Main Experiment: Ammonium concentrations and ammonification rates in soils (Site A, Ext. A, B and E plots)

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Dataset Abstract

Soil sampling was carried out on a subset of 100 plots of two overlapping extinction scenarios on Site A (Extinction scenario A and B). The sampüles were collected from young forest communities composed of 1 - 24 species (see general plot information concerning community compositions of the BEF-China experiment: http://china.befdata.biow.uni-leipzig.de/datasets/71; Species nomenclature following the Flora of China). The species composition covers two overlapping species pools and also includes two commercially relevant tree species monocultures (Extinction scenario E, Pinus massoniana and Cunninghamia lanceolata). Moreover, we also sampled plots without trees.
Sampling was carried out in July 2015.

Dataset Design

Within the plots, we collected soil samples from 12 random positions which followed a frame around the central 8 x 8 trees of every plot. Soil cores with a diameter of 13 mm were taken from the first ten centimeters of the top layer. These subsamples were pooled plotwise, freshly sieved in 2 mm fraction, homogenized and stored in the fridge for analyses.

Spatial Extent

Plots of Exctinction scenario A and B (http://china.befdata.biow.uni-leipzig.de/datasets/71). 100 plots were sampled, including non-tree community plots and monocultures of Pinus massoniana and Cunninghammi lanceolata (Extinction Scenario E).

Temporal Extent

Sampling was carried out throughout July 2015.

Taxonomic Extent

No tree species were included in the analyses. However, soil cores were taken from communities comprising the following species (and their mixtures according to (http://china.befdata.biow.uni-leipzig.de/datasets/71):
Nyssa sinensis
Castanea henryi
Quercus fabri
Lithocarpus glaber
Quercus serrata
Koelreuteria bipinnata
Choerospondias axillaris
Castanopsis sclerophylla
Triadica sebifera
Liquidambar formosana
Sapindus saponaria
Schima superba
Castanopsis eyrei
Cyclobalanopsis myrsinifolia
Rhus chinensis
Cyclobalanopsis glauca
Castanopsis carlesii
Melia azedarach
Triadica cochinchinensis
Diospyros japonica
Acer davidii
Cinnamomum camphora
Daphniphyllum oldhamii
Quercus acutissima
Pinus massoniana
Cunninghamia lanceolata

Data Analysis

Nitrogen mineralization rates were determined from 10 g fresh soil extracted with 100 ml 1 M KCl. After reacting with a sodium salicylate solution to a indophenol colour complex (Kandeler and Gerber 1988; Niklaus et al. 2001) NH4+ concentrations of the filtered extracts were measured colorimetrically (Microplate Reader Synergy Mx, BioTek, Winooski, United States). Another subsample of 10 g fresh soil was incubated at 40 °C in glas vials for seven days. To ensure anaerobic condition, the soil was water-logged with 15 ml H2O and vials were sealed with a crimp-cap to reduce oxygen exchange to a minimal level (Niklaus et al. 2001). Under anaerobic conditions, soil microbes only produce NH4+ instead of NO3- (Niklaus et al. 2001). After incubation, we filtered and extracted the samples with 85 ml 1.176 M KCl to ensure similar molarity to the non-incubated samples. Ammonium analyses were done analogous to the non-incubated samples. N-mineralization rates were calculated as the difference of the ammonium concentration in the incubated and non-incubated sample divided by the number of days of incubation (Niklaus et al. 2001).

Data columns available in the raw data part of this dataset

plot
plot samples were taken
Data group: Plot name Main experiment
Values
BC36
E23
E22
E24
C32
site
site samples were taken
Data group: Experimental Site
Values
A
div
plot tree species richness
Unit: tree species
Data group: Tree species richness
Values
24
16
0
1
2
NH4fresh
NH4fresh
Data group: Ammonium
Values
0.17751165123001583
10.32407900748706
0.7054992764109983
0.5565020770503535
0
NH4inc
NH4inc
Data group: Ammonium
Values
45.71990490016505
43.998271146834675
44.08858526236796
46.06215846994536
42.70546772286854
NH4rate
ammonium production in the incubated soil per day, concentrations given in µg ammonium per g soil (dry mass) per day
Unit: µg/g soil * d
Data group: Ammonification rate
Values
11.040048919685697
10.18286433431473
10.190714317286321
10.017887311246996
10.01089322598524