I am looking at having some trees prunned in my estate (small garden) and one of the things that has come up is the time of year the trees have to be pruned - i.e. usually in the autumn/winter when the sap is falling - and not in the spring summer when the sap is rising (not always the case but you can see where this is going)
is there an optimum time of year to fell a willow tree? would cutting it down in the autumn for example lead to lower sap content in the willow, for example? is the sap content in the spring higher and will this impact the clefts as the wood is growing faster?
Does the drying process take this all out of the equation?
Does anyone actually know much about trees and willow trees?!!!
I am a researcher in plant metabolism and can tell you a bit about the biology of the "sap movement". Essentially the tree is trying to move the nitrogen contained in the leaves to the bark for storage (as a protein called bark storage protein) through phloem right before winter, else it will be lost with the falling leaves in winter. Nitrogen in THE limiting nutrient for tree growth. And in spring the nitrogen stored in winter is broken down and sent to the shoots via xylem so that the tree can create leaves and carry out photosynthesis.
The soil in general is much drier in the winter than in spring and summer, however it could vary depending upon the location. And the transport by xylem MIGHT require more sap since it is flowing higher up the tree to support growth of shoots and leaves. Major chuck of the leaves is water, so a bit more sap in spring is likely. However, this is probably going to be discernible only in small branches not in the main trunk of the tree.
I am not 100% sure, but IMHO a woody tree is unlikely to have huge variations in moisture content between spring and winter. If I were you I would cut it in winter!