Purpose

Cheatgrass invasion of Intermountain sagebrush steppe in the western United States poses increasing challenges to the function and survival of this native ecosystem. The invasive success and persistence of cheatgrass has been attributed to the increasing soil total nitrogen, but mechanisms behind remain inconclusive. We hypothesized that soil microorganisms play a role in soil nitrogen associated with cheatgrass invasion.

Methods

We collected soil samples from the root zone of cheatgrass, native bunchgrass, and sagebrush at two depths and from two adjacent sites in April. We examined soil chemical properties (pH, moisture content, and NH₄⁺ and NO₃⁻ concentration) and soil microbial communities.

Results

We found that cheatgrass invasion was associated with different soil microbial community composition compared to native bunchgrass and sagebrush. In particular, we observed higher relative abundances of N2 fixers and ureolytic bacteria and lower relative abundance of denitrifiers providing a potential mechanistic belowground explanation of raising soil nitrogen.

Conclusions

Overall, our results indicate the importance of soil microorganisms in the dominance and persistence of invasive species. Targeted microbiome interventions should be considered to control cheatgrass invasion.

中文翻译：

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与山艾树灌木丛中金雀草入侵相关的土壤微生物群落和氮

目的

Cheatgrass 入侵美国西部的山间山艾树草原，给这个原生生态系统的功能和生存带来了越来越大的挑战。欺骗草的入侵成功和持久性归因于土壤总氮的增加，但其背后的机制仍无定论。我们假设土壤微生物在与金雀花入侵相关的土壤氮中发挥作用。

方法

我们在 4 月从两个深度和两个相邻地点收集了金雀花、原生丛草和山艾树根区的土壤样本。我们检查了土壤化学性质（pH、水分含量、NH ₄ ⁺ 和NO ₃ ^- 浓度）和土壤微生物群落。

结果

我们发现，与原生草丛和山艾树相比，金雀花入侵与不同的土壤微生物群落组成有关。特别是，我们观察到 N2 固定剂和尿素分解细菌的相对丰度较高，而反硝化剂的相对丰度较低，这为提高土壤氮含量提供了潜在的地下机制解释。

结论

总体而言，我们的结果表明土壤微生物在入侵物种的优势和持久性中的重要性。应该考虑有针对性的微生物组干预来控制作弊草的入侵。