organic carbon analysis of charcoal-enriched soils at

Natural Sciences Education bull Volume 46 bull 2017 1 of 6

StudENt ESSayS

Organic Carbon Analysis of Charcoal-Enriched Soils at Catoctin Mountain Park MD

Andrew Lindsay

aBStRaCtThe application of charcoal to soils to increase carbon stocks has been of great interest recently To gain a better understanding of the long-term effects of charcoal presence in soils historic charcoal production sites at Catoctin Mountain Park Maryland were studied for organic carbon content and compared to nearby unaffected soils Soil organic carbon concentrations were measured through loss on ignition and organic carbon stocks were calculated for fixed depths of 80 cm Both the organic carbon concentrations and organic carbon stocks indicate that historically affected charcoal hearth soils contain more carbon compared to unaffected controlled soil samples However there is some variation in organic carbon content between charcoal hearths located in different landscape positions Overall charcoal application to soils may increase organic carbon stocks for extended periods of time which can be of great importance for climate change mitigation and the enhancement of soil fertility

co Judith Turk School of Natural Sciences and Mathematics 101 Vera King Farris Drive Stockton University Galloway NJ 08205-9441 Corresponding author (judithturkstocktonedu lindsayagostocktonedu)

Published in Nat Sci Educ 46 (2017) doi104195nse2017010101 Received 9 Jan 2017 Accepted 9 Jan 2017

Copyright copy 2017 by the American Society of Agronomy 5585 Guilford Road Madison WI 53711 USA All rights reserved

This study on soil organic carbon contributed to a larger research project with the purpose of determin-ing differences in soil properties in charcoal hearth

soils compared to surrounding unaltered sites Historic charcoal production has affected many forests in the east-ern United States because of charcoalrsquos importance in the iron industry Historically large areas of forests would be intensively managed for charcoal to support many operating iron furnaces (Hart et al 2008) All iron was only produced using charcoal as the fuel up until 1830 (Straka 2014) To produce the charcoal timber would be charred and con-sumed in hearths which are dry level clearings ranging from about 9 to 15 meters in diameter Since this process of making charcoal requires the burning of wood while being deprived of oxygen the timber in hearths would be packed with piles of soil to limit oxygen consumption and fire tem-perature during the burn (Hart et al 2008) Today the evi-dence of historic charcoal production is still observed since the remains of charcoal hearths can be found scattered all over the eastern United States near old iron furnaces

Studying organic carbon concentrations in soils historically affected by charcoal is important because of the recent interest in amending soil with charcoal to possibly raise carbon stocks and enhance soils Increasing carbon stocks is important because of improvement of soil quality and climate change mitigation through carbon sequestration (Woolf et al 2010) Therefore the objective of this research was to examine any differences in organic carbon content between selected charcoal-affected hearth soils and non-affected control soils in Catoctin Mountain Park Maryland

MEtHOdS

Study Site description and Sample Collection

Charcoal hearths located in Catoctin Mountain Park Maryland were identified and examined for this study This park is part of the Catoctin Mountain Ridge on the Appalachian Mountains (Fig 1) Due to the presence of a nearby iron furnace that operated using charcoal fuel from 1776 to 1883 this site was subject to historic coal burnings (National Park Service 2016) As a result there are over

f i R S t P l a C EThis was written as a scientific paper with an audience of researchers

The research reported in this paper was part of a larger project and data may be used again in reporting the results of that paper

Published February 9 2017

2 of 6 Natural Sciences Education bull Volume 46 bull 2017

Fig 1 This map shows the location of Catoctin Mountain Park in Maryland The inset image shows greater detail of Catoctin Mountain along with the five hearths analyzed

Fig 2 This image shows the relative landscape positions for each hearth examined at Catoctin Mountain Park Elevation was plotted from South to North starting at a position located close to the mountain top site (MT) MFNE and MBNE represent the mountain flank and mountain base sites on the northeast mountain aspect MBSE and MFSE represent the mountain base and mountain flank sites on the southeast mountain aspect


140 charcoal hearths in the park (National Park Service 2013) For this study hearths were identified using LiDAR imaging in the same manner as Risboslashl et al (2006) The LiDAR data was obtained using the ldquoLiDAR Topography Serverrdquo from MD iMAP

Hearth soils could also be distinguished in the field by their relative flatness and grassy vegetation compared to the rest of the landscape Five different hearths were selected for analysis At each hearth soil pits were excavated examined and compared to non-hearth soils located approximately 20 meters away In order to conduct organic carbon and bulk density analyses in the lab soil samples and clods were collected for each identified soil horizon

The five sample sites were distinguished based on their mountain landscape position (Fig 2) Two sites that were examined were located on the northeast mountain aspect one of which was on the mountain base (known as MBNE) and the other was on the mountain flank (known as MFNE) Two other sites selected for analysis faced the southeast aspect one of which was on the mountain base (known as MBSE) and the other was on the mountain flank (MFSE) The final site was classified by being on a mountaintop and is therefore known as MT

