Study On Phytolith-occluded Carbon Sequestration Potential Of Above-ground Apart Of Two Important Species Of Sympodial Bamboo And Its Relationship With Available Silicon In Soils

Phytoliths are amorphous silicon dioxide granules produced in cell walls,cell lumina or intercellular spaces of plants during the process of silicification.In this process,a small amount of organic carbon is occluded in the phytoliths,that is called the Phyt OC?Phytolith-occluded organic carbon?.The Phyt OC is highly resistant against decomposition and may accumulate in soil environment for long periods?millennia?.The Phyt OC is considered to be an important fraction of soil organic carbon and substantially contributes to the long-term terrestrial carbon sequestration Thus,it is one of the important mechanisms for carbon sequestration in terrestrial plant ecosystems.Compare with the monpodial bamboos and mixed bamboos,sympodial bamboos have the characteristics of larger stalk,more rapid growth,developed root system and great biomass,so that it can absorb mono silicic acid?H₄Si O₄?in the growth process,thereby increasing the Phytolith and Phyt OC contents in plants.Dendrocalamopsis oldhami?Munro?Keng f.?DOK?and Dendrocalamus latiflorus Munro?DLM?are two important sympodial bamboo species in China.Scientific and accurate estimation of Phyt OC storage of DOK and DLM is of great significance for the study of the Phyt OC sequestration amounts of whole sympodial bamboo ecological system.This study selected two typical sympodial bamboos?Dendrocalamopsis oldhami?Munro?Keng f,DOK and Dendrocalamus latiflorus Munro,DLM?in the subtropical area of China as research subjects and collected their leaf,branch,and culm samples.Phytoliths in the samples were extracted by a microwave digestion method and their Phyt OC contents were determined by the alkaline solution method.At the same time,four kinds of extracting agents?acetic acid-sodium acetate,citric acid,sulfuric acid,and water?were used to extract available silicon?Si?in the soils under DLM stands and determine their contents.The purposes of this study are to investigate sequestration rates and storages of Phyt OC in above ground apart of DOK and DLM stands in order to more accurately estimate Phyt OC sequestration amounts of whole sympodial bamboo ecological system.At the same time,the best agent for extracting soil available Si was selected by correlation analysis.The main results and conclusions are as follows:1.The research of Phytolith and Phyt OC content of DOK and DLM body shows that:The content of Si in DOK and DLM leaves were37.53±2.97 g·kg^-1 and 34.05±1.38 g·kg^-1;Phytolith content were 100.80±6.46 g·kg^-1 and 84.06±3.98 g·kg^-1,both Si and Phytolith the DOK leaf is greater than the DLM.But The leaves of Phyt OC content is shown as the DLM is larger than the DOK,The content of Phyt OC in the dry biomass in the two was 1.64±0.16 g·kg^-1 and 2.22±0.08g·kg^-1;The Phyt OC stocks in the DOK and DLM leaf was 5.3 kg·hm^-2 and 6.3 kg·hm^-2,and the same is shown as the DLM is larger than the DOK.The content of Si?Phytolith?Phyt OC in the dry biomass and Phyt OC stocks in the branch and culm,the DOK is larger than the DLM.The Phyt OC sequestration rate of DOK and DLM are 0.051-0.131t-e-CO₂·hm^-2·a^-1 and0.0099-0.0139t-e-CO₂·hm^-2·a^-1,with the highest Phyt OC sequestration rate calculations,The DOK and DLM forest aboveground annually in China,can storage 1965.29 CO₂ and 1520.11 t CO₂,respectively.2.There were strong positive relationships between Si contents and Phytolith contents in the leaves of DOK?R²=0.6543,P<0.01?and DLM?R²=0.7620,P<0.01?.There were no relationships between Phytolith contents and OC in Phytoliths contents of the leaves of DOK and DLM.There were strong positive relationships between Phytolith contents and Phyt OC contents in the leaves?dry weight?of DOK?R²=0.79,P<0.01?and DLM?R²=0.25,P<0.01?.3.The experiments of extracting the soil available Si and Phyt OC by different extraction agents showed that there was a significant positive correlation between the soil available Si contents extracted by 4 extraction agents and Phytolith contents in the leaves of DLM.The correlation coefficients for 4 extraction agents were in the order:0.01 mol·L^-1 sulfuric acid solution?R²=0.29,P<0.01?>water?R²=0.206,P<0.01?>p H4 HOAc-Na OAc?R²=0.202,P<0.01?>0.025 mo L·L^-1 citric acid solution?R²=0.186,P<0.01?.There was a significant positive correlation between the soil available Si contents extracted by 4 extraction agents and Phyt OC contents in the leaves of DLM.The correlation coefficients for 4 extraction agents decreased in the order:0.025 mol·L^-1 citric acid solution?R²=0.342,P<0.01?>0.01mol·L^-1 sulfuric acid solution?R²=0.314,P<0.01?>p H 4.0 HOAc-Na OAc?R²=0.306,P<0.01?>water?R²=0.187,P<0.01?.Therefore,it is ideal to use 0.01 mol·L^-1 sulfuric acid and 0.025 mol·L^-1 citric acid solution as the extraction agent of soil available Si in the study of the correlation between the content of soil available Si and Phytolith or Phyt OC contents in the leaves of DLM,but 0.01 mol·L^-1 sulfuric acid is the best in the acid ground.