Public Lab Research note


Tales from the Cryptogam

by cfastie | December 24, 2015 23:43 | 70 views | 3 comments | #12541 | 70 views | 3 comments | #12541 24 Dec 23:43

Read more: publiclab.org/n/12541


Above: Little planet projection of a spherical panorama stitched from 25 photos taken by a Canon S100 on a Saturn V Rig atop a 24 foot tall carbon fiber pole. The green area at the center is a cryptogam garden.

The forest floor under most coniferous forests is covered with moss. Many species of moss and other cryptogams (e.g., liverworts, hornworts, ferns, clubmosses, horsetails) can tolerate low light and acid soil and are well adapted to dominate under a continuous forest canopy. The forest floor under deciduous forest is typically covered with dead leaves instead of moss (an observation). The annual deposit of dropped leaves could be what prevents moss growth (a hypothesis). If the mat of leaves is an important obstacle to moss growth, then removing the leaves periodically should allow moss to grow under a deciduous forest (a test of the hypothesis).

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Continuous moss cover (mostly Hylocomium and Rhytidiadelphus) under a Sitka spruce forest in Southeast Alaska.

In 2009, I raked the leaves from a few hundred square feet of forest floor under a forest of maple, beech, birch, aspen, and pine in my backyard in Vermont. I repeated this once a year except for the year I never got around to it. I usually raked in the fall after most trees had lost their leaves, but sometimes I did it in the spring.

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Above: The forest floor under a mostly deciduous forest before I started removing leaves (top), immediately after leaves were removed for the first time (middle), and after six years of more or less regular annual leaf removal (bottom). Leaves were raked a couple of weeks prior to taking the lower photo. Don't know what became of the boy.

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Above: The forest floor under a mostly deciduous forest before I started removing leaves (top), immediately after leaves were removed for the first time (middle), and after six years of more or less regular annual leaf removal (bottom). Leaves were raked a couple of weeks prior to taking the lower photo.

Some moss was present before the raking started, especially on local high points (like boulders) where wind removed leaves, and steep slopes where leaves were more likely to fall away. After four or five years of removing leaves, moss covered more than half of the soil surface that had been free of moss. Neglecting to rake the leaves for a single year set back the moss invasion dramatically. This result is consistent with the hypothesis that deciduous leaves covering the ground every year prevent moss from spreading over very much of the forest floor.

To photograph the entire moss garden, a Saturn V Rig was attached to a Ron Thompson Gangster Pole. I did not use the uppermost two pole sections, so the total pole height was about 24 feet. A piece of flexible high-pressure PVC tubing (OD 17/32”) allowed the camera rig to hang vertically from the pole top. This tubing fits over the shaft on which the Saturn V Rig rotates and was secured with a cotter pin. The other end of the tubing fits snugly in the top of the (third smallest section of the) pole. A short piece of carbon fiber tube stiffened this joint, and duct tape wrapped over the joint held the tubing securely inside the pole.

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Above: A piece of carbon fiber tube inside the flexible tubing stiffens the connection.

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Above: The flexible PVC tubing (OD 17/32”) fits inside the top end of the third smallest carp pole section.

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Above: Duct tape secured the connection between the carp pole and the PVC tubing.

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Above: Detail of a little planet panorama of the moss garden taken from about 20 feet above the ground.

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Above: The south wind that brought 64°F air to Vermont on Christmas Eve was gusting to 30 mph overnight. One of the victims of this wind was a dead standing birch tree that I heard crash to the ground from inside the house. Sometimes you don't have to wait long between repeat photos to learn something about forest dynamics.


3 Comments

Thank you for sharing this very nice project! In a comparable climate zone in southern Sweden we must have more earthworms (eating the dead leaves) or less deciduous trees as there are a lot of moss in the woods. Perhaps less oak... Either way, I enjoyed your scientific approach!

God fortsättning (merry continuation [of the holiday season])

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Martenskram, I am in Västerås, where in Sweden are you? We have birch, pines, firs, and some hardwoods like oak. I agree, moss has no problems covering the forest floor here, We had a big forest fire near here 2 summers ago, and the forest floor burned up, leaving just rocks. It looks very different than one would expect, and we are curious as to how recovery will proceed. Interesting project here.

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This is very good data -- two independent reports that moss grows under deciduous forests in Sweden. Martenskram suggested two hypotheses that could explain why these Swedish forests differ from my Vermont forest:

1) There are fewer or smaller trees in the Swedish forests so there are fewer leaves.
2) Something removes the leaves fast enough that moss is not smothered by them.

Do grasses or herbs also grow under these forests? That would suggest that there is a lot of light and maybe more active organic matter turnover.
Are the forests young? Maybe the moss is residual from a time when a few small trees produced fewer leaves.
Are the trees small or widely spaced? Vermont has warmer summers (and colder winters) than Stockholm and might support more productive forests. So maybe there are not enough leaves produced in the Swedish forests to smother the moss.

There are lots of deciduous forests in Vermont with big populations of European earthworms in the soil and the leaves are eaten very fast. I don't recall that moss was common in those forests (maybe the worms eat the moss too). My forest apparently does not support many introduced earthworms.

It's very easy to find deciduous forests here with very little moss on the ground.

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