Abstract

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Dataset Citation

Verity Salmon, Colleen Iversen, Joanne Childs. 2021. NGEE Arctic Plant Traits: Fine Roots, Kougarok Road Mile Marker 64, Seward Peninsula, Alaska, 2016. Next Generation Ecosystem Experiments Arctic Data Collection, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee, USA. Dataset accessed on [INSERT_DATE] at https://doi.org/10.5440/1735941.

Dates

2016-07-25 - 2016-07-27

Geographic Location

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Methodology

Soil core collection Cores were collected on July 25 through July 27th, 2016 at the Kougarok hillslope site on the Seward Peninsula. Two cores were collected within each of the twelve biomass plots sampled and were designated core replicates A and B. A battery-powered drill and a modified diameter hole saw was used to extract soil cores. In most plots the hole saw had a 3” diameter but in the very rocky soil at the NAMC plots we used the 2 7/8" diameter hole saw collect cores. All cores were collected down to the depth of permafrost or rock. The depth of each hole was measured after core collection. In the NAMC plots, cores were collected in vegetated areas rather than in unvegetated soil. In TTWBT and TT plots where tussock forming sedges alter microtopography, cores were collected in tussocks. Immediately following collection, the total length of the core was checked and the depth of the organic layer was recorded. The core was then sectioned into 10-cm depth increments using either clippers (for organic soil) or a knife (mineral soil). If the organic-mineral transition occurred within a 10-cm depth increment, the sample was separated into smaller depth intervals. All samples were then designated part of the organic or mineral horizon. All soil samples were transported back to Nome in coolers and frozen for shipment to ORNL. Core Processing In the laboratory, soil samples from each depth interval were split vertically in half. One half was used for a determination of soil texture, gravimetric water content, bulk density, bulk soil %C and %N, and water extractable total nitrogen, inorganic nitrogen, phosphorus, and organic nitrogen. The remaining half of the soil core was used for determination of fine root biomass, rock volume and weight, and pH of root-free soil. Soil properties are reported in “NGEE Arctic Plant Traits: Soil Cores, Kougarok Road Mile Marker 64, Seward Peninsula, Alaska, 2016” Fine Root Biomass and Length The remaining half of the soil cores had all live fine roots (<2mm diameter) carefully removed. Only live roots were considered, and dead roots were identified as those that were 1) visibly ragged, hollow or flat (presumably due to from decomposition) 2) offered no resistance to being pulled apart by tweezers. Due to the potential presence of aerenchyma in some species present at the site, floating roots were not considered dead. For some plant communities (TT, WBT, DSLT) the extensive volume of fine roots and the matted, dense soil organic matter made picking half a core within one week of thaw impossible. In these instances, a smaller subsample was picked and scaled up based on live fine roots per cm3 soil. We found that fine roots could not reliably be attributed to specific plant functional types or species. After fine roots were removed from soil, they were carefully rinsed clean with DI water to remove all soil materials. Fine roots were then scanned for length using WinRhizo (Regent Instruments, Inc., Québec, Canada) at 1400 dpi to resolve the diameter of distal shrub fine roots that were often less than 100 μm. Fine roots were then oven-dried at 70 °C and weighed to determine root biomass. Fine Root %C, %N, delta13C, and delta15N Dried fine root samples were ground to a fine powder (SPEX SamplePrep 2010 Geno/Grinder, Metuchen, NJ). Samples were then sent to UC Davis Stable Isotope facility for determination of %C, %N, delta13C and delta15N.

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