For each control site the taxonomic classifications of the soils were determined The sites on the southeast mountain aspect MBSE and MFSE along with the mountain top site MT were all classified as Hapludalfs The sites on the northeast mountain aspect MFNE and MBNE were classified as Eutrudepts and Paleudalfs respectively

Experimental MethodsThe organic carbon content was determined by loss on

ignition (Nelson and Sommers 1996) The parameters of the muffle furnace used in the listed method were adjusted so that the mass of organic matter in dried soil

samples would be burned off in a more convenient length of time The samples were exposed to the muffle furnace set at 550oC for 4 hours When measuring organic carbon approximately 5 g of soil was used for each sample and the mass difference was determined after the ignition of organic matter To convert mass of organic matter to carbon the organic matter in the soils were assumed to be 58 carbon by mass To calculate carbon stocks for each excavated soil pit bulk density measurements were required Therefore a Next Engine 2020i scanner was used to determine bulk densities by the three-dimensional scanning method (Rossi et al 2008)

Carbon stocks (in kgm2) were then calculated using the following equation

b1

Carbon Stock [ (1 )]n

i i ii

T C xr=

= times times times minussum [1]

where T represents horizon thickness (m) rb is bulk density (kgm3) C is concentration of organic carbon (kgkg) and x is the rock and gravel fraction by volume (m3m3) (Turk and Graham 2009)

RESultS aNd diSCuSSiONWhen comparing hearth soils to their corresponding

control sites there were observable differences in soil color The surface soils of all hearths appeared to be significantly darker An example of this trend can be viewed in Fig 3 which illustrates the darkened A horizon at the MFNE hearth compared to the control soil The darkened color in the hearth soils indicates that there are likely greater organic carbon concentrations as a result of historic charcoal production This was confirmed through direct measurement of organic matter concentrations

Fig 3 Images of excavated soils pits located at the MFNE (mountain flank northeast) site The darkened A horizon in the hearth image (A) indicates an increased organic carbon content from historic charcoal production The unaffected control (B) has a much lighter A horizon


Fig 4 Soil organic carbon depth analysis for all sites


At the surface organic carbon percentages for all sites with the exception of MBNE were found to be greater in hearth soils (Fig 4) For the A horizons the average organic carbon percent for the charcoal-affected hearth soils was 2139 compared to 1121 for non-hearth control A horizons However the horizon thickness and degree of difference in organic carbon concentrations for the high carbon charcoal-layers varied between sites The MBSE site was found to have the thickest high carbon charcoal-layers in the hearth and the MT site was found to have the greatest difference in soil organic carbon concentration Based on the landscape positions of these two sites it can be inferred that the increases in thickness and organic carbon percentages were due to these sites being subject to less erosion The MBSE and MT site had slopes of 9 and 6 respectively whereas the other sites had greater slopes and were therefore subject to more erosion The sites MFNE and MFSE which were located on mountain flank landscape positions had slopes of 20 and 17 The MBNE site which is in a mountain base position had a slope of 18 Further sampling of hearths located in similar landscape positions to the ones selected in this study is needed to statistically confirm trends relating organic carbon increase to landscape position

The carbon stocks calculated for the control and hearth soils of all sites provided further insight into the difference in organic carbon stored in soils as a result of historic charcoal production (Table 1) The carbon stocks were calculated to a fixed soil depth of 80 cm The analysis of organic carbon stocks appears to differ slightly from organic carbon concentrations (Fig 4) This can be attributed to variations in horizon thickness bulk density and the fraction of rocks which are all are taken into account in the calculation of the carbon stock After testing normality for the differences in carbon stock values for all sites a paired T test showed that organic carbon stocks of hearth soils were nearly significantly different from adjacent control soils (p = 00837) The average carbon stock for the hearth soils was 413 kgm2 and the control average was 298 kgm2 Normality for the paired differences was accepted using the Shapiro-Wilk test Assuming that these averages are representative for the park and 140 hearths of approximately 12 m-diameter can be found throughout the 25 km2-park total soil carbon for the park can be calculated to have increased from 745000 Mg to 745200 Mg as a result of charcoal production This calculation suggests that the small footprint of the hearths limits their total carbon storage to a negligible increase indicating that much wider scale application of charcoal is needed to contribute to climate change mitigation A more accurate approximation of charcoal hearth contribution to

total carbon storage of the park might be obtained by taking into account differences in carbon storage between landscape positions and weighting the averages according to area occupied by each landform and the distribution of hearths across the landscape of the park If most hearths are located at sites with lower slope gradients the total contribution to carbon storage can be expected to increase due to lower erosion rates and greater long-term carbon storage

With the exception of the MBNE site all hearth soils were found to have greater carbon stocks compared to the control soils At this sight the hearth contained a higher concentration of rock fragments compared to the control soil which contributed to the calculation of a lower carbon stock Like the organic carbon concentrations seen in Fig 4 the greatest increase in carbon stock was found at the MT site As noted earlier this site was found to have the least slope which would lead to less erosion and allow for more charcoal to be stored in the long term In a similar study conducted by Borchard et al (2014) soil organic carbon stocks were calculated for historic charcoal production sites in middle range mountains in Germany and were also found to be greater than in control soils Carbon stocks for the upper 20-cm calculated in that study averaged 49 kgm2 for control soils and 220 kgm2 for hearth soils on acidic soils and 72 kgm2 for control soils and 176 kgm2 for hearth soils on calcareous soils In our study the difference between carbon stocks of hearth and control soils was similar to those found in Germany showing an increase of 115 kgm2 compared to 104-174 kgm2 found by Borchard et al (2014) The biggest difference between the studies was the greater carbon stocks of the control soils in our study

