Laura Leonard Colorado School of Mines lleonard@mines.edu https://orcid.org/0000-0002-3309-9110 Eoin Brodie Lawrence Berkeley National Laboratory elbrodie@lbl.gov Kenneth Williams Lawrence Berkeley National Laboratory khwilliams@lbl.gov Jonathan Sharp Colorado School of Mines jsharp@mines.edu U.S. DOE > Office of Science > Biological and Environmental Research (BER) http://dx.doi.org/10.13039/100006206 fundingOrganization 2021 This data package contains text files that describe geochemical measurements collected from 2017-2019 during isolated conifer needle decomposition field studies in Crested Butte, Colorado. The geochemical measurements were collected across three elevations (2,800–3,500 m) ranging from montane to subalpine ecoregions. The data sets within include total carbon and nitrogen content and fourier-transform infrared spectroscopy (FTIR) results for the initial needles collected in 2016 and after decomposition in 2019. Data collection results from August 2020 are also included from when the experimental plots were removed to understand final concentrations of soil extractable carbon and nitrogen content as well as mass balances from litter bag deployments. Soil porewater results are also provided from 2017-2019 for DOC, TN, UV254, and specific UV absorbance (SUVA) analyses at 15 cm soil depth. Gas flux raw data provides CO2, CH4, N2O, and NH3 measurements above needle decomposition over the three study years. Finally, soil samples for microbial DNA extractions were collected from the upper soil depth. This raw data is available in the NCBI SRA database under SRA accession numbers PRJNA605259 and PRJNA715914. These data sets were generated to investigate the isolated decomposition of spruce and lodgepole conifer needles. The goal of this work was to determine the roles of elevation, soil type, seasonal changes in soil moisture, and snowmelt timing on litter decomposition processes. Results from this work are detailed in the reference paper "Effect of elevation, season and accelerated snowmelt on biogeochemical processes during isolated conifer needle litter decomposition. DOI: 10.7717/peerj.11926." Needle Decomposition Nutrient Cycling Soil Respiration Climate Change Biogeochemistry Lodgepole Spruce Early Snowmelt CATEGORICAL:NONE Soil Gas Flux Soil Porewater Soil Microbial DNA Extractions Soil Extractions Needle Litter CN Needle Litter FTIR Soil Moisture Soil Temperature VARIABLE:NONE

Leonard LT, Brodie EL, Williams KH, Sharp JO. 2021. Effect of elevation, season and accelerated snowmelt on biogeochemical processes during isolated conifer needle litter decomposition. PeerJ 9:e11926 https://doi.org/10.7717/peerj.11926

This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. The established plot located at the Lower Montane (Lower) ecoregion (38.92° N, 106.95° W, elevation 2,800 m). Spruce, Lodgepole, and Control samples were in this experimental field plot in Crested Butte, Colorado. The designated area was approved by the Rocky Mountain Biological Laboratory. -106.95 -106.95 38.92 38.92 The established plot located at the Lower Subalpine (Middle) ecoregion (38.96º N, 107.03º W, elevation 3,100 meters). Spruce, Lodgepole, and Control samples were in this experimental field plot in Crested Butte, Colorado. The designated area was approved by the Rocky Mountain Biological Laboratory. -107.03 -107.03 38.96 38.96 The established plot located at the Upper Subalpine (Upper) ecoregion (38.97° N, 107.04° W, 3,500 m). Spruce, Lodgepole, and Control samples were in this experimental field plot in Crested Butte, Colorado. The designated area was approved by the Rocky Mountain Biological Laboratory. -107.04 -107.04 38.97 38.97 2017-06-01 2020-08-29 Laura Leonard lleonard@mines.edu https://orcid.org/0000-0002-3309-9110 MECHANISTIC AND PREDICTIVE UNDERSTANDING OF NEEDLE LITTER DECAY IN SEMI - ARID MONTANE ECOSYSTEM S EXPERIENCING UNPRECEDENTED VEGETATION MORTALITY As described in the in the reference paper, needle litter samples were collected in August 2016 from below lodgepole pine (Pinus contorta) and Engelmann spruce (Picea engelmannii) tree stands. Study plots were established at the elevations and are referred as the Lower Montane (Lower), Lower Subalpine (Middle), Lower Subalpine early snowmelt (Middle-ES) and