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BBC News Online: Sci/Tech
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Wednesday, 12 June, 2002, 18:46 GMT 19:46 UK
Fungi help trees to 'mine' calcium
Maple tree BBC Not all trees can access rock minerals: The maple
cannot
US scientists say some trees send down fungal tendrils into rock faces
to "mine" calcium, a process previously thought impossible.
The authors, whose work is published in Nature, say the process does
not occur in all tree species.
The discovery is important for understanding the effects of acid rain
and has implications for forest management.
The team was led by Professor Joel Blum of the department of
geological sciences, University of Michigan, US.
It found that trees which release particles of ectomycorrhizal fungi
into a common calcium phosphate mineral, apatite, found in rocks, are
able to extract calcium.
Researchers knew that fungi could penetrate such minerals, but
Professor Blum's findings are the first to show that trees use apatite
as a source of calcium.
New calcium source
"The previous view was that all the trees in the forest get their
nutrients from the plant-available soil pool", he said.
"The conclusion we came up with from this study was that, while some
trees are only able to use the soil pool, others can send down fungal
extensions and find the apatite. Instead of drinking their calcium,
they mine it."
Leaf BBC
This process of "rock-eating" does not occur in all tree species. By
analysing calcium-to-strontium ratios in leaves and needles, the team
found that levels of ectomycorrhizal fungi had a bearing on whether a
tree could mine calcium.
Spruce and fir trees, which have high levels of the fungi, can get
calcium from rocks, while sugar maples, which have lower levels,
cannot.
The scientists also found that calcium levels in trees were vital for
understanding the effects of acid rain on forest ecosystems.
As acid deposition drains levels of calcium and soil takes thousands
of years to develop, the damaging effect of acid rain is not easily
remedied.
Knock-on effect
Although the discovery that some trees can obtain calcium from rock as
well as from soil helps them to resist the effects of acid rain,
Professor Blum is cautious.
"We don't want to suggest that there is no longer a need for concern
about acid rain depleting calcium from forests", he said.
"Our research shows that some trees have other strategies for getting
their calcium, which may be important when the plant-available soil
pool starts running out.
"But trees that don't have the ability to go deeper are still in the
same dilemma they've always been in."
The findings are also important for forest management techniques.
Researchers usually take calcium samples from the soil surface to
determine whether there is enough of the mineral for re-growth after
logging.
Professor Blum has shown that samples may have to be taken deeper in
order to determine the presence of apatite.
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Related to this story:
Finding those elusive fungi (10 Dec 01 | Sci/Tech) 'Growing' fire
threat to tropical forests (27 Dec 00 | Sci/Tech) Fantastic fungus
find (07 Aug 00 | Sci/Tech)
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Internet links: Nature | University of Michigan Department of
Geological Sciences | British Columbia Ectomycorrhizal Research
Network |
The BBC is not responsible for the content of external internet sites
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