The tallest known tree on earth is located in Redwood National Park in northern California. More than twelve hundred years old, it is approximately 380 feet tall--and still climbing! For more than twelve hundred years, a little sprout has grown, survived fires, drought, and logging, and flourished undiscovered. Tall-tree researchers found the tree in 2006 and at more than 380 feet today--and still growing--it's the tallest tree known on earth.    A unique, vibrant ecosystem hides high in the coast redwood's canopy: huckleberry bushes, ferns, and mosses grow atop its branches, while salamanders and squirrels scamper from limb to...