Tussocks : biogenic silica hot-spots in a riparian wetland
Faculty of Sciences. Biology
Wetlands: journal of the Society of Wetland Scientists / Society of Wetland Scientists [McLean, Va]
, p. 1115-1124
University of Antwerp
Understanding the factors determining the size and extent of Si cycling in wetlands is important, as more and more research shows they interact strongly within riverine Si fluxes. One key factor is the size of the ecosystem Si reservoir, which strongly depends on the occurrence of organisms specialized in biological Si processing. Our study was aimed to test whether tussocks, a common growth form of sedges, can efficiently retain biogenic silica. As such, they take advantage of efficient recycling of a private Si stock, providing them with a competitive advantage. We showed that tussock development caused a patch-like distribution of biogenic silica (BSi) in wetlands. While in a managed wetland (where tussocks are absent) BSi was uniformly distributed over surface layers, tussock development in an unmanaged wetland strongly interfered with BSi distribution. A mosaic of BSi richer inter-tussock soils and BSi poorer soils under tussocks developed, resulting from the active uplift of Si into the tussock from soil below the tussocks. Tussocks affected the role of wetlands as silica hot-spots and biogenic Si sinks near rivers. This implies that future studies should focus on quantifying the effect of tussock development, and human management, on system scale BSi storage.