Mycorrhizal associations of temperate forest seedlings mediate rhizodeposition, but not soil carbon storage, under elevated nitrogen availability,Global Change Biology

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Mycorrhizal associations of temperate forest seedlings mediate rhizodeposition, but not soil carbon storage, under elevated nitrogen availability
Global Change Biology ( IF 10.8 ) Pub Date : 2024-08-07 , DOI: 10.1111/gcb.17446
Amelia A Fitch _{1,

2} , Sarah B Goldsmith ₁ , Richard A Lankau ₃ , Nina Wurzburger ₄ , Zachary D Shortt ₁ , Augustos Vrattos ₁ , Ella N Laurent ₁ , Caitlin E Hicks Pries ₁

Affiliation

Tree‐mycorrhizal associations are associated with patterns in nitrogen (N) availability and soil organic matter storage; however, we still lack a mechanistic understanding of what tree and fungal traits drive these patterns and how they will respond to global changes in soil N availability. To address this knowledge gap, we investigated how arbuscular mycorrhizal (AM)‐ and ectomycorrhizal (EcM)‐associated seedlings alter rhizodeposition in response to increased seedling inorganic N acquisition. We grew four species each of EcM and AM seedlings from forests of the eastern United States in a continuously 13C‐labeled atmosphere within an environmentally controlled chamber and subjected to three levels of 15N‐labeled fertilizer. We traced seedling 15N uptake from, and 13C‐labeled inputs (net rhizodeposition) into, root‐excluded or ‐included soil over a 5‐month growing season. N uptake by seedlings was positively related to rhizodeposition for EcM‐ but not AM‐associated seedlings in root‐included soils. Despite this contrast in rhizodeposition, there was no difference in soil C storage between mycorrhizal types over the course of the experiment. Instead root‐inclusive soils lost C, while root‐exclusive soils gained C. Our findings suggest that mycorrhizal associations mediate tree belowground C investment in response to inorganic N availability, but these differences do not affect C storage. Continued soil warming and N deposition under global change will increase soil inorganic N availability and our seedling results indicate this could lead to greater belowground C investment by EcM‐associated trees. This potential for less efficient N uptake by EcM‐trees could contribute to AM‐tree success and a shift toward more AM‐dominated temperate forests.

中文翻译：

在氮利用率升高的情况下，温带森林幼苗的菌根联合体介导根际沉积，但不介导土壤碳储存

树-菌根关联与氮 (N) 有效性和土壤有机质储存模式相关；然而，我们仍然缺乏对哪些树木和真菌特征驱动这些模式以及它们如何响应土壤氮可用性的全球变化的机械理解。为了解决这一知识差距，我们研究了丛枝菌根（AM）和外生菌根（EcM）相关幼苗如何改变根际沉积以响应幼苗无机氮获取的增加。我们从美国东部的森林中连续种植了四种 EcM 和 AM 幼苗13环境受控室内的 C 标记气氛，并受到三个级别的影响15 N标记肥料。我们追踪幼苗15 N 吸收来自和13在 5 个月的生长季节中，C 标记的输入（净根沉积）进入排除根或包含根的土壤。在含根土壤中，幼苗的氮吸收与 EcM 相关幼苗的根际沉积呈正相关，但与 AM 相关幼苗则不然。尽管根际沉积存在这种差异，但在实验过程中，不同菌根类型的土壤碳储存没有差异。相反，含根的土壤失去了碳，而不含根的土壤则增加了碳。我们的研究结果表明，菌根关联调节了树木地下碳的投资，以响应无机氮的可用性，但这些差异并不影响碳储存。全球变化下持续的土壤变暖和氮沉降将增加土壤无机氮的有效性，我们的幼苗结果表明，这可能导致 EcM 相关树木对地下碳的投资更大。 EcM树吸收氮效率较低的潜力可能有助于AM树的成功以及向AM为主的温带森林的转变。

更新日期：2024-08-07

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