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Roger the shrubber

deciduous trees and climate change

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Apologies if this has already been covered. I work in north London and herts. Tip pruning a apple tree the other day I noticed sap is up and buds are starting to swell and it got me thinking that since the leaves did not fall until December and it looks like the buds will be bursting soon ( if it does not snow) what are the effects on trees of a reduced dormant season ( because I am sure there will be some negative issues) as trees are by there their design need a rest in winter (dormancy)before using the energy in spring for regrowth. I have looked on forestry commission re: climate change and trees-there is info on there regarding forests but nothing on trees in a urban environment. The other thing I was thinking was, most tree seeds need a period of extreme cold to germinate so if the temperatures throughout the winter are not low enough will the seeds be sterile? Any thoughts appreciated-im just curious....

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Without going into too much detail, the things that come to mind are:

 

Not all tree seeds require a period of cold to germinate (stratification), and every seed has a different required temperature tolerance. If temperatures do not satisfy the requirements of a seeds germination, it will continue to be dormant until next season. Seeds can remain dormant for many years! This way they only germinate when it is right for the species.

 

Regarding climate change, the only interesting points I know are that global warming results in an overall drop in photosynthesis. There is MORE CO2, but that means less available nitrogen. This means less amino acids, less proton pumps, and basically less photosynthesis. More light is a factor, but the limit of photosynthesis is capped by the amount of CO2, so the only affect that has is to increase temperatures, and therefore transpiration (which means stomata close resulting in less gaseous exchange, and again, less photosynthesis)

 

I'm not sure what the effects of a reduced dormant season is when there is a mild autumn/winter, however when leaves are dropped, the useful elements are recycled and reabsorbed by the process of senescence, so I cant imagine that there will be a great net loss... if anything if it has been in leaf longer, it has been able to build up and store more chemical energy from photosynthesis!

 

Hope this is somewhat helpful and not completely incorrect

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Apologies if this has already been covered. I work in north London and herts. Tip pruning a apple tree the other day I noticed sap is up and buds are starting to swell and it got me thinking that since the leaves did not fall until December and it looks like the buds will be bursting soon ( if it does not snow) what are the effects on trees of a reduced dormant season ( because I am sure there will be some negative issues) as trees are by there their design need a rest in winter (dormancy)before using the energy in spring for regrowth. I have looked on forestry commission re: climate change and trees-there is info on there regarding forests but nothing on trees in a urban environment. The other thing I was thinking was, most tree seeds need a period of extreme cold to germinate so if the temperatures throughout the winter are not low enough will the seeds be sterile? Any thoughts appreciated-im just curious....

 

 

tree's weren't designed they evolved, and they've evolved though worse conditions than these.

 

all those tv experts an so called scientists will say that there could be problems but if the tree senses that it's ok to bloom i'll defer to 200 million years of evolution, not a scientist!

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In 2013 my apples were a whole month late coming into bud, they might do the same again this year if it goes cold.

As a fruit grower I keep a close eye on the apple trees and what they are doing. Mild weather now might well cause them to show signs of movement but any cold and they will go backwards.

 

Have not seen any signs at all of movement on mine yet and I spent the whole of the last two days looking.

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I'm not being argumentative, but why are you sure there are negative effects and how do you know trees by design require a rest in winter?

 

Hi, I am a arboriculturist and horticulturist not an ecologist, however everything I have studied in the natural world, eco systems are connected for example bees, one specific species becomes extinct , the species of plants that the bee pollinated become extinct and it spirals up the food chain.

 

In reply to your question how do I know trees require a period of dormancy- only what I have read.. shigo, modern arb page 268 and 271, phenology.

If the period before dormancy trees expend lot of energy laying on new wood and storing energy Quote shigo- "Every living system must rest" , Perhaps after autumn the leaf abcission zones take so much energy from the system the levels of potential energy need to rest before onset of highly photosynthetic period - spring, -

 

who knows mate I'm just interested in this subject and throwing it out there to you all I don't claim to have all the answers....

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I'll have a look at my copy of Shigo. Living systems may benefit from rest, but it is a period during which energy is expended but not replaced and exposure to disease is high but defences are low. I just wonder if the benefits of rest for trees outweighs the drawbacks?

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I am not convinced that trees need a rest. If there was a process that they underwent during this 'rest' that in some way benefited them, then I could agree but I am not aware of any such process. If you view it as a condition enforced by an absence of conditions suitable for growth rather than any sort of restorative process it may help.

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