Lichens are fungus and algae in a
symbiotic relationship. The fungus is the visible part of the lichen, and it
acts as a protector for the algae, enabling it to survive in harsh conditions
that it would not be able to survive in alone. The algae contains chlorophyll,
which enables it to photosynthesise, providing nutrients for the fungus. The
same fungus can combine with different algae, and similarly the same algae can
combine with different fungi, to make variations of lichens.
Lichens can live and grow almost
anywhere, from rocks to trees to desert sand, and as they are often the first
to inhabit hostile conditions, they provide the foundations for a lot of
environments. To enable them to survive extremely difficult conditions, lichens
are able to shut down metabolically but still survive until the conditions turn
favourable again. Most lichens grow very slowly - only about a millimetre per
year.
The explanation of why lichens
would be found on one side of the log but not the other, is most likely because
the side the lichens were not growing on was the side touching the ground, and
the exposed side is a better environment for the lichens, with more space, air
and sunlight.
Sources:
http://www.countrysideinfo.co.uk/fungi/lichens.htm(Zoe)
After talking about this with Maggie, I have come to the conclusion that lichens would actually prefer the underside of logs. This is because if they are exposed to direct sunlight they will dry out, so they need damp conditions with a bit of indirect sunlight as well. (Zoe)
ReplyDeleteZoe, you mention that lichens grow really slowly. One reason is that they can survive with very little water, so exposed upper surfaces of logs should be okay. Maybe another factor is competition - other things grow faster, so block the light that lichens need. Therefore, lichens could be forced to exist only in places which are too harsh for their competitors,
DeleteThat's interesting, if lichens grow in harsh places because that is where there is no competition, it also explains how they can grow in desert sand. (Zoe)
DeleteAction point for everyone! get a lichen identification card and try to identify some lichens this spring. Different identification cards are used for different substrates (eg bark of trees, gravestones).
ReplyDeleteIf you don't fancy lichens, try it for any other animal or plant group. Keep it manageable and fun! Then you can try to identify a completely different group the following year.
Duncan