Stable isotope analysis in tree rings of conifer species relevant to fire history study

Smoke and particulate matter released from forest fires, affecting the photosynthetic rate and stomatal conductance, may change the isotope composition in tree rings. Therefore, analysis of tree-ring isotopes could be a promising approach to monitor fires. We hypothesized that forest fires could influence the abundance of carbon (δ 13 C), oxygen (δ 18 O) and nitrogen (δ 15 N) isotopes and the radial growth of tree rings of conifers through their impact on the physiological processes. We collected wood cores from four coniferous species in northern and southern China. The isotope composition of these samples was analysed to shed light on the correlation between fire occurrence and tree-ring isotopes. We found that fires led to an increase in δ 13 C but a decrease in δ 15 N in the whole wood, while significant increases of above 0.5‰ in δ 13 C and a decrease of 0.2 to 0.5‰ in δ 18 O in the α-cellulose were observed. Meteorological factors including precipitation and relative humidity influenced the isotope abundance. Besides, forest fires inhibited the radial growth of conifer trees, particularly Cryptomeria fortunei . Our results suggest that variations in δ 13 C and δ 18 O abundance in tree rings play an essential role as an indicator of forest fire occurrence, providing additional insights into the study of fire history. This article is part of the theme issue ‘Novel fire regimes under climate changes and human influences: impacts, ecosystem responses and feedbacks’.