Merino wool? Yes. It makes a good base layer. For spring and fall, anyway. In the heat of summer(>80F,) I prefer a cotton T shirt. It seems to absorb water, hold it and distribute it better than any synthetic. Wool is not quite as good as cotton, but close. It does not soak water into the fibers as well as cotton.
When you first put it on, it can feel slightly warm. This will cause your skin to sweat a little. This will dampen the cloth, and distribute the moisture for evaporation. It will then feel cooler. A similar effect to an old "swamp" cooler. This will cut back your sweating. So, the micro-climate will remain moist, and, you will retain overall moisture. As it gets cooler over the course of a day, it will dry...adding a heat layer. Merino wool is good for both, cold and warm, types of hiking weather. The down side is the cost. A good UL merino wool T shirt can cost around $30-60. They also come in various weights. The lightest is good for late spring, summer, early fall.
Ibex is a good brand. I have one of their long sleeve UL's that has lasted about 5 seasons now. Smartwool Lightweighs are a bit heavier. Not the best for hiking much above 65-70F. The Capalene stuff in light weight isn't real bad, but it dries too quickly to do much good with moisture. Cotton retains permethryn very strongly compared to poly. Wool not as well as cotton. Important in the bug laden ADK's (blackflies, mosquitoes, deerflies, horseflies, ticks, etc.)