Stemflow research
Another piece of research paraphernalia visible in the forest looks, at first glance, like a very large fungus. It is actually a "stemflow collar". Stemflow (rainwater running down the bole of tree) accumulates a significant amount of cations which are transported to the forest floor and into the soil. Stemflow is therefore an important component of nutrient cycling in the forest. Researchers at Hubbard Brook have built stemflow collars to capture stemflow and analyze its chemical content. The collars are constructed from a polyurethane foam that is applied around the bole of a tree. Polyurethane was chosen because it is chemically inert and will not contaminate the stemflow solution. As it expands, the foam fills the cracks in the bark and adheres to the tree, eventually hardening in place and creating an effective water barrier. Once the foam has hardened, a trough is dug in the top of the collar and a funnel and bottle collection apparatus positioned under the low point in the trough where water will drip out. As water flows down the bole during a precipitation event, it is intercepted by the collar and drains into the funnel and bottle, and is eventually taken away for analysis.
The following references pertain to stemflow at Hubbard Brook:
Likens, G. E. and J. S. Eaton. 1970. A polyurethane stemflow collector for trees and shrubs. Ecology 51(5):938-939.
Eaton, J. S., G. E. Likens and F. H. Bormann. 1973. Throughfall and stemflow chemistry in a northern hardwood forest. J. Ecology 61(2):495-508.
Lovett, G. M., S. S. Nolan, C. T. Driscoll and T. J. Fahey.
1996. Factors regulating throughfall flux in a New Hampshire forested landscape.
Can. J. For. Res. 26:2134-2144.