Re: Extent of Conifer Encroachment into Subalpine Meadows

Tuesday, January 12, 2010
Auditorium, Yosemite Valley
Noon to 1 p.m.

Extent of Conifer Encroachment into Subalpine Meadows in Yosemite NP
Kaitlin Lubetkin, PhD Candidate, UC Merced

Woody species have been encroaching into a variety of grassland ecosystems over the past 150 years, including many Sierran meadows. Encroachment into individual meadows has been intensively studied in a few specific meadows, but no broad, landscape scale study of conifer encroachment into meadows has been conducted. Kaitlin has initiated such a landscape scale study of conifer encroachment. She will present preliminary results from her study within Yosemite last summer, documenting the extent and severity of meadow encroachment in Yosemite.

This competition between trees and grass is not always to the advantage of the trees. There are many areas where grass is the dominant plant and encroaches on the adjacent forests. Trees cannot out-compete grass in very damp, shallow, dry conditions or when the soil is extremely compact (one example is the Hayden Valley in Yellowstone). I understand that some ecologists suggest that certain grass populations can last for hundreds of years and are older than some adjacent forests.

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The cure for a fallacious argument is a better argument, not the suppression of ideas.
-- Carl Sagan

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eeek
Tuesday, January 12, 2010
Auditorium, Yosemite Valley
Noon to 1 p.m.

Extent of Conifer Encroachment into Subalpine Meadows in Yosemite NP
Kaitlin Lubetkin, PhD Candidate, UC Merced

My hiking companion and I ran across Kaitlin and her research advisor while going up toward the pass between Roosevelt and Upper McCabe Lakes during the past Labor Day weekend and spent about 20-30 min. talking with them. If anyone from the forum attends the seminar, please post a synopsis of their findings. Thanks much.

I thought that this was the natural progresssion of the ecocycle: Lake-meadow-forest...meadows are not necessarily a permanent state, even though the tourists and some animals may prefer it that way.

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Bee
I thought that this was the natural progresssion of the ecocycle: Lake-meadow-forest...meadows are not necessarily a permanent state, even though the tourists and some animals may prefer it that way.

Not if the meadows are above the historical tree line.

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Bee
I thought that this was the natural progresssion of the ecocycle: Lake-meadow-forest...meadows are not necessarily a permanent state, even though the tourists and some animals may prefer it that way.

Agreed, that is the classic view that I recall also. However, two geologists on separate occasions have told me (so I don't have a specific article to support this point) that some ecosystems have forests giving way to grasslands. I'm a little over my head here (although that does stop me for opening my mouth), but there seem to be land areas where the meadows are the terminal condition and "grow into" the forests. Perhaps this succession is more common in Yellowstone where the accumulation of clay and chemical conditions clearly kill trees. The Hayden Valley in Yellowstone allegedly has been grass covered and essentially treeless for thousands of years as it is composed of heavy sediment from an ice age flooded extension of Yellowstone Lake that has been unfavorable for trees due to chemical content and density of the soil (clay). The Great Plains prairie may have been similar situation, although that soil is different from Yellowstone I believe. Partly may may relate to the definition of "terminal"? If something remains the same for thousands of years, is that terminal? If fire in normal, that is a major factor in this event-- more damaging to small trees than faster growing grasses and scrubs. One could imagine a forest subjected t repeated fires would tend to become more patchy, diversified with different plant species and presumably areas that do not get overgrown again with trees. Are we seeing some of that in the Central Valley where there are few young oak trees and fewer and fewer old Valley Oaks? Another factor may be animal or human influence. Riparian areas tend to accumulate willows, however, over grazing by elk can eliminate the trees and grasses take over in the barren land right down to the water edge.

What defines a climax plant condition if change continues to occur? One can imagine that at the edges of forests, diseases and fire are going to work against trees more than grasses that are faster growing and, relative to their above ground parts, are more deeply rooted than trees tend to be. Perhaps erosion, wind, sunlight, fire, water conditions or altitude are a deciding factors as skalkowski suggests.

This is slightly different situation but along certain tropical coastlines, don't mangrove trees grow into the water, hold soil which eventually displaces the water to an extent that results in grass accumulating and the trees dying off?

Ain't ecology great?

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The cure for a fallacious argument is a better argument, not the suppression of ideas.
-- Carl Sagan



Edited 1 time(s). Last edit at 01/08/2010 04:57AM by Frank Furter.

For your enjoyment:
One of the many meadows in Yosemite (my personal favorite is Rodgers):
(of which this isn't)

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bill-e-g
For your enjoyment:
One of the many meadows in Yosemite (my personal favorite is Rodgers):
(of which this isn't)

Looks like the flat area just north of Polly Dome Lakes. Does the trail follow right along the right hand side of this meadow? Yeh, I know,---what trail?



Edited 1 time(s). Last edit at 01/09/2010 07:40AM by tomdisco.

