Our study on the role of biotic resistance to invasion was published in 2018. We studied how native grassland communities affected growth, reproduction and survival during the adult life-stage of the high-impact woody invader Chromolaena odorata under different water availability treatments. We found that savanna grasslands have a strong competitive effect on invasion by the exotic woody shrub C. odorata, reducing growth and reproduction, but not survival. We found no evidence that biotic resistance was stronger under more unfavourable abiotic conditions, as C. odorata was equally impacted in all water treatments. The high survival rates of C. odorata suggest that competitive interactions are not likely to prevent invader persistence in the landscape. Invader persistence is important in determining longer term invasion success as well as invader impact and the concept of persistence should not be overlooked in studies on invasive species.
Our project on climate-vegetation feedbacks in African grasslands and savannas shows that these systems provide important benefits for climate regulation that are often overlooked, but could have large implications for successful climate change mitigation. These include their radiative properties, high infiltration rates and high soil carbon pools, among others. Current climate change mitigation policies have a strong focus on tree planting and large afforestation programs are currently unrolled over Africa. We draw parallels between the tundra biome and these tropical grassy biomes to argue that afforesting grasslands will not reduce global warming. Moreover, it would have devastating effects on biodiversity and counteract mitigation efforts. We discuss the different climate benefits of tropical grassy biomes and why we need to consider their importance for climate change mitigation, not only in terms of biogeochemical feedbacks (i.e. carbon storage), but also in terms of biophysical feedbacks (i.e. hydrological processes, longwave radiation), taking into consideration fire and herbivory as important and essential drivers of these systems.
The final results of these projects will contribute to Europe’s knowledge-based society by providing important knowledge on climate change and invasive species that is of the highest priority in the EU.
