Estimating gap age using tree-ring width in combination with carbon isotope discrimination in a temperate forest, Northeast China

Abstract

Key message: The accuracy of gap age estimation can be improved from 5–6 to 2 years by analyzing the annual width and carbon isotope discrimination of the rings of gap-surrounding trees. Context: Gap age has a direct link to the composition and structure of regeneration. However, the accuracy of gap age estimation is still limited. Aim: We aim to improve the accuracy of gap age estimation by analyzing the width in combination with carbon isotope discrimination (∆13C) of the rings of gap-surrounding trees. Methods: Twenty-four gap-surrounding trees (nine Ulmus laciniata, eight Fraxinus rhynchophylla, and seven Juglans mandshurica) were selected from eight artificial gaps created in December 2004. First, the growth release (i.e., peak time of percent growth change) for sample trees was measured based on the tree-ring width to identify the rough time range of gap formation. Then, the ∆13C of rings during the time range were analyzed for determining the precise year of gap formation. Results: The peak time of percent growth change occurred from 2005 to 2010 for U. laciniata, 2004 to 2008 for F. rhynchophylla, and 2002 to 2007 for J. mandshurica. Within the range of 2002 to 2010, the ∆13C of rings for all sample trees significantly reduced in 2005–2006 (p < 0.05), which was the estimated year of gap formation. Conclusion: The introduction of ∆13C analysis could effectively reduce the estimating deviations of gap age by only considering tree-ring width analyses and finally improve the accuracy of gap age estimation within 2 years, which can provide reliable information for gap management.