Soil Data for a Collapse-Scar Bog Chronosequence in 

Koyukuk Flats National Wildlife Refuge, Alaska, 2008

By Jonathan A. O’Donnell, Jennifer W. Harden, Kristen L. Manies, and M. Torre Jorgenson

Open-File Report 2012–1230

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

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Suggested citation:

O’Donnell, J.A., Harden, J.W., Manies, K.L., Jorgenson, M.T., 2012, Soil data for a collapse-scar bog 

chronosequence in Koyukuk Flats National Wildlife Refuge, Alaska, 2008: U.S. Geological Survey 

Open-File Report 2012–1230, 11 p.

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iii

Contents

Abstract ......................................................................................................................................................................... 1

Introduction.................................................................................................................................................................... 1

Study Region ................................................................................................................................................................. 1

Soil Sampling................................................................................................................................................................. 3

Soil Sample Preparation and Drying.............................................................................................................................. 4

Soil Carbon and Nitrogen Measurements...................................................................................................................... 4

Radiocarbon Measurements.......................................................................................................................................... 5

Dataset Descriptions...................................................................................................................................................... 5

Acknowledgments.......................................................................................................................................................... 6

References Cited........................................................................................................................................................... 6

Appendix 1. Site Descriptions........................................................................................................................................ 7

Appendix 2. Data File Descriptions (Field, Physical, and Chemistry)............................................................................. 9 

Figure

1. Map of Koyukuk Flats study site.............................................................................................................................. 2 
1

Soil Data for a Collapse-Scar Bog Chronosequence in 

Koyukuk Flats National Wildlife Refuge, Alaska, 2008

By Jonathan A. O’Donnell, Jennifer W. Harden, Kristen L. Manies, and M. Torre Jorgenson

Abstract

Peatlands in the northern permafrost region store large amounts of organic carbon, most of 

which is currently stored in frozen peat deposits. Recent warming at high-latitudes has accelerated 

permafrost thaw in peatlands, which will likely result in the loss of soil organic carbon from previously 

frozen peat deposits to the atmosphere. Here, we report soil organic carbon inventories, soil physical 

data, and field descriptions from a collapse-scar bog chronosequence located in a peatland ecosystem at 

Koyukuk Flats National Wildlife Refuge in Alaska. 

Introduction

Peatlands comprise approximately 19 percent of the northern circumpolar permafrost region and 

store 277 petagrams of organic carbon (OC; Tarnocai and others, 2009), much of which is stored in 

frozen peat deposits (Tarnocai and others, 2007). Having developed over thousands of years since the 

last glaciation (Harden and others, 1992), northern peatlands have generally functioned as long-term 

sinks for atmospheric carbon dioxide (CO2) and sources of atmospheric methane (CH4), (Smith and 

others 2004). However, climate-driven changes in permafrost extent or wildfire frequency could reduce 

the sink strength of northern peatlands (Turetsky and others, 2011) through the release of organic carbon

stored in frozen or saturated peat (Turetsky and others, 2002; Dorrepaal and others, 2009). Permafrost 

degradation is of particular concern, given the recent acceleration of permafrost thaw in subarctic 

peatlands (Payette and others, 2004; Camill, 2005) and future projections of circumpolar permafrost 

thaw (Lawrence and others, 2008).

Here, we report soil OC inventories from a collapse-scar bog chronosequence located in a 

peatland ecosystem at Koyukuk Flats National Wildlife Refuge in Alaska. We sampled organic and 

mineral soils in 2008 in lowland black spruce (Picea mariana) stands and from collapse-scar bog sites 

that vary in age since permafrost thaw. These data were originally reported and used to parameterize a 

mass-balance model of peatland and permafrost OC dynamics in a study by O’Donnell and others 

(2012). Findings from this study indicate that deep OC stocks harbored in Holocene peatland deposits 

may be vulnerable to thaw and subsequent loss to the atmosphere as CO2 and CH4. 

