the number of resident species over time, the entire landscape can lose diversity.  If that happens, it’s unlikely that the diversity will recover because there are no places for the lost species to recolonize from.

 Ideally, every prairie would have multiple management treatments applied to various parts of it each year.  For example, a portion might be burned, a portion idled, and a portion grazed, with those treatments shifting from place to place each year – not necessarily in a predictable manner.  In a prairie managed that way, most or all plant species are likely to find favorable conditions in which to grow and bloom every few years – something that is critical to their long-term survival.  Animals and insects in a prairie that has multiple management treatments across it have a good chance to find suitable habitat each year by moving to the portion of the prairie that is most favorable in that year.

Light grazing on a restored Platte River Prairie - cattle are grazing the grass but leaving most wildflowers ungrazed. Periodic grazing can certainly change the appearance of a prairie, but plants that are grazed recover quickly. In the meantime, the grazing can provide different habitat structure and opportunities for plant species that are normally suppressed by dominant grasses.

 Some prairies are small enough that splitting them into multiple management units is not feasible.  In those cases, just shaking up the management so that it’s not exactly the same each year can be important.  Idling a different portion of the prairie each year – even if those portions are small – can provide a refuge for some of the plant and animal species that might not do well under the management applied to the majority of the prairie.  However, when prairies are both very small AND isolated from other prairies, some insect and animal species will simply be unlikely to survive long-term, even with good non-repetitive management.  In those cases, the management objectives may need to be altered – those sites could be treated more like museum pieces than prairies.

 Regardless of a prairie’s size, repetitive management over time can limit its biological diversity.  Prairies evolved under chaotic conditions; fires, grazing, outbreaks of herbivores, and drought came and went, and prairie animals and plants developed strategies to adapt.  Not only can prairie species survive management that changes year to year, they can thrive on it.

 Conclusion

Relying on idealistic visions of what prairies should look like (Calendar Prairies) creates an unrealistic image of what prairies really are.  Prairies evolved as dynamic natural communities that changed in appearance from day to day and year to year.  Rather than selling the public and ourselves on the idea that prairies should consistently look like showy flower gardens, we should celebrate and facilitate their changeable nature.  Real prairies are much more interesting (and valuable) than flower gardens anyway.

Prairie Seed Dispersal

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Plants don’t have the ability to walk or fly, but many can send their seeds far out into the world.  Some seeds have the capability to travel very long distances, giving plants the opportunity to colonize new places.

There are few seeds more familiar to prairie hikers than milkweed seeds.

In reality, most seeds don’t travel far from their parent plant.  If you’ve ever come across a milkweed plant with recently-opened pods, you’ve seen that the ground around the plant is often covered with milkweed seeds – even though milkweed seeds have the capability to ride the wind.  While it might seem like failure, dropping a high percentage of its seeds probably makes a lot of sense.  If the plant is able to grow and produce seeds, its current location must be suitable habitat.

Although most apples don’t fall far from the tree, so to speak, some percentage of a plant’s seeds often do travel to new sites – sometimes many miles from their starting place.  Once those seeds land, the challenges are just beginning.  The vast majority of seeds never germinate and become new plants because to do so it must end up somewhere that provides just the right conditions.  The odds are very high against a seed landing in a place where there is bare soil for germination, available root and light space to grow, and suitable habitat for survival.  However, having a few seeds that do manage to establish new populations is so important to the survival of the species, plants invest a lot of resources in this high risk strategy.  Read more about the ecology of seed dispersal in an detailed article by Henry Howe and Judith Smallwood.

Prairie plants have developed an incredible array of seed transport mechanisms.  Seeds can be carried by animals, wind, and water, and each has special physical characteristics that help it travel.

Prairie wild rose fruit in cross-section, showing the hard seeds inside.

Some plants wrap large hard seeds inside fruits that animals like to eat.  When the fruit is eaten, the seeds travel through the animal’s digestive system and out the back end – usually some distance from the parent plant.  Prairie wild rose hips, for example, are a food bonanza for a number of wildlife species.  Besides being tasty and rich in Vitamin C and other nutrients, they are also available during the late fall and winter when it can be difficult for animals to find other food.  Prairie grouse, turkeys, and many other species find them particularly attractive.  While the fruits are nutritious and provide value to the animal, the seeds inside the fruit are hard enough that they pass undigested through the animal and are deposited in a pile of fertilizer – giving potential new seedlings a jump start.

Violets produce seeds in pods that pop open when ripe, ejecting the seeds a short distance from the plant.  However, the seeds of violets are also attractive to ants, which transport them to their tunnels where they are often deposited in trash heaps where conditions are favorable for germination.  (For more on prairie ants, read James Trager’s excellent introduction)

Blue violet seeds.

Sandburs, and many other species, use animals to move their seeds but not because the seeds are particularly edible.  Instead, the plants use specialized spines, hooks, or other structures that get caught on animals as they pass by.  This sometimes allows the seeds to be carried many miles before they fall – or are scraped off.  Historically, bison were major carriers of seeds and often deposited them in wallows, where the bare soil may have helped provide for successful germination.

Sandburs are loaded with spines that help them hitch rides with any animal (or hiker) that happens by.

One of the most common strategies for seed dispersal by prairie plants is to employ the help of the nearly omnipresent wind.  A wide variety of species, including asters, goldenrods, milkweeds, thistles, wild lettuces, and many others, produce long feathery appendages, wings, or other structures that help catch the wind and carry seeds long distances.  Others simply produce seeds so small and light that they can easily be blown around.  While wind dispersal often carries seeds further than animals do, it is also the strategy that gives plants the least control over the final destination.  Animals are fairly likely to carry and drop seeds within the same habitat type, giving seeds at least some hope of finding good places to grow, but casting seeds to the wind is much riskier.

The last seed of a wild lettuce flower hangs on - until the next gust of wind happens by.

Seeds that grow in wetlands or wet prairies often build seeds that float and can be dispersed by moving water (or by wind blowing them across water bodies).  This seems like a logical strategy to help seeds move because it keeps them within the moist habitats they need for establishment.  Some water-dispersed seeds are simply so small that they don’t break through the surface tension of water.  Others have hairs or other structures that help them float.  Still others have hollow spaces that make them buoyant.

Wetland seeds floating on the water's surface.

Regardless of the particular strategy a plant species uses to disperse its seeds, prairie plants can benefit from the ability to transport seeds away from their parent.  Many perennial plants employ rhizomes or runners, in addition to seeds, to help start new plants short distances from the parent, and those reproductive stems help new plants establish because they have an “umbilical cord” of support from their parent.  However, that asexual reproduction doesn’t allow plants to move their progeny very far, and doesn’t involve cross-pollination that can help a species maintain high genetic vigor.

For annual plants, seed production is the only strategy for movement and survival because the parent dies after a single season.  Because annuals only get one shot at flowering, they usually do so prolifically, and spread their seeds far and wide.  This helps them be prepared for any kind of disturbance (burrowing animals, intensive grazing, etc.) that creates bare ground or suppresses surrounding vegetation – the perfect conditions for annuals to grow and flower.

Whether seeds are transported by animals, wind, or water, they are built for the task.  Seed dispersal is one of my favorite discussion topics during prairie hikes because people of all ages can appreciate the amazing strategies plants have developed to move their seeds around the landscape.  In fact, it’s such an interesting subject, it’s easy to get carried away…

Behind the photos – several of the photos in this post were taken in a simple homemade photo studio made from a cardboard box, tissue paper and a desk lamp.

A homemade photo studio – cardboard box, tissue paper, and a desk lamp.