Early positive spatial selection effects of beta-diversity on ecosystem functioning

Context: Metacommunity theory predicts that diversity arising at larger spatial scales (spatial β-diversity) may increase ecosystem functioning if there are positive spatial selection effects whereby species dominate in mixtures at places where they are most productive in monocultures. However, beta-diversity effects on ecosystem functioning remain understudied and unquantified experimentally. Objectives: Our experiment tests for spatial selection effects in survivorship among transplanted seedlings of the dominant species of five major habitats (grassland, oak savanna, deciduous forest, coniferous forest, bog) at Cedar Creek Ecosystem Science Reserve. Methods: We established monocultures and mixtures of dominant species in five habitats and estimated survivorship at the end of the first growing season of the experiment, partitioning net biodiversity effects into its components of complementarity effects and selection effects, which include spatial selection effects. Results: At this early experimental stage, we found positive selection effects, due mostly to average selection effects across all habitats. We also found a significantly positive spatial selection effect, indicating that the habitats where species tended to be more abundant in mixtures were also those where they tended to survive more in monocultures. Results: At this early experimental stage, we found positive selection effects, due mostly to average selection effects across all habitats. We also found a significantly positive spatial selection effect, indicating that the habitats where species tended to be more abundant in mixtures were also those where they tended to survive more in monocultures. Conclusion: Overall, our results are consistent with theoretical predictions that additional effects of plant diversity on ecosystem functioning, beyond those observed in local experiments within local habitats, may arise at landscape scales from dispersal and spatial sorting of species across a heterogeneous landscape. Further study will be needed to determine how survivorship patterns develop over time within and among habitats and how growth and reproduction contribute to plant productivity and other ecosystem functions.