Giant root-rat engineering and livestock grazing activities regulate plant functional trait diversity of an Afroalpine vegetation community in the Bale Mountains, Ethiopia

Abstract Disturbances from rodent engineering and human activities profoundly impact ecosystem structure and functioning. While we know that disturbances modulate plant communities, it is important to comprehend the mechanisms through which rodent and human disturbances modulate the functional trait composition of vegetation communities. Here, we evaluated the changes in functional trait diversity and composition of Afroalpine vegetation communities in the Bale Mountains of Ethiopia along gradients of engineering disturbances of a subterranean endemic rodent, the giant root-rat (Tachyoryctes macrocephalus RÜPPELL 1842) and human activities (settlement establishment and livestock grazing). We conducted RLQ (co-inertia analysis) and fourth-corner analyses to test for trait-disturbance (rodent engineering/human activities) covariation. Overall, our results show an increase in plant functional trait diversity with increasing root-rat engineering and increasing human activities. Functional traits, such as large seed mass, stoloniferous vegetative propagation and a prostrate stem were associated with increasing root-rat engineering, while leaf size and leaf nitrogen content were associated with increasing human activities. The results suggest that disturbances by rodents filter plant traits related to survival and reproduction strategies, whereas human activities such as livestock grazing act as filters for traits related to leaf economics spectrum along acquisitive resource use strategy. Overall, our results show that both rodent engineering and human activities act as habitat filters, but each favouring different combinations of traits reflecting specific adaptation strategies.