Methods for Cone Pond Watershed: Soil Profiles (Pedons), 1988-2023
Purpose and site selection
This dataset documents pedons (soil profiles) sampled at Cone Pond Watershed, Thornton, New Hampshire. Sampling was conducted from 1988 to 2003. In addition, notes from less detailed observations of soils made in 2023, for soil model validation, are included in a separate table.
The first four pedons (CWL-1 to CWL-4) were sampled in 1988 during construction of tension-free lysimeters. Four sites spanning the elevational range of the west branch of the inlet to Cone Pond were sampled by Greg Lawrence, then a Post-Doc at the University of Maine. This work was part of the establishment of watershed studies at Cone Pond led by James W. Hornbeck, USDA Forest Service, Northeastern Forest Experiment Station, Durham, NH. Don Buso and Scott Bailey assisted.
The next set of twelve pedons (CPW-1 to CPW-12) were sampled in 1990. Sampling sites were co-located with throughfall sampling sites and were scattered along a trail that traversed the perimeter of the watershed of the main inlet to Cone Pond. The main purpose of these samples was to support the calcium cycling work of Scott Bailey’s PhD dissertation and Marita Hyman’s mineral weathering studies, as part of her M.S. thesis, both at Syracuse University (Bailey et al. 1996; Hyman et al. 1998). Ralph Perron, USFS assisted with these samples and the pits were reviewed by Joseph Homer, SCS (now NRCS).
The last set of pedons (CP-1 to CP-8) were sampled 1995 to 2003 for a variety of purposes. Pits for CP-1 to CP-4 were dug by Scott Bailey and Ralph Perron and were described by Joe Homer and Steve Hundley, NRCS. These pits were chosen as examples of four soil units used to partition watershed scale soil pool estimates. Discussion with NRCS centered on the comparison of the soil units used at Cone Pond, which were precursors to hydropedology research at Hubbard Brook (Bailey et al. 2014), versus NRCS soil series recognized in Grafton County by NRCS. CP-5 to CP-8 were dug and described by Scott Bailey. CP-5 and CP-6 were established as part of a regional study of sugar maple health and growth (Hallett et al. 2006; Long et al. 2009). Pits CP-5 and CP-8 were in biomass monitoring plots used for an interwatershed nutrient cycling study (Park et al. 2008). The impetus for sampling CP-7 is no longer known.
Soil observation sites CP1 to CP 6 were geolocated at the time of sampling by collection of a minimum of 200-point measurements with a Trimble gps unit with external hurricane antenna. Post processing was conducted in Trimble Pathfinder software using data from the Vermont Department of Transportation CORS, Bradford Vermont as the base station to achieve 1-2 m horizontal precision. The other soil observations, made before the advent of GPS, were originally located on a detailed map of the watershed created by Tony Federer in OCAD using the USGS Waterville Valley Quadrangle (1:24000) as a base. The Federer map was georeferenced by Olivia Fraser and approximate sampling location coordinates were read from this map and visited by Bailey in 2023. In cases where evidence of the original sampling site was still present (e.g. lysimeter or pvc pipe monument), gps data were collected in 2023 with a Trimble gps unit and processed as above. Soil observations were also made in 2023 to ensure consistency with the original descriptions.
Soil pedon sampling and description
Soil pits for complete pedon description and sampling were hand dug, generally about 1 m across (i.e. along the contour) by 0.5 m wide by 1-1.25 m deep. A strong attempt was made to sample well into the C horizon in order to sample it objectively and distinctly from a transitional zone, which was commonly present, and described as a BC or CB horizon. In a few instances sampling continued deeper, generally with an auger, to gather samples for evaluation of weathering and variation within the C horizon. Depth of sampling was curtailed where bedrock was shallow, or where digging was inhibited by extreme boulder content. A tarp was placed on the upslope side of the pit to protect the forest floor for clean description and sampling and was not trod upon to preserve the upslope face of the pit for horizon description and sample collection. A second tarp was placed to the side or immediately downslope of the pit to contain the spoil pile and minimize the footprint of disturbance. Pits were refilled immediately after sampling. The forest floor was set aside in several blocks during digging and was replaced upright upon pit refilling. Horizon description and abbreviations for horizon physical attributes generally follow SCS/NRCS practices, later documented by Schoeneberger et al. (2002). Earlier profiles were only generally described while later profiles were described at a moderate level of detail.
Soil sample preparation and chemical analyses
Soil horizon samples were collected from the entire upslope face of the soil pit and placed in plastic bags for transport to the laboratory. Smaller samples were collected from multiple locations across the face, within each horizon, to generate an overall sample of one to two L. Each subsample was collected from across the entire depth represented by the horizon. Relatively large sample size, and composites from across the pit face minimized the effects of small-scale variation. In the lab, samples were laid out on plastic trays for air drying. Drying was facilitated by using a fork to break up peds and stir the samples once every several days, and by use of fans to circulate air. Air drying generally achieved about 1% water content as measured by mass loss of subsamples in a drying oven. Air-dry samples (except Oi and Oe horizons) were screened though a 2 mm sieve and split using a riffle sampler into portions for chemical analyses and archiving. Oi and Oe horizons were not immediately analyzed; smaller Oi and Oe samples were stored directly in archive jars to minimize sample loss by grinding, while larger samples were ground in a Wiley mill prior to storage.