Study Region

We conducted our studies in the Koyukuk National Wildlife Refuge (NWR), one of the largest 

lowland basins in interior Alaska (fig. 1). Koyukuk NWR covers 14,160 square kilometers (km2) of 

wetlands on the abandoned floodplains and drained thaw-lake basins adjacent to the Koyukuk River, 

and spans from the southern foothills of the Brooks Range to its confluence with the Yukon River near 

Galena, Alaska. Peat deposits at Koyukuk NWR are thick (1–4 meters) relative to other peatlands in 
2

Alaska and are advantageous for studying long-term OC accumulation rates. There are abundant 

thermokarst features in the region, with a range of post-thaw successional stages within close proximity 

of each other. The Koyukuk Flats study area (N. 65.19 ̊, W. 155.36 ̊; datum = NAD83) is located about 

50 km north of Galena and was accessed via floatplane. Logistical support was provided, in part, from 

the U.S. Fish and Wildlife Service located in Galena. From 1971 through 2000, the mean annual 

temperature in Galena averaged -3.8 °C, with the annual maxima occurring in July (20.4 °C) and 

minima in January (-26.9 °C) (Alaska Climate Research Center, http://climate.gi.alaska.edu/). During 

that same period, annual precipitation averaged 331 millimeters (mm), with 40 percent of the annual 

precipitation falling from July through September. Snow typically covers the ground between the 

months of October and April, with an average maximum accumulation of 50 centimeters.

Figure 1. Map of Koyukuk Flats study site. Open circles represent the permafrost plateau (PP), young bog (YB) 

and old bog (OB) study sites. Unlabeled circles represent additional survey points along the transect where 

site characteristics were described but peat samples were not collected. The map insert shows the location of 

Koyukuk Flats National Wildlife Refuge in Alaska.

To address our study objectives, we measured soil hydrologic, thermal, and OC dynamics across 

a permafrost thaw chronosequence. A soil chronosequence is a series of sites that have similar factors, 

such as climate, vegetation, slope, and parent material, but differ in age of the landform. Our 

chronosequence consisted of sites with permafrost plateaus, drying margins, and collapse-scar bogs that 

varied with respect to time of permafrost thaw and bog initiation (which we refer to as our young and 

old bog sites). Bog size was used as a proxy for age during bog selection. While all of our sites had 

similar climate, slope, and parent material, vegetation composition differed across landform ages, 

limiting our ability to isolate the effect of time from vegetation succession. The age of young bogs 

ranged from 31 to 61 years (yrs), as determined by the difference in mean age of mature black spruce 
3

trees on nearby permafrost plateau sites (96 ± 13 yr, n = 9) and the age of dead black spruce trees found 

in collapse-scar bog features. Tree cores were obtained at breast-height, sanded upon returning to the 

laboratory, and then scanned at a resolution of 1200 dots per inch (dpi). These images were then 

imported into CooRecorder (V.7; http://www.cybis.se/forfun/dendro/), where the tree rings were 

counted manually. The age of two old bogs (400 and 1,215 yrs, respectively) were determined by 

radiocarbon (14C) dating of organic matter at the interface of forest-derived and collapse-scar bogderived peat. Drying margin sites are transitional between the permafrost plateau and collapse bog sites, 

where the permafrost has begun thawing but subsidence has not yet occurred. 

Vegetation composition varied with landscape position and collapse-scar bog age. Permafrost 

plateaus were dominated by black spruce and Sphagnum fuscum. We also commonly observed the 

presence of Andromeda polifolia, Ledum palustre, and Rubus chamaemorus. Drying Margins of 

collapse-scar bogs were dominated by Cladina spp. (C. stellaris, C. arbuscula, C. rangiferina, C. mitis) 

and L. decumbens. Young bogs were dominated by Eriophorum scheuchzeri and numerous Sphagnum

spp., including S. jensenii, S. riparium, and S. lindbergii. In the old bogs, we primarily observed the 

mosses Sphagnum balticum and Sphagnum flexuosum and shrubs Andromeda polifolia and Oxycoccus 

microcarpus. 

