An Old Field Bonanza of Life

September 1, 2014

Nature Notes by Bill Dunson





Sometimes you are surprised by the abundance of life in an unexpected place. One such paradoxical reservoir of biodiversity is the old field, perhaps thought of as a neglected former pasture or hayfield, or a place where low nutrients and poor soil make agriculture marginal. Yet where it can be difficult or impossible to grow crops, wildlife may thrive. Poor soil especially makes it possible for some species of orchids to occur that do poorly against competition with grasses. While attending a workshop at the Matthews State Forest , near Galax, VA, I happened to see an unusual orchid blooming, the ragged fringed orchis , Platanthera/Habenaria lacera, in a small old field that had been preserved among some hayfields. I did a careful inspection of the field one morning and found to my delight two more orchids, one uncommon (Spiranthes vernalis = spring ladies tresses ) and one common (Spiranthes lacera v. gracilis = slender ladies tresses ). Orchids produce numerous tiny seeds that need to establish a symbiotic relationship with a fungus to successfully germinate and grow. Thus their occurrence often seems to be ephemeral and hard to predict.

While surveying this field for orchids early one morning I was amazed to find a wide diversity of insect life. For example there was a monarch butterfly apparently sleeping in the field. As it warmed up a meadow fritillary, an eastern tailed blue and a Peck’s skipper were flying about the field. The blue is interesting since it has a false head on the rear of the wings with fake antennae and eyes; this arrangement in hairstreak butterflies has been found to deflect the attacks of predators, such as jumping spiders, away from the vulnerable head. An even more striking insect, the yellow collared scape moth was also present. This tiger moth is apparently protected by its strong resemblance to a wasp, allowing it to be active in daytime. Lurking among the vegetation there was also a well camouflaged praying mantis, the tiger of the Lilliputian world of the old field.

Within this old field there were several different “zones” which were distinguished by the primary vegetation present. The upper zone on the right in the photograph had isolated clumps of little blue stem grass and this is where all of the orchids occurred. To the left and lower on the slope there were fewer bluestems and many purple topped grasses. Lower still there were dense growths of goldenrod, with additional changes as one approached a creek in the valley below. The association of the orchids with little bluestem is intriguing since we have found on our farm that this native grass seems to grow primarily on impoverished soils; it does not compete well with other grasses.

So in this neglected area of old field, there were two rare orchids, and a cornucopia of insect life that dazzled my mind. Long may this old field survive and provide a refuge for rare plants and life of all kinds.

Bill Dunson

About Bill Dunson

Bill Dunson, born in rural Georgia, skipped 12th grade and went directly to Yale. Bill subsequent-ly received a PhD in Zoology from the University of Michigan, studying softshell turtles. Bill is Professor Emeritus of Pennsylvania State University thanks to a career spent entirely at that institution, teaching and doing research on the physio-logical ecology and ecotoxiciology of reptiles, amphibians and fish. Always curious about nature, Bill has dedicated his life to learning and sharing his knowledge with others. He has served on many advisory boards here in Southwest Florida to preserve the water that gives life to our region.

View all posts by Bill Dunson