Response of Lodgepole Pine Growth to Co2degassing at Mammoth Mountain, California

We conducted dendroclimatic and stable isotope analyses of lodgepole pines (Pinus contorta) located in high-mortality sites at Mammoth Mountain (California, USA) to test for tree responses to magmatic degassing. Existing climatic and tree-ring data from nearby Yellowstone National Park were used for comparison. Sampled trees were scarcely sensitive to climate, and their growth showed an overall decline during the 20th century. Past growth rates of currently dead and stressed pines plummeted after 1990, when degassing of magmatic CO2 was first reported in the area. No consistent or strong correlation was found with monthly and seasonal climatic parameters. Stable carbon isotopes were measured on holocellulose extracted from annual rings of a dead pine, a stressed pine, and a live pine. The δ13C signature of the dead and stressed pines showed enrichment in heavy carbon beginning in 1990, which could be related to stomatal closure following impairment of root systems by high levels of magmatic CO2 in the soil.