The Impacts of Drought on Plant-Soil-Microbe Interactions in a Tropical Rainforest Ecosystem

Abstract

As direct mediators between plants and soil, roots play an important role in metabolic responses to environmental stresses such as drought. Yet, root responses to drought are vastly uncharacterized on a species-specific level, especially in tandem with their rhizosphere soils and microbial communities. First, we aim to examine the effects of drought on root metabolic profiles and carbon allocation pathways of three tropical rainforest species by combining cutting-edge metabolomic and imaging technologies. Second, we focus on integrating microbial community analysis using 16S rRNA gene amplicon sequencing with high-resolution organic matter characterization (meta-metabolome) to fully encapsulate microbial influence of species-specific roots to rhizosphere soil organic carbon turnover. Linking the root-rhizosphere interface to its molecular processes will further determine how drought stress affects soil dynamics. To this end, we performed in-situ position-specific 13C-pyruvate labeling on roots before and during a 65-day drought experiment in an enclosed tropical rainforest. In situ metabolic and microbial rhizosphere profiles of three plant species, Piper auritum, Hibiscus rosa sinensis, and Clitoria fairchildiana revealed drastically different drought-response mechanisms, enhancing our understanding of niche rhizosphere-root chemistry and how this differs between drought-tolerant and drought-sensitive plant species. Our in-situ approach revealed how species-specific microbial interactions systematically progressed with the root metabolome; as roots responded to drought, their associated microbial communities adapted and supplemented drought avoidance strategies for plants. We suggest that multiple techniques can be combined to identify how plants cope with drought through different drought tolerance strategies and the consequences of such changes on belowground soil organic matter and microbial composition. Collectively, these findings highlight the importance of considering species-specific responses of plants to drought under climate change, which could have profound impacts on C cycling at the ecosystem-scale.