Data from: Precipitation legacy effects on gross N mineralization and nitrification rates in a Pinyon-Juniper dryland under altered precipitation
Data files
Jun 12, 2026 version files 29.65 KB
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GrossNRatesData_dryad.xlsx
25.61 KB
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README.md
4.04 KB
Abstract
Precipitation variability is increasing globally, altering the frequency and severity of drought and extreme rainfall events with consequences on soil nitrogen (N) cycling. Arid conditions can alter N cycling by increasing soil inorganic N concentrations due to diffusion constraints that decouple N sources and sinks, making this N more susceptible to loss. Further, shifts in precipitation patterns in one season can alter N cycling in ways that can “carry-over” N into subsequent seasons, known as precipitation legacies. However, it is not well understood how these legacies affect soil N availability through changes in inorganic N production, such as the rates of gross N mineralization and nitrification. To this end, we manipulated the amount and timing of precipitation in a pinyon–juniper dryland using four treatments that either added or excluded precipitation during the winter or summer months. We then measured the effects of each treatment on soil N cycling using isotope pool dilution. Excluding precipitation in the winter wet season—which induced the longest drought among treatments—reduced gross N mineralization by ~2.5× and gross nitrification rates by ~9.5× compared to ambient conditions (gross N mineralization = 0.30 ± 0.08 µg N g-1 soil h-1; gross nitrification = 0.19 ± 0.05 µg N g-1 soil h-1). This winter drought treatment also produced a legacy effect the following summer, where gross N mineralization was ~2× lower than that observed under ambient conditions (0.41 ± 0.19 µg N g-1 soil h-1). Soil N concentrations were 6× greater than ambient conditions (0.5 ± 0.2 µg NO3– -N g-1 soil) under experimental winter drought, corresponding with lower gross rates of inorganic N production. Under these persistent, albeit slow, inorganic N production rates that outpaced N immobilization, N accumulated under increasingly arid conditions and carried over between seasons as influenced by changes in precipitation patterns.
https://doi.org/10.5061/dryad.6q573n683
Description of the data and file structure
This data was collected for understanding how seasonal altered precipitation affects gross N transformations - specifically N mineralization and nitrification in dryland soils. In order to do this, we manipulated the amount and timing of precipitation in a Pinyon-Juniper dryland in southern California using four treatments that either added or excluded precipitation during the winter or summer months (beginning at the end of summer 2018). We collected soil samples at the end of winter and summer 2023, after approximately five years of treatment. We then measured gross rates of N mineralization and nitrification in the laboratory using an isotope pool dilution technique on soil samples that were wetted to stimulate microbial activity. We also measured bulk soil δ15N values as an index of ecosystem N retention in response to shifts in precipitation during both winters and summers.
Everything in this file is organized by season sampled (either winter or summer) and treatment (Control, winter-, winter+, summer- and summer+).
Files and variables
File: GrossNRatesData_dryad.xlsx
Description:
Variables:
- Plot number = identification number for each plot, correlating to a specific precipitation treatment
- Season = season that the sample was collected, indicating which precipitation treatment is active
- Treatment = precipitation treatment assigned to plot and season, including control (receives ambient precipitation all year round), winter + (receives additional precipitation during the winter season, ambient precipitation in the summer), winter- (excludes all precipitation in the winter season, ambient precipitation in the summer), summer + (receives additional precipitation during the summer season, ambient precipitation in the winter), and summer- (excludes all precipitation in the summer season, ambient precipitation in the winter)
- Gross Min = gross mineralization rate (ug N per gram of soil per hour)
- Total N = total dissolved inorganic N (NH4+ pool + NO3- pool) in mg/L
- Gross Nit = gross nitrification rate (ug NO3- per gram of soil per hour)
- NO3 = nitrate pool in mg/L
- GWC = gravimetric water content as %
- DNRA = dissimilatory nitrate reduction to ammonium as ug N-NH4+ per gram soil
- NH4 = ammonium pool in mg/L
- MAP = mean annual precipitation in mm
- MB C/N = microbial biomass carbon or nitrogen content as ug C/N per gram soil
- Net Nit/Min = net nitrification and N mineralization rates measured in situ over a period of 30 days as ug N per g soil per day
- mm per rain = average volume of precipitation per precipitation event
- Gross Amm = gross ammonium production ug N-NH4+ per g soil per day
- pH = pH value of soil water slurry (1:1 slurry)
- NH4 post = ammonium pool post isotope pool dilution in mg/L
- ug N = total N from elemental analyzer in ug N per gram of soil
- d15N = natural abundance delta 15 N in permil
- mgC = total C from elemental analyzer in mg C per gram of soil
- d13C = natural abundance delta 13 C in permil
- %C = percent of C per gram of soil
- % N = percent of N per gram of soil
- C:N = total carbon to total nitrogen ratio
- N:M = gross nitrification to gross mineralization rate
- organic N = organic N pool as the difference between total N and total inorganic N
Notes:
- missing values are indicated by blank cells
- winter- only has 3 plots because one plot received precipitation when it wasn't supposed to and was consistently an outlier in many related measurements
Code/software
I used R studio for all of my data analysis and plots. Code used for analysis may be provided upon request.
Packages include: dplyr, here, ggplot2, readxl, gridExtra, tidyverse, ggpubr, report, nlme, lme4, emmeans, Matrix, multcompview
We manipulated the amount and timing of precipitation in a Pinyon-Juniper dryland in southern California using four treatments that either added or excluded precipitation during the winter or summer months (beginning at the end of summer 2018). We collected soil samples at the end of winter and summer 2023, after approximately five years of treatment. We then measured gross rates of N mineralization and nitrification in the laboratory using an isotope pool dilution technique on soil samples that were wetted to stimulate microbial activity. While this approach cannot yield in situ gross N transformation rates for dry soils because adding the isotope label required wetting the soils, it did enable us to make relative comparisons among treatments and assess the relative sensitivity of microbial communities governing both gross N mineralization and nitrification to drought stress. This approach is also representative of what occurs when autumn rainfall wets dry soil. We also measured bulk soil δ15N values as an index of ecosystem N retention in response to shifts in precipitation during both winters and summers.