Cross-section of Whitebark Pine
The tree rings in this whitebark pine (Pinus albicaulis) cross-section provide a view back in time. Scientists study the patterns of tree ring growth, scars, and wood coloration to determine how long the tree lived, record changes in climate, and even track past fires, insect attacks, and earthquakes! Follow the date stamps on the tree rings to learn the life history of this 300-year-old tree, which began life in 1708 in the Tobacco Root Mountains of southwest Montana:
1723: The 15-year-old sapling remarkably survived a fire that burned and killed half of the protective skin (cambium) around the small stem.
1805: The Lewis and Clark Expedition passed through this area on their Corp of Discovery journey.
1863: The tree was again burned and damaged in a fire during what was known as the “Civil War Drought”, evident by a large charcoal-lined scar and two round lobes of post-fire growth.
1889: Montana became the 41st state in the Union.
2007: A changing climate of the northern Rockies in the late-20th and early-21st centuries resulted in warmer, drier growing seasons that reduced the growth of the tree. Fewer hard freeze events and longer warm seasons allowed for an outbreak of the Mountain Pine Beetle (Dendroctonus ponderosae), which carries a blue stain fungus that caused the blue stain discoloration seen around the edge of the cross-section. Though it is unknown which factors (i.e. drought, beetle, and fungus) were the ultimate cause, each stressor likely contributed to the death of the tree in 2007.