KINGS OF THE NORTHERN FORESTS

A look at the trees, shrubs and perennial plants that bolster life in Ecoregion 5

- JEFF COX

The white oak is the keystone tree of North America's Ecoregion 5 (marked in light blue on the map opposite). That means it supports all the participants in the ecosystem. For example, the Canada jays in this illustration directly benefit from white oak when they eat its acorns.

I COULD HEAR the caterpillars chewing the leaves of the mighty black oak tree just a few steps from my back door one spring morning in 1995, shortly after we moved to this woodland site in Sonoma County, California. Caterpillars hung on long silk strands from the tree's canopy that threw shade over our house. I feared they'd defoliate the sheltering tree, so I called the county's agricultural agent to see if there was a non-toxic way to rid it of these pests.

"Don't you touch them!" he shouted over the phone. "This is the year in their life cycle when they feed on the deciduous oaks. It doesn't harm the trees at all, and those caterpillars are a major food source for our birds. Just let nature do its thing." In that simple explanation, ecological insight evolved in me. My involvement in organic gardening had taught me not to poison the animal or plant life in the garden so that nature could release its built-in benefits, but I hadn't enlarged my vision to include the wild system growing and chewing and slithering and flying all around me.

The black-capped chickadee is an indirect beneficiary of the white oak; the bird doesn't feed on the tree itself, but on the thousands of caterpillars that prefer oak leaves.

The fisher, a weasel family member that lives in Ecoregion 5, depends on a healthy wooded habitat where it can hunt smaller mammals like squirrels and chipmunks.