Temporal changes in nutrients in forest soil and roots and root biomass of Fagus sylvatica after P and N fertilization

We report data for nutrients in the organic layer and in mineral soil of Fagus sylvatica forests after P and N fertilization. We separated soil and roots and also report data for root biomass and nutrient contents in these soil layers. In addition, relative soil water contents and pH were measured. The samples were collected in three forests and repeatedly in spring and fall from 2016 to 2018. 

Methods
STUDY DESIGN (as described by Clausing et al. 2021): The data was collected from European beech dominated forests in Unterlüss (LUE) (52°50'21.7"N, 10°16'2.3"E), Mitterfels (MIT) (48°58'34.1"N, 12°52'46.7"E) and Bad Brückenau (BBR) (50°21'7.2"N, 9°55'44.5"E) beech forests in Germany. Each site is composed of plots with treatments of either P (fertilized with phosphorus in form of potassium dihydrogen phosphate (KH2PO4), dosage 50 kg P ha-1), N (fertilized five times with nitrogen in form of ammonium nitrate (NH4NO3), dosage 5 x 30 kg N ha-1), P+N and unfertilized (Con). N was applied five times and P was applied once in the P and P+N plots. The fertilizer treatments and controls were replicated three times per site (12 plots per site).
Unterlüss fertilization dates: P (2016-08-16) and N (2016-08-16, 2017-05-04, 2017-09-21, 2018-04-17 and 2018-09-17).                                       
Mitterfels fertilization dates: P (2016-08-12) and N (2016-08-12, 2017-05-15, 2017-10-05, 2018-05-03 and 2018-10-02).                                       
Bad Brückenau fertilization dates: P (2016-08-05) and N (2016-08-05, 2017-05-10, 2017-09-28, 2018-04-23 and 2018-09-25).

DATA COLLECTION: 12 Soil cores (21 cm depth x 5.5 cm diameter) were collected from each plot, separated into organic layer and mineral soil. The organic samples were pooled to yield one sample. The mineral samples were pooled to yield one sample per forest plot. The soil was sieved (4 mm mesh size) and weighed. Fine roots were collected and weighed. Soil water content, pH, and soil and root elements were analysed separately after drying the samples at 40 ℃. Soil and root elements were measured by inductively coupled plasma–optical emission spectroscopy (ICP-OES). Carbon (C) and nitrogen (N) were measured with a CN analyzer.

SAMPLING DATES
Unterlüss sampling dates: T0: 2016-08-15, T1: 2017-05-03, T2: 2017-09-20, T3: 2018-04-16 and T4: 2018-09-17.                                       
Mitterfels sampling dates: T0: 2016-08-11, T1: 2017-05-15, T2: 2017-10-04, T3: 2018-05-02 and T4: 2018-10-01.                                       
Bad Brückenau sampling dates: T0: 2016-08-04, T1: 2017-05-09, T2: 2017-09-27, T3: 2018-04-23 and T4: 2018-09-25.

Reference:

Clausing, S., Likulunga, E.L., Janz, D., Feng, H., Schneider, D., Daniel, R., Krüger, J., Lang, F., Polle, A., 2021. Impact of nitrogen and phosphorus addition on resident soil and root mycobiomes in beech forests. Biology and Fertility of Soils. doi: 10.1007/s00374-021-01593-x.