长期秸秆还田对水稻根系碳矿化与激发效应的影响

长期秸秆还田改变水稻土环境条件，从而会影响水稻残留根系碳在土壤中的矿化和激发效应，其影响的方向和强度尚不明确.因此，基于长期定位施肥试验，采用¹³C-CO₂同位素标记技术，结合室内模拟培养试验，研究不施肥（CK）、单施化肥（CF）和秸秆还田配施化肥（CFS）这3种长期处理下，水稻根系和土壤本身有机碳的矿化特征，分析根系的激发效应的强度与方向，以及各处理CO₂释放量的来源组成.结果表明，经过120 d的室内淹水培养，根系残留（R）将CO₂累积释放量增加了617.41~726.27 mg·kg^-1.CFS+R和CF+R处理根系来源CO₂累积释放量分别为470.82mg·kg^-1和444.04 mg·kg^-1，根系的矿化率分别为18.8%和17.8%，均显著高于CK+R处理（384.19 mg·kg^-1，15.4%）.3个处理的土壤本身有机碳产生的CO₂累积排放量无显著差异，但CFS+R处理的土壤本身有机碳矿化率（4.2%）显著低于CF+R和CK+R处理（5.4%和5.8%）.CFS+R处理中根系的CO₂累积激发效应为29.6%，显著低于CK+R处理的42.5%，高于CF+R处理的14.4%.淹水水稻土CO₂累积释放量中23.47%~27.59%来源于根系，其余来源于土壤，其中，激发效应引起的CO₂释放量占比在CFS+R处理中比CK+R处理小，比CF+R处理大.综上，淹水水稻土长期秸秆还田会提高根系碳的矿化潜力，但是更有利于土壤本身有机碳的稳定.

Effect of Long-term Straw Returning on the Mineralization and Priming Effect of Rice Root-carbon

Long-term straw returning to the field changes the environmental conditions of rice paddy soil, which affects the mineralization and priming effect of residual rice roots in the soil, but the direction and intensity of its influence is not clear. Therefore, based on a long-term fertilization field experiment, ¹³C-CO₂ isotopic labeling technology and laboratorial incubation were used to analyze the characteristics of mineralization of rice roots and native soil organic carbon, the intensity and direction of the priming effect, and the source partitioning of CO₂ emissions in three treatments, consisting of no fertilization (CK), chemical fertilizer (CF), and straw returning with chemical fertilizer (CFS). The results showed that after 120 days of flooding incubation, the root residue (R) increased the cumulative CO₂ emissions by 617.41-726.27 mg·kg^-1. The cumulative CO₂ emissions from roots and root mineralized proportions in the CFS+R and CF+R treatments were 470.82 and 444.04 mg·kg^-1, respectively, and 18.8% and 17.8%, respectively. These were significantly higher than those in the CK+R treatment (384.19 mg·kg^-1, 15.4%). There was no significant difference in the cumulative CO₂ emissions from native soil organic carbon among the three treatments. However, the mineralized proportion of native soil organic carbon in the CFS+R treatment (4.2%) was significantly lower than that in the CF+R and CK+R treatments (5.4% and 5.8%). The priming effect in the CFS+R treatment was 29.6%, which was significantly lower than that in the CK+R treatment (42.5%) and higher than that in the CF+R treatment (14.4%). A total of 23.47% to 27.59% of the cumulative CO₂ emission of the flooded paddy soil was from the roots, and the remainder was from the soil. In addition, the proportion of CO₂ emission caused by the priming effect was smaller in the CFS+R treatment than that in the CK+R treatment and larger than that in the CF+R treatment. In summary, the long-term straw returning in the flooded paddy soil will increase the mineralization potential of rice roots, but it is more conducive to the stability of the native soil organic carbon.