Soil Warming Accelerates Biogeochemical Silica Cycling in a Temperate Forest

Abstract

Biological cycling of silica plays an important role in terrestrial primary production. Soil warming stemming from climate change can alter the cycling of elements, such as carbon and nitrogen, in forested ecosystems. However, the effects of soil warming on the biogeochemical cycle of silica in forested ecosystems remain unexplored. Here we examine long-term forest silica cycling under ambient and warmed conditions over a 15-year period of experimental soil warming at Harvard Forest (Petersham, MA). Specifically, we measured silica concentrations in organic and mineral soils, and in the foliage and litter of two dominant species (Acer rubrum and Quercus rubra), in a large (30 × 30 m) heated plot and an adjacent control plot (30 × 30 m). In 2016, we also examined effects of heating on dissolved silica in the soil solution, and conducted a litter decomposition experiment using four tree species (Acer rubrum, Quercus rubra, Betula lenta, Tsuga canadensis) to examine effects of warming on the release of biogenic silica (BSi) from plants to soils. We find that tree foliage maintained constant silica concentrations in the control and warmed plots, which, coupled with productivity enhancements under warming, led to an increase in total plant silica uptake. We also find that warming drove an acceleration in the release of silica from decaying litter in three of the four species we examined, and a substantial increase in the silica dissolved in soil solution. However, we observe no changes in soil BSi stocks with warming. Together, our data indicate that warming increases the magnitude of silica uptake by vegetation and accelerates the internal cycling of silica in in temperate forests, with possible, and yet unresolved, effects on the delivery of silica from terrestrial to marine systems.

Spatial variations of litterfall silicon flux and plant-available silicon in highly weathered soil in a lowland mixed dipterocarp forest of Lambir Hills National Park in Borneo

“…For better understanding of Si dynamics in soil water, future study should measure Si concentration in soil water at frequent intervals on a longerterm (e.g. Gewirtzman et al 2019) in relation to litter decomposition and rainfall patterns.…”

High Productivity Makes Mangroves Potentially Important Players in the Tropical Silicon Cycle

“…Sediment ASi concentrations are on par with those reported for temperate forests (Gewirtzman et al, 2019) and several temperate salt marshes, both from North Carolina (United States) (Norris and Hackney, 1999) and an outlet of the Yangtze River (China) (Hou et al, 2010). However, the ASi concentrations (0.42-1.94% Si) measured in the top 2 cm of the mangrove sediments we studied here are drastically lower than those reported for the top 1 cm of sediment in two New England temperate salt marshes (∼4% ASi by dry weight) (Carey and Fulweiler, 2013).…”

Long‐Term Changes in Concentration and Yield of Riverine Dissolved Silicon From the Poles to the Tropics

“…Increases in Si fluxes have been observed in streams of the high Arctic in areas with high rates of permafrost thaw and increased active layer depth, which was related to increases in rates of chemical weathering and soil‐water interactions (Carey et al., 2020; Frey & McClelland, 2009). In temperate forested ecosystems, long‐term warming experiments have resulted in faster internal Si cycling between vegetation and soil solution (Gewirtzman et al., 2019). Tighter terrestrial Si cycling thus reduces the Si available for hydrologic transport into adjacent river ecosystems and reduces net exports.…”