Research On Silicon Distribution And Phytolith Carbon Sequestration In Temperate Shrubland And Desertification Of Grassland

Global warming has become a recognized global environmental problem, and how to reduce the content of carbon dioxide and other greenhouse gases in the atmosphere has also become the hot issue which got great attention from people. Phyt OC is organic carbon occluded during the formation of phytolith in plant. Since phytoliths is difficult to be decomposed and destroyed, after the apoptosis and death of plants, the Phyt OC can be preserved in soils and sediments for a long time(Several thousands years) and absent from the global C cycle. So as a kind of long-term and safe mechansim of carbon sequestration, phytoliths has received more and more attention from researchers. Shrubland is one of the important terrestrial ecosystem carbon sink system, doing some researches on the phytoliths C sequestration of shrubland is very meaningful; since grassland desertification phenomenon has become more and more serious, researches on the effects of desertification on phytolith carbon sequestration in grasslands is very necessary for people to learn about.grasslands regulatory phytolith carbon sequestration mechanism.This study selected the typical temperate shrubland and desertification of grassland in North China to be study objects. The samples were fused with Li-metaborate and dissolved with dilute nitric acid and measured by ultraviolet spectrophotometric method to analyze silicon(Si) content of different plants;then in order to extract phytoliths and checked C content of phytolith the samples need to experience the microwave digestion, Walkley-Black method and potassium dichromate oxidation heating method. The researches of the Si content in different plants and the phytolith carbon sequestration of shrublands,effects of desertification on phytolith carbon sequestration in grasslands can provide some scientific references for the future researcher on shrubland Si cycle and global pyhtolith carbon sequestrationThe Si content of biomass in shrubland is related to the classification of botanical system. The specific detail was: the Si content of Commelinids embranchment was higher than other plants in monocots, the Si content of Asterales embranchment was higher than other plants in Eudicot.Ecologically, the average content of silicon of herb layer(9.02 mg g–1) is higher than shrub layer’s(4.14 mg g–1). This study estimated the rate of phytolith C sequestration in temperate shrubland in North China was 0.11 ± 0.11 × 106 Mg CO2 yr–1, and approximately 64% of which was contributed from herb layer(0.07 ± 0.07 × 106 Mg CO2 yr–1).The phytolith content of biomass was in the range of 1.59 – 88.90 mg g–1, the C content of phytolith is in the range of 4.81 – 72.27 mg g–1, the Phyt OC content of biomass was in the range of 0.03– 1.26 mg g–1. The pyhtolith production flux of the five shrublands was in the range of 31.73 – 203.30 kg ha–1 yr–1 with an average of 97.51 kg ha–1 yr–1, the total changing trend in the following decreasing order: Ostryopsis davidiana-shrubland> Spiraea salicifolia-shrubland > Armeniaca sibirica-shrubland >Ziziphus jujuba-shrubland > Vitex negundo-shrubland. The Phyt OC production flux of five shrublands was in the range of 4.12 – 7.94 with average 5.95 kg CO2 ha–1yr–1, and decreased in the following order:Ostryopsis davidiana-shrubland > Spiraea salicifolia-shrubland ≈ Armeniaca sibirica-shrubland >Ziziphus jujuba-shrubland > Vitex negundo-shrubland. This study estimated the rate of phytolith C sequestration in temperate shrubland in North China was 0.45 ± 0.09 Tg CO2 yr–1,the phytolith C of215 × 106 ha shrublands in China was 1.28 ±0.25 Tg CO2yr–1, and the rate of phytolith C sequestration of shrubland in the world was 15.78 ± 3.12 Tg CO2 yr–1.The phytolith content of biomass was in the range of 6.05 – 79.96 mg g–1, and our results showed that grassland desertification phenomenon is more serious, the more phytolith content of biomass(SDG > MDG ≈ NDG > LDG). The C content of phytolith of all samples was in the range of 3.25 –23.63 mg g–1, and showed that desertification is more serious,the less C content of phytolith(LDG ≈NDG > MDG > SDG). The Phyt OC content of biomass was in the range of 0.02 – 1.21 mg g–1 and similar in the four desertification grasslands types(LDG ≈ MDG ≈ NDG ≈ SDG). The ANPP in desertification grassland was the biggest and most important factor for Phyt OC flux(NDG> LDG ≈MDG> SDG). Combined with the area of desertification grassland, the study estimated the rate of phytolith C sequestration in desertification grassland was 6.90 ± 1.72 × 104 Mg CO2 yr–1, and 20.81 ±3.63× 104 Mg CO2 yr–1 in temperate grassland total of North China.