Abstract

We test whether the invasive earthworm Lumbricus terrestris and leaf litter of the invasive herbaceous plant Alliaria petiolata interact to influence the native plant, Podophyllum peltatum, using both observational field data and a multi-year experiment. We hypothesized invader interactive effects on the native plant might result from either changes in allelochemical distribution in the soil or nutrient availability mediated by the invasive earthworm pulling leaf litter down into the soil. Within the field data we found that Alliaria petiolata presence and higher soil nitrogen correlated with reduced Podophyllum peltatum cover, and no evidence for an invader–invader interaction. Within the factorial experiment, we found a super-additive effect of the two invaders on plant biomass only when activated carbon was present. In the absence of activated carbon, there were no differences in Podophyllum peltatum biomass across treatments. In the presence of activated carbon, Podophyllum peltatum biomass was significantly reduced by the presence of both Lumbricus terrestris and Alliaria petiolata leaf litter. The absence of an effect of Alliaria petiolata leaves without activated carbon, combined with a failure to detect arbuscular mycorrhizal colonization, suggests that indirect effects of allelochemicals on arbuscular mycorrhizal fungi were not the primary driver of treatment responses. Rather direct nutrient availability might influence a potential interaction between these invaders. Leaf nitrogen content was higher and leaf CO₂ concentration was lower in the presence of Lumbricus terrestris, but treatment did not influence maximum photosynthetic rate. While the field data do not suggest a negative interaction between these invaders, the experiment suggests that such an interaction is possible with greater environmental stress, such as increasing nitrogen deposition. Further, even plants with rapid physiological responses to increased nitrogen availability may have other physiological limits on growth that prevent them from compensating from the harm caused by multiple invaders.

中文翻译：

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入侵性陆生mb虫与入侵植物小蒜蒜对美国俄亥俄州东北部的原生植物鬼臼的潜在相互作用

摘要

我们使用实地观测数据和多年实验，测试了入侵性Lu藜和入侵性草本植物小蒜Alliaria petiolata的凋落物是否相互作用，从而影响了本地植物Podophyllum peltatum。我们假设入侵者对本地植物的交互作用可能是由于土壤中化感化学分布的变化或由入侵性worm将枯枝落叶拉入土壤所介导的养分利用率造成的。在田间数据中，我们发现小花Alliaria petiolata的存在和较高的土壤氮含量与象牙鬼臼的减少有关。掩盖，也没有证据表明入侵者与入侵者之间存在互动。在析因实验中，我们仅在存在活性炭的情况下才发现这两种入侵者对植物生物量具有超加和作用。在没有活性炭的情况下，整个处理过程中，鬼臼的生物量没有差异。在存在活性炭的情况下，ter藜和小葱蒜叶凋落物的存在显着降低了鬼臼的生物量。没效的Alliaria petiolata没有活性炭的叶子，加上未能检测到丛枝菌根定植，表明化感药物对丛枝菌根真菌的间接作用不是治疗反应的主要驱动力。相反，直接的养分供应可能会影响这些入侵者之间的潜在相互作用。rest藜存在下叶片氮含量较高而CO ₂浓度较低，但处理并未影响最大光合速率。虽然现场数据并未表明这些入侵者之间存在负面的相互作用，但实验表明，这种相互作用在更大的环境压力下（例如增加的氮沉积）是可能的。此外，即使对增加的氮利用量具有快速生理反应的植物也可能​​对生长具有其他生理学限制，从而阻止了它们对多种入侵者造成的伤害进行补偿。