Hello jiinu,
I dont know about the first part, but i can tell you that EF 3.1 has a 0 approach to biogenic carbon, compared to other methods that has a -1/+1 approach. This means that EF 3.1 does not give you "minus" CO2 when the tree is growing, but then it also does not give you "plus" CO2 when you burn wooden products.
Methods such as the one used for EPDs, considers CO2 storage when the tree grows, and releases it when incinerated.
Hope this helps.