Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources in Three Gorges Reservoir Region, School of Life Sciences, Southwest University, Chongqing, China.
Key Laboratory of Hangzhou City for Ecosystem Protection and Restoration, College of Life and Environmental Sciences, Hangzhou Normal University, Hangzhou, China.
PLoS One. 2019 Jan 23;14(1):e0206165. doi: 10.1371/journal.pone.0206165. eCollection 2019.
Many ecosystems may suffer from both nutrient enrichment and exotic plant invasions simultaneously. Much has been known that nutrient inputs can promote growth and expansion of exotic invasive plants in wetlands, and that allelopathic effects of the exotic invasive plants can inhibit the growth of coexisting native plants, contributing to their invasion success. Thus, we hypothesized that allelopathic effects of exotics on natives in invaded ecosystems can be enhanced by nutrient enrichment. To test this hypothesis, we conducted two greenhouse hydroponic experiments. One is the monoculture experiment in which a widespread exotic invasive perennial Alternanthera philoxeroides and a native perennial Ludwigia peploides subsp. stipulacea in monoculture were subjected to five levels of nutrient supply. The other is the mixture experiment in which the two species in mixture were subjected to five levels of nutrient supply, each with and without activated carbon addition. Both A. philoxeroides and L. peploides grew better under higher level of nutrient availability in monoculture experiment. In the mixture experiment, A. philoxeroides formed less total and root biomass while L. peploides formed more in response to activated carbon addition and all of the responses had larger degree at higher level of nutrient availability, indicating A. philoxeroides had significant allelopathic effects on L. peploides and the effects was significantly enhanced by nutrient enrichment. Such results support our hypothesis and reveal a novel mechanism for exotic plant invasion in eutrophicated and invaded wetlands, i.e. nutrient enhancement of allelopathic effects of exotics on natives.
许多生态系统可能同时遭受营养富集和外来植物入侵的影响。已知大量的养分输入可以促进湿地中外来入侵植物的生长和扩张，而外来入侵植物的化感作用会抑制共存的本地植物的生长，从而促进它们的入侵成功。因此，我们假设养分富集可以增强外来植物对入侵生态系统中本地植物的化感作用。为了验证这一假设，我们进行了两项温室水培实验。一个是单一栽培实验，其中广泛分布的外来多年生植物空心莲子草和本地多年生植物节节菜在单一栽培条件下，分别接受五个水平的养分供应。另一个是混合栽培实验，两种植物在混合栽培条件下，分别接受五个水平的养分供应，每个水平都有加和不加活性炭的处理。空心莲子草和节节菜在单一栽培实验中，在较高水平的养分供应条件下生长得更好。在混合栽培实验中，空心莲子草形成的总生物量和根生物量较少，而节节菜形成的生物量较多，这是由于活性炭的添加，而且所有的响应在较高水平的养分供应下都有更大的程度，表明空心莲子草对节节菜有显著的化感作用，而养分富集显著增强了这种作用。这些结果支持了我们的假设，并揭示了富营养化和入侵湿地中外来植物入侵的一种新机制，即养分增强了外来植物对本地植物的化感作用。
