Rhizosphere priming effects on soil carbon and nitrogen mineralization
Rhizosphere priming effects on soil carbon and nitrogen mineralization
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DOI：
10.1016/j.soilbio.2014.04.033
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发表时间：
2014-09
影响因子：
9.7
通讯作者：
B. Zhu;B. Zhu;J. Gutknecht;J. Gutknecht;D. Herman;D. Keck;D. Keck;M. Firestone;W. Cheng
中科院分区：
文献类型：
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作者：
B. Zhu;B. Zhu;J. Gutknecht;J. Gutknecht;D. Herman;D. Keck;D. Keck;M. Firestone;W. Cheng
活根及其根际沉积物影响微生物活性和土壤碳（C）和氮（N）矿化。这种所谓的根际引发效应（RPE）近年来越来越受到重视。然而，RPE的大小及其驱动机制仍然难以捉摸。在这里，我们调查了RPE的两种植物（大豆和向日葵）生长在两种土壤类型（农场或草原土壤），并在两个物候阶段（营养和成熟阶段）在88天的温室实验采样。我们测量了土壤C矿化使用连续13 C-标记方法，和量化的总氮矿化与15 N池稀释技术。我们发现，活根显着提高土壤C矿化，由27- 245%。这种积极的RPE对土壤碳矿化没有变化的两种土壤或两个物候期，但显着更大的向日葵相比，大豆。RPE的大小与根际呼吸速率在所有的处理呈正相关，这表明处理之间的RPE的变化可能是由根系活力和根沉积量的变化。此外，在5个处理中，活根对总氮矿化率的促进作用为36-62%，而在其他3个处理中，活根对总氮矿化率的影响不显著。我们还量化了土壤微生物生物量和胞外酶活性时，植物在营养阶段。一般来说，活根使微生物量碳增加0- 28%，β-葡萄糖苷酶活性增加19- 56%，氧化酶活性增加0- 46%。这些结果与同期测得的土壤C（45-79%）和N（10-52%）矿化的正根际效应一致。我们还发现β-葡萄糖苷酶活性与土壤C矿化速率之间以及氧化酶活性与总N矿化速率之间存在显著的正相关关系。这些关系为RPE的微生物活化假说提供了明确的证据。我们的研究结果表明，根-土-微生物相互作用可以通过根际效应促进土壤C和N矿化。RPE与根际呼吸速率和土壤酶活性之间的关系可用于在土壤有机质模型中明确表达RPE。
Living roots and their rhizodeposits affect microbial activity and soil carbon (C) and nitrogen (N) mineralization. This so-called rhizosphere priming effect (RPE) has been increasingly recognized recently. However, the magnitude of the RPE and its driving mechanisms remain elusive. Here we investigated the RPE of two plant species (soybean and sunflower) grown in two soil types (a farm or a prairie soil) and sampled at two phenological stages (vegetative and mature stages) over an 88-day period in a greenhouse experiment. We measured soil C mineralization using a continuous13C-labeling method, and quantified gross N mineralization with a15N-pool dilution technique. We found that living roots significantly enhanced soil C mineralization, by 27–245%. This positive RPE on soil C mineralization did not vary between the two soils or the two phenological stages, but was significantly greater in sunflower compared to soybean. The magnitude of the RPE was positively correlated with rhizosphere respiration rate across all treatments, suggesting the variation of RPE among treatments was likely caused by variations in root activity and rhizodeposit quantity. Moreover, living roots stimulated gross N mineralization rate by 36–62% in five treatments, while they had no significant impact in the other three treatments. We also quantified soil microbial biomass and extracellular enzyme activity when plants were at the vegetative stage. Generally, living roots increased microbial biomass carbon by 0–28%, β-glucosidase activity by 19–56%, and oxidative enzyme activity by 0–46%. These results are consistent with the positive rhizosphere effect on soil C (45–79%) and N (10–52%) mineralization measured at the same period. We also found significant positive relationships between β-glucosidase activity and soil C mineralization rates and between oxidative enzyme activity and gross N mineralization rates across treatments. These relationships provide clear evidence for the microbial activation hypothesis of RPE. Our results demonstrate that root–soil–microbial interactions can stimulate soil C and N mineralization through rhizosphere effects. The relationships between the RPE and rhizosphere respiration rate and soil enzyme activity can be used for explicit representations of RPE in soil organic matter models.