Greater soil water and nitrogen availability increase C : N ratios of root exudates in a temperate steppe
Greater soil water and nitrogen availability increase C : N ratios of root exudates in a temperate steppe
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温带草原土壤水和氮的有效性增加，根系分泌物的碳氮比增加
DOI：
10.1016/j.soilbio.2021.108384
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发表时间：
2021-08-19
影响因子：
9.7
通讯作者：
Xiao, Chunwang
中科院分区：
文献类型：
--
作者：
Li, Chao;Liu, Lu;Xiao, Chunwang
更好地了解根系分泌物的速率和化学计量特征如何响应氮沉降和降雨模式的变化，对于预测未来环境变化对生态系统功能和服务的影响至关重要。在此，我们进行了一项田间试验，研究了降水减少（与正常降雨对照相比减少50%）、降水增加（增加50%）、氮增加（类似于10 g N m（-2）yr（-1））及其相互作用对温带草原优势种根系C和N分泌速率以及根系分泌物C：N比的影响。我们假设，增加土壤水分和氮的有效性将增加根系分泌物的C：N比，因为植物将生长更多，并保留更多的N在其生物量，从而具有较低的根系N分泌速率。我们发现，根N分泌速率（范围从-18%到+11%）比C分泌速率（范围从-6%到+11%）响应于降雨和N处理的变化更大。此外，氮添加及其与降雨处理的交互作用降低了4-18%的根系N分泌速率，因此增加了8-27%的根系分泌物的C：N比相比，控制;然而，相反的模式被发现在降雨减少。此外，根C分泌速率响应降雨和N处理的变化与植物生物量的变化无关。相反，根系N分泌速率随着植物生物量的增加而降低，导致根系分泌物的C：N比随着植物生物量的增加而总体增加。总的来说，我们的研究结果揭示了根分泌物的C：N化学计量可塑性响应资源修改。这些发现对于理解根际植物-土壤-微生物相互作用和环境变化下的生态系统功能具有重要意义。
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 (similar to 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% similar to +11%) than C exudation rates (ranging from -6 similar to +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.