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The influence of roots on mycorrhizal fungi, saprotrophic microbes and carbon dynamics in a low-phosphorus Eucalyptus forest under elevated CO2
Functional Ecology ( IF 4.6 ) Pub Date : 2021-05-13 , DOI: 10.1111/1365-2435.13832 Laura Castañeda‐Gómez 1 , Jeff R. Powell 1 , David S. Ellsworth 1 , Elise Pendall 1 , Yolima Carrillo 1
中文翻译：
CO2升高的低磷桉林根系对菌根真菌、腐生微生物和碳动态的影响
更新日期：2021-05-13
Functional Ecology ( IF 4.6 ) Pub Date : 2021-05-13 , DOI: 10.1111/1365-2435.13832 Laura Castañeda‐Gómez 1 , Jeff R. Powell 1 , David S. Ellsworth 1 , Elise Pendall 1 , Yolima Carrillo 1
Affiliation
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- Elevated atmospheric carbon dioxide (eCO2) can impact soil organic matter (SOM) dynamics by changing the rates of carbon (C) losses and gains. In the rhizosphere, these changes are usually assumed to be the result of root-mediated eCO2 impacts on saprotrophic microbes via altered below-ground C allocation. This C allocation can also impact mycorrhizal fungi and their role in SOM dynamics. However, direct field quantifications of the influence of roots on both mycorrhizal fungi and saprotrophs together with SOM dynamics in forests exposed to eCO2 are rare. This is especially true in phosphorus (P)-limited systems, even though ecosystem responses to eCO2 are known to depend on P availability.
- We assessed root mediation of eCO2 impacts on saprotrophs, mycorrhizal fungi, and C dynamics of root litter and mineral soil C (SOM-C) in a mature, P-limited Eucalyptus woodland exposed to eCO2. We used a novel nested-mesh-bag method to manipulate roots access to the substrates in a 1-year field incubation. We used an isotopic approach to trace C dynamics and performed a comprehensive microbial community analysis, along with nutrients and enzymatic activity measurements.
- Roots increased microbial biomass, fungal:bacterial ratio, plant-derived C gains and substrate C losses while decreasing P availability and specific enzymatic activity. eCO2 increased bacterial relative abundance in root litter and protozoa in SOM-C, but it did not enhance root impacts or mycorrhizal fungi biomass.
- Our combination of in-situ approaches allowed us to demonstrate that while roots have multiple impacts on soil microbial communities and C dynamics, they are not the main drivers of responses to eCO2 in this P-limited forest. Other factors beyond enhanced root-derived below-ground C inputs such as seasonality of nutrient and water availability, and shifts in plant communities may be more important in modulating eCO2 impacts on soil dynamics in P-limited systems.
中文翻译：
CO2升高的低磷桉林根系对菌根真菌、腐生微生物和碳动态的影响
- 升高的大气二氧化碳 (eCO 2 ) 可以通过改变碳 (C) 损失和增加的速度来影响土壤有机质 (SOM) 动态。在根际，这些变化通常被认为是根介导的 eCO 2通过改变地下碳分配对腐生微生物影响的结果。这种 C 分配也会影响菌根真菌及其在 SOM 动态中的作用。然而，在暴露于 eCO 2 的森林中，根对菌根真菌和腐生菌的影响以及 SOM 动态的直接现场量化很少见。尽管已知生态系统对 eCO 2 的响应取决于 P 可用性，但在磷 (P) 限制系统中尤其如此。
- 我们评估了在暴露于 eCO 2的成熟的限磷桉树林地中，eCO 2对腐生菌、菌根真菌以及根凋落物和矿质土壤 C (SOM-C) 的 C 动态的影响的根介导。我们使用一种新颖的嵌套网袋方法来操纵根在 1 年的田间孵化中进入基质的途径。我们使用同位素方法追踪 C 动力学并进行了全面的微生物群落分析，以及营养物质和酶活性测量。
- 根增加了微生物生物量、真菌：细菌比率、植物来源的 C 增益和底物 C 损失，同时降低了 P 的可用性和特定的酶活性。eCO 2增加了 SOM-C 中根凋落物和原生动物中细菌的相对丰度，但它没有增强根影响或菌根真菌生物量。
- 我们结合原位方法使我们能够证明，虽然根对土壤微生物群落和 C 动力学有多种影响，但它们并不是在这片限磷森林中响应 eCO 2的主要驱动因素。除了增强的根部衍生的地下 C 输入之外的其他因素，例如养分和水可用性的季节性以及植物群落的变化，在调节 eCO 2对限磷系统中土壤动态的影响方面可能更为重要。
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