DOI: 10.23637/keyrefoapgspecies
title: Dataset: Park Grass Changes in Mean Species Numbers 1864-2011

description: The Figure shows the impact of selected treatments on the number of species comprising 1% or more of the biomass. Applying N as sodium nitrate (orange line N*) or ammonium sulphate (blue line N) quickly decreased species numbers relative to the unfertilised control. The continued application of ammonium decreases species numbers further because of its acidifying effect on the soil (pH 3.6 in 2011, solid blue line), reducing the number of species to one or two, Holcus lanatus (Yorkshire Fog) and Anthoxanthum odoratum (Sweet Vernal Grass). However, even on the nil plot (solid green line) the number of species has decreased. This may be due to changes in atmospheric inputs and/or changes in sward management.

Applying chalk (dotted lines) increased soil pH (pH 6.2 in 2011, dotted blue line) and helped some of the species return to the original numbers. Recent work (Storkey et al 2015) showed that on some plots withholding N helped increase species diversity as did decreased atmospheric N deposition, as evident in the species numbers of the nil plot (solid green line).
description: The botanical composition of the plots was studied by visual surveys and by looking at the percentage contribution of the various species to the hay harvested. The most recent comprehensive surveys of botanical composition made just before the first cut, were done annually between 1991 and 2000 (see Crawley et al, 2005). From 1991 to 2000, six randomly located quadrats measuring 50cm x 25cm were located within each of the plots in early June, immediately before the first cut. The herbage was cut with scissors to ground level and plant material taken back to the laboratory where it was sorted into species. Samples were oven-dried at 80 °C for 24 hours, after which dry mass was determined for each species. A survey of plant diversity carried out by transects in 1993 and May 1994, before the first cut of each year. In each surveyed transect the number of reproductive plants of each species was recorded (Kunin, 1998). 
Earlier surveys of the botanical composition of Park Grass were carried out from 1862 to 1976. Between 1920 and 1990 visual surveys were made twice a year, before the hay was cut in June and again in the autumn, but no analyses were carried out between 1949 and 1972. Further full botanical analyses were carried out on limited plots between 1973 and 1976 (Williams 1978). Samples of plant material were taken from each plot, separated into the different species and weighed. This open access summary data is derived from annual plot data for the relevant selected plots and treatments.
description: Summary data of the number of species comprising 1% or more of the biomass, in relation to six treatments on Park Grass: No fertiliser cotrol; nitrogen fertilser as sodium nitrate; nitrogen as ammonium sulphate (each with and without chalk).
description: Fertiliser treatments since 1856;
No fertiliser - Plot 3: No fertilizer or manure
N*2PKNaMg - Plot 14: 96kgN as sodium nitrate plus P, K, Na and Mg
N2PKNaMg - Plot 9: 96kgN as ammonium sulphate plus P, K, Na and Mg

Chalk: Ground chalk (CaCO3) applied approximately every four years 1903 - 1964 then as required to maintain pH at around 6.
description: Older historical information is taken from original raw data sheets and analysis files, held in the archives at Rothamsted Research, and the Annual Rothamsted Yield Books. Data since 1991 is souced from current Rothamsted scientists. All raw data is stored in the e-RA database DET. The data in e-RA are subject to rigorous quality control procedures from the point of collection in the field to entry into the database. See Park Grass Botanical Information and of the 'Park Grass Plots at Rothamsted 1856 - 1976' for further details on methods utilised.