Research On Phytolith Carbon Sequestration Of Quercus Acutissima Forest Ecosystem In Jurong City, Jiangsu Province

PhytOC is the most stable and safe carbon except organic mineral complexes,charcoal,etc,in the soil.It can be stable in the soil for thousands of years to ten thousands of years,and does not participate in the atmospheric carbon cycle,it is a stable and safe carbon sink in the soil,at present phytolith carbon sequestration has become a new hot spot in global carbon sink research.In this paper,different ages of forest Quercus acutissima（17a,26a,and 65a）were selected as the object which are in Jurong,Jiangsu Province,and we selected the samples of tree layer,shrub layer,herb layer,litter layer and soil layer of Quercus acutissima forests,measured their contents of the available silicon,phytolith,phytOC etc.,we also determined phytOC sequestration of various levels of Quercus acutissima forest ecosystem,and estimated the phytolith carbon sequestration rate of tree layer in order to provide the theoretical basis of phytolith carbon sink function and carbon circle for north subtropical Quercus forest ecosystem in China.The main results are as follows:（1）The available silicon contents in different organs of tree layer was 15.19³50.82mg·kg^-1,and the order was fine root>large root>thick root>branch>leaf>root pile>bark>trunk;phytolith contents was 1.11⁴3.38 g·kg^-1,the order was fine root>large root>trunk>leaf>thick root>root pile>bark>branch;phytOC contents was 0.11⁰.40 g·kg^-1,the order was leaf>large root=fine Root>trunk>bark>thick root>root pile=branch.This article clarifies the content of phytOC in the shrub layer,and there are certain differences in different indexes of different organs,therefore,when we estimating the phytOC sequestration and the phytolith carbon sequestration rate,the index content of an organ cannot be taken as the content of the entire forest ecosystem.（2）The available silicon contents in soil was 45.74¹53.32 mg·kg^-1,the phytolith content was 7.10⁸.23 g·kg^-1,the phytOC was 0.088⁰.287 g·kg^-1.This article clarifies the content of phytOC in the soil layer,and the ratio of phytOC to organic carbon in each layer of soil was 0.3¹.49%,which increased with the increase of soil depth,indicating that phytOC was more stable than other forms of carbon.（3）The phytOC sequestrations of different forest ages were in the following order:medium-aged forest(1482.72 kg·hm^-2)>mature forest(1183.75 kg·hm^-2)>young forest(1174.85 kg·hm^-2).Among them,the phytOC sequestration in the tree layer was 5.16²8.09kg·hm^-2,which accounts for 0.439².373%of the total phytOC sequestration of Quercus acutissima forest;the phytOC sequestration of the soil was 1166.51¹462.93 kg·hm^-2,accounting for more than 97%;phytOC sequestration in shrub layer,herb layer and litter layer were 0.07⁰.29 kg·hm^-2,1.33¹.69 kg·hm^-2,1.74².25 kg·hm^-2,shrub layer,hurb layer and litter layer accounting for less than 0.15%.Therefore,soil is not only the main carbon pool of organic carbon stocks in forest ecosystems,but also is the main storage place for phytOC sequestration.（4）The phytolith carbon sequestration rate was 2.94¹2.47 kg-e-CO²·hm^-2·a^-1 in different forest ages of Quercus acutissima.According to the seventh national forest inventory of the area of Quercus forest（1610.3 million hm²）,and based on the average of phytolith carbon sequestration rate(8.20 kg-e-CO₂·hm^-2·a^-1)at different tree ages in the tree layer,so the annual phytolith carbon storage was 1.32×10⁵ t CO₂ of the tree layer of Quercus forest in China,which can offset the CO₂ emissions from the combustion of 5.04×10⁴ t of standard coal,that can effectively mitigate the greenhouse effect.