Migrating Siberian Shrubs

Trees and forests of continental Asia

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edfrank
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Migrating Siberian Shrubs

Post by edfrank » Tue Jan 24, 2012 8:07 pm

Migrating Siberian Shrubs
http://earthobservatory.nasa.gov/IOTD/v ... c=eoa-iotd
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In the 2011 Arctic Report Card, scientists concluded that the Arctic environment has undergone a fundamental shift in conditions. Recent years—warmer, greener, less icy—are likely the new normal for the Far North. One sign of the Arctic’s ongoing transformation is the spread of shrubs across the tundra.

The pair of images above show a site on the Siberian tundra near Russia’s Yennisey River as they appeared in the summers of 1966 (top) and 2009 (bottom). The top image is from Gambit, a declassified spy satellite, and the lower image is from GeoEye-1, a commercial satellite. In the 43 years between images, shrubs colonized virtually all the previously open tundra around a cluster of lakes. The images are from a study done by Gerald Frost, a Ph.D. student at the University of Virginia.

The conversion of tundra to dense shrubland triggers a cascade of changes in how the ecosystem functions. Observations from Europe, Alaska, and Siberia in recent decades have shown plant communities became less diverse as mosses, lichens, and other low-growing plants disappeared under the shade of shrubs. The loss of lichens, in particular, could pose a problem for caribou and reindeer, which forage on them extensively.

The change from tundra to shrubland can also affect the thawing of permafrost. In the winter, shrubs trap snow, and the insulating effect can make the soil temperature up to 30 degrees Celsius warmer than the air temperature. In the summer, though, the shrubs provide shade, which tends to keep soil temperatures in shrub-covered areas cooler than those in open tundra.

Whether the arrival of shrubs will accelerate permafrost melting or slow it will depend on whether the summer cooling or the winter warming is stronger. The outcome of the competing influences has global implications: thawing permafrost has become another source of atmospheric carbon dioxide, the most important long-lived greenhouse gas.

Read more at Shrub Takeover One Sign of Arctic Change in NOAA’s ClimateWatch Magazine.

References
Myers-Smith, I. H., Forbes, B. C., Wilmking, M., Hallinger, M., Lantz, T., Blok, D., Tape, K. D., et al. (2011). Shrub expansion in tundra ecosystems: dynamics, impacts and research priorities. Environmental Research Letters, 6(4), 045509.
Schuur, E. A. G., Vogel, J. G., Crummer, K. G., Lee, H., Sickman, J. O., & Osterkamp, T. E. (2009). The effect of permafrost thaw on old carbon release and net carbon exchange from tundra. Nature, 459(7246), 556-559.
"I love science and it pains me to think that so many are terrified of the subject or feel that choosing science means you cannot also choose compassion, or the arts, or be awe by nature. Science is not meant to cure us of mystery, but to reinvent and revigorate it." by Robert M. Sapolsky

Joe

Re: Migrating Siberian Shrubs

Post by Joe » Tue Jan 24, 2012 8:11 pm

I'm not an ecologist- merely a forester- but I'd suggest that the statement "plant communities became less diverse as mosses, lichens, and other low-growing plants disappeared under the shade of shrubs" is premature.
Joe

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edfrank
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Re: Migrating Siberian Shrubs

Post by edfrank » Tue Jan 24, 2012 9:31 pm

Joe,

I don't know, but it is something they can look at right now. There are existing patches of shrubs and existing patches open tundra in this area. I am sure they have looked or can look at the diversity in each of the existing situations and compare them.

Ed
"I love science and it pains me to think that so many are terrified of the subject or feel that choosing science means you cannot also choose compassion, or the arts, or be awe by nature. Science is not meant to cure us of mystery, but to reinvent and revigorate it." by Robert M. Sapolsky

Joe

Re: Migrating Siberian Shrubs

Post by Joe » Wed Jan 25, 2012 7:17 am

edfrank wrote:Joe,

I don't know, but it is something they can look at right now. There are existing patches of shrubs and existing patches open tundra in this area. I am sure they have looked or can look at the diversity in each of the existing situations and compare them.

