稻田与旱地土壤自养微生物同化碳在土壤中的矿化与转化特征

选择亚热带地区3种典型稻田和旱地土壤,应用碳同位素^14C-CO₂标记示踪技术结合室内模拟培养试验,研究自养微生物同化碳(“新碳”)在土壤碳库中的矿化和转化特征.结果表明: 在100 d的培养期内,“新碳”的矿化经历了先上升、10 d后缓慢下降、最后渐趋稳定的3个阶段.“新碳”的矿化比例为8.0%～26.9%,矿化速率为0.01～0.22 μg ¹⁴C·g^-1·d^-1,其中,稻田土壤为0.01～0.22 μg ¹⁴C·g^-1·d^-1,旱地土壤为0.01～0.08 μg ¹⁴C·g^-1·d^-1,而原有有机碳的矿化比例为1.6%～5.7%,矿化速率为1.3～25.66 μg C·g^-1·d^-1.土壤活性碳库\可溶性有机碳(DOC)、微生物生物量碳(MBC)\]中,¹⁴C-DOC在培养初期(0～10 d)先上升,升高幅度达0.3 mg·kg^-1,10～30 d又迅速下降,下降幅度达0.42 mg·kg^-1,至30 d后缓慢下降.¹⁴C-MBC的波动与¹⁴C-DOC不同,在培养初期(0～10 d)先迅速下降,10～30 d又迅速上升,至40 d后缓慢下降并趋于稳定.水稻土¹⁴C-DOC/DOC的转化更新速率明显大于旱地,而旱地¹⁴C-MBC/MBC的转化更新速率大于水稻土.

Characteristics of the mineralization and transformation of autotrophic microbes-assimilated carbon in upland and paddy soils.

In this study, the mineralization and decomposition of autotrophic microbe assimilated carbon (new carbon) and native organic carbon in three upland and three paddy soils in subtropical China were measured using the ¹⁴C-labelled tracer technique. The results showed that, during the 100-d incubation, the mineralization of the ‘new carbon’ displayed three stages: a rise in the first 10 days, a slowdown from 11-d to 50-d, and a stabilization stage after 50 d. The mineralization ratio of the ‘new carbon’ ranged between 8.0% and 26.9% and the mineralization rate ranged from 0.01 to 0.22 μg ¹⁴C·g^-1·d^-1 (0.01-0.22 μg ¹⁴C·g^-1·d^-1 in paddy soils and 0.01-0.08 μg ¹⁴C·g^-1·d^-1 in upland soils). However, the mineralization ratio and rate for native SOC were 1.55%-5.74% and 1.3-25.66 μg C·g^-1·d^-1, respectively. In the soil active C pools, the ¹⁴C-dissolved organic carbon (DOC) first rose by as much as 0.3 mg·kg^-1 in the early stages of incubation (0-10 d), decreased rapidly by 0.42 mg·kg^-1 from 10-30 d, and then declined gradually. The fluctuation of the ¹⁴C-microbial biomass carbon (MBC) differed from that of the ¹⁴C-DOC. At the beginning stage of the incubation (0-10 d), the ¹⁴C-MBC decreased rapidly, and then rapidly increased from 10 to 30 d, and the rate of increase reduced and was gradually stabilized after 40 d. The ¹⁴C-DOC/DOC renewal rate in the paddy soil was significantly higher than in the upland soil while the ¹⁴C-MBC/MBC renewal rate in the upland soil was significantly greater than in the paddy soil.