Upper Subalpine (Upper). Roughly 8 x 8 m plots were established at the three elevations with 25 cm diameter and 18 cm height polyvinyl chloride (PVC) rings deployed throughout to hold replicates of the the lodgepole, spruce, and bare soil control samples. The plot matrix consisted of 4 × 250 g of spruce, 4 × 250 g lodgepole, and 4× needle-free controls. The LS-ES plot served as a duplicate to the LS plot for induced early snowmelt experiments that allowed comparisons to normal snowmelt conditions. Unshielded microclimate sensors buried at roughly 12 cm were established at the LS-ES plot to monitor hourly soil moisture and temperature in order to estimate early snowmelt rates. A subset of each needle type (spruce and lodgepole) was used for compositional analysis from each sample PVC ring after three years of decomposition in 2019. Needles were set in a dark and dry location at room temperature to air dry. Once air-dried, the needles were ground to a fine powder and submitted in triplicate for total carbon and nitrogen analysis at Colorado State University’s Ecocore facility with the LECO TruSpec CN analyzer and Fourier Transform Infrared (FTIR) analysis at Lawrence Berkeley National Laboratory. Litter bags were deployed at each elevation in August 2017 and left to decompose until August 2020. The needle bags were constructed with 2 g each of archived lodgepole and spruce needles in a single layer of white nylon mesh fabric (23 × 23 openings per 2.54 cm) that were further wrapped in one layer of window screen (17 × 13 openings per 2.54 cm). Mass balance was determined by calculating the difference in mass after decomposition from the initial 2 grams. As described in the in the reference paper, soil gas flux measurements were conducted using a Picarro G2508 cavity ring-down spectroscopy analyzer. Measurements were possible only at the Lower Montane (Lower), Lower Subalpine (Middle), and Lower Subalpine early snowmelt (Middle-ES) plots. A closed system was established using two lengths of norprene tubing and an airtight PVC chamber to circulate the headspace. After steady state was established by linear trends of production or removal, data collection was initiated for 2 min. The Hutchinson & Mosier method provided with the Picarro computer software was used to compute a best fit for each gas trend to calculate the fluxes. Gas production or removal were monitored accordingly for each sample replicate of spruce, lodgepole, and controls. As described in the in the reference paper, soil porewater was collected from Soil Moisture’s 1905L06 15 cm lysimeters installed in the center of each PVC ring using a Luer-lok 50 mL vacuum syringe. The samples were filtered to 0.45 µm and frozen the same day of collection for storage at −20 °C until analysis. A portion of the samples were thawed and acidified with hydrochloric acid for total dissolved nitrogen (TN) and dissolved organic carbon (DOC) using a Shimadzu TOC-550A Total Organic Carbon Analyzer. The remaining unacidified sample was used for specific UV absorbance (SUVA) analysis with a DU 800 Spectrophotometer. Sample replicates were analyzed when possible for spruce, lodgepole, and controls. As described in the in the reference paper, soil extractions were conducted with soil underlying the needles for each sample type (spruce, lodgepole, and controls) in August 2020. The soil samples were sieved at 2 mm and a 2:9 solid mass to liquid weight ratio using 40 mL liquid volume for extraction in 50 mL centrifuge tubes. The tubes were placed on a shake plate for one hour, then centrifuged and filtered at 0.45 µm. Aliquots of the filtrate were acidified with hydrochloric acid and analyzed according to the methods outlined in Step 3 for soil TN and DOC in addition to ammonium concentrations measured using the sodium salicylate method and absorbance at 650 nm with a DR 3900 Hach Spectrometer. In addition, extractable nitrite and nitrate were measured using an ICS-5000 ion chromatography analysis consisting of an ICS-5000 DC Conductivity Detector, an ICS-5000 DP Isocratic Pump, and an AS-DV Autosampler. The soil extraction results were normalized by air-dried weights. Jonathan Sharp Colorado School of Mines, Golden, CO jsharp@mines.edu Principal Investigator RawData_PeerJ2021.zip application/zip