Rainfall and land use control Si cycling in wet tropical Andosols
(2019)
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- Abstract
- Plants take up silicon (Si) from soil solution, and form biogenic silica bodies (phytoliths) that return to soil with plant debris. In soils, phytoliths readily dissolve, and thus contribute to the reservoir of plant available Si. The soil-plant cycle of Si depends on soil type, plant species, climate and land use. We show that the control of soil weathering stage on the soil-plant Si cycle in the tropics depends on land use. In rice croplands, an increase in weathering leads to a decrease in annual plant Si uptakes. The opposite trend is observed for tropical forests. This difference is linked to contrasting rooting systems and subsequent biological pumping, which is much deeper in forest than in cropland. We further study the Si soil-plant cycle under forest and intensive cropping of banana and sugarcane on strongly desilicated Andosols in the humid tropical conditions of Basse-Terre, Guadeloupe. Here, we first set up a new protocol to estimate the pool of phytoliths in soil. Then, we show that mean annual rainfall (MAR) and land use control the fluxes of Si in these soil-plant systems. The increase in MAR increases the leaching of Si, decreases the amount of plant available Si, and enhances phytolith dissolution. Converting forest into banana and sugarcane cropland promotes the “mobility” of Si in the soil-plant system. Indeed, relatively to a neighboring forest, the annual Si plant uptake and return to soil is ~4 and ~10 times larger in banana and sugarcane, respectively. Moreover, the return of inedible plant parts to soil limits Si exports by crop harvesting, and built up an important soil phytolith pool that controls ~70-95% of the dissolved Si pool. This highlights how much the management of the inedible plant parts is important in cultivated ecosystems.
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Vander Linden, C. (2019). Rainfall and land use control Si cycling in wet tropical Andosols. https://hdl.handle.net/2078.5/124665