| 要旨トップ | 目次 | | 日本生態学会第73回全国大会 (2026年3月、京都) 講演要旨 ESJ73 Abstract

一般講演（口頭発表） H02-01 （Oral presentation）

#### Effect of litter on silicon cycling in a forest ecosystem - insight from a litter manipulation experiment【E】

*Ryosuke NAKAMURA（Kyoto University）, Emma SAYER（Ulm University）, S. Joseph WRIGHT（STRI）, Tetsuhiro WATANABE（Kyoto University）, Irene HOLST（STRI）, Edmund TANNER（University of Cambridge）

Silicon is a beneficial element for many plants and varies in leaf concentration approximately from 0.1% to 10% in dry weight among species. In natural ecosystems, silicon is taken up by plants from soil water, incorporated into leaves as opal phytoliths, and recycled through litterfall. It has long been considered that litter is a major source of silicon for plants owing to higher solubility of opal phytoliths than silicate minerals in the soil, but empirical evidence remains scarce. We hypothesized that litter increases silicon availability in topsoil and silicon uptake by trees in a lowland tropical forest. We tested our hypothesis in a long-term litter manipulation experiment in lowland tropical forest in Panama, where surface litter has been removed from five litter removal (L–) plots and added to adjacent litter addition (L+) plots every 4-8 weeks since January 2003, with five undisturbed plots as controls (CT). We collected leaf litter from five traps per plot in September 2022 and pooled it to make one composite sample per plot. We collected soil cores from 0-10 cm depth at four locations in each plot in November 2022 and composited them to make one sample per plot. In February 2024, live leaves were sampled from one mature individual of five common tree species in 4-5 plots per treatment. We measured water soluble silicon in the soil and silicon concentrations in live leaves and leaf litter. We also measured the composition of topsoil minerals (quartz, kaolin and gibbsite). Topsoil mineral composition did not differ among litter treatments but water-soluble silicon concentrations were highest in the L+ plot, followed by CT and L– plots. Foliar silicon concentration differed widely among the five species, with mean species values ranging from 1.2 - 55.4 mg Si g-1, but there was no difference among the litter treatments for any species. Leaf litter silicon concentration varied six-fold among plots but did not differ among litter treatments. Overall, our results do not support the hypothesis that litter is a major source of silicon for lowland tropical forest trees. Instead, we suggest that trees could act as pumps that transport silicon from deep soil to the surface through litterfall, and that silicon from litter may be mostly exported by run-off, without major reuptake by large trees.

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