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Indicator plants

Jari Oksanen jari at ibg.uit.no
Wed Apr 17 13:36:41 EST 1996

In article <Pine.HPP.3.91.960416142801.7769A-100000 at commlink.zdv.uni-tuebingen.de> martin adler <kapib01 at commlink.zdv.uni-tuebingen.de> writes:
>From: martin adler <kapib01 at commlink.zdv.uni-tuebingen.de>
>Subject: Re: Indicator plants
>Date: Tue, 16 Apr 1996 14:34:20 +0200

>On Tue, 16 Apr 1996, Mark Thorson wrote:

>> In article <4krbos$5u8 at altrade.nijmegen.inter.nl.net>,
>> Frits v/d Laan <f.vd.laan at inter.nl.net> wrote:
>> >I would like to get any information about plants that are known to 
>> >indicate at a early stage anything to do with there environment,
>> >shortage or to much of nutrician N, P, K, Mg etc.  or are sensitive for
>> >or atract insects earlier than most plants.
>> Lichens are indicators of air pollution.  Unlike vascular plants,
>> they don't have any way to get rid of toxins, so they are
>> particularly sensitive to environmental pollution.
Lichens are sensitive to some pollutants, but not to all. For instance, it is 
easy to find plants which are more sensitive to ozone. Lichens are traditional 
indicators of sulphur dioxide pollution, in particular. Traditionally they 
were used only in worst cases, where the complete absence of some species 
indicated really dirty air. They may not be as effective in finding small 
differences in air quality with cleaner air.

I'm not sure that the mechanism suggested above is the reason behind lichen 
sensititivity. They have within-cell detoxification mechanisms just as well as 
other fungi and algae. On the other hand, they are very good catchers of dry 
and wet deposition, and the "symbiotic" balance between fungus and alga is 
easily de-stabilized.

>some (epiphytic) mosses are as well. e.g. (in central europe) most 
>orthotrichum spec. tend to disappear with increasing air pollution (
>or over-nutrition), a few like o.diaphanum tend to profit from this as 
>long as the changes are not too severe.

>concerning lichens, there are a few that are rather resistant and may
>profit from environmental changes, such as xanthoria parietina or 
>lecanora muralis.

If an environmental variable has an effect on the abundance or condition of a 
plant species, then the abundance or condition of that plant species can be 
used as an indicator of that environmental variable. That means, all plants 
are indicator plants. The problem is to find their indicator values (I can 
imagine two meanings for "indicator value", but both are research problems). 

Original poster asked about "indicator" plants used in mythical agriculture. I 
won't bother her /him with my response, but I removed the alt.groups.
--- Jari Oksanen Tromssa, Ruija / Romsa, Norga / Tromsø, Norge

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