Basically what’s happening for you is the sandy soil drains away any water and prevents it from being absorbed into the log. What dries a log is the ambient humidity being lower than what is inside of a log. With dry winds the log becomes dedicated very quickly and because the trapped water is always trying to remain in a balance it seeks areas of low moisture(outside the log). In a very humid area like the coastal rainforests of Vancouver island the humidity is often much higher and it rains frequently into the organic top layer the water doesn’t leave the log quickly and is held near the surface of the soil. This creates an environment where bacteria, insects, and fungus thrive, trees being full of carbohydrate are then a gigantic reserve of energy that allows the cellular structure to be broken down by decomposition. When logs are being used for structural timber you don’t want any of the lignin to deteriorate by being rotted out as this will reduce the strength that the wood has. I hope that answered at least in part what you were asking.
