Tuesday, April 24, 2007

My Bioblitz 2007--Indian Hill

The hill behind my house is a rough circular mound of basalt boulders and rubble about 400 feet in diameter. It lies atop one of the N-S running ridges of Oregon’s Coast Range. The elevation at the top is about 990’ and the elevation at the lowest base is about 850’. In the Eocene(50-60 million years ago) this land was underwater. Lava flowed occasionally, bubbling out and hardening into seafloor basalt “pillows”. The rock-pillows range from 6’D boulders at the base of the hill, to grapefruit and smaller cobbles on the top of the hill, and no other hill in the area has as many rocks. By the Miocene(20 million years ago), this land had been lifted up, both by shifting faults and subduction zone scraping action, and formed into Oregon’s Coast Range. (Photo of mossy "pillows" and my teeny house).
My hill lies in a transition zone between oak savannah of the western foothills of the Willamette Valley and conifer forest of the interior Coast Range. From about 3-4,000 years ago to roughly the end of the nineteenth century, the local native Americans, the Kalapooya, burned the Willamette Valley the and Coast Range foothills each year to encourage grasses for game, to help the large acorn-bearing oaks grow wide without competition, and to provide habitat for other food plants(camas, tarweed). To the east of the hill lies a 100+ acre cow pasture that retains much of the savannah characteristics, and to the west conifer forests stretch to the sea. (Here is a photo of the cow pasture, showing the open field with spreading oaks, as well as scattered young firs. The pasture is grazed for about 2 months out of the year.)
Here is an old oak stump that bears the marks of those old grass fires--
Since the fires stopped, the conifer forest has been creeping back through the oaks. Eventually the oaks will die, shaded by the taller firs. Here is a photo(in the bottom third portion) that shows what the crown of the hill looks like with oaks(grey, no leaves yet), maples(new green) and firs. The upper two thirds of the photo shows the transition to second-growth conifers, on into the west.

Surprisingly, for all its backwoods reputation today, this area(and the valley shown in the photo above) was one of the first homesteaded in the Willamette Valley. The first post office in Oregon was in this valley(a settler decided he wanted to be the first post office in Oregon, and simply set up shop). A boundary tree(and its replacement since the first one fell), used in marking the land for homesteading claims, marks the NE corner of our land. We call our hill “Indian Hill” because local rumor says it is so rocky because the Indians buried their folks up there, and covered them with rocks. It certainly would make a great place for a grave, in my opinion!! But it sure would be hard digging with all that rock! And we haven’t found any bones…All those rocks and dry southern exposures used to be home to rattlesnakes, one of the few places rattlers could survive in the Willamette Valley. They’re gone now(?!), the settlers shot them and let their pigs loose on the hills to fatten up on snake and acorn.
Next up, a description of the Hill's layout, and the list of trees, shrubs, and plants found on Indian Hill.


Neil said...

Tremendous pictures and an excellent overview. I'm looking forward the the next post!

Jeremy Bruno said...

Yes, what a beautiful area. Someday I'll get out west...

burning silo said...

Wonderful post, Celeste! I like how you started off with the geology of the land as that's so important to an understanding of habitat. I'm looking forward to reading more!