Silicon isotopic composition of boreal forest vegetation in Northern Sweden

Results for the analyses of composite plant samples for the eight most prolific species in the boreal forest yielded a surprisingly homogenous Si isotopic composition, expressed as δ29Si (± expanded combined uncertainty) and δ30Si, ranging from (− 0.15 ± 0.11)‰ to (0.13 ± 0.06)‰ and (− 0.31 ± 0.08)‰ to (0.22 ± 0.13)‰, respectively. Isotopic and elemental analyses of local airborne particulate material suggest that the exogenous Si contribution varies between < 1% and > 70%, indicating that the potential surface contribution must be considered during Si uptake studies. The present study thus provides evidence that thorough appreciation of the forms of Si in plants is an absolute requirement when assessing the plant impact on the Si cycle via the difference in dissolution kinetics for phytoliths and lithogenic Si.