Data from: Plant species richness belowground: higher richness and new patterns revealed by next generation sequencing

Variation in plant species richness has been described using only aboveground vegetation. The species richness of roots and rhizomes has never been compared with aboveground richness in natural plant communities. We made direct comparisons of grassland plant richness in identical volumes (0.1x0.1x0.1m) above and below the soil surface, using conventional species identification to measure aboveground richness and 454 sequencing of the chloroplast trnL(UAA) intron to measure belowground richness. Sequencing detected most species expected and only these species were used both above- and belowground analyses. We described above- and belowground richness at multiple spatial scales (from a neighborhood scale of centimeters to a community scale of hundreds of meters), and related variation in richness to soil fertility. At neighborhood scales, belowground richness was up to two times greater than aboveground richness. The relationship between above- and belowground richness was significantly different from linear: increases in aboveground richness stopped even as increases in belowground richness continued. Belowground richness exceeded that aboveground also at the community scale, indicating that some species are temporarily dormant and absent aboveground. Similar to other grassland studies, aboveground richness declined with increasing soil fertility; in contrast, the number of species found only belowground increased significantly with fertility. These results indicate that conventional aboveground studies of plant richness may overlook many coexisting species, and that belowground richness becomes relatively more important in conditions where aboveground richness decreases. Using molecular tools to measure plant belowground richness can considerably alter perceptions of biodiversity and its responses to natural and anthropogenic factors