Empirical and modelled carbon, nitrogen and phosphorus content of plants and soils from Wardlow Hay Cop, UK

Empirical data:
Above ground biomass carbon was determined from the dry weight of a sward harvest for each nutrient treatment and in both grasslands. Soil organic C and total soil N was determined by acid stripping dried soil to remove carbonates and then analysing it in an isotope-ratio mass spectrometer. Total soil P was taken from previous research at Wardlow. These data were converted into model-compatible units (grams per metre squared) prior to their use in the modelling study. Plant C and soil C and N was collected from all four nutrient treatments; a distilled water control, a low nitrogen (3.5 g N m-2 yr-1) a high nitrogen (14 g N m-2 yr-1) and a phosphorus addition (3.5 g P m-2 yr-1). Total soil P data was only available for the control and high nitrogen treatments.

Modelled data:
These data were used to calibrate two P-cycling parameters within the N14CP model in order to simulate the nutrient manipulation experiment within the model. After assessing the model’s performance using the empirical data, we investigated the consequences of long-term N deposition and nutrient manipulation on the C, N and P pools of soil and the above ground biomass C pool. All modelled data is in grams per metre squared unless stated otherwise in the metadata. Some modelled data, notably the timeseries, spans the years 1800 – 2020 in order to model changes on longer timescales. Note that the empirical data relates only to the year 2019 in which it was collected, which represents 24 years of experimental nutrient addition.