Research On The Potential Of Phytolith Sequestration Carbon From Atmosphere In Soil-plant Ecosystem Of Typical Wetland

IPCC indicates that as global increase of atmospheric CO₂concentration may causedangerous climate change, various approaches that can securely reduce and sequestrate carbonemissions are being pursued, and among the most promising is the terrestrial biogeochemicalcarbon sequestration. Carbon bio-sequestration within the phytoliths of plants, a mechanism oflong-term biogeochemical carbon sequestration, may play a major role in the global carbon cycleand climate change. The widespread wetland ecosystem with fast plant growth and high biomassis an important terrestrial carbon sink, and play an important role in global carbon cycle andglobal climate change.This study selected plant and soil samples in Xixi wetland, Baiyangdian reed wetland andJiaxing paddy soil ecosystem, respectively. The plant phytolith extraction was undertaken withmicrowave digestion procedures and the determination of occluded carbon in phytoliths was basedon dissolution methods of phytolith-Si. We checked the variation of phytolith and phytolith carboncontent in different samples to understand the role of phytolith in coupled biogeochemical cycle ofsilicon and carbon.（1） The phytolith content ranged from10.1mg g^-1to70.9mg g^-1in18plants in Xixi wetlandecosystems, with a CV （coefficient of variation） value of810%. The fluxes of phytolith productionof herb-dominated fen plants ranged from4.5g-m^-2-a^-1to39.7g-m^-2-a^-1, and the rate of carbonbio-sequestration within phytoliths were0.3⁷.7g-e-CO-12-m2a-. In China,0.04×10⁶to1.05×10⁶t CO₂equivalents per year may be sequestrated in phytoliths of herbaceous-dominated fen plants.Globally, taking a fen area of1.48×10⁸ha and the largest phytolith carbon biosequestration flux（7.7g-e-CO--12-m2a） of PhytOC for herb-dominated fen plants, about1.14×10⁷t CO₂equivalentsper year would have been sequestrated in phytoliths of fen plants. If other wetland plants havesimilar PhytOC production flux with herb-dominated fen plants (7.7g-e-CO₂-m^-2a^-1), about4.39×10⁷t-e-CO₂-a^-1may be sequestrated in the phytoliths of world wetland plants. The dataindicate that the management of wetland ecosystems （e.g., selection of plant species） to maximizethe production of PhytOC have the potential to bio-sequestrate considerable quantities ofatmospheric CO₂.（2） In the Baiyangdian reed wetland ecosystems, the results showed that the phytolith the occluded carbon content of phytoliths decreased as: leaf (76mg g^-1)> sheath (64mg g^-1)> root(22mg g^-1)> stem (22mg g^-1)>and stem (17mg g^-1)> leaf (16mg g^-1)> root (14mg g^-1)>sheath (10mg g^-1). The total flux of phytolith production in reed was86.6¹01.1g-m^-2-a^-1andthe flux of carbon sequestration within phytolith in reed was4.0⁵.2g CO₂-m^-2-a^-1. The resultsshowed that the distribution of phytoliths with in grassland and rice soil has a concentration ofphytoliths in topsoil with a decline in abundance with depth. The phytolith content in soil surfaceand soil profile has an increasing trend with the SOC content and that exits a positive correlation（R²=0.505, p <0.05and R²=0.4569, p <0.01, respectively）. Then in reed wetland ecosystemswith100years of soil deposition, the flux of phytoliths accumulation is33.70g-m^-2-a^-1and that ofPhytOC accumulation is0.03g CO₂-m^-2-a^-1in soil layer （0¹5cm）. In Baiyangdian reedecosystems with planting area of1.83×10⁸m2, the rate of PhytOC for aboveground reed is about2.01×10⁸g CO-2-a1and that for0¹5cm soil layer is about5.49×10⁶g CO₂-a^-1.（3） In the paddy soil ecosystems, there were substantial differences in the content of thephytolith and phytolith carbon from different rice organs. They decreased in the following orderamong different organs: sheath> leaf> stem> root> grains and stem> leaf> grains> sheath>root. The total flux of phytolith production in the aboveground of rice was1203kg-ha^-1-a^-1, andthat of underground in rice was126.9g-m^-2-a^-1. In rice ecosystems with50years of cultivation,the phytolith accumulation flux in surface soil （0¹0cm） was40.38kg-hm^-2-yr-1, which wasequivalent to the flux of root phytolith production, implying that the rice straws are rarely returnedto the paddy soil. The production flux of rice phytolith to sequestrate the atmospheric CO₂was4.7²7.9g-m^-2-a^-1and the accumulation flux of paddy soil phytolith sequestrate the atmosphericCO₂was0.2⁰.9g-m^-2-a^-1. The biogeochemical carbon sequestration flux of phytoliths in5ricecultivars is approximately0.3¹3.0g-e-CO--12m2-a. From1950to2010, about2.37×10⁸t of CO₂equivalents might have been sequestrated within the rice phytoliths in China. Assuming amaximum phytoliths carbon bio-sequestration flux of13.0g-e-CO₂m^-2-a^-1, the global annualpotential rate of CO₂sequestrated in rice phytoliths would approximately be1.94×10⁷t.（4） The data also show that the PhytOC content of rice depend on both the content ofphytoliths and the efficiency of the carbon occluded within phytoliths during rice growth.