Lichen: Encyclopedia II - Lichen - Ecology

Lichen - Ecology

Because lichens are morphologically small relative to most terrestrial plants, yet require access to sunlight in order to grow, most forms are attached to either large boulders, other inert surfaces, or woody plants in somewhat to completely open or exposed situations. However, where adequate moisture exists, lichens develop on surfaces (particularly those of slow-growing trees) in forests as part of an epiphyte community. Stability (that is, longevity) of a surface is a commonality of most lichen habitats. Lichens are relatively slow-growing, and do not always compete well against even similarly low-growing mosses or liverworts where conditions of adequate moisture will favor the latter.

Lichens are a part of the food available for many animals, such as reindeer, living in arctic regions. The larvae of a surprising number of Lepidoptera species feed exclusively on lichens. These include Common Footman and Marbled Beauty. Although lichens typically grow in harsh environments in nature, many lichens are sensitive to man-made pollutants. Hence, they have potential as pollution indicator organisms. When growing on mineral surfaces, some lichens slowly degrade their substrate by secreting acids that dissolve the minerals, contributing to the process of weathering by which rocks are gradually turned into soil. While this contribution to weathering is usually benign, it can cause problems for man-made stone structures. For example, there is an ongoing lichen growth problem on Mount Rushmore National Memorial that requires the employment of mountain-climbing conservators to clean the monument.

The European Space Agency has discovered that Lichens can survive unprotected in space. In an experiment led by Leopoldo Sancho from the Complutense University of Madrid, two species of lichen – Rhizocarpon geographicum and Xanthoria elegans – were sealed in a capsule and launched on a Russian Soyuz rocket on 31 May 2005. The Lichens were exposed to temperatures ranging from -20°C to 20°C, the vacuum of space and radiation for 15 days. Afterward, they were found to be in the same state as at the start of the experiment.

Adapted from the Wikipedia article "Ecology", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki