Wonder Plot Study Tells Story of Development

Expanding the legacy of research at the Fritz Wonder Plot, Big River, CA

Wonder Plot.
Wonder Plot.

In 1923 Emanuel Fritz, then a Professor of Forestry at UC Berkeley, and Woodbridge Metcalf secured for study a one-acre grove of second growth trees along the Big River in Mendocino County. By that year, much of California’s old-growth redwood had been logged and a second generation of trees had begun to grow. Fritz and Metcalf intended to study tree growth on their plot in order to better understand just how a second growth forest develops.

“Little did I think then that I would ever see the plot again,” Fritz wrote in 1960, “…I have been on the plot nearly every year since 1923 and hope to make what will likely be my last measurement in 1963.” In fact, he took measurements of the plot’s trees until 1983, when he was 97 years old. After Fritz died in 1988, the legacy of his work was carried on by researchers who traced his steps in recording data. The collective study of this ‘Wonder Plot,’ named for its trees’ outstanding growth over the decades, has provided one of the most complete descriptions to date of how an older second growth forest matures.

In his pursuit to document the forest’s development, Fritz each year counted trees, mapped their locations, measured the diameter at breast height of tree trunks, and estimated the average height and total volume of the entire stand in board feet. He found that, with time, the number of trees on the plot decreased, the average tree diameter at breast height increased, the estimated average tree height increased, and the estimated stand volume increased.

These findings mean that as a forest grows older, its trees become fewer, taller, and bulkier. Dominant trees out-compete less dominant trees for light. Less dominant trees die off while others burn or topple over in strong winds and floods, allowing light into the forest. The living trees take advantage of the new source of light and “release,” or burst in growth. This fundamental process of death making way for growth has been understood by foresters and ecologists for decades, but Fritz’s data is the first robust, quantitative proof of it for second growth redwood.

In telling a consistent story, void of holes, the work researchers have done to continue Fritz’s study has been critical. They were even able to describe the effects of a violent windstorm in 1998 that knocked down several trees on the plot. They found that the opened canopy led to an upstart of new trees—a third-growth generation. The new trees add structural complexity to the forest, giving it a look less like an even aged tree farm and one more like an old growth forest. This observation accentuates the absolute necessity for natural disturbance in a developing forest.

Looking back, it’s clear that Fritz accomplished a great deal in his study of the ‘Wonder Plot’ and that those interested in forest ecology and conservation are indebted to him forever. His only regret? Not studying redwood forest development in a variety of habitats. “I wish we had laid out 100 such plots in the 1920s scattered over the redwood belt on different kinds of soils, slopes, elevations, aspects, etc.,” he wrote. “The data they would have yielded would now be invaluable.”

Matt Gerhart and the Mendocino Land Trust plan to continue making Fritz’s measurements in the future and have identified new areas of research to be applied to the plot. It’s a pleasure to think that this acre of forest, observed by two interested individuals, can provide us for centuries to come with a glimpse into how second growth redwood forests in similar habitats develop, and an even greater pleasure to know that conservationists can use Fritz’s observations to assess and improve the health of young forests.

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