This is Short-pointed Flat Sedge (Cyperus acuminatus). Up until this May, when the Indiana Department of Natural Resources - Division of Nature Preserves published a revised list of endangered, threatened, and rare plants, Short-pointed Flat Sedge was considered endangered in Indiana; its status has now been downlisted to watch list, meaning that enough occurrences of the species have been found in the state to remove it from the endangered, threatened, and rare lists. I knew this species the second I saw it, in part because I had seen it at Goose Pond Fish and Wildlife Area earlier in the year, but also in part because I had been asked to verify identifications of this species by two other JFNew monitoring biologists, both of whom found the species in mitigation wetlands (wetlands created or restored in areas that were previously upland) this year. One of our biologists found this species at a site in southern Indiana, where it seems to be becoming more and more common, but another of our biologists found it at a mitigation site in Lake County, all the way in the northwest corner of the state. The latter was quite a find, as the only previous record of this species from the northern 1/2 of the state was from Porter County in 1888 (Rothrock 2009). In addition, Rothrock (2009) notes that Short-pointed Flat Sedge is probably extirpated from Michigan and that it is likely limited to southern Indiana.
So why has this species been increasing in Indiana? Could it have just been overlooked for so many years? It is an inconspicuous plant, but this probably isn't the only reason. As Rothrock (2009) notes, its habitat is "wet, often sandy, disturbed soil, especially on pond margins." Short-pointed Flat Sedge is an annual, a pioneer species, a colonizer. Its ecological niche is to provide early cover after soil has been disturbed. It doesn't seem to persist as other plants move in and compete for resources. Disturbed, early successional communities like this are not heavily botanized, so maybe it has been overlooked for this reason. Or maybe there is just more habitat for it now because there is more soil disturbance and conversion of agricultural fields to "natural" communities. It is also interesting to note that Short-pointed Flat Sedge is shown from more than 3/4 of the United States on the USDA/NRCS Plants page, but clicking on the states to see county distributions, there are only a couple of states that show this species as present in half of their counties (USDA, NRCS 2010). Although its range is widespread, its distribution appears to be scattered. I can't help but to wonder if it is increasing outside of Indiana as well.
Rothrock, P.E. 2009. Sedges of Indiana and the Adjacent States: The Non-Carex Species. Indianapolis: Indiana Academy of Science.
USDA, NRCS. 2010. The PLANTS Database (http://plants.usda.gov/, 22 October 2010). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.