Invasive plants disrupt native biodiversity and ecosystem functions and their distribution increase with ongoing global land-use changes. Clarifying plant nitrogen (N) uptake and use strategies mediated by rhizosphere microbes is key to understand the success of plant invasion. We used N labeling to assess the N uptake rate and N use efficiency (NUE) of four invasive species and their native congeners growing either alone (without competition) or pairwise (interspecific competition). Functional gene abundance and enzyme activities in the soil were linked to the richness and community composition of rhizosphere bacteria. Without competition, invasive plants have larger biomass (∼40%) and NUE (∼68%) than native plants, but the native plants had a faster NO uptake rate (∼10%) than invasive plants. Interspecific competition decreases the plant biomass but increases the NUE of both invasive and native plants and increases the NH and NO uptake by invasive plants. Consequently, invasive plants produce more biomass due to their stronger competitive ability (higher Relative Competition Index) and faster NH uptake rate than the native plants. Invasive plants have a larger microbial biomass, higher activity of β-D-cellobiosidase, faster nitrification, denitrification, and nitrogenase activity, and higher abundances of , , and genes than native plants when growing pairwise. Competition leads to the enrichment in a set of OTUs in the rhizosphere of invasive and native plants compared with those grown alone, and the enrichment of another set in invasive compared with native plants grown together. Structural Equation Models showed that the plant biomass, N uptake rate, and NUE are influenced by rhizosphere bacteria via the acceleration of N transformation in the soil. We conclude that the competitive advantage of invasive plants is achieved by fast NH uptake, rather than by strengthening NUE as would be the case in the absence of competition. These findings provide important insights into the critical mechanisms of plant N uptake during invasion by alien plants.

中文翻译：

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入侵植物的竞争力是由氮利用策略和根际微生物组介导的

入侵植物破坏了本地生物多样性和生态系统功能，其分布随着全球土地利用的持续变化而增加。阐明根际微生物介导的植物氮 (N) 吸收和利用策略是了解植物入侵成功与否的关键。我们使用氮标记来评估四种入侵物种及其本地同系物单独生长（无竞争）或成对生长（种间竞争）的氮吸收率和氮利用效率（NUE）。土壤中的功能基因丰度和酶活性与根际细菌的丰富度和群落组成有关。在没有竞争的情况下，入侵植物比本土植物具有更大的生物量（∼40%）和NUE（∼68%），但本土植物比入侵植物具有更快的NO吸收率（∼10%）。种间竞争降低了植物生物量，但增加了入侵植物和本地植物的 NUE，并增加了入侵植物对 NH 和 NO 的吸收。因此，入侵植物由于其比本地植物更强的竞争能力（更高的相对竞争指数）和更快的NH吸收率而产生更多的生物量。成对生长时，入侵植物比本地植物具有更大的微生物量、更高的 β-D-纤维二糖苷酶活性、更快的硝化、反硝化和固氮酶活性，以及​​更高的 、 和 基因丰度。与单独生长的植物相比，竞争导致入侵植物和本地植物根际中一组OTU的富集，以及与一起生长的本地植物相比，入侵植物根际中另一组OTU的富集。结构方程模型表明，根际细菌通过加速土壤中的氮转化来影响植物生物量、氮吸收率和氮利用效率。我们的结论是，入侵植物的竞争优势是通过快速 NH 吸收来实现的，而不是像在没有竞争的情况下那样通过加强 NUE 来实现。这些发现为外来植物入侵期间植物氮吸收的关键机制提供了重要的见解。