DEDHAM, Maine — Wyatt Beauchamp, 10, scrambled to the top of a pile of haystacks in his family’s high-tunnel greenhouse Tuesday morning, a vantage point that gave him a good view of the excitable flock of chickens that live at his family’s Lone Spruce Farm. He wore a red plaid jacket and a baseball cap, and was confident and full of mischief as he swayed on the stacks, made designs in the frost on the greenhouse roof and threw a handful of hay down at his mother.