Warming and elevated nitrogen deposition accelerate the invasion process of Solidago canadensis L.

Abstract

Abstract Background Invasive species can threaten native diversity and alter ecosystem processes while interacting with other components of global environmental change. Invasive plants are becoming increasingly problematic and this can be stimulated by changes in the environment. However, existing studies have primarily investigated the effects of environmental change on a specific stage of plant invasion rather than the continuous invasion process. Methods A space-for-time substitution experiment was performed to investigate how warming and nitrogen deposition affects the invasion process of a plant. Specifically, different ratios of invasive Solidago canadensis L. to native Artemisia argyi Levl. et Van were employed as a proxy to represent successive levels of invasion. A total of seven treatments were applied in the experiment: ambient (CK), N addition (+ 5, + 12 g m−2 year−1), warming (+ 1.15, + 1.86 °C) and their interaction (5 g N m−2 year−1 + 1.15 °C, 12 g N m−2 year−1 + 1.86 °C). The growth performance and competitiveness of S. canadensis were investigated. Results The competitiveness of Solidago canadensis decreased linearly with its invasion degree (p < 0.05). Non-linear regression showed that S. canadensis invasion levels of 53%, 53%, 68%, 55% and 58% were the critical thresholds for shifting the direction or magnitude of chlorophyll, leaf nitrogen, leaf shape index, diameter, and root/shoot ratio, respectively. Compared with the ambient treatment (CK, no warming and no N addition), the diameter, height, biomass and relative competitiveness of S. canadensis were each limited by warming, to a certain extent, whereas these and the above parameters were significantly increased by nitrogen deposition. The interaction of increased temperature and nitrogen deposition led to significant increases in the growth and competitiveness of S. canadensis, and this effect was detected in every stage of the invasion, throughout the invasion process. Conclusions Environmental change might have a continuous, progressive, and augmentative effect on the phenotypic traits of S. canadensis. This study provides fairly robust evidence that environmental change promotes the invasion process of S. canadensis in general, not simply in specific stages. In the future, rather than focusing on specific stages, experimental studies should consider examining invasion on a broader scale.