Leaf wax n-alkanes and δ13C values of CAM plants from arid southwest Africa

We analysed leaves from 42 plants from the South African Succulent Karoo. Whole leaf δ13C values clearly differentiated 3 different populations, consisting of plants operating under obligate CAM (crassulacean acid metabolism), facultative CAM and C3 modes. In contrast, the leaf wax n-alkane δ13C data from these metabolic groups showed a broader overlapping distribution. CAM plants operating under full CAM mode produced a wide range of apparent 13C fractionation. Succulent/CAM plant wax yield was considerable (up to 23 mg/g in our plants), so its contribution to soil composition and sedimentary leaf wax composition should not be dismissed. The presence of CAM plant wax n-alkanes in sedimentary n-alkanes could therefore be a problem for accessing ecosystem scale C3-C4 proportion.