Chemical analyses of the 1988 pits were made at the laboratory of Ivan Fernandez, University of Maine at Orono. Methods followed Robarge and Fernandez (1987). Chemical analyses of the 1990 samples were made by Pavel Kram at the laboratory of Chris Johnson, Syracuse University and generally followed the same methods. The more recent sample analyses were performed at the USDA Forest Service, Northern Research Station laboratory in Durham, NH. pH was measured in a 0.01 mol L-1 CaCl2 solution by the method of Robarge and Fernandez (1987). Measurements were repeated until the pH reading was stable within 0.02 pH units. Salt extractions were made with two methods including extraction by 1 mol L-1 KCl for Al and acidity (Robarge and Fernandez 1987), and by 1 mol L-1 NH4Cl via mechanical vacuum extraction for exchangeable cations (Blume et al. 1990). Exchangeable acidity was determined by potentiometric titration (Robarge and Fernandez 1987). Salt extracts were analyzed for elements via inductively coupled plasma spectrophotometry (ICP). Results for replicate samples, representing variation due to subsampling, extraction, and analysis by ICP, were generally within 15% difference from the reported value. Most analytes were well above detection limits except some samples where Ca and Mg were below detection at 0.006 cmolckg-1 and 0.0004 cmolckg-1, respectively. Organic matter content was measured by loss on ignition (Robarge and Fernandez 1987). Replication of all analyses was generally +/-15% or less. Ross et al. (2015) addressed differences in methods for forest soil analysis; for reference, the Durham lab is identified as laboratory 1.
Reconnaissance soil observations
Reconnaissance pedons, observed at a lower level of detail, were observed by Scott Bailey, Olivia Fraser, and Emily Piché in 2023 to provide independent validation of a hydropedologic model of soil distribution developed at Hubbard Brook Experimental Forest. Small pits, about 25 cm diameter by 40+ cm deep were hand dug and described at a level sufficient to classify the pit by soil unit (i.e. hydropedologic unit, or hpu). Sampling locations were chosen at random by Fraser. An iPhone was used to navigate to the chosen sites where observations were made and an Arrow gps unit was used to confirm the location.
References cited
Bailey, S. W., Hornbeck, J. W., Driscoll, C. T., & Gaudette, H. E. (1996). Calcium inputs and transport in a base‐poor forest ecosystem as interpreted by Sr isotopes. Water Resources Research, 32(3), 707-719.
Bailey, S. W., Brousseau, P. A., McGuire, K. J., & Ross, D. S. (2014). Influence of landscape position and transient water table on soil development and carbon distribution in a steep, headwater catchment. Geoderma, 226, 279-289.
Blume, L. J., Schumacher, B. A., Schaffer, P. W., Cappo, K. A., Papp, M. L., van Remortel, R. D., Coffey, D. S., Johnson, M. G., & Chaloud, D. J. (1990). Handbook or Methods for Acid Deposition Studies Laboratory Analyses for Soil Chemistry; U.S. Environmental Protection Agency, Environmental Monitoring Systems Laboratory: Las Vegas, NV.
Hallett, R. A., Bailey, S. W., Horsley, S. B., & Long, R. P. (2006). Influence of nutrition and stress on sugar maple at a regional scale. Canadian Journal of Forest Research, 36(9), 2235-2246.
Hyman, M. E., Johnson, C. E., Bailey, S. W., Hornbeck, J. W., & April, R. H. (1998). Chemical weathering and cation loss in a base-poor watershed. Geological Society of America Bulletin, 110(1), 85-95.
Long, R. P., Horsley, S. B., Hallett, R. A., & Bailey, S. W. (2009). Sugar maple growth in relation to nutrition and stress in the northeastern United States. Ecological Applications, 19(6), 1454-1466.
Park, B. B., Yanai, R. D., Fahey, T. J., Bailey, S. W., Siccama, T. G., Shanley, J. B., & Cleavitt, N. L. (2008). Fine root dynamics and forest production across a calcium gradient in northern hardwood and conifer ecosystems. Ecosystems, 11, 325-341.
Robarge, W. P., & Fernandez, I. J. (1987). Quality Assurance Methods Manual for Laboratory Analytical Techniques. Revision 1; U.S. EPA. And USDA Forest Response Program; Corvallis Environmental Research Laboratory: Corvallis, OR.
Ross, D. S., Bailey, S. W., Briggs, R. D., Curry, J., Fernandez, I. J., Fredriksen, G., ... & Warby, R. A. (2015). Inter‐laboratory variation in the chemical analysis of acidic forest soil reference samples from eastern North America. Ecosphere, 6(5), 1-22.
Schoeneberger, P. J., Wysocki, D. A., Benham, E. C., & Broderson, W. D. (2002). Field book for describing and sampling soils, Version 2.0. Natural Resources Conservation Service, National Soil Survey Center, Lincoln, NE.
