Question
It's a mature tree that leafed out this spring with several dead limbs.  The trunk exhibits black streaking (bark is missing to the cambium layer which is black), 2 -3 inches wide, from base to the top similar in location,length, etc. to a lightning strike except that did not happen.  We had a dry year last growing season.

Answer
Sounds like a disease called hypoxolyn canker. Hypoxylon cankers are prevalent and highly visible disease problems affecting oaks and other hardwoods in Florida. Hypoxylon spp. are not considered aggressive killers. Instead, they are usually secondary in that they take advantage of trees suffering from any number of injuries of stresses. Hypoxylon cankers are often the finishing blow to oaks suffering from water stress, root disease, soil compaction, construction damage or other, related injuries.

Trees with extensive Hypoxylon infections are usually beyond repair. Removal of severely infected trees to reduce local sources of inoculum (i.e., infectious spores) is recommended. Careful pruning of branches that have localized infections should help prevent advancement of the fungus within the infected trees. Prevention of infections through avoiding wounds, root damage, etc., and providing adequate moisture via irrigation to susceptible trees during prolonged periods of dry weather is the best method of control. The presence of Hypoxylon cankers is usually an indicator of severe stress and often a warning to take precautions to reduce stresses (if they can be identified and reduced) affecting nearby trees of the same species.
Watering during dry periods with 1 inch of water (place a pan under the tree and turn the sprinkler on and when the pan has 1 inch of water in it stop). Fertilize the trees with 10-10-10 fertilizer at the rate of 1 lb per inch of trunk diameter scattered around the tree and watered in good. This should help the trees regain their health.