Relationship between foliar δ13C and sapwood area indicates different water use patterns across 236 Salix genotypes

Abstract

Key message: The relationship between sapwood area and foliar δ13C values varies among 236 Salix genotypes, indicating different water use patterns across these genotypes. Abstract: The relationship between leaf δ13C and plant size (represented by e.g. total leaf area) has been used to analyze different water use patterns of plants. However, the total leaf area (TLA) is difficult to assess in trees. Our aims were to (i) identify a feasible predictor for TLA; (ii) estimate the effects of TLA on leaf-level δ13C and δ18O values; and (iii) evaluate whether the relationship between leaf-level δ13C and a TLA proxy can be used to discriminate between different water use patterns. Various leaf and shoot traits of up to 236 Salix genotypes field-grown in Sweden and Italy were assessed and analyzed. Accumulated shoot diameter and sapwood area (SA) calculated from it were the best predictors for TLA. The SA was significantly correlated with foliar δ13C, but not δ18O values in some genotypes. The effects of SA on foliar δ13C values varied significantly among genotypes, and the foliar δ13C–SA relationship could be used to discriminate between different water use patterns across 236 Salix genotypes. Our results demonstrate a great variability of water use patterns across taxonomically closely related plants, and may also have implications for Salix pre-breeding and selection for different drought conditions.