27 September 2008 - 12:35, Tinman said:
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Yesterday afternoon on a glorious, wind-still day, a large Monterey pine simply pitched over, smashing across the main path through Edgehill Mt Park and onto one of our primary planting areas.

This view looks uphill to the tree’s base, located about half way up the “upper slope”. The trunk runs downhill toward the camera. It stripped off large branches from adjacent trees and crushed the fence when it landed.

The crown splattered across the trail and part of last season’s plantings:

Fortunately, no one was injured by this — but they certainly could have been. Paul witnessed this from above on Edgehill Way where he was working at his nursery, and the tree simply gave way suddenly, quickly, and without warning. On a gorgeous day like yesterday, plenty of people could have been there.

What this event underscores is that the “forests” that newcomers and the naive think they see here in San Francisco are in fact nothing more than aging tree plantations. This particular tree was part of Adolph Sutro’s quixotic quest to make San Francisco look like the hills of his home region in Germany — and to scoop up some fat tax breaks then available as well as to create timber to feed the sawmill he constructed at the base of Golden Gate Heights.

These trees are now a century old and are nearing the end of their natural life spans. Even where they are not diseased or encumbered by thick wraps of ivy and cape ivy, these trees simply are dying a natural death.

As these trees come down, sunlight penetration to the understory is greatly improved, allowing a more complex and better-suited-to-our-climate plant community to emerge. It is actually a good thing that these trees die and fall; with each one that does, Sutro’s errors are corrected.

Nevertheless, there are a number (granted, a small number — but a very, very vocal number) of people in San Francisco who aggressively oppose cutting any of these trees. Paradoxically — and of course consistency is never part of their position — they turn around and savage the RPD whenever a tree does fall and cause damage — such as the horrific death of a dog walker at Stern Grove earlier this year. They damn RPD when it takes trees out — and when it doesn’t.

In any case, regardless of what humans think one way or another, the situation ultimately will be decided by immutable laws of gravity and organism senescence. We’ve just witnessed incontrovertible proof of this again at Edgehill.

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13 July 2008 - 10:19, Tinman said:
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Ehrharta erecta is probably the most pernicious invasive we deal with at Edgehill. It is a perennial bunch grass that flowers and produces seed all year ‘round, unlike our native bunch grasses that only seed once per year. Ehrharta likes it wet, so in exposed areas (such as the eastern flank of Mt D), you don’t find it. However, the fog drip on Edgehill is sufficient that ehrharta is aggressive and exuberant.

The drought this year has really handicapped the ehrharta compared to the natives. In fact, our band of volunteers and staff have managed to keep the ehrharta quite well controlled in our principal work areas. This month’s workparty in fact pretty much eradicated all the ehrharta that was up, and things now look quite good:

Of course, the seed bank is lurking there and waiting for more wet in order to sprout away. Ehrharta will never be eradicated, just controlled. So we will always have motivation to return and pull again on another day.

This photo does reveal another of our major management headaches, though: the leaf litter from the blue gum eucalyptus. These trees shed high volumes of slowly-degrading leaves that cover up everything on the ground. Small seedlings of other plants are simply smothered by this leaf litter. This is one of the reasons why eucalyptus trees are rightly described as the biggest weeds in California. These particular trees were planted by Adolph Sutro over 100 years ago and are nearing the end of their expected lifetimes. Once they finally die and fall, well, good riddance.

This photo also shows (in the background) another problem found everywhere in San Francisco’s tree plantations that most people mistake for “forests”. Note the thick cylinders of ivy that encase the trunks of the trees. The ivy grows this way because of the fog drip from the trees. Eventually the ivy smothers the tree and its weight helps pull the tree over in the high winds we routinely get here. However, this is really a just end to the problem, as without these planted trees, the conditions that create these weedy monocultures wouldn’t exist. So in fact, this is merely an appropriate natural negative feedback loop that limits the damage inflicted by misguided human actions like Adolph Sutro’s those many years ago.

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