In case you don’t recall, Phase One involved a shaky estimate of herbaceous stem density in the sideyard of Scribble Central Command: approximately 126,000 shoots of tenacious (though pretty) weeds.
Phase Two actually began the same day, with an attempt to estimate biomass rather than blithely quote shady statistics about “stems.” I was after dry biomass, because I wanted to estimate the amount of carbon in the yard.
Hewing to my no-resource-consumption ethic, I resisted baking the clippings in the oven and instead locked them in my car, windows up, and left them in the sun for a week and a half. Then I bagged up the clippings and took them to the farmer’s market, where I sheepishly asked a vendor to weigh the bag for me and not comment on the suspicious tangles of dried herbs.
This being Santa Cruz, I got a “No problem, dude” and an answer: 0.44 pounds. (Can you change the readout to grams? “Uh, I probably could, but I don’t want to get confused.”)
No matter. A few seconds with Google Calculator and I have an answer of 199.580643 grams in my 0.312 sq-meter bicycle-tire plot. Let’s just call it 200 grams. For the 56% of my yard that rates a “seriously overgrown” designation, that works out to 87.95 kilograms of weeds. To put it another way, that’s roughly one entire Scribbler, spread out over the yard, in bone-dry vegetable matter. If you consider that people are famously 70% water, then we’re really talking about 3 and 1/3 properly dried-out Scribblers to equal the sideyard’s two-month output.
(That is, of course, assuming that all the dry mass is carbon, which criminally ignores all the nitrogen, phosphates, heme groups, etc. that plants contain. Famous weed scientists, including but not limited to Dr. Beth Newingham, are encouraged to contact this blog with adjustments.)
Of course, while plants are busy making things like snapdragons and cherries, they’re also making things like carrots and potatoes. I’ve measured the so-called aboveground biomass and can only guess at the amount of belowground biomass twining through the soil. Plant ecologists try to help us with this by measuring “root-to-shoot” ratios, but turns out the ratios are quite variable. Annual plants have less root and more shoot, as you might expect; perennials store energy for next year in a tap root. Drier land promotes larger roots and smaller shoots.
Still, take a middling number from the range of ratios, let’s say 1:1 to make it easy, and that means there’s the equivalent of another 3-and-a-third Scribbler-masses lying under the ground out there. Creepy.
(Again, plant ecologists are encouraged to weigh in with realistic numbers.)
Can it really be that my humble sideyard has ingeniously sequestered some 180 kilograms of carbon [or, slightly more honestly, 72 kg - thanks moley] from the atmosphere since just this March? I think I need to contact Richard Branson and Al Gore about that $25 million prize they recently announced.
Alas, it’s not quite that simple, as you may have read in the recent post about the Twilight Zone. That carbon is sequestered for only as long as the plant matter remains plant matter. Cut it, compost it, let it die a natural death in winter, feed it to a cow, burn it – do what you like – the carbon will float innocently back into the air and resume trapping heat. Darn.
Still, it’s impressive. Watching grass grow may be boring, but thinking about molecules being snagged out of midair and assembled into a 180-kg forest before your very eyes is something else.
Image: aerial (roof-based) reconnaissance of the SCC sideyard. Readers with expertise in image rectification are invited to help out. The dark, nearly circular splodge in center-right is the bike-tire sampling spot being reclaimed by sun-mad burclover. At bottom left is the completely anonymous Subaru.
Next up: biomass with legs.