Tuesday, September 08, 2020

Just trunks

Most of the forests accessible from roads on Vancouver Island have been logged off several times; the trees are mostly small and often close together. In a few places, small pockets of second-growth forests can still be found. Dalrymple Trail winds through one of these; the forest was replanted sometime in the middle of last century.

Most of these trees are Douglas-fir. They are tall trees; from ground level, the view is mostly trunks. Up above, the branches allow some sunlight to penetrate, so the understory hosts a fair crop of huckleberry and salal bushes, besides the usual ferns and mosses. But the trunks are what commanded my attention.

So tall, so straight! The trunk passes through the branches of the smaller surrounding trees, spreading its own branches far above.

Rugged, deeply furrowed bark, with minor fire damage.

Old Douglas-firs are very fire-resistant, due largely to the protective bark that
develops with age. In contrast, the thin bark of young trees offers little protection,
even from low-intensity fires. The thin bark begins to thicken and develop vertical
fissures as trees mature. (Dept. of Natural Resources, WA)

Fire is always a threat to our trees, whether as a result of human interference or started by lightning strikes. (I have seen, on a mountain side across the valley, where lightning struck the forest, and a tall tree burst into flames. Luckily, this was during a heavy rainstorm, and the fire was quickly drenched.) Once a fire is going, the smaller trees are vulnerable; the old Douglas firs shrug it off.

One of the few signs that were readable on the trail. The #7 probably refers to the long-gone explanatory pamphlets.

The bottom of a fire-scarred trunk.

Detail of that trunk.

So stripy! The black stripes are burnt bark. The warm brown lines are undamaged bark. And the greens: on the far right, there's moss, a dull, green. The pale green and greenish yellow stripes are a dust lichen, one of the Lepraria species.

Many older trees wear a coating of this tiny lichen. It appears as dust on the surface, and does not produce fruiting bodies, like other lichens, but spreads as the powdery dust blows or washes away.

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La mayoría de los bosques en la isla de Vancouver han sido cosechados varias veces; los árboles de ahora son relativamente chicos y cercanos el uno del otro. (Piensa palillos de dientes en una cajita.) En algunos lugares grupos de árboles de crecimiento secundario todavía existen. El sendero Dalrymple serpentea por uno de éstos; los árboles fueron sembrados allá por mediados del siglo pasado.

La mayor parte de estos árboles son los Douglas-fir, Pseudotsuga menziesii, Son árboles muy altos; desde el suelo, la vista consiste principalmente de troncos. Allá arriba, los ramos permiten la entrada de un poco de sol, así que aquí abajo, crecen los arándanos rojos y los arbustos de salal, además de los helechos y musgos que siempre se encuentran. Pero eran los troncos que más me llamaban la atención.

Los Douglas-fir ancianos son muy resistentes al fuego, lo que es un constante peligro en estos bosques, si por actividades de los humanos, o por relámpagos. He visto, en una montaña al otro lado del valle donde vivía, cuando un relámpago pegó en un árbol alto, y de inmediato el árbol estalló en llamas. Por suerte, estaba lloviendo fuertemente, y el agua pronto apagó el fuego.

La corteza gruesa de los Douglas-fir los protege, y aunque árboles más pequeños se queman, los grandes aguantan.

En estos troncos, en las últimas fotos, se ven las manchas negras donde el fuego quemó la parte exterior de la corteza sin dañar al árbol. Las partes color café muestran el color natural de la corteza.

Las rayas verdes son, a la derecha, en un verde oscuro, musgo. Y las demás, en verde claro, son de un liquen muy fino, como un polvo, que es muy frecuente en troncos viejos en la sombra. Son del género Lepraria.




1 comment:

  1. A nephew from London UK has done three season in BC forests, planting seedlings. When he visited us last Christmas he said this year would probably be his last. I think he was going to visit a cousin on Van.Island...and then the pandemic caused a lot of plans to be cancelled!

    ReplyDelete

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