Co-evolution of xylem water and soil water stable isotopic composition in a northern mixed forest biome

Abstract. Plant–soil water isotopic dynamics in northern forests have been understudied relative to other forest types; nevertheless, such information can provide insight into how may respond hydroclimatic change. This study examines the co-evolution of xylem and soil stable compositions a mixed Ontario, Canada. Gross precipitation, bulk were sampled from pre-leaf out post-senescence 2016 for eastern white cedar, hemlock, red oak pine. Near-bole contents mobile measured last three species. Mobile did not deviate significantly local meteoric line (LMWL). In contrast, near-surface showed significant evaporative enrichment LMWL peak leaf under all tree canopies, while was depleted 18O particularly 2H throughout growing season. Inter-species differences deviation their temporal changes emerged during season, with coniferous species becoming isotopically enriched, that became more 18O. These divergences occurred despite thin cover (generally <0.5 m depth bedrock) which would constrain inter-species rooting depths this landscape. Isotopic fractionation at root via evaporation through bark are among most plausible potential explanations deviations between compositions. Differences timing intensity use deciduous trees account inter-specific variations composition its evolution season