Mr tree

[Tony Croft aka hamadryad]

The lichens on trees does interest me but currently I know very little (nothing) about the subject. One very basic question - does lichen actually harm the tree? When I see a tree covered in lichens, especially fruit trees, they always look to be in very poor health. In laymans terms please, how do they react with the tree? Many thanks, Ed.

 

whilst the lichens themselves are harmless they indicate a progression to a damp moss dominated environment, this can maintain damp, even acidic conditions favouring lower plants and tree pathogens.

[BenR]

I think it depends on the situation Hama. I would agree with you on the mosses because I think they require more water.

 

Lichens however can completely dehydrate and survive for years in dry conditions. There are lichens growing in the Negev desert in Israel for example. One of the driest places on the planet. They rehydrate when it rains and then photosynthesise briefly.

 

In the UK they are on most trees and get all of the water they need from stemflow when it rains. So I don't think that is any more damp than normal conditions. However, when you start getting mosses and actual brypohyte matts which retain water and can develop their own soils in the trees (Those Sillett papers we were talking about mention this) I would agree that the conditions must be very damp, which as you say favours pathogens.

[RobArb]

is there any literature in the shape of books, that explain lichens and mosses in laymens turns from the ground up...

 

i.e a novice like myself who is learning and keen to learn but does want to get minid boggled straight away... a beginners book:biggrin:

 

not read your dissertation yet ben, finished off my assignment first got a free few days now though so will give it a read

 

also bought mattheck's book hama, tis on its way:thumbup:

[Tony Croft aka hamadryad]

I think it depends on the situation Hama. I would agree with you on the mosses because I think they require more water.

 

Lichens however can completely dehydrate and survive for years in dry conditions. There are lichens growing in the Negev desert in Israel for example. One of the driest places on the planet. They rehydrate when it rains and then photosynthesise briefly.

 

In the UK they are on most trees and get all of the water they need from stemflow when it rains. So I don't think that is any more damp than normal conditions. However, when you start getting mosses and actual brypohyte matts which retain water and can develop their own soils in the trees (Those Sillett papers we were talking about mention this) I would agree that the conditions must be very damp, which as you say favours pathogens.

 

I know as well as you do! and I know all about those lichens that absorb fog too. I also think you knew EXACTLY where I was going with the comment. Like I did say, the lichens themselves are not the issue!

[mrtree]

Lichens do not need (in most cases) liquid water, they can adsorb water vapour from the air. In terms of succession they are first and then things such as mosses and bryophytes (hornworts and liverworts) come in as they need a little organic matter to set their rhizoids (primitive roots) into and require liquid water.

 

As these cryptogramic mats form they also become home to lots of microorganism such as algae and cyanobacteria. As such they are little working ecosystems and in old trees are likely responsible for a lot of nitrogen fixation and nutrient cycling.

 

The holding of water and habitation by pathogens is something I do not believe, or at least believe is a serious problem in healthy trees. Crypotgramic mats are an intregal part of many forest ecosystems and as such I believe that while pathogenic organisms may inhabit these places I do not think they are dominate or negatively affect most trees or we would have seen the loss of trees from environments with cryptogramic mats.

 

There has been some research done on these aerial mats and soils but I wonder if a interesting PhD could be done on them in urban trees. Is the relative absence of crytogramic mats in urban trees a problem for the health of the tree? Have we lost an important part of the food web? One need only look at the life (cyanobacteria and algae) in the water that is held within the complex network of leaves of mosses to realize there is huge amount of life that may be beneficial to the overall tree environmant.

[BenR]

Yea, Im sure you know exactly what I was talking about Hama. But I just thought it was worth clarifying for the benefit of anyone else interested in the subject.

 

Just a quick search on google for : 'lichens bryophytes and fungi management'

The first link (other than the google scholar articles)

 

This may give a bit of an overview.

[mrtree]

An excellent starter book on lichens is Lichens by William Purvis ISBN 978-0-565-09153-8

 

Also consider Lichens by Oliver Gilbert from the New Naturalist series. The book is now available as print on demand. By the way the whole NN series is amazing

 

Books such as Lichen Biology 2nd ed. by Thomas Nash are also excellent but far more complex.

 

There is also Mosses and Liverworts by Ron Porley and Nick Hodgetts in the New Naturalist series.

 

British Lichen Society and NHBS also have various small publications and cards about lichens that inhabit tree surfaces

[BenR]

Top post Mr.Tree.

 

In one of Steve Sillett's papers, he mentions finding some sort of organism in the water of these mats (Can't for the life of me remember what) that only normally exists in sea water. Go figure.

 

Oh and check this link: Error For an online key to identifying lichens

 

Also : [ame]http://www.amazon.co.uk/Pollution-Monitoring-Lichens-Naturalists-Handbook/dp/0855462892/ref=sr_1_9?s=books&ie=UTF8&qid=1299101398&sr=1-9[/ame]

 

This was a good one for my dissertation and has a good key too!

Edited March 2, 2011 by BenR
more info

[mrtree]

Also try a book Forest Canopies, 2nd. ed. by Lowman and Rinker to get an idea of forest canopy complexity and diversity in natural ecosystmes

[Tony Croft aka hamadryad]

Lichens do not need (in most cases) liquid water, they can adsorb water vapour from the air. In terms of succession they are first and then things such as mosses and bryophytes (hornworts and liverworts) come in as they need a little organic matter to set their rhizoids (primitive roots) into and require liquid water.

 

As these cryptogramic mats form they also become home to lots of microorganism such as algae and cyanobacteria. As such they are little working ecosystems and in old trees are likely responsible for a lot of nitrogen fixation and nutrient cycling.

 

The holding of water and habitation by pathogens is something I do not believe, or at least believe is a serious problem in healthy trees. Crypotgramic mats are an intregal part of many forest ecosystems and as such I believe that while pathogenic organisms may inhabit these places I do not think they are dominate or negatively affect most trees or we would have seen the loss of trees from environments with cryptogramic mats.

 

There has been some research done on these aerial mats and soils but I wonder if a interesting PhD could be done on them in urban trees. Is the relative absence of crytogramic mats in urban trees a problem for the health of the tree? Have we lost an important part of the food web? One need only look at the life (cyanobacteria and algae) in the water that is held within the complex network of leaves of mosses to realize there is huge amount of life that may be beneficial to the overall tree environmant.

 

forest decline is driven by the increasing dominance of the mosses.

 

something Dr lee Klinger is rather apt at describing.

 

and trees didnt evolve sloughing bark in a polluted environment

Edited March 2, 2011 by Tony Croft aka hamadryad