养分化学计量比对稻田土壤葡萄糖矿化及其激发效应的影响

选择13C-葡萄糖作为稻田土壤典型易利用态外源有机碳,通过室内培养试验,研究不同C/N/P/S计量比条件下,葡萄糖分解矿化的动态规律及其激发效应。结果表明,稻田土壤中葡萄糖-碳(C)快速矿化,60 d培养实验后,有65.5%~74.6%的葡萄糖-C矿化。养分元素的添加使土壤中葡萄糖-C快速转化碳库的比例逐渐由58%增加至65%,从而使葡萄糖-C矿化率提高了3.9%~12.5%,养分元素的添加量与葡萄糖-C快速转化碳库的比例和矿化率均表现出显著的正相关关系(R2=0.63,p0.05;R2=0.83,p0.05)。葡萄糖-C矿化过程中,导致稻田土壤碳的累积负激发效应为-370~-570 mg kg-1,养分元素添加比例越大,其负激发效应越强,二者呈显著的负相关性(R2=0.66,p0.05)。研究表明,稻田土壤中易利用态碳的矿化受C/N/P/S元素计量比的影响,高比例养分元素的添加,促进土壤中易利用态碳的矿化,抑制土壤原有有机质的分解,增强负激发效应。本研究可为深入了解稻田生态系统碳循环、实现农田土壤肥力提升和温室气体减排提供理论依据。

Effect of Stoichiometric Ratio of Soil Nutrients on Mineralization and Priming Effect of Glucose in Paddy Soil

Objective]The turnover of liable organic carbon(C)sources in soil is a key component of the cycle of soil carbon. Liable C sources(i.e. glucose),derived from C deposition in rhizosphere and other extraneous C inputs,are important sources of the C pool in the soil. Therefore,studying the turnover of liable C sources as affected by stoichiometric ratio of soil nutrients may help reveal mechanisms of the eco-stoichiometric regulation of the turnover of extraneous C in paddy soil. [Method]In this study,an in-lab incubation experiment was conducted using 13C-glucose as extraneous organic C typical in paddy soil to explore quantitatively dynamics of decompositing mineralization and priming effect of glucose as affected by C/N/P/S stoichiometric ratio. [Result]Results show that glucose was rapidly mineralized in the paddy soil so that 65.5% to 74.6% of the added glucose-C was mineralized after 60 d of incubation. The addition of nutrient elements not only increased glucose mineralization rate,but also raised the proportion of glucose-C available to soil microbes from 58% to 65%,thus accelerating glucose turnover rate in the soil. The amount of nutrient elements added was found significantly and positively related to both proportion of the microbe-available C pool in and mineralization rate(R2 = 0.63,p <0.05;R2 = 0.83,p<0.05)of glucose C,which suggests that the addition of nutrient elements promoted the microbial utilization of extraneous C in the soil,and stoichiometric ratio of the nutrient elements regulated the dynamic of glucose mineralization. With the addition of glucose-C,the decomposition of the soil native organic matter was inhibited,and the cumulative negative priming effect was -370 to -570 mg kg-1. The higher the amount of nutrient elements added,the stronger the negative priming effect observed,and the two were obviously in negative correlation(R2 = 0.66,p<0.05), indicating that the soil microbes preferentially utilize the added glucose-C to sustain their growth. The supply of N,P and S reduced the dependence of microbes on nutrient elements in the soil native organic matter,and thereby slow down the decomposition of soil organic matter. [Conclusion]Mineralization of liable C in paddy soil is affected by C/N/P/S stoichiometric ratio. The addition of a high ratio of nutrient elements promotes mineralization of liable C in paddy soil,inhibits decomposition of native soil organic matter,and intensify negative priming effect. All the findings in this study demonstrate that application of liable C and fertilizers to paddy soils could effectively inhibit decomposition of soil native organic matter,and stimulate accumulation of soil organic matter,thus building up soil fertility.