Grass functional trait responses to experimental warming and fire in Afromontane grasslands

Abstract

Climate change is one of the main challenges facing humanity in the coming century. To understand the impact of climate change on biodiversity and ecosystem functioning, we urgently require a better understanding of plant responses to climate change. To address this knowledge gap we established a full-factorial warming experiment using open-top chambers (OTCs) inside a long-term fire-manipulation experiment in Afromontane fire-climax grasslands. Fire is an essential ecosystem driver in these grasslands, but has rarely been included in experimental climate change research. To assess growth responses to elevated temperatures and fire frequency, we measured four functional traits: vegetative height, leaf area (LA), specific leaf area (SLA), and leaf dry matter content (LDMC). Grasses responded to fire exclusion with increased height, and lower LA, SLA, and LDMC. Grasses responded to warming with lower height and LA, and higher LDMC, suggesting that plant growth was negatively affected by warming. This response was mostly attributed to intra-specific trait variability, highlighting an important role for trait plasticity in community-level processes to mediate the response of montane grassland communities to elevated temperatures and associated drought effects. These results are a first step towards establishing a more mechanistic basis for understanding future climatic changes in Afromontane grasslands.