I will get to the lichen topic, and some splendid links to research, but first a few detours around a little park:
Valiently, this rose and many others were still blooming today.
And the hydrangeas, having lost all their leaves to frost, have begun to leaf out anew.
Sweet Alyssum persists, filling gardens with its scent!
Now, warning, what follows may not be suitable viewing for children or the faint of heart:
One lichen predominates but others are appearing. Above is a photo of a poison ivy vine attached to a tree, with what I think is a different lichen than the usual, thriving around its roots. There are apparently many different species.
The conifer in the center is almost bare - the trunk to the right is a deciduous tree, but the one on the left is a pine, completely bare of needles.
Both are hosting a strange lichen, and oozing sap. Aren't these the most fascinating formations?
I think in the above crust, I can see the face of Jesus! If enough readers click on it, Sarah Palin will read my blog and I will be saved in the coming Rapture!
In a wander around the pond, there are many fallen branches, rotted inside, and covered with lichen on the outside.
This is the most ubiquitous, but there are others.
This horrifically nasty green is spreading as well.
Although the flowery blue is more prevalent.
Another delightful aspect of the condition of trees is the rapidly accelerating loss of bark.
In the specimen above it's possible to discern where the bark is separating from the trunk.
And it's really obvious here. That would be the equivalent to finding patches of your skin falling off. Not normal!
Areas bare of bark like this branch are common.
On the trunk of the sycamore, below, is a strange and spreading blackness, and the yellow areas are where the bark has dropped off. Makes a nice abstract, no? I can just see it, in MOMA.
This pair of dogwoods have it all! Covered with lichen, and patches of no bark - not to mention a backdrop of pines with about 25% of the needles they should have.
I'm taking pictures of particular trees on a regular basis, for comparative purposes.
For now, these samplings will have to suffice.
But before going on to the truly mesmerizing links on the lichen significance, let us just take a moment to wonder with awe, WHY THE FUCK ARE DAFFODILS EMERGING IN DECEMBER??
I did state this wasn't suitable for children.
This magnolia tree was the most gorgeous thing ever when blooming last spring - I am so annoyed I didn't take a picture.
It came to mind at a lunch in May when oldest skeptical daughter pointed out that many flowering trees were especially lovely, as though that indicated my concerns were unfounded. I pointed out that actually, it likely meant they were probably doing the same thing coniferous trees do, when they sense their own demise - throw all their energy into reproduction.
The magnolia was covered with seed pods for the past several weeks, which now litter the ground beneath, along with broken branches. I've never seen magnolia seeds, anywhere, before. Here's one close up, it's a fascinating image if you click on it:
Now, on to the significant science:
In the past few days, thanks to the miraculous nimbleness of the intertubes, I have found several studies that are riveting to read, in the context of my interest in the visible, irreversible decline of trees.
Here is a
link that has this, and much more, to say:
Acid rain does not usually kill trees directly. Instead, it is more likely to weaken the trees by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowly released from the soil. The main atmospheric pollutants that affect trees are nitrates and sulphates. Forest decline is often the first sign that trees are in trouble due to air pollution.
Due to an unfortunate lack of funding to continue this excellent site,
this is the message I got when I tried to follow through on references - but there is still much information to be found there, for instance this
page about how toxins in the air from emissions translate into depletion of nutrients in the soils...leading to the death of trees.
Next and more interesting still is the question of lichens, which are turning the trees into pillars of mottled greyish growths. In more advanced cases the bark is splitting and peeling from branches and trunks. It's quite apparent to me that the rampant spread of lichen is in directly opposite proportion to the decline of trees - although whether it is a cause or a symptom, I can't say.
Most thrilling, with terrific photographs and loads of links to other research, is this
Irish site which states unequivocally, on a page about
lichens as biomonitors of pollution, that
"Lichens traditionally have the name of indicating that the environment is clean. This is a simplistic view however. Some lichens will only survive in a clean environment, while others flourish with certain pollutants.
For example, some species of the genus Xanthoria establish and grow abundantly in nitrogen rich areas, such as near farms or chemical factories, while species of the genus Usnea are sensitive to the amount of sulphur in the air and will only grow in areas where the air sulphur content is low.
Lichens, unlike most living organisms, are unable to ‘refuse’ entry to many chemicals into their bodies. This means that chemicals can freely invade them and interfere with their metabolic processes, often killing the lichen, but sometimes increasing their growth rate. Also, lichens are unable to excrete or secrete these chemicals and so they accumulate within the thallus. The lichen is therefore an excellent bioaccumulator. Lichenologists can monitor pollution levels in a habitat by looking at the species present and analyzing specific species to see which toxins have accumulated...
...Thus lichens can be used to give a description of the state of an ecosystem without having to employ the use of expensive (and error prone) scientific equipment."
