A visit to grasslands in the Ochoco Mountains, Oregon
The Ochoco Mountains are rich in grasses in a variety of habitats, including scablands, woodland understories and moist prairies. We started in the scablands on this outing in early June.
Scablands
Danthonia unispicata
One-spike oatgrass grows in the scablands and in the compacted soil along the roadsides, proving itself adapted to soils that are saturated during the winter and bone-dry during the summer. It is easily recognized by the copious hairs on the sheaths and the single spikelet (sometimes two) at the top of the culms.
Sandberg bluegrass (Poa secunda)
Poa secunda is a mainstay grass species of the scablands. If flowers earlier than the oatgrass and the whole plant dries down and survives the summer heat/drought in a dormant state.
Bottlebrush squirreltail (Elymus elymoides) is another common grass in the scablands. Its inflorescence is a spike that falls apart along the rachis when the seeds mature.
Lemmon's needlegrass (Eriocoma lemmonii) was just starting to flower in early June. Its florets have long awns that help disperse and position the seeds for optimal seedling establishment.
Several grass species are invading the scabland habitats: Ventenata, bulbous bluegrass, and Japanese brome.
Ventenata dubia is easily recognized from a distance early in the growing season as dense yellow-green patches.
Bulbous bluegrass is a perennial, but its populations fluctuate widely from year to year, probably based on the timing of precipitation.
Most of the time bulbous bluegrass reproduces asexually: florets are replaced by plantlets in the inflorescence. The structures that appear to be awns are developing leaves.
Japanese brome occurs in small patches in disturbed areas, and appears a lesser threat than the other two species.
Forest understory
Woodland understory grasses include pinegrass, Alaska oniongrass, and Wheeler's bluegrass.
Pinegrass (Calamagrostis rubescens) is strongly rhizomatous and rarely flowers while growing in the shade. After wildfire or other disturbance that opens the canopy, it flowers abundantly and folks who assumed they always recognize this grass are sometimes puzzled.
Melica subulata develops corms at the base of the stalk which are attached to short rhizomes (hence the oniongrass name). Leaves are characteristically a shiny yellow-green and the sheaths are closed nearly to the top.
The prime of Miss Poa wheeleri
From late May into mid-June, Poa wheeleri takes center stage in the Ochocos, dangling its lovely flowers in the breezes.
Short rhizomatous, Poa wheeleri grows in loose clumps. Its spikelets are larger and fewer in number than on Poa pratensis and the florets lack cobwebby hairs on the callus.
The flowers are all female, any anthers are vestigial or fail to develop. Seeds are produced apomictically. (Apomixis is asexual development of seed or embryo without fertilization.) Poa wheeleri is a high polyploid species (2n = 56, 61, 63, 64, 66, 67, 70, ca. 74, 75, 79, 80, 87, 89, 90, 91). It probably arose from hybridization between Poa cusickii and another member of the Poa nervosa complex (Flora of North America Vol. 24 page 546). Apparently, freed by apomixis from the constraints of pairing chromosomes, it has drifted into an impressive array of large and variable numbers of chromosomes.
Other understory grasses were not yet flowering, including Festuca idahoensis and Elymus glaucus, so I will save those for another time and move on to the mesic prairie grassland habitat.
Prairie grasslands
I spent an afternoon searching for Graphephorum wolfii in Long Prairie, without success. The cows had just arrived there, but were hanging around near the reservoir so it seemed like a good time to look. Perhaps wolf trisetum is there, and it was too early to recognize it.
Tufted hairgrass (Deschampsia cespitosa) inflorescences were starting to expand and junegrass (Koeleria macrantha) was not far behind.
A variety of sedges mingled with the grasses, but the only one I could identify with confidence was Carex filifolia. The others were too immature.
That's all for now. Thanks for joining me on this adventure to the Ochoco Mountains.
