Melinis minutiflora

Brazilian native species were all affected by shading, two of them by competition with M. minutiflora, and one of them by fertilization. Two Hawaiian native plants were affected by shade and competition with M. minutiflora, whereas one native species was not affected by any of the experimental factors (Zenni et al. 2019)

The exotic grass had no discernable effect on initial seedling emergence, as defined by the number of seedlings present at the end of the first growing season. Subsequent seedling survival in plots dominated by M. minutiflora was less than half that of plots dominated by native species. Consequently, at the end of the third growing season, invaded plots had only 44% as many seedlings as plots with native grasses. Above‐ground grass biomass of invaded plots was more than twice that of uninvaded plots, while seedling survival was negatively correlated with grass biomass, suggesting that competition for light may explain the low seedling survival where M. minutiflora is dominant (Hoffman and Haridasan 2008).

We observed that the removal of invasive grasses, mainly M. minutiflora, decreased overall soil fertility in comparison to plots where invasives were not removed (Figure 3; Table 1). Phosphorous (F4,105 = 12.07, p < .001), potassium (F4,105 = 12.46, p < .001) and nitrogen (F4,105 = 12.87, p < .001) had lower concentrations in invasive removal plots than those where invasives were not removed (Zenni et al. 2020)

Simulations with the BehavePlus 5 indicated that fires would be more destructive in the fields invaded by molasses grass (Fig. 4 and 5). From 2010 to 2013, the relative air humidity was ≤ 18% on 13 days. Considering the more critical periods with 18% dead biomass moisture and 15 km/h winds, in areas with high invasion rates vs. non-invaded areas (Fig. 4 and 5), fire fronts would advance 2.5 times faster (9 m/min vs. 22.1 m/min), the fire intensity would be 17.3 times greater (569 KW/m vs. 9868 KW/m), the flame length would be 2.8 times greater (1.4 m vs. 5.3 m), and the heat per unit area (independent of wind velocity) would be 7.1 times higher (3792 Kj/m2 vs. 26778 Kj/m2).

After 2 years of invasive species removal, we found a total of 67 plant species across the 100 experimental plots. In the native uninvaded Cerrado plots we found 129 plant species. Combined, the 25 invaded plots had a total of 16 species, the 25 M. minutiflora removal plots had a total of 39 species, the 25 U. decumbens removal plots had a total of 17 species, and the 25 M. minutiflora and U. decumbens removal plots had a total of 37 species. There was a significant effect of invasive species removal on plant species richness (χ2 = 298.34, p < .001, Figure S2). Compared to the invaded plots (no removal), M. minutiflora (d = 1.5 ± 0.64 CI) and M. minutiflora and U. decumbens (d = 1.19 ± 0.62 CI) removal positively affected plant richness (Figure 1; Table S1). Plant species richness doubled when M. minutiflora was removed, but richness on these plots was still four times lower than Cerrado plots (Figure 1; Table S1).