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Plant wax n-alkanes serve as reliable biomarkers given their abundance, stability, and distribution in the sedimentary record. As a result, their utility as isotopic indicators of vegetation and hydroclimate is well-established. A less well studied aspect of plant n-alkanes is the use of their molecular distributions, or differences in the relative abundances of homologues, for chemotaxonomy. Limited plant n-alkane datasets from southern and western Africa suggest molecular distributions can differentiate C4 grasses from C3 woody vegetation. Here we examine a suite of plants from East Africa, where almost no plant biomarkers data exists from modern plants. In this study, over 100 samples of 19 species of plants were collected monthly from the Samburu National Reserve in Kenya from October 2001 to March 2003, across multiple growing seasons; n-alkane distributions and concentrations from both individual species and designated plant functional types (PFTs) - based on both photosynthetic pathway and growth form - were investigated. Previously published n-alkane data from western and southern Africa, or the "All Africa" dataset, were examined to further understand potential spatial differences in biomarker distributions. n-alkane distributions in both datasets vary in both individual species and within PFTs. Principal Components Analysis (PCA) was used to analyze distributions of n-alkanes in individual species and in PFTs, to determine the primary sources of variability. Results indicate that n-alkane distributions can be used to separate some individual species - namely, C4 grasses - and can be used to separate PFTs. C4 grasses and C3 woody vegetation were successfully separated in both datasets. Additionally, we found that n-alkane concentrations vary by four orders of magnitude across homologues and PFTs. A compiled African plant data set shows that C31 concentration is the most representative of the plant community for C4 grasses, C3 shrubs, and C3 trees and thus, is most ideal for stable isotope vegetation reconstructions. These data suggest that an organic geochemical approach to plant taxonomy is crucial to future biomarker applications for reconstructing vegetation distribution and structure in past ecosystems.
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n-Alkane Distributions of Modern Plants from C3-Dominated Eastern African Ecosystems
This dataset comprises plant wax n-alkane chain length concentrations and C25-C35 relative abundances of 209 plant specimens from two Kenyan C3-dominated ecosystems, representing a wide range of plant functional types (PFTs). Plant samples were collected in 2018 from Mount Kenya National Park (n=122) and Kakamega National Forest (n=87). At Mount Kenya National Park, samples were collected along an elevational transect (~2400 m to ~3600 m above sea level) from five different ecotones: lower montane forest, bamboo zone, upper montane forest, ericaceous shrubland belt and Afroalpine moorland. Kakamega National Forest is ~1600m above sea level and samples were collected from an open glade, forest path edge, and closed canopy forest. All plant samples were identified to family level, most to genus or species level. Information on collection habitat, photosynthetic pathway, and plant functional type are included. The goal of this dataset was to assess n-alkane distributions for chemotaxonomic signals. Sample analysis took place at Lamont-Doherty Earth Observatory and Harvard University between 2022-2024. n-Alkane data were quantified using a gas chromatograph mass selective detector (GC-MSD) and a flame ionization detector (FID), and response factor corrections were calculated and applied to measured n-alkane peak areas in order to calculate corrected concentrations. The odd n-alkane C25-C35 concentrations were relativized to sum to 1 for the final relative abundance data. For more detailed information, please consult the associated manuscript on the n-alkane distributions and their chemotaxonomic significance: Tweedy et al., 2025.
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- PAR ID:
- 10651458
- Publisher / Repository:
- PANGAEA
- Date Published:
- Subject(s) / Keyword(s):
- Africa alkanes C3 distribution grass Kenya Plant wax proxy Event label Sample code/label LATITUDE LONGITUDE ELEVATION DATE/TIME Species Family Subfamily Additional information Growth form Photosynthetic pathway Microhabitat Vegetation type n-Alkane C10, per unit sediment mass n-Alkane C11, per unit sediment mass n-Alkane C12, per unit sediment mass n-Alkane C13, per unit sediment mass n-Alkane C14, per unit sediment mass n-Pentadecane, per unit sediment mass n-Alkane C16, per unit sediment mass n-Alkane C17, per unit sediment mass n-Alkane C18, per unit sediment mass n-Alkane C19, per unit sediment mass n-Alkane C20, per unit sediment mass n-Alkane C21, per unit sediment mass n-Alkane C22, per unit sediment mass n-Alkane C23, per unit sediment mass n-Alkane C24, per unit sediment mass n-Alkane C25, per unit sediment mass n-Alkane C26, per unit sediment mass n-Alkane C27, per unit sediment mass n-Alkane C28, per unit sediment mass n-Alkane C29, per unit sediment mass n-Alkane C30, per unit sediment mass n-Alkane C31, per unit sediment mass n-Alkane C32, per unit sediment mass n-Alkane C33, per unit sediment mass n-Alkane C34, per unit sediment mass n-Alkane C35, per unit sediment mass n-Alkane C36, per unit sediment mass n-Alkane C37, per unit sediment mass n-Alkane C38, per unit sediment mass n-Alkane C39, per unit sediment mass n-Alkane C40, per unit sediment mass Sum n-alkanes C25-C35, per unit sediment mass n-Alkane C25, fractional abundance n-Alkane C27, fractional abundance n-Alkane C29, fractional abundance n-Alkane C31, fractional abundance n-Alkane C33, fractional abundance n-Pentatriacontane, fractional abundance Average chain length, odd Carbon Preference Index, n-Alkanes (C25-C35) Sampling by hand World Flora Online Gas chromatography - Flame Ionization Detection (GC-FID) and Gas chromatography - Mass spectrometry (GC-MS)
- Format(s):
- Medium: X Size: 10019 data points Other: text/tab-separated-values
- Size(s):
- 10019 data points
- Sponsoring Org:
- National Science Foundation
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