Plant invasion under multiple global change factors

Abstract

With the accelerating pace of the Anthropocene, our ecosystem has undergone significant changes, such as global warming, elevated atmospheric carbon dioxide concentration, drought, and biological invasion. These global change factors (GCFs) frequently interact, leading to compounded effects on ecosystems. Among these, numerous studies have elucidated that many other GCFs also act on plant invasion. However, most of these studies only focus on a single GCF. Our understanding of how multiple GCFs influence plant invasions remains limited. Here, I seek to determine whether multiple GCFs promote plant invasions. In the first Chapter, I conducted a meta-analysis testing how two global change factors jointly affect plant invasions. The results revealed that alien species outperformed native species in several GCF combinations, with the two GCFs acting additively during this process. Subgroup analysis showed that the relative benefits of aliens over native plants were particularly apparent when they grew in competition with one another, and that the results were largely the same when the aliens were restricted to naturalized or invasive species. To address the question across a broader gradient in the number of GCFs (i.e. more than three), in the second Chapter, a greenhouse experiment was conducted to test how native and non-native species respond to increasing number of GCFs (0,1,2,3,4,5). I found that GCF number had no influence on community productivity but increased the biomass proportion of non-native plants. Furthermore, the increasing GCF number enhanced biomass but had no influence on height for non-native plants, whereas both biomass and height decreased for native plants. In Chapter 3, to generalize my conclusions, I conducted another meta-analysis that included more GCF types and a wider range of species. When exposed to two GCFs simultaneously, the performance of naturalized aliens and native plants remained consistent, but the advantage of invasive plants over native plants became slightly more pronounced. Invasive plants showed stronger positive responses compared to natives during germination and reproduction. Overall, my thesis demonstrates that non-native species generally benefit more—or suffer fewer negative effects—from multiple global change factors across all three Chapters. This outcome is influenced by several additional drivers, including competition, invasion stage, life history stage, and the specific types of global change factors involved.