Influence of Volcanic Eruptions on Xylem Growth Patterns

Xylem formed in four pine trees growing near Paricutin Volcano, Mexico, during 8 years of volcanic activity had several kinds of abnormalities, including narrow, wide, asymmetrical, and incomplete annual growth layers, and abnormally low, as well as high, ratios of dense to porous wood. Five other pine trees were studied 12 years after volcanic activity had ceased. Only one of them was consistently producing normal annual growth layers. Among the others porous wood was produced almost exclusivcely, making it impossible to correlate growth layers with years. Reduced supplies of photosynthate, poor aeration, and abnormal supply of auxin may be responsible for the abnormal growth pattern.