Diversity: Green in All Seasons

Tales of an old timer have it that the diverse native grasslands, with special mention given to the Ozark glades (native grasslands growing where bedrock is at or near the soil surface), grew grass year-round for livestock and wildlife.  The old timer continued that there was no need to feed hay in winter because there was always something green.  How can this be when the native grasslands are so well known for their summer grass growth and profusion of blooms?

 One of the famous grasses-of-summer is Big Bluestem.  Today, with a touch of snow still remaining on the ground, only last year’s leaves and stems of the Big Bluestem remain above ground, and these are brown and dead.  This plant will show no signs of life until it sluggishly wakes up sometime in mid to late April.  This grass is classified in a group called warm season grasses, and this group contains other well-known grasses of our grasslands (e.g. Indiangrass, Little Bluestem, Switchgrass, Eastern Gama Grass).    

 The answer to the old timer’s mystery however lies in the fact that there is another class of plants in addition to those grasses-of-summer, known as cool seasons.  Take for instance a lesser-known species, Virginia Wild Rye.  Peeking out of the snow today is 3-4” of green growth that is actively collecting sunlight.  Though it may not be measurably growing aboveground in the snow, it is growing new roots below ground and getting ready for the warmer weather when it will quickly take off and grow. 

 On the outside, warm season plants just grow in a different season than cool season plants, but on the inside of the plant, there is actually a different way that the plant photosynthesizes (the plant’s process of collecting sunlight, carbon dioxide, and water to make food).  The warm season plants have an added step in the photosynthetic process that makes it more efficient at higher air temperatures than the photosynthetic process of cool season plants.  Due to this difference in the warm season plants, they are also more efficient with water because water is not lost through the leaf’s stomata while it collects carbon dioxide from the air as it is in cool season plants.  Grasses are most commonly thought of in the classifications of warm and cool season, but the wildflowers (also called forbs) also vary in the seasons of their growth; most are technically cool season, but each species still has a unique season of growth. 

 When both the warm and cool season groups of plants are present, the growing season can be extended from as little as one third of the year to three quarters of the year!  This has obvious benefits to both wildlife and livestock:  if there are actively growing plants, there is quality forage, and, if the plants are growing nearly year-round, there will be more to eat.  In fact, a diversity of plants can produce more than twice as much growth than a single high-producing species planted alone1

 From the perspective of folks who want to restore a rare and declining habitat (e.g. savanna, glade, prairie) or folks who want to landscape with native plants, there are also benefits to having plants that grow in each season.  It reduces the weed competition (Mother Nature will put something there if you don’t), takes more carbon out of the air and puts it in the soil (whether you believe in climate change or not, be assured that putting carbon in the soil in the form of organic matter is a good thing for the soil and the plants growing in it), and makes for healthier soils (the microscopic creatures in the soil have a more steady food supply with a diversity of plants). 

 Diversity is as good as it gets!

1 The statement that diverse native grasslands can produce twice as much forage as a monoculture of Switchgrass is based on very interesting research by David Tilman and others and published in an article titled “Carbon-Negative Biofules from Low-Input High-Diversity Grassland Biomass”, which is found in Science Volume 314 and published in 2006.




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