Counting Pollen Grains in Oak Woodlands

Kyle Funk, a research assistant with Walt Koenig, is winding down a spring and summer working on the oak woodlands. Walter recently received funding from NSF to explore what controls the apparent synchrony in acorn crops across California. From boom to bust, each year seems to be similar across vast areas of California. Oak pollen, both how much and how synchronous may account for some of the variation in acorns; if the oak flowers don’t get pollen, the acorns won’t fill out.

Walt found a company in England (Burkhard Manufacturing) who makes a unique machine that samples pollen in the air (Photo). The large fin on the back keeps the device pointed into oncoming breezes. These are mounted up on towers, at least 10 feet in the air. A large fan underneath blows air through a slit inside a chamber. If you open the chamber (photo) you can see the slot, and a steel wheel that rotates slowly. The fan blows air (and pollen) on the rim of the wheel. Kyle would put sticky tape on the wheel’s rim, and could tell which section of the wheel represented each day of the week. By removing the tape, each day’s pollen was captured. Then the pollen is put on a microscope slide and can be stained (fuschin red) and examined under a microscope.

Kyle then had to consult as many illustrated books as possible to learn the various kinds of pollen- pine, oak, grass, etc. In general, he can now tell oak pollen, but the various species of oaks are a challenge. Walt is studying many of the oaks, but the common ones here are coast live oak, valley oak and blue oak. As the data come in- daily pollen counts- Walt will be using it to help tease out the factors that control the acorn crop. The acorn crop in California is probably the single most influential variable affecting wildlife populations, including deer, pigs, and of course, the acorn woodpecker!