Text by Mariana Dairel
One of the major threats to tropical savannas is the invasion of exotic grasses. Savannas are systems frequently disturbed, and the fire is one of these disturbances. Different strategies for post-fire vegetation community regeneration are observed. New individuals can be recruited from the soil seed bank, and areas under natural regeneration can be more easily invaded when these exotic newcomers (e.g. exotic grasses) are already in the system.
During my Master’s, I studied how the presence of invasive grasses affects the dynamics and composition of the soil seed bank in invaded and non-invaded areas from open savannas. And what did we find? The soil seed bank is a potential source of invasion in non-invaded plant communities since the presence of invasive grasses seeds can be observed. In invaded areas, where the aboveground vegetation is already dominated by these invasive grasses, the soil seed bank is homogenous, being dominated by them (98%).In non-invaded areas, the soil seed bank presented a high density (65%) of native species. However, the dominance of invasive grasses was significant (35%, of the total seeds belonging to the invasive species Urochloa brizantha). The presence of invasive grasses in the soil seed bank from non-invaded areas is an indication that the invasive species is already in the system, and changes in the aboveground vegetation could accelerate the invasion process. Therefore, in order to manage and control these African grasses, we should not only aim the aboveground control but also, management efforts in the soil seed bank should be considered as a restoration tool to control and to avoid the establishment of invasive species in open savannas of Cerrado.
Project:
> How fire season affects Cerrado vegetation? (FAPESP JP 2015/06743-0)
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