Fire effects on phytolith carbon sequestration

Phytolith have been recognized as an important soil bioavailable Si source for plants, as well as a sink of C and heavy metals in soils. Though the impacts of fire and heat on phytolith sequestration of some nutrients (phosphorus, potassium) and heavy metals have been addressed, little attention has been paid to fire's effects on phytolith carbon sequestration. In this study, the carbon and dissolved Si content of phytoliths extracted from 6 common grass species and their burned ashes, as well as phytoliths collected from different areas (burned, transitional, and unburned) of a pine forest, were compared to characterize the effects of open fire on phytolith carbon content, solubility, and carbon sequestration. The carbon content and Si dissolution of ashed phytoliths varied between plant species, and differed with phytoliths from modern plants. The topsoil phytoliths had increased carbon content, and generally decreased solubility across the gradient of unburned, transitional, and burned pine forest. We therefore conclude that open fire can cause changes in phytolith related carbon content and solubility, as well as its preservation in soils. This study provides new perspective on the effects of open fire on phytolith carbon sequestration and its estimation.