Causation of false ring formation in Pinus banksiana: A comparison of age, canopy class, climate and growth rate

Abstract

False rings may provide a new source of proxy data for historical environmental conditions once the causes of their formation are understood. The objective of this research was to compare tree age, canopy class, temperature, precipitation, and growth rate as potential causal factors in false ring formation in Pinus banksiana Lambert. Our data consisted of 180 P. banksiana tree cores from three stands in northern lower Michigan. All cores were cross-dated and measured and false rings were identified by anatomical features within the wood. Frequency of false rings varied, with 48%, 78%, and 80% of the cores having at least one false ring in the three stands. Although there was within-stand synchrony in the timing of false ring formation no significant correlations existed between temperature and precipitation records and frequency of false ring production. Event years (periods of high false ring formation) were identified and superposed epoch analysis detected significantly higher growth rates preceded periods of false ring formation at one of the study sites. Canopy class had a significant influence on a tree's likelihood of producing false rings: suppressed trees were not likely to produce false rings while codominant and intermediate trees were more likely to produce false rings. Tree age also influences propensity of false ring production with rings formed during the early years of a tree's life being more likely to contain false rings than rings formed later in life. Based on the results of this study, we recommend that dendroecologists include false ring analysis in their historical stand reconstructions to improve their ability to distinguish between releases in growth triggered by canopy gaps (associated with formation of false rings) versus releases in growth triggered by climate (no association with false rings).