Soil respiration is tightly linked to rhizosphere processes, which are characterized by high spatial variability. We tested whether planar optodes can be applied to capture this spatial variability of CO₂ in the rhizosphere. Maize (Zea mays) was grown in rhizoboxes and CO₂ concentration around roots was measured at three volumetric soil water contents (VWC) using planar optodes_. Gradients of CO₂ were clearly visible around root tips but less pronounced around mature root parts probably due to high root respiration and microbial activity around tips. Saturating the soil from 21% VWC increased the measured CO₂ concentration from 0.23 to 1.47 μmol CO₂ L⁻¹_. Statistical comparisons between VWC levels indicated that small changes in soil WC might strongly affect CO₂ measurements. However, provided that the soil moisture is kept constant, optode measurements of CO₂ can be used in moist soil samples to quantify relative differences in CO₂ concentration between treatments or soil regions.

土壤呼吸与根际过程紧密相关，根际过程具有高度的空间变异性。我们测试了是否可以将平面光电二极管应用于捕获根际中CO _2的这种空间变异性。玉米（Zea mays）在根际箱中生长，并使用平面光电二极管在三种体积土壤水含量（VWC）下测量了根周围的CO ₂浓度_。根尖周围清晰可见CO ₂梯度，而在成熟根部周围则不太明显，这可能是由于根尖周围的高呼吸作用和微生物活性所致。使土壤中的VWC饱和度为21％，将测量到的CO ₂浓度从0.23增加到1.47μmolCO ₂ L^-1 _。VWC水平之间的统计比较表明，土壤WC的微小变化可能会强烈影响CO _2的测量。但是，只要土壤湿度保持恒定，就可以在潮湿的土壤样品中使用CO _2的光电测量来量化处理或土壤区域之间CO ₂浓度的相对差异。