Carbon and nitrogen dynamics in subsoils after 20 years of added precipitation in a Mediterranean grassland
Data files
Aug 05, 2025 version files 145.34 KB
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FTIR_elemental_data_merged.csv
82.64 KB
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mean_BD_WC_pH.csv
12.20 KB
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mean_cstock_300cm.csv
16.24 KB
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README.md
4.59 KB
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Sample_Metadata_Precipitation_Expt.xlsx
29.68 KB
Abstract
Precipitation is a major driver of ecosystem change and the physicochemical characteristics of soil. Under different climate change scenarios, increased drought frequency and changing precipitation are predicted to impact Mediterranean ecosystems, including in Northern California. Studies based on two major climate models examined the impact of increased precipitation in parts of California, where the additional precipitation occurred during winter or spring months. It was found that altering precipitation seasonality has significant impacts on plant community dynamics, microbial and fungal dynamics, and abiotic soil processes. Subsoils are large carbon reservoirs. However, most studies investigating precipitation effects on soil organic matter (SOM) primarily focus on near-surface soils. Recent studies indicated different responses to environmental perturbation in surface (<30 cm) versus deep soils (>30 cm) due to important differences in physicochemical characteristics. Here, we present soil data at depth (~300 cm) from a 20-year precipitation manipulation experiment. We determined changes in total elemental concentration and stable isotope composition of soil C, N, δ13C, and δ15N for ambient control vs. additional precipitation in the winter and spring months. The addition of winter precipitation resulted in the largest cumulative C stock (0–300 cm); however, there were no statistically significant changes in carbon stock throughout the depth profile. However, there was evidence for vertical translocation of carbon to deep soil layers, specifically of plant-derived carbon, with both winter and spring precipitation additions. The precipitation addition in winter also resulted in the highest subsoil carbon stock compared to the control (ambient) and spring treatments. Overall, added winter precipitation led to the best conditions for carbon accumulation since the added precipitation coincides with lower temperatures and improved growing conditions at our field site. This study highlights the importance of the timing of precipitation events, especially with regard to deep carbon stocks (>1 m).
There are 4 xlsx files associated with this dataset:
- Sample_Metadata_Precipitation_Expt.xlsx gives associated metadata with each sample ID. This metadata includes the location where it was sampled, the replicate, the depth, and so on.
- FTIR_elemental_data_merged.csv gives all the isotopic, elemental, and FTIR data associated with each sample ID. NAs refer to missing or lacking data. This data sheet partially represents data that comes out of the Stable Isotope Ecosystem Laboratory at UC Merced, with metadata attached for each sample. The measurements included in this datasheet (C% and N%) make it possible to calculate carbon stocks, an important bulk density-corrected factor, for each site. Measurements of stable isotopes δ13CC andδ15NN were also important markers of decomposition and turnover for the sites we were analyzing. This isotopic and elemental base has been merged with DRIFTS data (Diffuse Reflectance Fourier Transformed Spectroscopy). This data gives information on the presence of certain key function groups present in organic matter. Columns in this dataset with the int_ prefix refer to integrated peak areas for spectral ranges of interest (these are defined in the associated publication). We then calculated proportions of our peak areas of interest, which are the columns that have _prop suffixes.
- mean_cstock_300cm.csv reports the mean carbon stock and standard error for each 10cm interval for each treatment (control, spring, winter)
- mean_BD_WC_pH.csv reports the mean and standard error for each physical and chemical parameter for each 10cm interval. These parameters include bulk density, water content, and pH in H2O and CaCl2.
Description of the data and file structure
The information included in Sample_Metadata_Precipitation_Expt is largely descriptive. This information is largely redundant and is also included in the files with elemental/isotopic data. The sample ID column in this file refers to the unique 3-digit code I assigned every sample I collected. The field site column refers to the site at which the sample was collected. The replicate column refers to the numbered replicate it was at that particular field site. The date collected column refers to the calendar date the sample was collected on. The depth column refers to the depth at which the sample was collected in cm.
The raw data for the elemental and isotopic analyses are included in FITR_elemental_data_merged. The identifier column in this dataset refers to the unique identifier assigned by the Stable Isotope lab at UC Merced. The Sample ID refers to the unique 3-digit code assigned to each sample. The amount column refers to the mass of sample in mg that was weighed and combusted for the elemental analysis. The Area 28 column is the area under the curve for the N2 peak, and is used to compute the d15N_corrected within the isotope lab software. The Area 44 column is the curve for the CO2 peak, and is used to compute the d13C_corrected within the isotope lab software. The d13C_corrected is the stable isotope value in per mil. The d15N corrected is the stable isotope value in per mil. The N_wt_percent value is the N content of the sample reported as percent (%). The C_wt_percent value is the C content of the sample reported as percent (%). The C/N is the C: N ratio computed based on the N and C weight percents. The C_stock is the computed C stock value with a coarse fraction correction, and reported as g/cm2. The C_stock_CF column is the computed C stock value without a coarse fraction correction, reported as g/cm2.
The rest of the columns in this data are from Sample_Metadata_Precipitation_Exp, and are described in the above paragraph.
The mean_cstock_300cm file includes data to compute C stocks. The treatment column in this file refers to field water addition treatment (Control, Winter, Spring). Bulk density refers to the bulk density (reported as g/cm3) collected. The coarse fraction refers to the lab-measured coarse fraction (reported as a fraction, unitless). The C_stock is the mean computed C stock value and reported as g/cm2 for each 10cm depth interval. All missing data represented as NA.
The mean_BD_WC_pH file is the mean data for three key physical and chemical parameters for soils at this site. Namely, Bulk Density (reported as g/cm^3), Water Content (reported as g/g), and pH in both H2O and CaCl2. This sheet reports mean values for each of these characteristics for each treatment.