What are the main drivers of the silicon cycle in a volcanic watershed (Guadeloupe)

Silicon(Si)is the second most abundant element of the Earth crust. Its cycle is tightly linked to the carbon(C)cycle as Si fluxes from land to ocean tremendously impact the C storage capacity of the oceans. Both the agricultural land use and the soil weathering degree impact these fluxes. However,little is known about the relative importance of the land use or of the soil weathering degree on the Si fluxes among one watershed. In this study,we quantified the Si pools in fluxes in banana,sugar cane,and forested plots on the volcanic island of Basse Terre(Guadeloupe)under different climatic conditions to determine the impa ct of the soil weathering degree and of the land use on the Si cycle. Si fluxes werealso quantified in two rivers at different stations with different proportion of their watersheds covered by crop lands to define if agricultural land use may importantly impact the river Si fluxes towards oceans. The Ge/Si ratio was used as a tracer to determine the main contributor of Si in the rivers.