植物-土壤-微生物系统的C、N、P含量内稳性是调控脆弱生态系统养分循环的关键机制。针对科尔沁沙地风沙土C、N、P化学计量失衡及有机改良效应不明的问题，通过田间试验，对比了生物炭与秸秆添加对燕麦种植系统元素计量特征的影响。试验设置对照组（CK）、生物炭添加组（低量B1:3%、中量B2:5%、高量B3:10%）和秸秆添加组（低量S1:3%、中量S2:5%、高量S3:10%），并基于生态化学计量学与内稳性理论，解析了植物（燕麦）、土壤和微生物的C:N:P的响应特征。结果表明：（1） 中高量生物炭（B2和B3）显著优化了系统的养分循环，在调控C、N、P分配方面优于秸秆。具体表现为：生物炭对燕麦茎叶的C、N、P含量无显著影响，但显著提高根系C、N、P含量，尤其B3梯度下，根系C、N、P含量较对照组分别提高了45.2%、65.2%、71.4%，较秸秆S3梯度分别高出28.7%、60.2%、14.5%。同时，生物炭显著提升土壤和微生物C、N、P含量，较对照组分别提高240.2%、157.8%、81.2%和95.3%、88.7%、134.7%，较秸秆S3梯度分别高出118.4%、81.4%、17.5%和61.2%、21.7%、43.5%。此外，生物炭显著降低茎叶、根系及微生物的C:N和C:P，同时提高土壤C:N和C:P，表现出双向调节作用，而秸秆处理未显现此效应。（2） 生物炭和秸秆添加下，根系的内稳性较弱，对外源养分输入的响应更为迅速，而茎叶和微生物的内稳性较强。（3） 植物和微生物的C、N、P元素内稳性整体表现为C>N>P，比值内稳性表现为N:P>C:P>C:N。综合而言，生物炭通过增强植物（燕麦）对N、P的吸收和同化，显著提升了植物-土壤-微生物系统的固碳和元素内稳性，其中高量（B3）生物炭效果最为显著。本研究为沙地农业系统的可持续管理及生物炭资源化利用提供了重要的理论依据和实践指导。

Stoichiometric homeostasis of carbon (C), nitrogen (N), and phosphorus (P) in the plant-soil-microbial continuum is crucial for the maintenance of nutrient cycling stability in fragile ecosystems. To address the challenges of imbalanced C:N:P stoichiometry in eolian sandy soils and the uncertain effects of organic amendments in the Horqin Sandy Land, this study conducted a field experiment to compare the impacts of biochar and straw additions on the stoichiometric characteristics of C, N, and P within an oat cultivation system. The experimental design included a control group (CK), biochar amendment treatments (low B1: 3%, medium B2: 5%, and high B3: 10% by mass), and straw amendment treatments (low S1: 3%, medium S2: 5%, and high S3: 10% by mass). Grounded in ecological stoichiometry and homeostasis theory, this study systematically analyzed the C:N:P response characteristics of oat plants, soil, and microbial communities. The results showed that (1) Biochar amendments (B2 and B3) significantly enhanced the C-N-P cycling efficiency of the oat system and demonstrated superior regulation over elemental allocation compared with straw addition. While biochar had negligible effects on C, N, and P content in oat shoots, it considerably increased these nutrients in the roots. Under the B3 treatment, root C, N, and P content increased by 45.2%, 65.2%, and 71.4%, respectively, relative to the control (CK), outperforming straw S3 by 28.7%, 60.2%, and 14.5%. Soil C, N, and P pools exhibited even greater responses: biochar B3 elevated soil C (240.2% vs. CK; 118.4% vs. S3), N (157.8% vs. CK; 81.4% vs. S3), and P (81.2% vs. CK; 17.5% vs. S3) contents. Microbial biomass followed a similar trend, with C, N, and P increasing by 95.3%, 88.7%, and 134.7% over CK, and by 61.2%, 21.7%, and 43.5% over S3, respectively. Additionally, biochar significantly reduced the C:N and C:P ratios in the shoots, roots, and microbial biomass while increasing these ratios in the soil. This bidirectional regulatory effect was not observed with straw treatment. (2) The homeostasis of oat roots under biochar and straw addition exhibited weaker stability and higher sensitivity to exogenous nutrient inputs compared with stems, leaves, and microorganisms. (3) The C, N, and P concentrations in the plants and microbial biomass of different organs of jasmine followed the order of C>N>P, and the C:N, C:P, and N:P ratios followed the order of N:P>C:P>C:N. Collectively, biochar amendments significantly enhanced the C sequestration capacity and elemental stoichiometric stability of the plant-soil-microbial continuum by improving the oat’s N and P assimilation efficiency. The high-dose biochar (B3 treatment) demonstrated the most pronounced effects. This study establishes a mechanistic foundation for sustainable management of sandy agroecosystems and provides practical guidelines for using biochar as a carbon-negative soil amendment in arid regions.