Phytolith-occluded Carbon Sequestration Of Typical Monopodial Bamboo Ecosystems In China

Phytolith or plant opal,as it is often called,formed in the living plants through absorbing soluble monosilicic acid from the soil and depositing in the cell walls,cell lumina and intercellular spaces by transpiration.This siliceous mineralization has caused some organic carbon?circa 0.1%-6%?storing in the Phytolith.Besides,this organic carbon was called Phytolith-occluded carbon?PhytOC?.The bamboo ecosystem is an important part of terrestrial ecosystems.And with recent further study on the bamboo forest carbon sink,PhytOC has been proved to be of importance in reducing atmospheric CO₂ concentration.Therefore,how to improve the estimation of carbon pool and storage rate of phytolith is very important in studying the measurement of carbon sink in the forest soil in the world.In this thesis,the object of this paper was to investigate cumulative characteristics and spatial distribution of PhytOC in eight monopodial bamboo species and estimate its sequestration capacity in monopodial bamboo forests in China,based on the new determination method.The primary results of this study were summarized as follows:1.Determination of PhytOC Content Using Alkali Dissolution-SpectrophotometryThe study showed that Alkali Dissolution-Spectrophotometry method used to determine the PhytOC content has the advantage of decreasing carbon loss,being easy to operate and lowering cost.It had fewer effects on human health and environment than the hydrofluoric acid method.Besides,compared with Elementar Vario MAX CN,the method is not only inexpensive and effective but also not limited by sample quantity,laboratory researchers and equipment.The results obtained from these two methods also have a good correlation coefficient?R2=0.9895?.Therefore,Alkali Dissolution-Spectrophotometry method is feasible and valid to test the content of Phyt OC.2.Spatial distribution of PhytOC in different aboveground organs of eight monopodial bamboo speciesThe results showed that the average leaf Phyt OC content of all eight monopodial bamboo species ranged from 2.72 ± 0.29 g · kg^-1to 6.21 ± 0.31 g · kg^-1 with the highest in Phyllostachys prominens and the lowest in Pleioblastus amarus?Keng?keng,respectively.Besides,the average branch PhytOC content of all eight species ranged from 0.98 ± 0.02 g · kg^-1 to 3.02 ± 0.80 g · kg^-1 with the highest in Phyllostachys heterocycla?Carr.?Mitford cv.Pubescens and the lowest in Pleioblastus amarus?Keng?keng,while the average clum PhytOC content ranged from 0.79 ± 0.09 g · kg^-1 to 1.63 ± 0.17 g · kg^-1 with the highest in Phyllostachys glauca McClure and the lowest in Bambusa piscatorum McClure.There was significant linear correlation between the contents of phytolith and PhytOC in the leaves,branches and culms,respectively.3.Spatial distribution of PhytOC in the soils of eight monopodial bamboo species.The results showed that the average PhytOC content in the soils of all eight monopodial bamboo species ranged from 0.05 ± 0.01 g · kg^-1 to 0.99 ± 0.35 g · kg^-1.The ratio content of PhytOC to SOC increased with the soil depth,whereas the accumulation of PhytOC among layers of soil is irregular.It was also found that there was significant linear correlation between the contents of PhytOC in soils and phytolith or organic carbon in phytolith,as well as between the silicon and phytolith.4.PhytOC stockpile and production fluxin eight monopodial bamboo ecosystemsThe results showed that the average PhytOC stockpile of the eight monopodial bamboo ecosystems were in the following order: Phyllostachys glauca McClure(90.36 kg · ha^-1)>Phyllostachys heterocycla?Carr.?Mitford cv.Pubescens(66.18 kg · ha^-1)>Pleioblastus amarus?Keng?Keng f.(65.58 kg · ha^-1)>Pseudosasa amabilis?McClure?Keng f.(56.47 kg · ha^-1)>Bambusa piscatorum McClure(43.63 kg · ha^-1)>Phyllostachys heteroclada Oliver(41.10 kg · ha^-1)>Phyllostachys prominens(40.59 kg · ha^-1)>Indocalamus tessellatus?Munro?Keng f.(8.35 kg · ha^-1).The average PhytOC stored in different organs of monopodial bamboo species and soils varied substantially.Average 95.6 % of total PhytOC stockpile in whole bamboo ecosystems was stored in the soils.The PhytOC stocks in leaves,branches and culms of all eight monopodial bamboo species ranged from 5.06 kg · ha^-1 to 24.70 kg · ha^-1,5.28 kg · ha^-1 to 21.50 kg · ha^-1and 3.29 kg · ha^-1 to 46.38 kg · ha^-1,respectively.The PhytOC storages in aboveground organs and soils in Chinese monopodial bamboo forests were 30.15 × 104 t and 1145.43 × 104 t,which were equivalent to 110.53 × 104 t and 4.20 × 107 t e-CO₂,respectively.The average aboveground Phyt OC production flux of eight monopodial bamboo species was 31.67 kg · ha^-1 · a^-1.In addition,the total aboveground PhytOC production flux of Chinese monopodial bamboo forest was 18.53×104 t · C · a^-1,which was equivalent to 67.93 × 104 t-e-CO₂.