Root depth distribution and the diversity-productivity relationship in a long-term grassland experiment

• Published in: Ecology (Durham) 2013-04, Vol.94 (4), p.787-793
• Main Authors: Mueller, Kevin E, Tilman, David, Fornara, Dario A, Hobbie, Sarah E
• Format: Article
• Language: English
• Subjects: Aboveground biomass; Animal and plant ecology; Animal, plant and microbial ecology; Biodiversity; Biological and medical sciences; Biomass; C4 grass; complementarity; Correlation analysis; Fundamental and applied biological sciences. Psychology; General aspects; grass; Grasses; Grasslands; interspecific interactions; legume; Legumes; Nitrogen; Plant ecology; Plant roots; Plants; Productivity; Root biomass; Rooting depth; Soil resources; species richness
• ISSN: 0012-9658; 1939-9170
• DOI: 10.1890/12-1399.1

The relationship between plant diversity and productivity in grasslands could depend, partly, on how diversity affects vertical distributions of root biomass in soil; yet, no prior study has evaluated the links among diversity, root depth distributions, and productivity in a long-term experiment. We used data from a 12-year experiment to ask how plant species richness and composition influenced both observed and expected root depth distributions of plant communities. Expected root depth distributions were based on the abundance of species in each community and two traits of species that were measured in monocultures: root depth distributions and root-to-shoot ratios. The observed proportion of deep-root biomass increased more than expected with species richness and was positively correlated with aboveground productivity. Indeed, the proportion of deep-root biomass explained variation in productivity even after accounting for legume presence/abundance and greater nitrogen availability in diverse plots. Diverse plots had root depth distributions that were twice as deep as expected from their species composition and corresponding monoculture traits, partly due to interactions between C 4 grasses and legumes. These results suggest that the productivity of diverse plant communities was partly dependent on belowground plant interactions that caused roots to be distributed more deeply in soil.