DOI: 10.5061/dryad.x0k6djhwt
title: Data from: Extractable soil lead (Pb) levels associated with increased soil carbon content in Mid-Atlantic turfgrass soils

description: We conducted an observational study at 62 golf courses at varying
 distances from urbanized areas in the temperate, mesic U.S. mid-Atlantic
 region, measuring soil carbon stocks in minimally managed areas where
 cool-season turfgrasses had grown without disturbance for at least 25
 years. In 2009-2010, soils were sampled to 30 cm, and site and management
 variables were recorded. Total and permanganate oxidizable soil carbon
 were quantified, and potential explanatory factors were explored using
 multiple regression analysis. The strongest interaction that can
 be seen in these observations is a positive, log-log, 'broken
 stick' or threshold relationship between soil Pb and total soil
 C.  Our analysis suggests that above a threshold of ca. 4 mg
 extractable Pb/kg soil, lead (Pb) was strongly and positively correlated
 with soil carbon.  Increasing minimum daily temperature in
 February was also positively correlated with soil carbon, and several
 other correlations can be observed. Large quantities of Pb have been
 distributed atmospherically over the last century. If the Pb effects
 observed here are widespread (e.g., in other regions and ecosystems), they
 could impact global carbon cycle modeling and/or uncertainty. A better
 understanding of Pb effects on soil carbon turnover, erodibility, and
 mineralization dynamics, particularly under disturbed or agricultural
 soils, is urgently needed, and we encourage other soil scientists to
 investigate.
description: <strong>Context of data
 collection</strong>: We utilized undisturbed
 soils along an urban-rural transect throughout Maryland and Washington,
 D.C., in the mid-Atlantic region of the U.S. to study the complex
 interactions of multiple global change factors *in toto. *Fifty-two public
 and private golf facilities in continuous operation for &gt; 25 years
 were identified with the assistance of the Mid-Atlantic Association of
 Golf Course Superintendents in early 2009. These businesses were generous
 in allowing us to collect soil samples and make other observations.  The
 latitude and longitude of each sampling location is included in these
 data, but the names of the golf courses are not. Of the
 52 golf courses located, seven facilities included two entire, separate
 courses constructed in different years, each of which was treated as a
 separate, independent sampling site. Three additional facilities included
 single courses that spanned two clearly different soil parent materials,
 ascertained by comparing auger samples (1.0 m depth) with area soil maps. 
 For these facilities, each of the two contrasting parent material areas
 were separately sampled and considered as independent sampling sites.  The
 total number of independent samples for the study was therefore 62. 
 Missing data are denoted with “NA”. For purposes of
 soil carbon, we detected and excluded one outlier, which is the sample
 identified as "JW6".  Total soil carbon is significantly higher
 at this location, and the soil contained visible charcoal.  The manager
 confirmed verbally that debris from the 1904 "great Baltimore
 fire" was buried at this facility.   If you are reanalyzing this
 dataset, please consider this aspect of site JW6.
 <strong>Brief Methods</strong>: 
 ·       Intact-core soil samples composited into 0-5, 5-15, and
 15 – 30 cm depth increments ·       Bulk density,
 course fragment content, soil total C content and POX C content were
 measured separately in each of the three composited depth increments and
 weighted averages over the full 30 cm profile calculated mathematically
 when indicated; total C and POX C also reported in units of Megagrams C /
 hectare for 0 to 5 and 0 to 30 cm depths. ·       Soil
 chemical analyses were conducted by the University of Delaware Soil
 Testing Lab on composite samples representative of the entire 0 – 30 cm
 depth (i.e. one sixth of the sample taken from 0 to 5 cm, one third from 5
 to 15 cm, and one half from 15 to 30 cm depth).  Therefore, there is only
 a single value per site representing the full 30 cm profile for these
 measurements.  ·       Permanganate-oxidizable
 C ·       Mehlich-3 soil extraction
 ·       Long-term soil temperature measurements via buried HOBO
 data loggers ·       Passive monitoring of ozone
 exposure via oxidation of indigo carmine dye ·      
 Exploratory multiple regression
description: # Extractable soil lead (Pb) levels associated with increased soil carbon
