A better understanding of how rates and stoichiometric signatures of root exudates respond to altered N deposition and rainfall patterns is critical for predicting future impacts of environmental changes on ecosystem function and services. Here, we conducted a field experiment examining the effects of rainfall reduction (−50% compared to the control with normal rainfall), rainfall addition (+50%), N addition (~10 g N m⁻² yr⁻¹), and their interactions on root C and N exudation rates and C : N ratios of root exudates from dominant species in a temperate steppe. We hypothesized that increasing soil water and N availability will increase C: N ratios of root exudates because plants will grow more and retain more N in their biomass, thus have lower root N exudation rates. We found greater changes in root N exudation rates (ranging from −18% ~ +11%) than C exudation rates (ranging from −6 ~ +11%) in response to rainfall and N treatments. In addition, N addition and its interactions with rainfall treatments decreased root N exudation rates by 4–18% and therefore increased C : N ratios of root exudates by 8–27% compared to control; however, a contrasting pattern was found under rainfall reduction. Furthermore, changes in root C exudation rates in response to rainfall and N treatments were not related to changes in plant biomass. In contrast, root N exudation rates decreased with increasing plant biomass, resulting in an overall increase in C : N ratios of root exudates with increasing plant biomass. Overall, our results reveal the C : N stoichiometric plasticity of root exudates in response to resource modifications. These findings have important implications for understanding rhizosphere plant-soil-microbe interactions and ecosystem functioning under environmental changes.

更好地了解根系分泌物的速率和化学计量特征如何响应改变的氮沉积和降雨模式对于预测环境变化对生态系统功能和服务的未来影响至关重要。在这里，我们进行了一项实地试验，研究了降雨减少（与正常降雨的对照相比为 -50%）、降雨量增加（+50%）、氮添加量（~10 g N m ^-2 yr ^-1)，以及它们对温带草原优势物种根系 C 和 N 渗出率和 C:N 比的相互作用。我们假设增加土壤水和氮的有效性会增加根系分泌物的 C:N 比，因为植物会生长得更多并在其生物量中保留更多的 N，因此根系 N 的渗出率较低。我们发现根系 N 渗出率（范围从 -18% ~ +11%）比 C 渗出率（范围从 -6 ~ +11%）响应降雨和 N 处理的变化更大。此外，氮添加及其与降雨处理的相互作用使根系 N 渗出率降低了 4-18%，因此与对照相比，根系渗出液的 C:N 比增加了 8-27%；然而，在降雨减少的情况下发现了一种对比模式。此外，响应降雨和氮处理的根 C 渗出率的变化与植物生物量的变化无关。相比之下，根系 N 渗出率随着植物生物量的增加而降低，导致根系分泌物的 C:N 比率随着植物生物量的增加而整体增加。总的来说，我们的结果揭示了根系分泌物的 C:N 化学计量可塑性，以响应资源修改。这些发现对于理解环境变化下的根际植物-土壤-微生物相互作用和生态系统功能具有重要意义。响应资源改变的根系分泌物的化学计量可塑性。这些发现对于理解环境变化下的根际植物-土壤-微生物相互作用和生态系统功能具有重要意义。响应资源改变的根系分泌物的化学计量可塑性。这些发现对于理解环境变化下的根际植物-土壤-微生物相互作用和生态系统功能具有重要意义。