Aims The ecological roles of dinitrogen-fixing plants (N 2 -fixers) in the early stage of primary succession remain unclear. We aimed to examine the effects of pioneer N 2 -fixers on the resource status and establishment of neighboring non-N 2 -fixing plants (non-fixers) in a newly formed glacier floodplain, eastern Tibetan Plateau. Methods We set up three plots in the floodplain and assessed the abundance, height, and coverage of two N 2 -fixing and three non-fixing species. We also collected plant and soil samples for the analyses of nutrient status and stable isotope signatures. Results The two N 2 -fixing species acquired > 80% of the nitrogen (N) from N 2 fixation. The cushion-forming N 2 -fixer Astragalus mahoshanicus increased the soil nutrient availability compared with the non-fixers and improved the microclimate beneath the cushions. Natural 15 N abundance indicated significant transfer of N from A. mahoshanicus to its neighboring non-fixers. Consequently, the neighboring non-fixers were significantly higher in N concentration, above-ground to below-ground biomass ratio and height and density than the non-fixers growing alone, but more deficient in some rock-derived nutrients. The other N 2 -fixer Hippophae rhamnoides (in seedling stage) generally did not increase the resource availability, and its neighboring non-fixers were similar in height and lower in density than the non-fixers growing alone. Conclusions The effects of pioneer N 2 -fixers on the resource status and establishment of neighboring non-fixers in the subalpine floodplain were species dependent and were related to the life history traits of the N 2 -fixers. A. mahoshanicus has the potential to be used in the restoration of newly exposed land in subalpine regions.

中文翻译：

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青藏高原东部新形成的冰川洪泛区先锋固氮植物对资源状况及邻近非固氮植物建立的影响

目的固氮植物（N 2 -fixers）在初级演替早期的生态作用尚不清楚。我们旨在研究先驱 N 2 固定剂对青藏高原东部新形成的冰川洪泛区中邻近非 N 2 固定植物（非固定剂）的资源状况和建立的影响。方法我们在洪泛区设置了三个样地，评估了两种固氮物种和三种非固氮物种的丰度、高度和覆盖率。我们还收集了植物和土壤样本，用于分析营养状况和稳定同位素特征。结果这两种固氮物种从固氮中获得了 > 80% 的氮 (N)。与非固定剂相比，形成垫层的 N 2 固定剂黄芪增加了土壤养分的有效性，并改善了垫层下的小气候。天然 15 N 丰度表明 N 从 A. mahoshanicus 显着转移到其邻近的非固定植物。因此，与单独生长的非固定植物相比，邻近的非固定植物在 N 浓度、地上部与地下生物量比以及高度和密度方面显着更高，但在某些岩石衍生养分方面更缺乏。其他N 2 固着沙棘（幼苗期）一般不增加资源可用性，其邻近的非固着株高相似，密度低于单独生长的非固着株。结论先驱N 2 固定者对亚高山漫滩中邻近非固定者资源状况和建立的影响具有物种依赖性，并与N 2 固定者的生活史特征有关。一种。