Soil Sampling

In August and September of 2008, we described and sampled soil horizons across a collapse-scar 

bog chronosequence following U.S. Department of Agriculture’s Natural Resources Conservation 

Service (USDA–NRCS) (Soil Survey Staff, 1998) and Canadian (Soil Classification Working Group, 

1998) methodologies. We sampled soil from replicate sites at permafrost plateaus (n = 3 sites; site ID = 

KFUW), Drying Margins of permafrost plateaus (n = 3; KFUD), young bogs (n = 3; KFUY), 

intermediate bogs (n = 3; KFUI), old bogs (n = 3; KFUO) and a collapse-scar fen (n = 1; KFUF). In 

collapse-scar bogs, we identified forest peat as organic matter derived from Sphagnum fuscum and 

Picea mariana ecosystems commonly observed on permafrost plateaus, and bog peat as organic matter 

derived from Sphagnum spp. commonly observed at the surface of young and old bogs. Fen peat 

horizons were typically composed of slightly decomposed moss and plant parts, such as Drepanocladus 

spp., Calliergon spp., Menyanthes trifoliata and Carex limosa. Mineral soil horizons (A, B, C) were 

characterized for texture and the presence of buried organic material. We also described and sampled 

lacustrine (or limnic) sediment below peat deposits. We used modified soil horizon codes according to 

the following scheme:

L Live moss, which are green and generally contain some leaf and needle litter.

D Dead moss, which is comprised of nondecomposed or slightly decomposed dead moss. The 

dead moss layer is characterized by fibric organic horizons that contain more moss than roots. 

F Fibric (according to Canadian soil system) or fibrous organic layers, which vary in degree of 

decomposition but in which roots are more abundant than recognizable moss parts. In most 

cases, these layers would be considered Oi layers (U.S. soil system) or upper duff (U.S. Forest 

Service (USFS) soil system). 

M Mesic (according to Canadian soil system) organic layers, which are moderately decomposed 

with few if any recognizable plant parts other than roots. M layers are generally Oe horizons 

(U.S. soil system) or lower duff layers (USFS soil system). 

H Humic (Canadian soil system) or sapric organic layers, which are highly decomposed. This layer 

generally smears upon squeezing and has no recognizable plant parts. H layers are generally Oa 

horizons (U.S. soil system) or lower duff (USFS soil system) layers.
4

A Mineral soil that forms at the surface or below organic horizons (U.S. and Canadian soil 

system), with less than 20 percent organic matter, as judged in the field.

C Mineral soil that has been little affected by pedogenic processes (U.S. and Canadian soil 

system).

LN Lichen

La Limnic sediments

Frozen samples were described with a lower case “f” preceeding the horizon code. All horizons 

within a soil profile were sampled for bulk density, chemical analysis, and to determine moisture 

content. 

At all sites, organic soil was sampled using a variety of soil knives, scissors and corers, in order 

to obtain a sample of known volume. For easily compressible, low-density samples, soil blocks were 

cut with scissors or serrated knives and dimensions were measured with a ruler. For less compressible 

shallow soils, samples were obtained with a 50-mm diameter corer rotated with a portable electric drill 

(Nadler and Wein, 1998). For deeper unfrozen peats we used a 70-mm diameter by 130-centimeter 

(cm)-long tube that was pushed and rotated into the peat by hand. A rubber cap was tightened over the 

corer to maintain a vacuum in the corer during extraction. At permafrost plateau sites, permafrost cores

(up to 5 meters) were obtained using a SIPRE (Snow, Ice, and Permafrost Research Establishment) 

corer (7.5-cm inside diameter) with a Tanaka power head. We sampled peat until either a basal mineral 

or limnic horizon was encountered to allow calculation of OC stocks relative to a standard basal layer 

across sites. After collection, samples were placed in clean ziplock bags and shipped to U.S. Geological 

Survey (USGS) laboratories in Menlo Park, California.

Soil Sample Preparation and Drying

Upon arrival of samples to the laboratory, samples were inventoried using the field sheets. All 

samples were placed on open shelves in an isolated room and allowed to air dry to a constant weight, as 

determined by weights obtained at least one week apart. Temperature during air-drying ranged from 20 

to 30 °C. After air-drying, samples were oven dried for 48 hours in a forced-draft oven. Samples that 

were classified as organic soil horizons (moss, litter) were oven-dried at 65 °C to avoid loss or alteration 

of organic matter by oxidation or decomposition. The remaining samples were oven-dried at 105 °C. 

