Study On The Distribution Of Photosynthetic Carbon Of Spartina Alterniflora In Plant-soil System

Soil organic carbon?SOC?pool is the largest of terrestrial ecosystems carbon pool which play an important roles in global carbon cycling.Atmospheric carbon?CO2?fixed by plants through photosynthes is referred to as the "photosynthetic carbon".And then the "photosynthetic carbon" is transformed into soil in the form of plant residue,root and rhizosphere carbon.The distribution of "photosynthetic carbon" in plant-soil system can affect the SOC cycling,turnover and dynamic.The application of fertilization and the plant straw to soil are effective measures to improve the soil organic carbon and soil nutrient content.But the allocation and fixed mechanism of"photosynthetic carbon" in plants-soil system after the application of fertilization or adding plant straw are unclear.This study applied ¹³CO2 pulse to label S.alterniflora during the growth period indoor and this experiment for four times in total,and estimate the effects of fertilizer and the plant straw on the allocation and fixation of photosynthetic carbon in S.alterniflora by tracing the fate of 13 C of each component in plant-soil system.The results revealed that:?1?The abundance of ¹³C value of S.alterniflora increased significantly.The amount of ¹³C fixed by the S.alterniflora's was 52.80 mg C· plant-1-276.81 mg C plant-1 with four times labeling.Fixed ¹³C increased along with the number of tags.The proportion of net fixed ¹³C was 32.48%?39.20%in the leaf;39.83%?47.65%in the stem;18.01%?20.34%in the root;0.30%?0.42%in the rhizosphere soil;0.08%?0.20%in the soil.The fixed ¹³C mainly concentrated in the aboveground parts of plant?stems and leafs?and presented as stems>leaf>root>rhizosphere soil>soil.The ¹³C value occurred in the plant-soil system as the order of stem>leaf>root>rhizosphere soil>soil.?2?After four times labeling,the abundance of ¹³C value of components increased in each treatment group.The abundance of ¹³C value was 93.67%?94.51%in the leaf,93.91%?94.47%in the stem,93.01%?94.14%in the root,92.05%?92.34%in the rhizosphere soil and 92.00%?92.14%in the soil,respectively.The fixed amount of ¹³C in plant with nitrogen and phosphorus treatment is higher than that of nitrogen treatment and phosphorus treatment.?3?The distribution proportion of net fixed ¹³C was 74.72%?86.81%in the aboveground and 13.19%?25.27%in the belowground.The proportion of net fixed ¹³C was 36.63%? 44.38%in the leaf;38.09%?45.82%in the stem;12.24%?24.16%in the root;0.34%?0.61%in the rhizosphere soil;0.22%?0.43%in the soil.The proportion of net fixed C of the components in plant-soil system presented as stem>leaf>root>rhizosphere soil>soil.Compared with the first tag,the allocation proportion in aboveground parts gradually reduced and increased gradually in underground parts,showing the ¹³C enrichment of soil organic carbon concentration.Fertilization influenced the allocation of photosynthetic carbon,N3,N+P3 and P2 fertilizer levels is advantageous to the distribution of photosynthetic carbon to the soil.?4?After added ¹³C straw,the ¹³C values of soil organic carbon were increased,which were significantly higher than the ¹³C values of CK.It show that the ¹³C values of soil organic carbon was influenced by the input of ¹³C straw and the cycling of newly input soil organic carbon was faster than the original soil organic carbon stored insoils.The straw carbon contribution to soil organic carbon content between 0.95?2.28 mg after three months.