Species mixture increases production partitioning to belowground in a natural boreal forest

Abstract

Most diversity and productivity relationship (DPR) studies have focused on one component of ecosystem production at one stage of stand development, which may have contributed to divergent DPR relationships. We tested the effects of species mixture on biomass production and its partitioning between aboveground (trees, understorey vegetation, and litterfall) and belowground (coarse and fine roots) with stand development in a post-fire boreal forest. We found an overyielding, i.e., species mixtures produce more than the average of its constituent monocultures, of total ecosystem production in young stands, but not in older stands. Species mixture led to more production partitioning belowground in all stand ages due to increased fine root production. The magnitude of the mixture effect on production partitioning to belowground increased with total production in species mixtures. Both aboveground production and its partitioning to aboveground increased significantly with the availability of soil nutrients. Our results suggest that it would be biased to infer the effects of plant diversity on total ecosystem production based on the estimates from one component of production or during one stand development stage.