After oven-drying, samples were thoroughly mixed, then split into subsamples for analysis and 

archiving (archive fractions of most of the samples described here are available by contacting J. Harden 

at the Menlo Park, Calif. office of USGS). These samples were then processed one of two ways, 

depending on horizon code. Mineral samples were gently crushed using a mortal and pestle, being 

careful to break only aggregates, and then sieved using a 2-mm screen. Soil particles not passing the 2-

mm screen were removed, weighed, and saved separately. Soil passing the 2-mm screen was then 

ground by hand using a mortar and pestle to pass through a 60 mesh (0.246 mm) screen. The ground 

material was mixed and placed in a labeled, glass sample bottle for subsequent analyses. Organic 

samples were weighed and roots greater than 1 cm in diameter were removed, weighed, and saved 

separately. The remaining sample was then milled in an Udy Corporation Cyclone mill (Ft. Collins, 

Colo.) to pass through a 0.5-mm screen. The milled sample was thoroughly mixed and a representative 

sample placed in a labeled, glass sample bottle for analytical chemistry.

Soil Carbon and Nitrogen Measurements

A Carlo Erba NA1500 elemental analyzer (EA) was used to determine total C and total N. We 

analyzed soil samples for total carbon and nitrogen using a Carlo Erba NA1500 elemental analyzer. We 
5

assumed that total carbon was equal to organic carbon, given the low pH of soil samples (pH < 6). 

Samples were combusted in the presence of excess oxygen. The resulting sample gasses were swept in a 

continuous flow of helium through an oxidation furnace, followed by a reduction furnace, to yield CO2, 

N2, and water vapor. Water was removed by a chemical trap, and CO2 and N2 were chromatographically 

separated before the quantification of C and N (Pella, 1990a, b).

All samples were compared to a main working standard, ethylene diamine tetra-acetic acid 

(EDTA), which has been calibrated through a set of international standards. The chemical formula for 

this compound corresponds to a C concentration of 41.09 percent and N concentration of 9.59 percent 

Additional working standards were analyzed as samples in all runs to check consistency and overall 

precision. Peach tree leaves (SRM–1547), issued by the National Institue of Standards and Technology 

(NIST), were included in runs comprised of organic soil. A marine sediment (MESS–1), issued by the 

Chemistry Division of the Canadian National Research Council, was included in runs comprised of 

mineral soils. Certified values for these standards were obtained from Becker (1990) and Govindaraju 

(1989), respectively.

Radiocarbon Measurements

We analyzed radiocarbon (14C) content on a subset of soil samples to evaluate accumulation 

rates and turnover times of organic carbon, to determine the age of old bog formation, and to determine 

the basal age of peat across study sites. When possible, we collected Sphagnum spp. moss parts for 14C 

analysis. To determine carbon accumulation rates in permafrost plateaus, we analyzed the 14C content of 

12 organic matter samples spanning depths of 2 cm to 405 cm below the ground surface. To age 

collapse-scar bogs, we analyzed 14C content of organic matter at the interface of peat derived from 

forest and collapse-scar bog vegetation. When field sampling permitted, we also analyzed 14C content 

of the lacustrine sediments (limnic, silt) beneath peat deposits. Samples were sent to the W.M. Keck C 

Cycle AMS Laboratory at the University of California Irvine for analysis as described in Southon and 

others (2004). Organic matter was combusted at 900 °C in evacuated, sealed quartz tubes in the 

presence of cupric acid (CuO) and silver (Ag) wire. Following cryogenic purification, carbon dioxide 

was reduced to graphite in a reaction at 500–550 °C using the sealed tube Zn reduction method (Xu and 

others, 2007). Radiocarbon data are reported as Δ14C, or the per mil deviation of the 14C/12C ratio in 

the sample from that of an oxalic standard that has been decay corrected to 1950 (Stuiver and Polach, 

1977). The Δ14C values we report have been corrected for mass-dependent fractionation using the in 

situ simultaneous AMS δ13C measurement. Age interpretation of organic matter samples with modern 

Δ14C signatures typically requires additional information, given the non-uniqueness of calculated 

turnover times and ages (Trumbore, 2000). 

