A Visual Illustration of Plant Diversity’s Importance

Last week, I took some photos that powerfully demonstrate the importance of plant diversity.

DCIM100GOPROG0080136.
Research plots at The Nature Conservancy’s Platte River Prairies.

Several years ago, we created some research plots to help us learn more about how plant diversity interacts with ecosystem function.  As you can see above, the plots include a grid of squares (3/4 acre in size), each planted with one of three seed mixtures: monoculture (big bluestem), low diversity (grasses and a few forbs harvested in the fall), and high diversity (100 species).  Working with academic partners, we have several research projects underway, including a couple that demonstrate the influence plant diversity has on the spread of invasive plant species.

Other researchers have found similar relationships between plant diversity and resistance to invasive species, but that is only one of many benefits from having a wide variety of plants in a prairie.  Both herbivores and pollinators benefit from having a broad selection of food choices available to them.  During extreme weather conditions (hot, dry, wet, cold), high diversity prairies always have plants that flourish under those conditions and help provide habitat and food conditions for animals.  Most importantly, because of these and other reasons, prairies with high plant diversity also have high total biological diversity, including more species of microbes, insects, other invertebrates and vertebrates.  That overall diversity is important for its own sake, but also because of the role each species plays in the functioning of the ecosystem.

The aerial photo I took from our small drone last week illustrates another benefit of plant diversity; prairies with high plant diversity have green vegetation for more of the growing season.  Every plant species starts and ends their growth period at different times.  Some start early, bloom, and are done before summer even starts.  Others bide their time and don’t bloom until late in the fall.  When you mix all those species together in one prairie, you end up with consistent, but ever-changing, availability of nutritious vegetation and flowers throughout the growing season.

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Labeled plots, showing the location of the various treatments.

Our monoculture research plots (big bluestem only) looked very different from our other plots last week because big bluestem was just starting to grow (on April 23).  Even after we burned all the plots this spring, allowing the soil to warm earlier than it otherwise would have, the most advanced big bluestem plants only had leaves of a few inches in length.  Our low diversity plots (mostly grasses) showed more green, but only due to the presence of one grass species, Canada wildrye (Elymus canadensis), a cool-season grass that begins its grown early in the year.  By contrast, the high-diversity plots had many plant species growing, with some close to blooming.

The monoculture plots were planted only with big bluestem,
The monoculture plots were planted only with big bluestem, which was just barely starting to grow last week.
Low diversity
The low diversity plots were slightly greener than the monoculture plots, mainly because Canada wildrye was growing quickly (most of the other grasses were just breaking dormancy).
high diversity
The high diversity plots had numerous species showing vigorous growth, even early in the season.

Although the visual differences between plots on April 23 are striking, they are ecologically significant as well.  Invertebrate and vertebrate herbivores (including cattle, if the plots were grazed) can find a variety of forage options in the high diversity plots right now – far more than in the low diversity or monoculture plots.  Within a week or so, the high diversity plots will also have several different kinds of wildflowers in bloom, providing resources for early-season bees and other pollinators.  The low diversity and monoculture plots will have far fewer resources for pollinators throughout the season.  Furthermore, invasive plants species trying to establish themselves within the high diversity plots face stiff competition from plants using wide range of growth strategies.  They will find a smaller amount of resistance in the other plots, where less diverse plant communities are not as efficient at taking up space and fully utilizing resources.

Plant diversity is incredibly important in natural systems for a variety of reasons, only a few of which are mentioned here.  We still have a lot to learn about how plant communities function, and how plant diversity plays into that.  However, we already know enough to recognize the value of having numerous players in the game.  It was fun to see a visual demonstration of that value last week.

 

17 thoughts on “A Visual Illustration of Plant Diversity’s Importance

  1. Kirk hohenberger April 28, 2015 / 8:04 am

    Makes perfect sense, how nature has been doing it forever. Total opposite that how conventional agricultural tries to do it ,monocultures and herbicides actually a war against nature, trying to have only one species of plant on hundreds of millions of acres .

  2. Leroy Haeffner April 28, 2015 / 8:22 am

    Chris I would like to share you blog on my FB page as this so perfectly shows when we are establishing prairie we need more diversity and that invasive may be better kept at bay with this alone. fighting invasives is all I get done this time of year and as a 64 year old man it is wearing me out. So it it is Ok I will share thanks

    • Chris Helzer April 28, 2015 / 8:25 am

      Please do! And good luck in your fight.

  3. Patti Holmlund April 28, 2015 / 8:50 am

    When I had a yard I pulled up “lawn” to let the “weeds” grow. Come summer and hot weather while all the yards on the block were brown and dead, mine was green and thriving. With birds, squirrels, chipmunks, and interesting “crawlies”. Sadly none of those “bone heads” never learned and every Spring continued to spread their “weed and feed” and missed out on so much color and the delicate beauty of “weeds”.

  4. Jim in IA April 28, 2015 / 9:18 am

    Reblogged. I hope that is ok with you.

  5. chris muldoon April 28, 2015 / 8:11 pm

    The monoculture plot sure looks “clean.” How do you keep non-native cool weather plants from getting a toehold there since it was planted several years ago?

    • Chris Helzer April 28, 2015 / 10:53 pm

      Hi Chris. Great question. There actually has been a little brome invasion along the edges of some plots, but it has been slower than I’d anticipated. The 20-foot mowed trips around each plot help with that. We’ll eventually have to figure out how or whether to deal with that invasion. Hopefully, we can at least learn from it. We’ve experimented with introducing brome plants into similar research plots nearby and found that plant diversity helped limit flowering of smooth brome, though we didn’t see any decrease in rhizomatous spread. We’ll probably try something similar with these plots (which were seeded in early 2010).

  6. Carol Denhof April 29, 2015 / 5:58 am

    Great post Chris. As you know, this is relevant for our longleaf systems as well. Would like to share on The Longleaf Alliance page as well. I’ll be very interested to see results from the study.

    • Chris Helzer April 29, 2015 / 6:05 am

      Thanks Carol, and yes, please share it. I’m always interested to hear perspectives from longleaf systems.

  7. Peter Dunwiddie April 29, 2015 / 11:31 am

    Chris, did you have to jump through any hoops to use a drone for this type of work? Just wondering what sort of obstacles the FAA is throwing up in this regard these days.

  8. Ken Graeve April 30, 2015 / 8:23 am

    Thanks Chris, what a great visual and explanation. i’ve shared it with a whole pile of folks here at Minnesota DOT who are involved with roadside vegetation management.

  9. georgewiman May 1, 2015 / 6:12 pm

    Not sure if this link will work, but here’s a neighbor’s lawn during a local drought in Illinois. On either side are lush green “neglected” lawns with lots of different kinds of plants. The philosophy would be “If it’s green and I can mow it, it can stay.” The lawn in the middle, the dead lawn, is a single carefully-cultivated species of some kind of pampered lawn grass. Any assumptions you are making as to which political party is represented by the respective households are probably right.

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