Key Laboratory of Wetland Ecology and Environment, State Key Laboratory of Black Soils Conservation and Utilization, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, China.
Department of Applied Biology, Technical University of Kenya, Nairobi, Kenya.
Glob Chang Biol. 2023 Dec;29(23):6741-6755. doi: 10.1111/gcb.16973. Epub 2023 Oct 10.
Large parts of the Earth are experiencing environmental change caused by alien plant invasions, rising atmospheric concentration of carbon dioxide (CO ), and nutrient enrichments. Elevated CO and nutrient concentrations can separately favour growth of invasive plants over that of natives but how herbivory may modulate the magnitude and direction of net responses by the two groups of plants to simultaneous CO and nutrient enrichments remains unknown. In line with the enemy release hypothesis, invasive plant species should reallocate metabolites from costly anti-herbivore defences into greater growth following escape from intense herbivory in the native range. Therefore, invasive plants should have greater growth than native plants under simultaneous CO and nutrient enrichments in the absence of herbivory. To test this prediction, we grew nine congeneric pairs of invasive and native plant species that naturally co-occurred in grasslands in China under two levels each of nutrient enrichment (low-nutrient vs. high-nutrient), herbivory (with herbivory vs. without herbivory) and under ambient (412.9 ± 0.6 ppm) and elevated (790.1 ± 6.2 ppm) levels of CO concentrations in open top chambers in a common garden. Elevated CO and nutrient enrichment separately increased total plant biomass, while herbivory reduced it regardless of the plant invasive status. High-nutrient treatment caused the plants to allocate a significantly lower proportion of total biomass to roots, while herbivory induced an opposite pattern. Herbivory suppressed total biomass production more strongly in native plants than invasive plants. The plants exhibited significant interspecific and intergeneric variation in their responses to the various treatment combinations. Overall, these results suggest that elevated CO and nutrients and herbivory may separately, rather than synergistically, impact productivity of the invasive and co-occurring native plant species in our study system. Moreover, interspecific variation in resource-use strategies was more important than invasive status in determining plant responses to the various treatment combinations.
地球的很大一部分正在经历由外来植物入侵、大气中二氧化碳（CO ）浓度升高和养分富集引起的环境变化。升高的 CO 和养分浓度可以分别促进入侵植物的生长，而不是本地植物，但食草动物的存在如何调节两组植物对同时的 CO 和养分富集的净反应的幅度和方向仍然未知。根据天敌释放假说，入侵植物物种应该将来自昂贵的抗食草防御的代谢物重新分配到更大的生长中，以逃避原产地区域强烈的食草作用。因此，在没有食草动物的情况下，入侵植物在同时的 CO 和养分富集下的生长应该大于本地植物。为了检验这一预测，我们在一个共同的花园中，在开放顶室中，在两个养分富集水平（低养分与高养分）、食草作用（有食草作用与无食草作用）和大气（412.9 ± 0.6 ppm）和升高（790.1 ± 6.2 ppm）CO 浓度下，生长了九对自然共生的入侵和本地植物物种的同属种对。升高的 CO 和养分富集分别增加了总植物生物量，而食草作用降低了生物量，无论植物入侵状态如何。高养分处理导致植物将总生物量的比例显著降低到根部，而食草作用诱导了相反的模式。食草作用对本地植物的总生物量产生的抑制作用比入侵植物更强。这些植物在对各种处理组合的反应中表现出显著的种间和种内变异性。总的来说，这些结果表明，升高的 CO 和养分以及食草作用可能分别而不是协同地影响我们研究系统中入侵和共生的本地植物物种的生产力。此外，资源利用策略的种间变异性比入侵状态更重要，决定了植物对各种处理组合的反应。
