KILLINGTON, Vt. (AP) — Aging athletes, new skis and a lack of snow are ganging up on the once-edgy sport of snowboarding, which has seen a marked drop in participation over the last decade.Industry experts say it’s a sign of the maturing of snowboarding, which grew at a rapid pace in the 1990s and early 2000s.Participation in the sport dropped 28 percent from 2003-2013, according to the National Sporting Goods Association. Downhill skiing also took a hit over that period but less of one — at 10 percent.“Snowboarding has definitely gone through a maturation phase,” said Jeff Boliba, vice president of global resorts for Vermont-based Burton Snowboards, which pioneered the sport. “We’ve hit our phases where it’s been the fastest growing sport in the world.