Planted Prairie vs. Fallow Field

At Ives Road Fen Preserve we have about 30 acres of planted prairie and 73 acres of former agricultural fields. The prairie had all weeds and other plants that were growing there eliminated with glyphosate before planting an assortment of prairie plant seeds. It has had several burns and extensive hand pulling of weeds. It has few invasives. The old agricultural field I did this comparison with has had most of the volunteer tree seedlings removed but no burns, no plantings other than a few oak seedlings this year, and minimal weeding. It has many alien plants, including spotted knapweed, sweet clover, common mullein, Queen Ann's Lace, toadflax, exotic grasses, and St. John's Wort.

On a sunny afternoon with a temperature of 74˚, I drove in, counted butterflies I could see from the track, then walked in 100 paces, counting additional butterflies I saw as I walked in. I used butterflies as a surrogate for all wildlife because they are easy to see, easy to identify, and present in numbers suitable for counting. Here are the results:

Common Sulphur: Two in the field, one in the prairie.

Cabbage White: Four in the field, two in the prairie.

Small moth: Four in the field, one in the prairie.

Monarch: None in the field, one in the prairie.

Pearl Crescent: Four in the field, none in the prairie.

Orange Sulphur: Two in the field, none in the prairie.

Praying Mantis: None in the field during the count but one seen later, one in the prairie.

Grasshopppers: Hundreds in the field, none in the prairie.

Birds: One sparrow in the field, one in the prairie.

Conclusion: The fallow field supports a greater variety and number of native animals than the planted prairie.

Reasons: The fallow field probably has a greater number of plant species than the planted prairie. The last prairie planting that Tom did had 65 species. There are over 700 plant species on the preserve. Not all of them are in the field but there are probably a lot more than 65. When the field was in crops it had no natives but remnant natives from the edges of the field, woods, railroad tracks and pastures have had time to recolonize. The plants in the field are more common plants than the ones planted in the prairie. Common plants are more likely to support many insects than uncommon plants. The seeds in the prairie all came from Lenawee County but if the insects they supported are miles away they will never get here. Identifying and moving the insects that depend on them is not a good use of resources.

Recommendations: If we have a bare field that just finished being cropped then planting uncommon showy prairie plants is good because it will accelerate its return to natural status and give us more diversity. If it has been out of crops for years and has asters, goldenrods and wild bergamot spread across it, it should only be overseeded, not glyphosated and started from the beginning. Spot removal of invasives by spraying or hand pulling would be fine.

Further research: There are many opportunities for student research projects on this topic. The count area and time could be defined more precisely. Counts could be done at different times of the year. More species could be counted. Species other than butterflies could be counted. An analysis could be done on what insects are supported by the plant species present or what plants are utilized by the insect species present. The role of fire on insect populations could be examined. Why are there no grasshoppers in the prairie?