Delignification - or chemical defibration.

Chemical delignification is a process that breaks down the lignin in timber. Lignin is an organic polymer that acts as a glue in timber (amongst other things), giving structural integrity to cell walls and thus holding the fibres together. It's the same material that gets attacked by fungal decay. The result is similar, the timber loses its structural integrity and slowly flakes apart. 

Chemical delignification gives this roof batten its "hairy" appearance.  

Delignification is often found in roof timber battens as depicted in these pictures, being caused by chemicals in the air. Often it is found near heavy industry, major roads or not far from the Sea.  

If there is significant damage caused by delignification then it's best to get it checked for structural integrity by a builder, seeing that roof battens are often affected by this phenomenon, caution should be exercised when walking around on roofs.

This chemical defibration was discovered in Newcastle, an area with historically a lot of heavy industry and is not too far from the ocean!

See a video showing the obvious effects of chemical defibration on roof battens.  

Timber post severly damaged by wood rot (fungal decay).

This highlights the damaging affect of fungal decay (commonly known as wood rot) on timber.
This post at the bottom of a staircase is severely structurally compromised as the fungus breaks down the timber structure.
This post was very fragile and could easily be broken into pieces by hand.
This was found during a termite inspection, many people do not realise how important it is for timber to be protected against fungal decay by sealing it. Although not as quick to act as termites are, ultimately it is just as destructive as it causes structural failure of the timber. It is also a conducive condition for termites.

Wood rot - timber in garden areas.

A rotting landscaping timber - due to constant moisture being present.

Quite often, wood rot is overlooked as a timber pest. But fungal decay can be a great cause of timber damage, as well as a sign that timbers are susceptible to termite attack.

It's important that any timber that is in ground contact is treated, and if it's not in ground contact that it's sealed. Otherwise it will easily rot especially if the climate or environment around the timber allows a constant supply of high ambient moisture to feed the fungus.

His timber post wasn't even in contact with the soil, but it's exposure to the elements have allowed it to rot significantly.