Linking microbial community composition to the ecological dominance of plants

William Marsh Rice University, Houston TX

Investigators

Abstract

Plant species abundance is an essential component of ecosystem biodiversity and function, but understanding what factors regulate rarity and commonness has been elusive. Numerous studies have compared traits that might distinguish between rare and common species (e.g. seed size) and tested factors potentially contributing to rarity (e.g. competition), but these efforts have not substantially explained observed variation in plant abundances. The proposed research will test the novel hypothesis that soil microorganisms, often overlooked by community ecologists, may explain rarity in plants through soil community feedbacks. In the feedback process, a plant species alters the composition of the soil microbial community, and the altered soil community then affects plant performance relative to other plants in the community. Negative feedback should drive plants toward rarity, whereas positive feedback should promote plant dominance. If feedback regulates plant rarity, then rare and common plant species should either support different soil microbial communities or respond differently to the same community. This prediction has not been tested. A field survey will be conducted to determine whether co-occurring rare and common grass species develop consistently different microbial communities in nature. The potential function of these microorganisms will also be compared by measuring activities for enzymes involved in carbon, nitrogen and phosphorous cycles. Then, using a reciprocal soil transfer experiment in the greenhouse (i.e. rare plants will be grown on common plants' soil and vice-versa), the second part of this study will test if rare plants experience more negative feedbacks than common ones. A fractionation experiment in which plants interact with different components of the microbial community (e.g. all microbes or bacteria only or fungi only) will help understand which microbes are more actively driving soil community feedbacks. The data generated have high potential to transform current understanding of the factors governing plant species abundance. Results will be disseminated to policy-makers and land managers through existing collaborations with the Nature Conservancy, US Forest Service, National Parks, and private seed companies. The research will integrate teaching and research by building partnerships with K-12 educators, by funding a female post-doc, and by training graduate and undergraduate students from diverse backgrounds.