Remote Sensing Reveals Fire-Driven Enhancement of a C4 Invasive Alien Grass on a Small Mediterranean Volcanic Island

The severity and the extent of a large fire event that occurred on the small volcanic island of Stromboli (Aeolian archipelago, Italy) on 25–26 May 2022 were evaluated through remotely sensed data to assess the short-term effect of fire on local plant communities. For this purpose, the differenced normalized burned index (dNBR) was also used to quantify the extent of early-stage vegetation recovery dominated by Saccharum biflorum Forssk. (Poaceae), a rhizomatous C4 perennial grass of Paleotropical origin. The burned area was estimated to have an extension of 337.83 ha, corresponding to 27.7 % of the island surface and to 49.8 % of Stromboli's vegetated area. On the one hand, this event considerably damaged the native plant communities, hosting many species of high biogeographic interest. On the other hand, Saccharum biflorum clearly benefited from fire. In fact, this species showed a very high vegetative performance after burning, being able to exert unchallenged dominance in the early stages of the postfire succession. Our results confirm the complex and probably synergic impact of different human disturbances (repeated fires and the introduction of invasive alien plants) on the natural ecosystems of small volcanic islands.