Abstract

Invasive plants often alter ecosystem function and processes, especially soil N cycling. In eastern United States forests, the shrub Rosa multiflora (“rose”) is a dominant invader, yet potential effects on N cycling are poorly understood. Moreover, invasive plant management can impact soil N cycling by decreasing plant N uptake and disturbing the soil. The objectives of this study were to evaluate N cycling along a gradient of rose invasion (observational) and investigate potential changes to N cycling (manipulative) under four different management strategies: (1) do nothing (the control), (2) invasive plant removal, (3) removal followed by native seed mix addition, (4) removal, native seed mix, and chipped rose stem addition. We selected three forest sites experiencing a Low, Medium, or High amount of shrub invasion, and measured N cycling in the early (June) and late (September) growing seasons. We found N was immobilized in June and mineralized in September. One year after experimental management, removal alone had no effect on N cycling compared to control plots, but addition of native seed mix and chipped stems reduced early-season nitrification in our Medium invasion site. Our findings suggest that rose invasion may increase N cycling rates when soils are dry, which may occur more frequently with future climate change. In addition, N cycling responds differentially to management in the year following invasive plant removal, but most noticeably under moderate rose invasion.

中文翻译：

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灌木蔷薇入侵森林中的土壤氮循环：土壤湿度和入侵密度的重要性

摘要

入侵植物经常改变生态系统功能和过程，尤其是土壤氮循环。在美国东部森林中，灌木蔷薇（“玫瑰”）是主要入侵者，但对氮循环的潜在影响却知之甚少。此外，侵入性植物管理可以通过减少植物氮吸收和扰乱土壤来影响土壤氮循环。本研究的目的是评估沿着玫瑰入侵梯度（观察）的氮循环，并研究四种不同管理策略下氮循环（操纵）的潜在变化：（1）不采取任何措施（对照），（2）入侵植物去除，(3)去除，然后添加原生种子混合物，(4)去除，原生种子混合物，并添加切碎的玫瑰茎。我们选择了三个经历低、中或高灌木入侵的森林地点，并测量了生长季节早期（六月）和晚期（九月）的氮循环。我们发现氮在六月被固定，并在九月被矿化。实验管理一年后，与对照地块相比，单独去除对氮循环没有影响，但添加本地种子混合物和切碎的茎减少了我们的培养基入侵地点的早季硝化作用。我们的研究结果表明，当土壤干燥时，玫瑰入侵可能会增加氮循环率，随着未来的气候变化，这种情况可能会更频繁地发生。此外，在入侵植物清除后的一年中，氮循环对管理的反应有所不同，但在中等程度的玫瑰入侵下最为明显。