Net fractionation of hydrogen isotopes in n-alkanoic acids from soils in the northern boreal forest

摘要: Abstract Plant-derived n-alkyl lipids are well-preserved in sedimentary archives, and their stable hydrogen isotope ratio (δDwax) is a proxy for precipitation δD climate. Net fractionation of H isotopes between plant source water and n-alkyl (ewax/water) the largest uncertainty interpreting this depends on type environment. Although popular proxies, n-alkanoic acids (n-acids) less frequently calibrated modern environments than n-alkanes. We constrain net (ewax/MAP – Mean Annual Precipitation) northern boreal forest based on n-C24,26,28 acids topsoils from 13-site network Yukon, Alaska Northwest Territories (60–68°N). n-Acid homologue distributions common plants (gymnosperm trees, shrubs, forbs, C3 grasses mosses) show that soil n-acids dominated by mosses, but with reduced carbon preference index compared to fresh possibly owing post-depositional degradation. Regionally averaged ewax/MAP values −93 ± 10‰, −101 ± 11‰ −95 ± 11‰ n-C24,26,28 acids, respectively, which similar reported low high latitude regions. find n-C26,28 (but not n-C24) significantly (p ≤ 0.05) smaller increasing decreasing mean annual temperature, factors covary across our network. Since typically known ancient deposits, we parsed dataset obtain latitude-specific ewax/MAP values 60–64°N (−107 ± 8‰ n-C26; −101 ± 8‰ n-C28) 65–68°N (−94 ± 11‰ −89 ± 10‰ n-C28). These soil-derived relevant hydroclimate reconstructions using fossil n-acids paleosols comparable paleoflora latitude.