Soil depth may affect plant diversity in two apparently opposing manners: on the one hand, deeper soil may increase the available space for below-ground niche partitioning, on the other hand, soil depth may have a negative effect on plant diversity by increasing productivity and the rate of competitive exclusion. Due to the scarcity of experimental studies that actively manipulate soil depth, the conditions under which each mechanism dominates are still unclear. Here, we studied the interactive effects of soil depth with common land use practices, namely, nutrient addition, trampling by grazers, and mowing on plant diversity in grasslands. We manipulated these factors in a full-factorial manner in grassland mesocosms. Soil depth had a strong positive effect on species richness under mowing, suggesting increased space for niche differentiation in deeper soils. In unmown plots, deep soils harboured a similar diversity of species as shallow soils, and our findings suggest that this effect on diversity is due to larger biomass and lower light availability on deep soils. Fertilization and trampling had no effect on diversity. Overall, our findings indicate that soil depth effects on grassland communities strongly interact with common land use practices. We therefore advocate the inclusion of soil depth effects in manipulative experiments and management plans.

Metadata for “Is more less? A comprehensive experimental test of soil depth effects on grassland diversity”

doi: 10.1111/oik.08535

File 1: plant_data.csv. Used for analyses of biomass, species richness and diversity

File containing biomass, richness and diversity data for all the mown plots in the experiment.

- plot: planting tub (80x80 cm2)

- subplot: plots (20x20 cm2) hosting experimental plant communities within each planting tub. Each planting tub was divided into 16 plots.

- soil_treat: manipulation of soil depth, either deep or shallow

- nutrients: fertilizer treatment (yes-no) 

- trampling: trampling treatment was applied (yes) or the plot was left untouched (no)

- clipping: the plot was either mowed (yes) or the vegetation was left undisturbed (no)

- biomass: measured only for the plots in which clipping was applied

- shannon_wiener: calculation of Shannon-Wiener index for each plot

- species_richness: number of species counted in each plot

- edge_number: position of the plot within the planting tube: corner, side or center

- total_species_sown: in each plot 40 species were sown.

- prop_species_emerged: calculated as species_richness/total_species_sown

File 2: plant_data_subset.csv. Used for analysing the effects of plot position within planting tub.

This consider a subset of plots so that the number of corner, side and center plots is equal.

The response variables are the same as in the file plant_data.csv