Journal
JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
Volume 119, Issue 1, Pages 95-109Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1002/2013JG002429
Keywords
Dissolved silicate; Land use; cover change (LUCC); Damming; Silica retention; Cascade reservoir; Jiulong River
Funding
- National Natural Science Foundation of China [41076042, 41376082]
- Fundamental Research Funds for the Central Universities [2012121053]
- Science Foundation of Fujian Province [2010Y0064]
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Natural and human factors controlling dissolved silica (DSi) export from the watershed were investigated for the Jiulong River watershed in Southeast China, which is a subtropical region where tectonic activity and high runoff combine to create a global hot spot for DSi flux. Results showed that river DSi was fairly high (24676 mu mol L-1) due to granite lithology and increased human perturbation. The percentage of granite, paddy soil, arable land, and forest land each explain 47-69% of the spatial variation in DSi level at the subwatershed scale. Land use change (deforestation for agriculture) and soil erosion increased DSi transfer from terrestrial systems towards the river. Discharge explains over 95% of the variation in DSi fluxes, and a discrepancy of up to 16% of watershed DSi export was observed between low and high flow conditions. DSi retention is more significant in the dry season, likely due to biological uptake by diatoms in reservoirs under low flow conditions and higher residence time. However, this may be offset by high runoff flush in the wet season, which might cause unfavorable conditions for diatom growth and DSi depletion. There has been little overall change in DSi in estuarine water in recent decades. However, seasonal variation and occasionally fluctuation of DSi during extreme hydrological events (rainstorms) does exist, with important implications for the coastal ecosystem. This research confirmed that human activities and land use change have substantially altered Si delivery, cycling and riverine export to the coast in this region. Key Points Land use/cover change explain most of stream DSi variation 16% reduction of DSi fluxes due to damming but offset by high runoff Human have altered riverine DSi delivery, cycling and seaward export
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