CONCluSiONBy measuring organic carbon concentrations and carbon

stocks of both hearth and control soils it was found that hearth soils affected by historic charcoal production contain more organic carbon This increased organic carbon storage at charcoal-affected sites is important because it can be useful for understanding the long-term effects of applying charcoal amendments to soil The increase in soil carbon storage is beneficial because organic carbon tends to increase soil productivity while helping mitigate climate change (Liang et al 2006) Organic carbon contents did vary between different landscape positions with greater carbon storage observed on hearths located at sites with lower slope gradients However more data is needed to statistically confirm this trend To better assess the effect of charcoal production on fertility of the soil the effective CEC (cation exchange capacity) is currently being studied for these sites

Table 1 Carbon stock values for all sites at a fixed depth of 80 cm Statistical tests were included to show normality of the carbon stock differences and that the groups are significantly differentdaggerDagger

Site Hearth Control Differencendashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndash kgm2 ndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndashndash

MT 485 184 301MFNE 418 279 139MBNE 241 358 ndash117MBSE 532 353 179MFSE 391 314 77Mean 413 298 115

Shapiro Wilk Calculated value for difference is greater than threshold Therefore accept hypothesis that the population is normally distributed W threshold = 0762 (alpha = 005) W stat = 0990

Paired T test T table value = 2132 (one tail alpha = 005) T stat = 168 P value = 00837


aCkNOwlEdgMENtThanks to Becky Lonocosky for issuing our permit

to conduct research at Catoctin Mountain Thanks also to Jennifer Gardner Jin Chen and Tyler Buck for their contributions in measuring soil bulk density This research was supported by a Research and Professional Development Grant from the Stockton University Office of Research and Sponsored Programs

REfERENCESBorchard N B Ladd S Eschemann D Hegenberg BM Moumlseler

and W Amelung 2014 Black carbon and soil properties at historical charcoal production sites in Germany Geoderma 232-234236ndash242 doi101016jgeoderma201405007

Hart JL SL Van De Gevel DF Mann and WK Clatterbuck 2008 Legacy of charcoaling in a western highland rim forest in Tennessee Am Midl Nat 159238ndash250 doi1016740003-0031(2008)159[238LOCIAW]20CO2

Liang B J Lehmann D Solomon J Kinyangi J Grossman B OrsquoNeill JO Skjemstad J Thies FJ Luizatildeo J Petersen and EG Neves 2006 Black carbon increases cation exchange capacity in soils Soil Sci Soc Am J 70 1719-1730 doi102136sssaj20050383

National Park Service 2013 Charcoal Interpretive Trail Catoctin Mountain Park Thurmont MD

National Park Service 2016 Catoctin iron furnace httpswwwnpsgovcatolearnhistoryculturefurnacehtm (accessed 23 Sept 2016) National Parks Service Washington DC

Nelson DW and LE Sommers 1996 Total carbon organic carbon and organic matter p 961ndash1010 In DL Sparks editor Methods of soil analysis Part 3 Chemical methods SSSA and ASA Madison WI

Risboslashl O AK Gjertsen and K Skare 2006 Airborne laser scanning of cultural remains in forestsmdashsome preliminary results from a norwegian project BAR International Series 1568107

Rossi AM DR Hirmas RC Graham and PD Sternberg 2008 Bulk density determination by automated three-dimensional laser scanning Soil Sci Soc Am J 721591ndash1593 doi102136sssaj20080072N

Straka TJ 2014 Historic charcoal production in the US and forest depletion development of production parameters Adv Historical Studies 3104 doi104236ahs201432010

Turk JK and RC Graham 2009 Soil carbon and nitrogen accumulation in a Forested debris flow Chronosequence California Soil Sci Soc Am J 731504ndash1509 doi102136sssaj20080106

Woolf D J Amonette A Street-Perrott J Lehmann and S Joseph 2010 Sustainable biochar to mitigate global climate change Nat Commun 156 doi101038ncomms1053


Fig 1 This map shows the location of Catoctin Mountain Park in Maryland The inset image shows greater detail of Catoctin Mountain along with the five hearths analyzed

Fig 2 This image shows the relative landscape positions for each hearth examined at Catoctin Mountain Park Elevation was plotted from South to North starting at a position located close to the mountain top site (MT) MFNE and MBNE represent the mountain flank and mountain base sites on the northeast mountain aspect MBSE and MFSE represent the mountain base and mountain flank sites on the southeast mountain aspect










b1


i i ii

T C xr=












































b1


i i ii

T C xr=



































organic carbon analysis of charcoal-enriched soils at

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