This photo is on the infamous Slim Shady trail. Although the trail is only designated as a blue, it offers a pretty solid challenge to both technically skilled and physically fit with its short punchy climbs and many optional lines. Additional info can be found here: MTB Project/Slim Shady
The plant is called a Century Plant. They are blooming everywhere in Sedona right now. Some have yellow flowers like this one, some red flowers. The booming signifies that the plant is near the end of its 10-30 year life.