The Influence Of Elevated CO₂ On Stability Of Photosynthetic Carbon

In order to study the mineralization process of the organic carbon in the "new" "old" organic carbon,the experiment was carried out on the basis of the potted wheat.The potted wheat is supplied with atom ¹³C-CO₂10% in spring wheat,and 350 ppm and 600 ppm are set at two CO₂ concentrations.80,120,180 kg N ha-1 are set at three nitrogen concentration.The soil of the mature period of wheat was 2 months of indoor culture,and every 3-4 days,the water content was maintained at 60% of the maximum water holding capacity in the field.Regularly measured respiration rate.Regularly take part of the soil to make amino sugar and phospholipid fatty acids.The results of the study show that soil respiration rate along with time is gradually reduced.The first week of the reduction rate is very fast,reaching 36%.Respiratory rate tends to be stable a month later.The respiratory rate of ¹³C decreased faster.When nitrogen concentration was N1,The respiration rate of the ¹³Csoil was reduced by22% in the first week.When nitrogen concentration was N2,The respiration rate of the ¹³Csoil was reduced by40% in the first week.When nitrogen concentration was N3,The respiration rate of the ¹³Csoil was reduced by55% in the first week Elevated CO₂ concentration increase respiration rate.The active nitrogen increased the activity and quantity of microorganism,and accelerated the decomposition and mineralization of organic matter.The results showed that: the content of amino sugar increased with time.When the concentration of CO₂ increased,the content of amino sugar increased,which was about 10% higher than that of conventional CO₂.Glu N was derived from the cell wall of the fungus;and Mur N was derived from the cell wall of the bacteria.In the present study,the value of Glu N/ Mur N was not significantly changed with the culture time.From the results of this study,increasing the concentration of nitrogen can increase the content of amino sugar,and promote the number and activity of fungi in soil.Because of the coupling effect between carbon and nitrogen,when the nitrogen was sufficient,nitrogen in the soil was rapidly decomposed.Resulting in the decomposition of organic matter in the soil reduced.When nitrogen is limited,high carbon and nitrogen can promote the demand of inorganic nitrogen,and promote the decomposition of organic matter in soil.The contents of various phospholipids fatty acids decreased with the time.Because with the increase of the culture time,the organic matter of the soil was gradually consumed by the microorganism.The activity and quantity of microorganism was also less and less,so the ratio of the isotope concentration of the fatty acids in the phospholipid was slowly decreasing.Different nitrogen concentration had different effects on the ratio of the concentration of the fatty acids in the phospholipids.The concentration of ¹³C was higher in the N3.The effect of CO₂ concentration on bacteria was greater than that of fungi.When the concentration of CO₂ increased,the photosynthetic carbon of bacteria was higher than that of conventional CO₂,and the photosynthetic carbon increased by about 8.5%.The growth of bacteria and fungi decreased with the culture time,but the change of the fungus was slightly higher.The largest of the-¹³C in the culture of the first week was gram negative bacteria;the smallest was gram positive bacteria.Culture to 1-2 months,fungi was the most active microorganisms.