Technical Comments

Comment on “Worldwide evidence of a unimodal relationship between productivity and plant species richness”

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Science  04 Dec 2015:
Vol. 350, Issue 6265, pp. 1177
DOI: 10.1126/science.aad4836

Figures

  • Fig. 1 Relationship between the mean number of species found in the plots of a single grid (number of species) and the total number of species found in that grid (local species pool).

    Each dot (n = 157) represents one 8- by 8-m grid containing 64 1-m2 plots. [Data from (9)]

  • Fig. 2 Relationship between mean percentage of local species pool represented in the plots and mean productivity (living+standing dead biomass) in the plots (n = 157).

    When only live biomass is used as a measure of productivity, a slightly positive relationship between these variables is observed (r2 = 0.0339, P = 0.0236), but there is no evidence of a hump-backed relationship. However, this positive relationship is strongly influenced by the data from the two most productive sites in the data set (i.e., the two data points at the top right of Fig. 2). These were both temperate wetland grasslands in Ohio [sites 90 and 92 in (9)] at which only a single species was recorded within the grids. This species was also found in all of the plots within each of the grids. Thus, a mean of 100% of the local species pool was present in the plots of both grids; excluding these data causes the relationship between percentage of local species pool represented in the plots and mean living biomass in the plots to become nonsignificant (r2 = 0.0082, P = 0.2717).[Data from (9)]

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