Mark Harmon, a longtime faculty member at Oregon State University, has been watching number 219, and more than 500 other logs nearby, decay for 40 years. He has trekked to this site in the H. J. Andrews Experimental Forest, a watershed nestled in Oregon’s western Cascade Mountains, at least 100 times. His goal: establish an exhaustive baseline dataset that any scientist could use to test hypotheses about tree decomposition or to compare patterns of decomposition in the Pacific Northwest with those in other regions. …In a 2020 analysis, Harmon and his colleagues estimated that decay rates can vary by a whopping 244-fold across species and climates. …Scientists used to assume that decomposition was instantaneous, Harmon says—that when a tree dies, it essentially disappears. “But that’s not true anywhere on Earth, and it’s never been true,” he says. A dead tree is “just a transition to something else.”