We manipulated key resources that influence plant diversity in tallgrass prairie (i.e., soil depth and nitrogen availability) to increase environmental heterogeneity prior to sowing native prairie species into a former agricultural field. We compared variability in nutrient availability, aboveground annual net primary productivity (ANPP), and the composition of species between replicate plots containing soil heterogeneity manipulations and plots with no resource manipulations (n = 4 per treatment) during the first 15 yr of community assembly as a test of the “environmental heterogeneity hypothesis.”
Data are corresponding to subplot and whole-plot analyses of the “Prairie Restoration Heterogeneity Plots” located at the Konza Prairie Long Term Ecological Research site in Manhattan, KS USA. Subplot and whole-plot data are in different tabs (pages) labeled within the Excel file. Data include annual aboveground net primary productivity (= ANPP in file name), available nitrate (= NO3 in file name), species diversity (= H in file name), species richness (= R in file name), and percent cover of each plant species (= SPCOV in file name).
Data correspond to an experiment that was a randomized complete block design with 4 whole-plot heterogeneity treatments replicated within each of 4 blocks (n = 16 whole plots); only the most heterogeneous (maximum heterogeneity = maxhet) and homogenous plots (control) are provided. Maximum soil heterogeneity was created using a 3 x 2 factorial combination of soil nutrient (3 levels) and depth (2 levels) manipulations; control plots contained no soil manipulations. The maximum heterogeneity plots contained a split-block design consisting of 3 vertical strips assigned to nutrient treatments (ambient=1, enriched=2 and reduced=3) and 4 horizontal strips assigned to alternating soil depth treatments (deep =1 and shallow =2). The maximum heterogeneity plots contained 2 replicates of 6 treatment combinations: deep soil at ambient (=control), enriched (=N) and reduced (=C) nitrogen availability, and shallow soil at ambient (=stone), enriched (=stoneN) and reduced (=stoneC) nitrogen availability. Each plot contained 12 subplots for sampling. Subplot data represent averages of multiple measurements within a subplot. Data corresponding to subplots 4 and 7 in plot 15 were removed after 2005 due to an herbicide application used to kill an invasive species. A period in the dataset indicates missing data.
HRE011 SUBPLOT DATA:
Aboveground net primary productivity (ANPP) was estimated by harvesting biomass from a 0.1 m2 quadrat in September, at peak biomass, from each of the 12 subplots within the maximum and control whole-plot treatments. Biomass was clipped at the end of each growing season in 1998, 1999, 2000, 2005, and 2012. Biomass was dried for 1 week at 60°C, sorted into this year’s and previous year’s growth, and weighed. Biomass in each subplot was multiplied by 10; ANPP units are g m-2 y-1.
Relative availability of nitrate (NO3-N = NO3) was quantified using buried ion-exchange resins in 1998, 1999, 2000, 2005, 2006, and 2012. Resin bags were constructed of nylon and contained 10 g of strongly basic anion exchange resins. Nitrate passively collected on resins for the growing season. Two resin bags were buried in the surface 10 cm of each subplot in June or July and retrieved in September or October, depending on the year. Nitrate was extracted from resin bags by shaking each bag in 75 mL of 2 mol/L KCl. Solutions were filtered through 0.4-μm polycarbonate membranes. Resin-collected NO3-N was determined on an OI Flow Solution IV autoanalyzer (OI Analytical, College Station, TX). Resin-collected NO3-N units are μg/bag.
Shannon’s diversity (H) was calculated for each subplot in 1998, 1999, 2000, 2003, 2005, 2006, 2009, 2011, and 2012. Diversity was calculated using the maximum cover of each species recorded during late spring and late summer plant surveys each year. Cover from two 0.25 m2 permanent sampling quadrats within each subplot were averaged prior to calculating diversity using the following equation: −Σplog10p, where p = the average proportional cover of each species within each subplot.
Species richness (R) was calculated for each subplot in the same years diversity was measured. Species richness in each subplot was measured by counting the number species recorded from two 0.25 m2 permanent sampling quadrats within each subplot.
The percent cover of each species (listed by scientific name acronym) was visually estimated in two permanent 0.25 m2 quadrats within each subplot, then averaged for each subplot in 1998, 1999, 2000, 2003, 2005, 2006, 2009, 2011, and 2012. The average cover values in each subplot were used to calculated species richness and diversity. Species are listed using the USDA Plants Database (http://plants.usda.gov/java/) acronyms unless the species could not be identified, in which case the acronym begins with UN. Full scientific names and authorities corresponding to each acronym are listed in the column description.
HRE012 WHOLE PLOT DATA:
DETAILS: These data pertain to Figure 2 (panels AC), Figure 3, Figure 4, Figure 5, and Appendix 4. The same response variables described for the subplots are provided for the whole-plots. Coefficients of variation in ANPP (CVANPP) and resin-collected NO3 (CVNO3) were calculated by dividing the standard deviation of subplots within a whole-plot by the mean (X 100). Plot-level richness was calculated by averaging the cover of all species from all subplots within a plot, then counting the total number of species. Whole-plot diversity was calculated using the average cover of each species recorded from the subplots within a plot. The average percent cover of each species was calculated from all subplots within a plot.