Counting the trees, by Fred Booker

There has been much ado over UC’s proposal to remove fire prone invasive eucalyptus, pine and acacia from the slopes of Claremont Canyon. UC’s plan has often been described by opposition forces as a “clear cut,” evoking images of the denuded hillslopes following old fashioned logging operations in the Northwest. As is often the case when making an argument not backed by facts, it is easier to persuade people to your side by creating an emotional response through negative imagery. To those of us who have worked in the canyon, this seemed an odd characterization of a diverse forest filled with a wide variety of other plants.

On two Saturday mornings volunteers for the Conservancy met in the upper canyon to survey tree density in sample plots within the eucalyptus groves growing on the south-facing slopes in the upper canyon from signpost 28 to signpost 26. The slopes here are often quite steep but by using the trail system we were able to travel through the grove looking for representative areas to sample, though, most could be characterized as areas where there is an open canopy. Five plots (50 feet by 50 feet) were measured and roped off. Volunteers then braved the spring flush of poison oak to count each tree species found within the plot. Numbers were then extrapolated to give a count per acre.

On March 8, seven volunteers measured three plots accessed from signpost 28. Here, the average tree count for eucalyptus was 353 trees per acre whereas the average bay and oak count was 387 trees per acre. The eucalyptus were mostly coppice trees, that is multiple stems growing from the stump of what was previously a single tree.

These trees had originally been logged following a hard freeze in the 1970s. At that time, however, the stumps were not treated with herbicides and the trees were allowed to regrow. Most of the bay and oak trees were less than four inches in diameter with only 11 percent measuring greater than five inches, the largest being eight inches.

On April 12th, four volunteers measured two plots accessed from signpost 26. Here, several large single-stem eucalypts were seen, though the coppice trees were still the norm. The first plot of the day had a much higher density of eucalyptus, 1380 trees per acre, but we still found 400 bay and oak trees per acre, a significant number. The last plot had as many of the smaller eucalyptus as the previous plot but significantly more of the large trees (greater than 20 inches in diameter) for a total of 720 trees per acre. Though the bays and oaks were relatively small, they totaled out at 900 trees per acre.

Several interesting observations were made during our two days of counting trees. When we averaged the totals for all sites, we discovered that there were almost as many bay and oaks as there were eucalyptus, 528 to 652, so the removal of the eucs could hardly be called a clear cut. The eucalypts were being attacked by a beetle (eucalyptus leaf beetle or tortoise beetle) that was eating the margins of the leaves. This was seen throughout the forest as we traversed the hillslope, resulting in reduced canopy cover and more light hitting the forest floor. Under the eucalypts, a tangle of broken branches, bark strips and poison oak made it hard to walk through. In contrast, we saw one small grove of old growth bay trees along the trail near signpost 26, which featured a closed canopy and little understory vegetation, meaning no poison oak and no large buildup of flammable fuels. Equally important, that same grove is considered habitat for the endangered Alameda whipsnake. In time, with the removal of the eucalyptus, the south-facing slopes of Claremont Canyon could look more like this.