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tomdisco

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bill-e-g
For your enjoyment:
One of the many meadows in Yosemite (my personal favorite is Rodgers):
(of which this isn't)

Looks like the flat area just north of Polly Dome Lakes. Does the trail follow right along the right hand side of this meadow? Yeh, I know,---what trail?

It's the meadow in Cold Canyon. Taken just below Elbow Hill (after coming from Virginia Lake).

You and others may get a kick out of this one taken on same trip:


Other great meadows you should check out:
- Givens
- Turner
- Westfall
- Rodgers
- Grace

(ok ok... at least go to Westfall)

Re this topic:
Do the fauna eating the flora have anything to do with it?

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bill-e-g
Re this topic:
Do the fauna eating the flora have anything to do with it?

The naturalists in Yellowstone make a big deal about the recovery of willows and aspens especially in riparian areas now that the elk cannot feed as wantonly due to the presence of wolves. On the surface, it seems unlikely that natural animal loads widespread on a system would change it massively, as that would approach depletion which would not support further animal grazing, but maybe. The impact of rabbits on Australia has been pretty extensive, apparently. In fact, as I think about it, there was a suggestion that the rabbits may have actually changed the climate in Australia by their impact on the flora. Can't give a reference, probably a PBS show.

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The cure for a fallacious argument is a better argument, not the suppression of ideas.
-- Carl Sagan

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Frank Furter
The impact of rabbits on Australia has been pretty extensive, apparently. In fact, as I think about it, there was a suggestion that the rabbits may have actually changed the climate in Australia by their impact on the flora. Can't give a reference, probably a PBS show.

A similar scenario played out in the U.S. during the Dust Bowl Era.
Summer daytime temperatures in the Great Plains frequently reached 120+°F during the mid-1930s primarily due to the loss of the groundcover and the subsequent changes in the active surface cooling mechanisms which resulted.

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bill-e-g

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tomdisco

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bill-e-g
For your enjoyment:
One of the many meadows in Yosemite (my personal favorite is Rodgers):
(of which this isn't)

Looks like the flat area just north of Polly Dome Lakes. Does the trail follow right along the right hand side of this meadow? Yeh, I know,---what trail?

It's the meadow in Cold Canyon. Taken just below Elbow Hill (after coming from Virginia Lake).

Trial-n-Error Guided Hikes strikes again!

btw. that's Miller Lake in the photo above with the Sawtooths and Whorl Mountain

There's a great 1964 study of how vegetation in Yosemite Valley has changed since 1850, a relatively short period of time overall, but incredibly full of changes to the natural plants and trees of the Valley. The study is titled "Influence of Modern Man on the Vegetation of Yosemite Valley", by Robert P. Gibbens and Harold F. Heady, published by the California Agricultural Experiment Station Extension Service. I have a copy I bought in the early 1980's. Check out some comparison views from Glacier Point (1866 & 1961) and Columbia Point (1899 & 1961):






The study states that "it seems most probable that fire was the major factor in suppressing the (the trees) before 1851", i.e. Native Americans did not suppress natural fires, while settlers after 1851 did suppress fires; introduction of grazing and possible lowering of the water table were also cited as factors, but contributed to the change in only a minor way. Striking differences, don't you think?

There is a cite somewhere stating that the Native Americans actually lit fires to burn the valley floor in an effort to keep things clean.

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Old Dude

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mrcondron
There is a cite somewhere stating that the Native Americans actually lit fires to burn the valley floor in an effort to keep things clean.

I thought it was to favor the oaks.

Favoring the oaks makes sense; I don't know a lot about native american culture, but I believe acorns from oaks were an important source of food for those who lived Yosemite Valley.

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vdrummer
Favoring the oaks makes sense; I don't know a lot about native american culture, but I believe acorns from oaks were an important source of food for those who lived Yosemite Valley.

So, what do you think is the natural state of Yosemite Valley? Are prescribed fires appropriate? I wonder how much wood was consumed by Native Americans for tools and in shelter and cooking/heating fires as opposed to burning entire forests.

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The cure for a fallacious argument is a better argument, not the suppression of ideas.
-- Carl Sagan

I'm sure that blowing a hole in Bridalveil Moraine to drain El Cap meadow had a drastic effect, plus other drainage work. There's more info in the Yosemite history documents.

As you note:

from
http://virtual.yosemite.cc.ca.us/ghayes/roadside.htm

This passage:

The road crosses the El Capitan recessional moraine. This Tioga till impounded the waters of the latest Lake Yosemite (Matthes, 1930). Early visitors to Yosemite Valley were treated to mosquito-ridden swamps because the recessional moraines impeded the flow of the Merced River. In 1879, Galen Clark had a deeper channel blasted through the moraine (Schaffer, 1997). The resulting lower water table may have allowed conifers to encroach the meadows at the lower part of the valley, and the river has entrenched several feet into the valley floor. The action did ease the mosquito problem, though.

Should we start a "Dam the Merced" Campaign to get the meadows back?

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The cure for a fallacious argument is a better argument, not the suppression of ideas.
-- Carl Sagan