Saturday, February 09, 2019

Sierra Sequoias from space

I wrote last year about the big trees of the Sierra Nevada mountains in California. One if the things that interested me was the ability of the Sequoia and the Sugar Pine to grow side-by-side, despite having very similar survival strategies- namely grow taller than everything else and live long enough for fire to clear our the shade tolerant trees so that your seeds can germinate.

Of course, as anyone who spends time on the forest knows, despite these trees having similar niches, they look quite different. The both have large trunks often bare of branches for the first 100 feet, but their vegetation has different forms. The Sugar Pine has very long, straight lateral branches, like the spars of a ship, while the sequoia crowns are more rounded. And because these trees are very large, it turns out that you can easily distinguish them in Google Earth. Here is a screenshot of the same grove I wrote about last year:

You can clearly see the long lateral branches on the pines (which also have somewhat bluer foliage). The larger, yellower trees with very wide trunks and rounded foliage are the sequoias.

Unfortunately, the sugar pine is in decline in many areas of its range, Here is a picture of dying trees in the national forest just south of the park:
The most obvious thing here is that the Sugar Pines are mostly dead. But there are other differences. Unlike in the National Park, here you cannot see the ground- the trees are growing too close together. One critique of the Forest Service is that it as lagged behind the Park Service in the use of controlled burns and recurrent fires. While I don't have the fire history of this exact area, the much thicker understory could be the result of decades of fire suppression. And if those trees are sucking up all the water, perhaps that has stressed the pines.

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