Sweating through Solheim`s field trips: Blue River Sand Barrens

glade mallow

poppy mallow

On our way to Blue River Sand Barrens, Steve pointed out two plants of interest: glade mallow (Napaea dioica), which is the only species that is endemic to Wisconsin, and poppy mallow (Callirhoe triangulata), a species of special concern in Wisconsin, rare globally as well.

sand barren

false heather

This ecosystem is partly or completely of anthropogenic origin, likely early plowing or grazing disturbed the vegetation and allowed the formation of eroded, sandy patches across the area. The attempt at farming ultimately failed, because the only way to successfully farm here is to irrigate like crazy. The landscape is now a quilt of sand barren and dry mesic prairie patches. The dry mesic prairie is dominated by grasses, with many forbs (clovers, legumes) in between. Both ecosystems require fire to maintain them, but not as frequently as a wet or wet mesic prairie would, because it's harder for shrubs to creep in the first place.

When the wind blows out the vegetation (a blowout), and ground cover is less than 50%, we call it a sand barren. Sand barrens are a tough environment, since they are very dry, hot, and the soil continuously moves, so we see only early colonizers like false heather (Hudsonia tomentosa), mosses, lichens and a fungus called earth star (Geaster spp.). Once these took root, other species can move in and succession continues. Since the pebbles are too heavy for the wind, we see a phenomenon called desert pavement, many colorful pebbles on the surface of the sand barren.

desert pavement

earth star

There are many ways (and combinations of these) to adapt to dry circumstances:

1. being succulent, like prickly pears (Opuntia humifusa). The flat, fleshy pads are covered with spines and short bristles, for maximum water retainment. The large, waxy yellow flowers bloom in late June. The common name refers to a pear-like fruit that turns red when mature. The fruits as well as the pads (when peeled) are edible.

prickly pear

2. being active in the spring, then either disappearing for the rest of the year, or going dormant for the summer and returning in the fall, when water is once again, available. This strategy is a characteristic of many annuals that thrive here. Being an annual would be hard in e.g. a prairie, since the vegetation is dense there and annuals would have to "start over" every year.

long-hair hawkweed

3. being hairy, like the long-hair hawkweed or prairie hawkweed (Hieracium longipilum), to prevent excess transpiration. Hawkweeds have a funny way of procreation, which is worth mentioning. A couple fancy scientific terms here: apomixis refers to the replacement of the normal sexual reproduction by asexual reproduction, without fertilization. Apomictically produced offspring are genetically identical to the parents. Pseudogamy refers to any reproductive process that requires pollination but does not involve male inheritance. So, this plant needs to be pollinated, but is not fertilized. Which is also why poor Mendel, who tried to prove his theories on hawkweed after peas worked just fine failed miserably.

resurrection plant reviving
after 3 hours of addition of water

4. being tough, waxy, with small leaves to survive the blowing wind, like false heather (above)

5. being able to dry out and then, when water is available, "ressurect": resurrention plants are a group of unrelated plants, a life form, who are capable of extreme dehydration, over month or even years.

6. producing milky juice, like most milkweeds, it cuts down on transpiration

A couple random fun pics I took from the area: