Associate Professor University of Minnesota St. Paul, Minnesota, United States
Abstract: Spatial 𝛽-diversity may increase landscape productivity if there are positive spatial selection effects. Alternatively, the dominant species in mixtures might not be the most productive species in monoculture leading to negative or neutral spatial selection effects. However, these hypotheses remain untested experimentally. Seedling survival can determine species establishment, influencing productivity later. We experimentally test whether transplanted seedlings of dominant species optimally sort among habitat types (grassland dominated by Andropogon gerardii, savanna by Quercus macrocarpa, deciduous forest by Acer rubrum, coniferous forest by Pinus strobus, bog by Larix laricina), creating positive effects of landscape diversity on seedling survival and net biodiversity effects at the LTER Cedar Creek Ecosystem Science Reserve. We estimated species-level survivorship at the end of the first growing season of the experiment and partitioned the net biodiversity effects (NBEsurv) into its components of selection effects (SEsurv) and complementarity effects (CEsurv) based on survivorship in each habitat.
At this early experimental stage, only L. laricina survived more in its home bog habitat where it dominates (56±1.1% survival), compared to other habitats (5±0.2% survival). Conversely, Q. macrocarpa survivorship was higher in outside habitats (92±0.2% survival) relative to inside its home habitat in the savanna (31±0.5% survival). The three remaining species thus far exhibited similar survivorship in their home habitats as elsewhere. NBEsurvwas positive in all habitats, but mainly in the bog and least in the grassland and savanna. SEsurv and CEsurv represented 2% and 98% of NBEsurv, respectively, in outside habitats, and 51% and 49% in home habitats. In the short-term, we found no strong evidence for a positive spatial effect across the landscape at the seedling stage. However, because one species indicated higher survival when growing in its home habitat in the bog relative to away habitats, flooding as an environmental filter might influence establishment early on for some species. Quercus macrocarpa seedling survival was positively associated with mesic, nutrient-rich habitats in other studies, which might explain why this species had increased survival outside its home habitat. Additionally, more mesic habitats (bog, forests) had higher NBEsurv compared to drier habitats (grassland and savanna), indicating that these dominant plant species in our study can have higher survivorship when growing in a mixture than in a monoculture, especially in these environments. We will continue to measure species growth and survivorship in subsequent years to test how local interactions and habitat differences contribute to biodiversity effects within and among these habitats.