Dataset Descriptions

There are three separate downloadable files containing the soil data collected from the sites 

described in this report. Appendix 2 describes in detail the data within the following three spreadsheet 

files: (1) KoyukukFlats_Field, contains field descriptions, such as root abundance, color, and soil 

texture, of the sampled soils; (2) KoyukukFlats_Physical contains physical descriptions of the samples, 

such as volumetric field moisture and bulk density, (3) KoyukukFlats _Chemistry contains elemental C, 

elemental N, Δ14C of soil organic matter, and loss on ignition (LOI) values. 
6 

Acknowledgments

We thank Trish Miller, Misha Kanevskiy, and Kim Wickland for their assistance in the field and 

Pedro Rodriguez for his assistance in the lab. Xiaomei Xu analyzed soil samples for radiocarbon at the 

University of California Irvine. Support for this work was provided by the National Science Foundation 

collaborative grant EAR–0630249, the Institute of Northern Engineering at the University of Alaska 

Fairbanks, and the U.S. Geological Survey Global Change program. 

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Appendix 1. Site Descriptions

This appendix describes the locations of each site sampled along the collapse-scar bog 

chronosequence at Koyukuk Flats National Wildlife Refuge. All study sites were accessed via 

floatplane from the village of Galena, Alaska. 

• KFUW 1—The plot is located at coordinates N65.19612o, W156.63472o (NAD83). The study plot 

is located in a poorly drained, mature black spruce stand with Ledum spp. and Sphagnum spp. The 

soil profile was sampled on August 25, 2008, by Jennifer Harden, Jonathan O’Donnell, and Misha 

Kanevskiy. 

• KFUW 2—The plot is located at coordinates N65.19664o, W156.63704o (NAD83). The study plot 

is located in a poorly drained, mature black spruce stand with Ledum spp. and Sphagnum spp. The 

soil profile was sampled on August 26, 2008, by Jonathan O’Donnell and Misha Kanevskiy.
8

• KFUW 3—The plot is located at coordinates N65.19748o, W156.63968o (NAD83). The study plot 

is located in a poorly drained, mature black spruce stand with Ledum spp. and Sphagnum spp. The 

soil profile was sampled on August 27, 2008, by Jennifer Harden, Jonathan O’Donnell, and Misha 

Kanevskiy. 

• KFUO 3—The plot is located at coordinates N65.19703o, W156.63840o (NAD83). The study plot 

is an old collapse-scar bog with Sphagnum spp. and the shrubs Andromeda polifolia and Oxycoccus 

microcarpus. The soil profile was sampled on August 27, 2008, by Torre Jorgenson, Jennifer 

Harden, and Jonathan O’Donnell.

• KFUO 4—The plot is located at coordinates N65.19587o, W156.63376o (NAD83). The study plot 

is an old collapse-scar bog with Sphagnum spp. and the shrub Andromeda polifolia and some 

sedges. The soil profile was sampled on August 27, 2008, by Torre Jorgenson and Jennifer Harden.

• KFUO 5—The plot is located at coordinates N65.19526o, W156.63591o (NAD83). The study plot 

is an old collapse-scar bog with Sphagnum spp. and the shrubs Andromeda polifolia and Oxycoccus 

microcarpus. The soil profile was sampled on August 28, 2008, by Torre Jorgenson and Trish 

Loomis (Miller).

• KFUI 1—The plot is located at coordinates N65.19630o, W156.63558o (NAD83). The study plot is 

an intermediate-aged collapse-scar bog with Sphagnum spp., Ledum decumbens, and Eriophorum 

scheuchzeri. The soil profile was sampled on August 25, 2008, by Jennifer Harden and Kim 

Wickland.

• KFUI 2—The plot is located at coordinates N65.19643o, W156.63626o (NAD83). The study plot is 

an intermediate-aged collapse-scar bog with Sphagnum spp. and Andromeda polifolia. The soil 

profile was sampled on August 29, 2008, by Jonathan O’Donnell.

• KFUI 3—The plot is located at coordinates N65.19o, W156.63o (NAD83). The study plot is an 

intermediate-aged collapse-scar bog with Sphagnum spp. and Ledum decumbens. The soil profile 

was sampled on August 26, 2008, by Jennifer Harden, Kim Wickland, Jonathan O’Donnell, and 

Misha Kanevskiy.

• KFUY 1—The plot is located at coordinates N65.19641o, W156.63665o (NAD83). The study plot 

is a young collapse-scar bog with Sphagnum spp. The soil profile was sampled on August 28, 2008, 

by Jennifer Harden.

• KFUY 2—The plot is located at coordinates N65.19639o, W156.63660o (NAD83). The study plot 

is a young collapse-scar bog with Sphagnum spp., Ledum decumbens, and Eriophorum scheuchzeri. 

