August was an exciting time for the SOS program in Alaska. We spent two weeks collecting seed from the Steese highway and the Dalton highway. The Steese sits in the White Mountains north east of Fairbanks. The Dalton starts north of Fairbanks and traverses the Yukon River, the Brooks Range and the Arctic Circle. We made 70 collections in total. Each collection represents a single population of a species. Stringent criteria ensure our collections obtain a representative sample of a robust population without harming its reproductive potential. Because of these criteria, only common, workhorse species are collected– not endangered, threatened or rare species.
Some of the coolest species we collected were: Triglochin palustre, a graminoid that looks and feels like barbed wire, Hedysarum alpinum, a forb whose seeds make the best money bag sound when shaken, and Beckmannia syzigachne, which seems to explode off the stem when touched. With a couple of prolific species, for example Calamagrostis canadensis or Chamerion angustifolium, we used pillowcases rather than cotton bags to hold our collection. At the end of our trip, we delivered our seed bounty to the Plant Materials Center in Palmer, Alaska.
Before our seed can be stored or used, it first must be cleaned. That means that the seed is stripped of any sheathes, chaff, stems, leaves or other litter. While it will take several months to clean it all, Kim and I were able to work at the PMC for a week to see how it’s done. Seed cleaning has two parts. First the seed needs to be dislodged from the larger pieces of plant material. Second, the materials need to be separated so that all the viable seed is in one neat pile and the rest is in another.
There are multiple methods for each part and the handling differs for each species. One that we used frequently for more fragile seeds was manual stripping and sorting. With this method, I would shake the seed from the stems and then shake them through a sieve and pan. This works well when the seeds need to be treated gently and for small amounts of seed. However, this method is time intensive and requires extended physical labor.
The other method that we used frequently involved the use of brush and air machines. The brush machine is exactly what it sounds like. The main body is a metal cylinder case that houses a spinning paddle of brushes. These brushes fit snuggly against a metal mesh cage that prevents the stems from going through the bottom slot—where the seed goes—and instead pushes the stems through an opening at the other end. An air machine can separate the smaller pieces, mostly seed and broken up dust. This machine brings the mixture into a wind tube. The user controls the air speed so that the dust is blown to the top and collected at the upper end while the heavier, full seed drops to the bottom collection cup.
We used both methods and depending on the seeds, we sometimes mixed the methods together. It was wonderful to learn how to use the machines as well as look at the seeds up close under the microscope. Many thanks to the seed guru, Lubo Mahlev, who guided our time at the PMC lab as well as Jen- a previous CLM intern-, Rob, Kyle, and Todd.