Thursday, November 23, 2006

Big Manzanita

The photo at right shows a big manzanita tree in the foreground, with pale green, round leaves and a red trunk, and the top of a pine in the background. I stood under the manzanita to take some photos of the fortress work site I posted about in the previous post. I was very surprised by the loud, constant drone of bees (see photo at right), hard at work harvesting pollen and nectar from the manzanita blossoms. Manzanitas bloom at odd times in every season except winter. This is most likely a strategy for maximizing their exposure to bees, and it seems to work.

This particular manzanita is in the uphill part of our yard, and it is substantially larger than the surrounding manzanitas. Since manzanita seeds sprout almost only after a fire, all the manzanitas in any given area tend to be the same age, and roughly the same size — so this one really stands out. From historical records, we know that a fire burned the entire Lawson Valley in 1973, so most of the manzanitas around here are now 32 years old, having germinated in 1974. I borrowed a core drill and cored this manzanita a few years ago, and discovered that it had germinated in 1962 or earlier — it’s now at least 44 years old, and clearly it survived the 1973 fire intact. We have no idea how this happened. From remnants of burned fence posts and barbed wire we’ve found in our yard, we believe that our property was a pasture in 1973. One possibility is that the farmer preserved this manzanita in the middle of the-then pasture, and the fire burned far enough away that it couldn’t make the leap to this tree. That’s just speculation, though; we really just don’t know. Whatever its history, this manzanita is now the largest and oldest manzanita that I know of in Lawson Valley. It seems likely that others were also preserved, but if so, I haven’t found them yet…

It sure makes a pretty picture in our back yard…

Fortress

Yesterday a crew of three worked — hard — all day long, doing the finishing trench work and leveling, placing the forms, and wiring up the rebar. The righthand photo shows the western trench, with the rather elaborate (and large!) rebar wired up in the configuration specified by the engineer who designed the building.

The horizontal rebar is located near what will be the bottom of the footing; there is no rebar up higher. Why? Because the bottom of the footing will be under tension (i.e., the weight of the building above will tend to pull it apart), while the top of the footing will be under compression (i.e., the weight of the building will tend to squash it together). The concrete without rebar is very strong in compression; the rebar is very strong in tension. The right material will be in the right place.

I can’t tell you how good it feels to see progress being made on this project! Even better, from watching these guys at work, it’s plain that the head mason — a man of about fifty — really knows what he’s doing.