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The mission of the International Association of Bryologists (IAB), as a society, is to strengthen bryology by encouraging interactions among all persons interested in byophytes.

Tuesday, August 12, 2008

diaspore bank samples - open boxes

Subject: diaspore bank samples
Date: Fri, 13 Aug 2004 16:23:48 +0200
From: H.J.During <>

Jakob Raath
Rhodes University
S Africa

Dear Jakob,
after my holidays I found the discussion initiated by you on Bryonet, and
though I hesitate to start it again there, I would like to send you some
comments. Your project is obviously very interesting for me, as I have
been doing several studies on bryophyte diaspore banks, including one on
samples from a savanna (Hazelside fire plots) in Zimbabwe, not too far from
your site and likewise often subject to fire. Your initial results sound
very good!
I have always used the same method as you did, soil samples spread out over
sterilized sand in closed boxes, the only difference perhaps being that I
used square boxes (7x7 cm, 5 cm high) which allow some more space for the
plants to grow and sporophytes to develop than petri dishes. I did get
fungal infections occasionally, but never losot complete cultures to them -
but they were obviously nastiest when the booxes were kept in the
greenhouse in our summer, with high temperatures and low light (direct
sunlight is screened away in our greenhouse). Fungi are much less of a
problem in growth cabinets, where I often worked at temperatures of 16 or
20 C to compensate a bit for the rather low light levels. For how long did
you cultivate the samples? My experience is, that the first half year or so
fungi are not really a problem, but later they may get worse (as may algae
be). Of course, in conditions with higher temperatures, as you are likely
to face in summer, things may ge a lot faster. And of course, avoid at all
times to expose your boxes or petri dishes to direct sunlight - such
exposure usually leads rapidly to very high temperatures killing your
bryophytes, and then an invasion of fungi is inevitable.
So, a solution to your problem may depend on the facilities available to
you. If you have no possibilities to control light and temperature more
rigorously, Janice's suggestion to put your samples in open containers in
much larger boxes which themselves are closed sounds very good to me - as
a control, you might add a few petri dishes with only sterilized soil, to
see which species might be blown in in your set-up. This method of open
dishes with the use of controls has been practised a lot by Irene Bisang in
her work on diaspore banks of agricultural soils.
I'm not sure how easy it is for you to obtain literature; if you need some
reprints (I wrote some review papers as well as some practical studies on
bryophyte diaspore banks) please do not hesitate to ask me.
I look forward to your response, and I hope that the e-mail address is correct.
Heinjo During
H.J. During
Department of Plant Ecology
F.A.F.C. Went Building, P.O. Box 800.84
NL-3508 TB Utrecht, The Netherlands
Tel. +31 30 2536847
Fax +31 30 2518366

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