| Phyt OC is the organic carbon stored in phytoliths during the formation of plant phytoliths.It has high stability and is of great significance in mitigating climate change and realizing carbon neutralization.Taking the typical karst ecosystem in Southwest China as the research area,taking 7 representative land use modes and 7 vegetation restoration modes as the research object,this study collected three soil layers of 0-5 cm,5-10 cm and 10-15 cm.The soil phytolith was extracted by the wet oxidation method,the carbon content in soil phytolith was determined by the spectrophotometry,the carbon storage of phytolith was estimated,and the response of soil Phyt OC content and storage in southwest karst ecosystem to the change of land use mode and long-term vegetation restoration was clarified.Through correlation analysis and principal component analysis,the coupling relationship between soil Phyt OC accumulation and soil environmental factors in southwest karst ecosystem was studied,and the influencing factors and internal mechanism of soil environment on soil Phyt OC accumulation in southwest karst ecosystem were clarified.The results provide a scientific basis for estimating the carbon sink potential of soil phytoliths and artificially increasing soil carbon sink in southwest karst ecosystem.The main results and conclusions are as follows:(1)In 0-15 cm soil,there were significant differences in soil phytolith,Phyt OC content,the proportion of Phyt OC to organic carbon and Phyt OC storage under different land use modes.Among them,the content of phytolith and Phyt OC in open forest land is the highest,the content of phytolith in dry land is also high,and the content of Phyt OC in grassland is also high.The Phyt OC/TSOC of grassland is the highest,which is 8.08%,indicating that the stability and potential of grassland soil Phyt OC are the strongest.Open woodland,dry land and grassland have higher Phyt OC reserves.Therefore,different land use modes will have an impact on soil Phyt OC accumulation.Scientific management and adjustment of land cover in southwest karst ecosystem will significantly enhance soil phytolith carbon storage in southwest karst area.(2)In 0-15 cm soil,there are significant differences in soil phytolith,Phyt OC content,the proportion of Phyt OC to organic carbon and Phyt OC storage under different vegetation restoration methods.Compared with the control bare land,the vegetation restoration method can increase the content of soil phytolith and Phyt OC and change the proportion of soil Phyt OC to total organic carbon.Among them,the content of phytolith and Phyt OC of Tectona grandis is the highest,and the content of phytolith and Phyt OC of Hylocereus undatus is also high.The Phyt OC/TSOC of Pennisetum sinese is the highest,which is 10.73%,indicating that the stability and potential of soil Phyt OC of Pennisetum sinese are the strongest.Tectona grandis,Hylocereus undatus and Pennisetum sinese have high phytolith carbon reserves.Therefore,different vegetation restoration methods will have a positive impact on the carbon accumulation of soil phytoliths,and increase the planting area of Tectona grandis,Hylocereus undatus and Pennisetum sinese as much as possible,which can significantly improve the carbon sequestration capacity of southwest karst ecosystem while ensuring economic benefits.(3)From the vertical direction,there is an obvious surface enrichment of soil phytolith under different land use modes,while the content of soil Phyt OC has no significant difference with the deepening of soil depth.The Phyt OC/TSOC of forest,open forest and grassland increases significantly with the deepening of soil depth,while other land use modes have no significant change.Under different vegetation restoration methods,there was no significant difference in soil phytolith,Phyt OC content and Phyt OC/TSOC with the deepening of soil depth.(4)The content of available silicon and phytolith in the soil of southwest karst ecosystem will have a very significant impact on the accumulation of Phyt OC.There is a positive correlation between soil p H and Phyt OC content to a certain extent.TSOC,TN,C:P and N:P will have a positive impact on soil Phyt OC accumulation.Among them,TSOC and TN have a greater impact on soil Phyt OC accumulation under different land use modes,while C:P and N:P have a greater impact on soil Phyt OC accumulation under different vegetation restoration modes.There is a certain degree of negative correlation between soil bulk density and Phyt OC content under different land use modes,while phytolith carbon accumulation under different vegetation restoration modes is less affected by bulk density. |
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