水稻光合同化碳向土壤有机碳库输入的定量研究:14C连续标记法

应用14C连续标记示踪技术,以当地主栽水稻品种"中优169"为供试作物,分别选取亚热带区4种典型稻田土壤,在密闭系统模拟研究水稻根际输入光合碳对土壤有机碳(SOC)及其组分的影响.结果表明,标记种植80 d后,水稻地上部和地下部的累积的总碳量范围分别为1.86～5.60 g.pot-1和0.46～0.78 g.pot-1.种植水稻后供试土壤的14C-SOC含量范围为114.3～348.2 mg.kg-1,而14C-DOC、14C-MBC含量范围为4.05～8.65 mg.kg-1、12.5～37.6 mg.kg-1.水稻生长期间内,不同土壤条件下,土壤14C-SOC与14C-水稻碳量的比率范围为5.09%～6.62%,这说明尽管不同土壤的光合生产能力不同,但根际沉积效率相似.土壤可溶解性有机碳(DOC)、微生物量碳(MBC)和SOC的更新率分别为6.72%～14.64%、1.70%～7.67%和0.73%～1.99%.而且,水稻光合碳的分配和转化对土壤活性碳组分的DOC、MBC含量变化影响较大,而对土壤有机碳影响较小.本研究进一步量化了水稻生长期间光合碳对土壤有机碳库各组分(SOC、DOC和MBC)的贡献,为水稻土有机质积累持续机制与固碳潜力研究提供了数据支撑.

Quantifying Rice (Oryza sativa L.) Photo-assimilated Carbon Input into Soil Organic Carbon Pools Following Continuous 14C Labeling

The microcosm experiment was carried out to quantify the input and distribution of photo-assimilated C into soil C pools by using a ¹⁴C continuous labeling technique. Destructive samplings of rice (Oryza sativa) were conducted after labeling for 80 days. The allocation of ¹⁴C-labeled photosynthates in plants and soil C pools such as dissolved organic C (DOC) and microbial biomass C (MBC) in rice-planted soil were examined over the ¹⁴C labeling span. The amounts of rice shoot and root biomass C was ranged from 1.86 to 5.60 g·pot^-1, 0.46 to 0.78 g·pot^-1 in different tested paddy soils after labeling for 80 days, respectively. The amount of ¹⁴C in the soil organic C (¹⁴C-SOC) was also dependent on the soils, ranged from 114.3 to 348.2 mg·kg^-1, accounting for 5.09% to 6.62% of the rice biomass ¹⁴C, respectively. The amounts of ¹⁴C in the dissolved organic C (¹⁴C-DOC) and in the microbial biomass C(¹⁴C-MBC), as proportions of ¹⁴C-SOC, were 2.21%-3.54% and 9.72%-17.92%, respectively. The ¹⁴C-DOC, ¹⁴C-MBC, and ¹⁴C-SOC as proportions of total DOC, MBC, and SOC, respectively, were 6.72%-14.64%, 1.70%-7.67%, and 0.73%-1.99%, respectively. Moreover, the distribution and transformation of root-derived C had a greater influence on the dynamics of DOC and MBC than on the dynamics of SOC. Further studies are required to ascertain the functional significance of soil microorganisms (such as C-sequestering bacteria and photosynthetic bacteria) in the paddy system.