Growth and Competition of the Tropical Invader Chromolaena odorata Are Inhibited by Late Arrival and Mitigated by...

Understanding how arrival order, nitrogen (N) availability and population density interact to shape plant invasion is critical for predicting and ameliorating biological invasions under global change. Chromolaena odorata is one of the most destructive invasive plants in tropical and subtropical regions, but the multifactorial drivers of its establishment and competitive dominance are not fully resolved.

We constructed artificial communities in a common garden experiment and manipulated the arrival order of C. odorata (early, simultaneous and late arrival relative to native species), species density (high, medium and low), and N addition (0 vs. 10 g N m^-2 yr^-1), and then examined their effects on growth performance and competitive dominance.

Early arrival did not increase growth performance of C. odorata, but it substantially enhanced the competitive dominance of the invasive species in most communities. However, late arrival caused substantial reductions in height, biomass, and RDI of C. odorata across all communities, with the most severe declines observed in treatment groups that did not receive N addition. N addition disproportionately promoted the growth of C. odorata regardless of arrival order and enhanced its competitive advantage when it arrived later than native species. In low-density C. odorata communities, N addition exhibited the strongest compensatory effect against growth suppression of the invasive species resulting from late arrival. Importantly, when C. odorata arrived later than native species in plots receiving N addition, its height and biomass were comparable to plants that arrived at the same time as native species in groups without N addition across most communities.

Arrival order is a critical determinant of C. odorata invasion success, with early arrival conferring competitive advantages and late arrival imposing severe competitive penalties due to competition with established native species. However, N addition can compensate for late-arrival disadvantages, particularly for low-density C. odorata, suggesting that N-enriched ecosystems may remain vulnerable to invasion, even when native communities are established. These results underscore the context-dependent nature of priority effects and highlight that managing colonization timing and nutrient inputs may be effective in similar localized settings, though future field-based, multi-season validation is clearly needed.