Pasture versus invasives: competing in newly-disturbed soil under a newly-opened canopy transitioning to silvopasture

Our process is essentially to seed disturbed areas, and also to survey plants growing in each area several times a season by photographing quadrat samples in disturbed and undisturbed, seeded and unseeded areas.

The disturbance we're following is twofold: first, a destructive storm uprooted hundreds of trees in the 4.5 acre area in July 2017 (the summer before beginning the project). This decreased canopy cover from about 80-90% to about 60%. The area is primarily early successional plants, including great quantities of a few invasive species (specifically, garlic mustard, honeysuckle, buckthorn, wild cucumber, multiflora rose). We wanted to see if we could limit their proliferation with a second, more thorough, and more even disturbance by swine, followed by overseeding with a pasture mix.

The area we experimented in was divided into sections of approximately .22 acre each, varying because boundaries worked around the varied terrain and brush. The disturbed sections ultimately comprised two strips running east to west on either side of a driveway. We left an undisturbed strip along the north and south sides of each disturbed strip for controls. When seeding, we divided each section in half from north to south, seeding both half the control strips and half the disturbed section in-between. We're still going through seeding records and entering data of what was seeded where and when, so the graphic below is approximate but provides a rough idea of how the sections were arranged (dark shading) and seeded (green shading).

Before seeding, we moved pigs through each section. We learned to put their feed around the base of brush we wanted to remove, so the pigs would root the ground up in those spots until we could easily pull up even large shrubs by their roots. We moved the pigs to the next section when the groundcover was nearly gone and nearly all the targeted brush (honeysuckle and buckthorn) was removed. We began with four pigs weighing around 150 pounds each in the southeastern-most section, and one pregnant sow in the northwestern-most section. After about a month, they moved west to the largest section, at which point three of the pigs were harvested and the sow and a gilt remained for a December farrowing. Eleven new piglets overwintered in a stick and straw shelter (yes, I know there's a story about that, but the big bad wolf didn't bother these little piggies) and were introduced to new pasture and split in to separate male/female herds in May. So for the western half of the above map, the seven young males moved along the north sections and the four young females plus the adult gilt and the sow moved across the southern sections. They moved about every 3 weeks until late September, when they were either harvested or moved out of the test area.

After each section of our site was disturbed, we seeded an organic pasture blend formulated as forage for swine. The blend was chosen based on Wisconsin's NRCS Conservation Practice Standard for Forage and Biomass Planting's Pasture for Hogs, limited by what organic seed was readily available. We landed on a mix of red clover, alfalfa, forage turnip, millet, sweet clover, alsike clover, buckwheat, and rye. At the time each area was seeded, only seed varieties within their planting window were broadcast, and other seeds were broadcast across previously seeded areas as their planting windows arrived, until each area was seeded by each seed variety once. Planting windows and seeding density were determined using the Midwest Cover Crops Field Guide, Second Edition, published by the Midwest Cover Crops Council and the Purdue Crop Diagnostic Training and Research Center. 

The idea of using a quadrat was suggested by Dylan Bruce, who I worked with to write another grant application that was not funded. He has much more experience in experimental design and I'm glad to have learned so much from him while working together. I made approximately 1-square-foot circular quadrats using PEX tubing and joints. When sampling, I walked a curving path through the area, tossing the hoop to make my selection more random. Then I photogaphed the quadrat, sometimes twice if I needed to capture a tall overstory and then the understory (see below).