The soil profile was sampled on August 26, 2008, by Jonathan O’Donnell, Jennifer Harden, and 

Kim Wickland.

• KFUY 3—The plot is located at coordinates N65.19626o, W156.63510o (NAD83). The study plot 

is a young collapse-scar bog with Sphagnum spp. and Eriophorum scheuchzeri. The soil profile was 

sampled on August 28, 2008, by Jennifer Harden.

• KFUN 1—The plot is located at coordinates N65.19652o, W156.63658o (NAD83). The study plot 

is a new collapse-scar bog with Sphagnum spp. The soil profile was sampled on August 26, 2008, 

by Jennifer Harden, Kim Wickland, and Torre Jorgenson.

• KFUD 1—The plot is located at coordinates N65.19558o, W156.63214o (NAD83). The study plot 

is drying margin of a collapse-scar bog with Cladina spp. and Ledum decumbens. The soil profile 

was sampled on August 29, 2008, by Torre Jorgenson and Jonathan O’Donnell.

• KFUD 3—The plot is located at coordinates N65.19o, W156.63o (NAD83). The study plot is drying 

margin of a collapse-scar bog with Cladina arbuscula. The soil profile was sampled on August 29, 

2008, by Torre Jorgenson.
9 

• KFUD 4—The plot is located at coordinates N65.19o, W156.63o (NAD83). The study plot is drying 

margin of a collapse-scar bog with Cladina arbuscula. The soil profile was sampled on August 29, 

2008, by Torre Jorgenson.

• KFUF 1—The plot is located at coordinates N65.19o, W156.63o (NAD83) and is a collapse-scar 

fen. Vegetation at the soil profile site was dominanted by Drepanocladus spp. and Menyanthes 

trifoliata. The soil profile was sampled on August 29, 2008, by Torre Jorgenson and Kim 

Wickland.

Appendix 2. Data File Descriptions

This appendix details what information is found within each of the columns of the three data 

files that accompany this report.

KoyukukFlats_Field

This file contains the field descriptions of the sampled soils and includes the following columns: 

Sample ID Sample identification: The first two letters in the sample labels represent the 

region of study, Koyukuk Flats (KF). The next two letters represent the site 

type. Site types include unburned wet (UW); unburned old bog (UO); 

unburned intermediate bog (UI); unburned young bog (UY); unburned new 

bog (UN); unburned drying margin (UD); and unburned collapse-scar fen 

(UF). The number that follows these four characters indicates the profile 

number. A decimal point separates the profile number from the basal depth of 

the sample (in cm). 

Depth Indicates the basal depth, in cm, of sampling increment.

Field Horizon 

Code 

Horizon type of the sample, as defined in the field. L = live moss; LN = 

lichen; D = dead moss; F = fibric organic matter (OM); M = mesic OM; H = 

humic OM; A = A mineral soil horizon; C = C mineral soil horizon; La = 

limnic horizon; and X = unknown horizon. Ob represents a buried organic 

horizon. A lower case “f” before a horizon code indicates that the sample was 

frozen when sampled.

Sample 

Description

A brief description of the sample.

Roots Root abundance and size using conventions of USDA–ARS (Soil Science 

Staff, 1998).

pH pH value of mineral soil measured in the laboratory. Deionized water was 

added to create a soil slurry (50 percent soil, 50 percent water) prior to 

measurement. 

Munsell Color Munsell color value according to the Munsell Soil Color Chart.

Von Post or 

Texture Class

If organic soil, the classification using a modified version of the von Post 

scale of humification (Damman and French, 1987). If mineral soil, the soil 

texture class as described in the field followed conventions of USDA–ARS 

(Soil Survey Staff, 1998). 

Height above 

mineral

Height of each basal depth above the mineral soil boundary, in cm. 

Therefore, the bottom organic layer is at zero and all mineral horizons are 

negative numbers.
10 

KoyukukFlats_Physical

This file contains physical data such as bulk density, volumetric moisture content, and particle size 

analysis. Column definitions are as follows: 

Sample ID Sample identification: The first two letters in the sample labels represent the 

region of study, Koyukuk Flats (KF). The next two letters represent the site 

type. Site types include unburned wet (UW); unburned old bog (UO); unburned 

intermediate bog (UI); unburned young bog (UY); unburned new bog (UN); 

unburned drying margin (UD); and unburned collapse-scar fen (UF). The 

number that follows these four characters indicates the profile number. A 

decimal point separates the profile number from the basal depth of the sample 

(in cm). 

