Data from: An African grassland responds similarly to long-term fertilization to the Park Grass experiment

We compared the results of a long-term (65 years) experiment in a South
African grassland with the world’s longest-running ecological experiment,
the Park Grass study at Rothamsted, U.K. The climate is warm and humid in
South Africa and cool and temperate in England. The African grassland has
been fertilized with two forms of nitrogen applied at four levels,
phosphorus and lime in a crossed design in 96 plots. In 1951, about 84% of
plant cover consisted of Themeda triandra, Tristachya leucothrix and
Setaria nigrirostris. Currently, the dominant species are Panicum maximum,
Setaria sphacelata and Eragrostis curvula, making up 71% of total biomass.
As in the Park Grass experiment, we found a significant (additive)
interaction effect on ANPP of nitrogen and phosphorus, and a (marginally
significant) negative correlation between ANPP and species richness.
Unlike the Park Grass experiment, there was no correlation between ANPP
and species richness when pH was included as a covariate. There was also a
significant negative effect of nitrogen amount and nitrogen form and a
positive effect of lime on species richness and species diversity. Soil pH
had an important effect on species richness. Liming was insufficient to
balance the negative effects on species richness of nitrogen
fertilization. There was a significant effect of pH on biomass of three
abundant species. There were also significant effects of light on the
biomass of four species, with only Panicum maximum having a negative
response to light. In all of the abundant species, adding total species
richness and ANPP to the model increased the amount of variance explained.
The biomass of Eragrostis curvula and P. maximum were negatively
correlated with species richness while three other abundant species
increased with species richness, suggesting that competition and
facilitation were active. Consistent with the results from the Park Grass
and other long-term fertilization experiments of grasslands, we found a
positive effect of soil pH and a negative effect of nitrogen amount on
species richness, a more acutely negative effect on species richness of
acidic ammonium sulphate fertilizer than limestone ammonium nitrate, a
negative relationship between species richness and biomass, and a positive
effect on species richness of lime interacting with nitrogen.