When I am out and about during winter, I notice many signs of plant life in spite of the cold and the flat, gray and white landscape.
Mosses are still out there in the winter, sometimes taking advantage of good sunshine conditions to actively “grow,” plus they are easily observable on tree trunks above the snow. Mosses undergo periods of photosynthetic activity whenever temperatures rise above freezing, perhaps even when the sun beats down on them for only a short period of time on a deep winter day.
I recently found a large yellow birch tree showing abundant patches of plants in striking patterns (See Figure 2 below ). Amongst the curling, shreddy yellow birch bark, I see little patches of small plants. The reddish-brown patches are a liverwort (Frullania) sprawling across the surface; and the snow stuck to the tree trunk is piled on top of tiny pillows or cushions of moss. Looking closer I see that the cushions are made up of little tufts of moss plants forming a colony (in the green ovals I outline in Figure 3 below).
It’s not unusual for trees in our forests to develop their own little ecosystem. This winter I have been using tools about mosses prepared by local ecologist Jerry Jenkins under the auspices of Northern Forest Atlas Foundation to interpret what I see in the field.
In the moss digital atlas, and the two versions of the field guide printed by Cornell University Press, Jerry Jenkins provides information to guide the observer to more enjoyment of the winter landscape. I used this information to “decipher” the trunk of the birch tree.
In the moss field guide (in particular Chart 1, Figure 4), Jerry Jenkins has identified a dozen common species on tree trunks and shows detailed pictures of them. Location and position on a tree trunk can even help predict the species. While the locations of patches of species can be relatively random, most appear to favor certain zones on the trunk, like the canopy, a mid-trunk vertical surface, or the swell on the butt of the tree. This zonation may be due to factors such as trunk rainfall paths, shelter from dry winds, nutrient availability, bark roughness and acidity.
– Lake Placid Land Conservancy