Tree-ring δ15N of Qinghai spruce in the central Qilian Mountains of China: is pre-treatment of wood samples necessary?

A knowledge of the tree-ring stable nitrogen isotope ratio (δ15N) can deepen our understanding forest ecosystem dynamics by indicating long-term availability, cycling and sources (N). However, radial mobility N blurs interannual variations in records. Previous studies chemical extraction tree rings before analysis had produced inconsistent results it is still unclear whether necessary to pre-treat wood samples from specific species remove soluble compounds determining δ15N values. We compared effects pre-treatment with organic solvents hot ultrapure water on concentration endemic Qinghai spruce (Picea crassifolia) growing interior central Qilian Mountains, China, during last 60 a. assessed different preparation protocols removal labile investigated need values rings. Increasing trends were consistently observed both extracted unextracted samples. The total removed was about 17.60%, a significantly higher amount sapwood section (P<0.01). decreased 1960 2019 Extraction increased markedly 5.2‰ reduced series. little effect, only slight decrease 0.5‰. Our showed that pattern inter-ring movement not minimized either or water. It unnecessary conduct for because its negligible effect N. variation trend influenced heartwood-sapwood transition zone. suggest climate-sensitive could be used explore ecophysiological while focusing variations.