Investigating the carbon isotope composition and leaf wax n-alkane concentration of C3 and C4 plants in Stiffkey saltmarsh, Norfolk, UK

Abstract

The carbon isotope composition of terrestrial plants records valuable ecophysiological and palaeoecological information. However, interspecies variability in 13C/12C, at both the bulk and compound-specific (CS) level, requires further exploration across a range of ecosystem types. Here, we present bulk and n-alkane δ13C values, and n-alkane concentrations, from seven plants (C3 and C4) growing in a temperate UK saltmarsh. Inter- and intra-species variation in n-alkane δ13C values among C3 plants ranged from 8‰ (n-C31) to 10‰ (n-C27) across the 2011 and 2012 growing seasons, exceeding variability in bulk tissue (7‰). In contrast, the C4 monocot showed < 2‰ seasonal shifts in bulk and CS values. As a result of the variability in our CS data, we calculate that n-alkane based C3/C4 reconstructions in temperate saltmarshes have a maximum uncertainty of ∼11%. For dicots and succulents, seasonal bulk and CS δ13C trends diverged, while for C3 and C4 monocots, bulk and CS values followed similar temporal patterns. Fractionation between bulk and n-alkane carbon isotope values varied from −4 to −10‰ for C3 plants, and reached −13‰ for the C4 monocot. We explain discrepancies between bulk and n-alkane δ13C values by referring to possible interspecies variation in salinity adaptation, which may influence the partitioning of pyruvate, shifting the isotopic composition of lipid biomarkers. These findings open new avenues for empirical studies to further understand the metabolic processes fractionating carbon during the synthesis of n-alkanes, enhancing interpretation of the biomarker signal from the geological record

Severe drought-influenced composition and δ13C of plant and soil n-alkanes in model temperate grassland and heathland ecosystems

“…6 and 7). A similar range of differences between bulk and compound specific δ 13 C value has been described for leaf biomass (Collister et al, 1994;Conte et al, 2003;Eley et al, 2016), roots (Wiesenberg et al, 2004;Chikaraishi and Naraoka, 2006) and soil (Cayet andLichtfouse, 2001, Wiesenberg et al, 2004).…”

The paleolimnologist's guide to compound-specific stable isotope analysis – An introduction to principles and applications of CSIA for Quaternary lake sediments

“…The δ 13 C values of alkyl lipids are susceptible to more specific and often local factors. Eley et al (2016) demonstrate that n-alkane δ 13 C values of C3 and C4 plants from a temperate 378 saltmarsh show a significant variability of δ 13 C values, with differences between C3 species of 379 up to 10 ‰ and pronounced intra-species differences across the growing season. In a tropical 380 wetland setting, Yamoah et al (2016) observe large-scale variability in n-alkane δ 13 C values, 381 with long-chain compounds becoming isotopically enriched during drier periods.…”

“…1550Therefore, the combination of paleohydrological and mineralogical data with source-sensitive 1551 CSI data is advisable. Where possible, alkyl lipids and their isotope values from extant sources 1552 should be investigated in order to reduce the uncertainty in the interpretation of CSI data from 1553 environmental archives (e.g.,Eley et al, 2016). Studies that use multiple n-alkyl compounds 1554 (e.g., n-alkanes, n-alkanoic acids) or combine δ 13 C and δ 2 H measurements are still few but 1555 will likely enhance our understanding of how alkyl lipids are ultimately preserved in geological 1556 records(Sachse et al, 2012;Sessions, 2016;Diefendorf and Freimuth, 2017).…”

Leaf Age Compared to Tree Age Plays a Dominant Role in Leaf δ13C and δ15N of Qinghai Spruce (Picea crassifolia Kom.)

“…In particular, leaf carbon isotope composition (δ 13 C), which reflects the balance between leaf conductance and photosynthetic rate [4], is widely used to analyze intraspecific or interspecific differences in photosynthetic and physiological characteristics [5,6], to measure the long-term water use efficiency under different environmental conditions and to reveal significant functional changes in plant metabolism and adaptation to various environmental stresses [7][8][9]. In addition, the natural abundance of 15 N in leaves or roots has been proposed as an important tracer to reflect the outcome of different processes affecting δ 15 N compositions, thereby providing an integrative measure of terrestrial N processes [10][11][12].…”

“…More importantly, variations of δ 13 C and δ 15 N values during different plant development and growth stages (for example, stand age class, tree age class) have been neglected. Currently, increasing attention has been paid to investigating the significant variations in stable carbon isotopes among different plant organs, such as leaves, stems, shoots, roots, or different plant species including C 3 and C 4 plants [3,[13][14][15]. However, research about the variations in the natural abundance of 13 C and 15 N with leaf habit, phenological leaf traits or leaf age class on intermediate scales remains incomplete [10,13].…”