Ed
I'm just suggesting that it's a different kind of diversity if shrubs take over from tundra. After all, tundra is considered a very basic ecosystem. When you have shrubs you may also get small trees and wildflowers- and a different or more diverse fauna. And probably more insect species, etc. Like I said, I'm merely a forester and I really don't know much about either the tundra or shrub ecosystems- I'm just making a wild guess on this.

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edfrank
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Re: Migrating Siberian Shrubs

Post by edfrank » Wed Jan 25, 2012 12:05 pm

The tundra has a wide variety of different mosses and lichens and is actually pretty complex at that level. You may be right, I was just meaning the comment may be based on observational data rather than speculation.

Ed
"I love science and it pains me to think that so many are terrified of the subject or feel that choosing science means you cannot also choose compassion, or the arts, or be awe by nature. Science is not meant to cure us of mystery, but to reinvent and revigorate it." by Robert M. Sapolsky

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jamesrobertsmith
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Re: Migrating Siberian Shrubs

Post by jamesrobertsmith » Wed Jan 25, 2012 5:34 pm

Whatever. We do know that this is all not a good thing. Plants can move in to new habitats, but many things are going to die off because they either can't move quickly enough or there won't be any suitable habitat for them at all. As Richard Leakey has argued, we are definitely neck-deep in a Sixth Extinction.

I read an interview a couple of years ago with a park naturalist in Denali NP where he spoke about having been able to watch the changes taking place there. Shrubs growing where there was only tundra, and trees where there had never been trees.

Haven't naturalists forecast the extinction of the North American pika? Its habitat will disappear faster than either the habitat or the animal will be able to migrate.

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Don
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Re: Migrating Siberian Shrubs

Post by Don » Wed Jan 25, 2012 6:49 pm

Ed/Joe/James-
Interesting considerations. While I try to steer clear of 'Henny Penny, the sky is falling' kinds of predictions, I'm not immune to the significant changes happening in Alaska environs, including ecosystems ranging from Arctic tundra to temperate rainforests. In the performance of my own profession (forestry), several decades back I was part of a multi-resource inventory analysis of Southeast Alaska. A part of the preparation for the inventory, I spent the winter analyzing and assembling imagery. And maps. In one instance, starting with the most recent USGS topo map (dated 1958 and 1:63,360 scale, the AK standard), I noted that the randomly placed inventory plot was located near the terminus of an unnamed glacier. In the back of my mind, I was thinking that this would be an interesting plot, depending on whether the glacier had receded, or extended over the years (in which case we'd toss out the plot as 'barren' of vegetation'). The next step was to compare more recent imagery (Ortho-rectified aerial photography, and satellite imagery). It had receded, vegetation was pioneering it's way back in, so it went into the summer's plots to visit. Several months later, we helicoptered out to the plot, and inventoried it.
Perhaps a lengthy way to make my point. My point? We as humans often lose track of the scale of the moment...our lives are but snap shots in time, and my several hours out at the foot of that receding glacier is almost infinitesimally small in the big picture of things. Is it something that we as humans are doing that is having a global impact? I can't say unquestionably yes, because there are unanswered questions, but we do have enough answers to suggest that climatological changes are somewhat outside of the range of recorded natural variation. The proxies we use to measure the "unrecorded" range of natural variation, such as ice cores, etc., suggest that our current blips aren't yet out of range of natural variation.
But for our own comfort, as well as the pika's, and the countless other entities, it would be sensible to act now, based on what we know of the moment, to reduce those activities that adversely impact our atmosphere.
Like the current state of our nation's politic...
-Don
Don Bertolette - President/Moderator, WNTS BBS
Restoration Forester (Retired)
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