Elevational transplantation suggests different responses of African submontane and savanna plants to climate warming

Abstract

Abstract Despite strong climate change in the tropics, little is known about the responses of tropical plants to changing environments. Moreover, while variation in responses to climate change across plant functional groups may help to predict future vegetation dynamics, tropical multi‐species studies are missing. To study plant responses to changes in temperature, we compared the survival, growth and reproduction of 101 herbaceous species originating from the savanna and the submontane vegetation zones in two experimental gardens representing the climate of both zones at Kilimanjaro, Tanzania. Additionally, we tested whether plant functional groups, such as annuals and perennials, shade‐tolerant and shade‐intolerant species, grasses and forbs, and natives and exotics differ in their responses to transplantation. We show that the submontane species in the lower Kilimanjaro area clearly prefer the cooler submontane temperature in terms of survival, growth and reproduction, while savanna plants can grow equally well under both, the submontane and the savanna temperature regimes. This suggests that tropical submontane plants will likely face severe challenges with future climate warming and that the upper distributional limit of savanna plants may be due to biotic interactions rather than to climate. Moreover, we found different responses of grasses and forbs, and natives and exotics to transplantation irrespective of their origin, underlining the importance of considering plant functional groups in climate change research. Synthesis. We demonstrate different responses of tropical submontane and savanna plants to experimental temperature variation. Together with the observed differences between important functional plant groups, this leads us to suggest that strong future changes in vegetation composition on African tropical mountains are likely.