Depth Indicates the basal depth, in cm, of sampling increment.

Field Horizon 

Code 

Horizon type of the sample, as defined in the field. L = live moss; LN = lichen;

D = dead moss; F = fibric organic matter (OM); M = mesic OM; H = humic 

OM; A = A mineral soil horizon; C = C mineral soil horizon; La = limnic 

horizon; and X = unknown horizon. Ob represents a buried organic horizon. A 

lower case “f” before a horizon code indicates that the sample was frozen when 

sampled.

Sample 

Description

A brief description of the sample.

Date Sampled Date during which the sample was taken (month/day/year).

Thickness Thickness of soil horizon, in cm.

>2 mm in 

Sample

Dry weight percent of soil particles not passing through a 2-mm sieve after 

gentle crushing.

>1 cm in 

Sample

Dry weight percent of roots larger than 1 cm in diameter in the sample.

Bulk Density 

(<2 mm)

Grams of oven-dried soil per cubic centimeter, with soil particles greater than 2 

mm and roots greater than 1-cm diameter removed. 

Bulk Density Grams of oven-dried soil per cubic centimeter for the entire soil sample with no 

fractions excluded. Calculated similarly to Bulk Density (< 2 mm) except the 

weight of particles greater than 2 mm and roots greater than 1-cm diameter have 

been included.

Volumetric 

Field Moisture

The percent water in the sample, by volume.

Moisture in 

Air-dry Sample

Percent, by weight, of moisture remaining in a sample after air-drying to 

constant weight as determined by subsequently oven-drying the sample. 
11 

KoyukukFlats_Chemistry

This file contains chemical data obtained from the elemental analyzer (EA) and the elemental analyzer 

mass spectrometer (EA/IRMS). Column definitions are as follows:

Sample ID Sample identification: The first two letters in the sample labels 

represent the region of study, Koyukuk Flats (KF). The next two letters 

represent the site type. Site types include unburned wet (UW); 

unburned old bog (UO); unburned intermediate bog (UI); unburned 

young bog (UY); unburned new bog (UN); unburned drying margin 

(UD); and unburned collapse-scar fen (UF). The number that follows 

these four characters indicates the profile number. A decimal point 

separates the profile number from the basal depth of the sample (in cm). 

Depth Indicates the basal depth, in cm, of sampling increment.

Field Horizon Code Horizon type of the sample, as defined in the field. L = live moss; LN = 

lichen; D = dead moss; F = fibric organic matter (OM); M = mesic OM; 

H = humic OM; A = A mineral soil horizon; C = C mineral soil horizon; 

La = limnic horizon; and X = unknown horizon. Ob represents a buried 

organic horizon. A lower case “f” before a horizon code indicates that 

the sample was frozen when sampled. 

Sample Description A brief description of the sample.

%C Percent by weight of total carbon in an oven-dried soil sample with 

material >2 mm or 1-cm diameter removed. 

%N Percent by weight of total nitrogen in an oven-dried soil sample with 

material >2 mm- or 1-cm diameter removed. 

LOI Loss-on-ignition value, in percent.

Bulk sample: Fraction 

Modern

Fraction modern for bulk soil sample.

Bulk sample: Δ14C Δ14C value for bulk soil sample. 

Bulk sample: ± Δ14C Standard deviation of Δ14C value for bulk soil sample. 

Bulk sample: 14C age Radiocarbon age of bulk soil sample, in years before present.

Bulk sample: 14C age 

error

Standard deviation of radiocarbon age for bulk soil sample, years.

Datable Material: 

Fraction Modern 

Fraction modern value for datable material (char, woody debris).

Datable Material: Δ

14C

Δ14C value for datable material (char, woody debris).

Datable Material: ± Δ

14C

Standard deviation of Δ14C value for datable material (char, woody 

debris).

Datable material: 14C 

age

Radiocarbon age of datable material (char, woody debris), years before 

present.

Datable material: 14C 

age error

Standard deviation of radiocarbon age for datable material (char, woody 

debris), years.

Notes Description of sample or datable material.