 content in Mid-Atlantic turfgrass soils Dataset DOI:
 [10.5061/dryad.x0k6djhwt](10.5061/dryad.x0k6djhwt) ## Description of the
 data and file structure We studied undisturbed soils along an urban–rural
 transect in Maryland and Washington, D.C., to examine the combined effects
 of multiple global change factors. In early 2009, we identified 52 golf
 facilities (in operation for over 25 years) with help from the
 Mid-Atlantic Association of Golf Course Superintendents. These facilities
 kindly allowed soil sampling and field observations. Latitude and
 longitude for each site are included, but golf course names are not. Seven
 facilities had two separate courses built in different years, each treated
 as an independent site. Three others had single courses spanning distinct
 soil parent materials, confirmed by auger sampling and soil maps; each
 area was sampled separately. This resulted in 62 total independent
 sampling sites. Missing values are marked as “NA”. The golf.data.csv data
 file contains all the measurement values and the golf.metadata.csv
 contains the description of the variables. | variable name | variable
 description | | :------------------------- |
 :---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | ID | arbitrary random alphanumeric identifier of sampling locations, all located  in the roughs of golf courses in Maryland and the District of Columbia, United States | | longitude | longitude of sampling location as measured by handheld GPS at time of sampling,  in decimal degrees | | latitude | latitude of sampling location as measured by handheld GPS at time of sampling,  in decimal degrees | | age | number of years since last physical disturbance of the sampled area, as reported by the golf course manager and/or records | | fert | number of times per year that fertilizer of any type, including mineral and organic amendments, was applied to the area in question, ranging from 0 to 3 | | ppmCO2twom | one-time spot reading, at the time of soil sampling,  of atmospheric levels of carbon dioxide (CO2) at two meters above the soil surface, measured with a portable LiCOR unit. Time and day of the week of sampling varied among sites. | | LANDSCAN | Because Orbital Carbon Observatory data were not available, Landscan 2008 data (UT-Battelle, LLC. http\://www\.ornl.gov/sci/landscan/landscan\_documentation.shtml) served as a proxy for carbon dioxide (CO2) concentrations in the air in the study area.  Landscan is a representation of the average ambient population over 24 hours in each 1-km square grid cell, comprising residents as well as people traveling through or temporarily in the grid cell, such as for work or commuting. Landscan values are assembled from census information, landcover, and other spatial data.  In this study, Landscan values (ambient population per grid cell) were assumed to capture local variation in atmospheric \[CO2] as impacted by residential and automotive fossil fuel emissions, as well as reduced photosynthetic drawdown in areas with a large proportion of pavement or buildings.   | | relOZONE | unitless ratio of oxone exposure (as ascertained by indigo carmine dye color change)  at sampling site divided by concurrent exposure at reference site, ranging from  0.38 – 2.17.  NA indicates that the passive ozone monitor at the site was physically damaged or lost. | | avetemp.degF | overall average of all hourly measurements of soil temperature at ca. 8 cm depth | | tempstdv.degF | standard deviation of all hourly soil temperature measurements at ca. 8 cm depth | | aveMINtemp.degF | average daily minimum temperature over all days from Dec. 5th, 2009, through May 24th, 2010 | | aveMAXtemp.degF | average daily maximum temperature over all days from Dec. 5th, 200, through May 24th, 2010 | | aveMINfeb.degF | average daily minimum temperature over the 28  days in February 2010, the coldest month for which hourly temperature measurements are available | | aveMAXmay.degF | average daily maximum temperature over the 31 days in May 2010, the warmest month for which hourly temperature measurements are available | | P.M3.mgperkg | Mehlich-3 P (mg/kg) | | K.M3.mgperkg | Mehlich-3 K (mg/kg) | | Ca.M3.mgperkg | Mehlich-3 Ca (mg/kg) | | Mg.M3.mgperkg | Mehlich-3 Mg (mg/kg) | | Mn.M3.mgperkg | Mehlich-3 Mn (mg/kg) | | Zn.M3.mgperkg | Mehlich-3 Zn (mg/kg) | | Cu.M3.mgperkg | Mehlich-3 Cu (mg/kg) | | Fe.M3.mgperkg | Mehlich-3 Fe (mg/kg) | | B.M3.mgperkg | Mehlich-3 B (mg/kg) | | S.M3.mgperkg | Mehlich-3 S (mg/kg) | | Al.M3.mgperkg | Mehlich-3 Al (mg/kg) | | As.M3.mgperkg | Mehlich-3 As (mg/kg) | | Cd.M3.mgperkg | Mehlich-3 Cd (mg/kg) | | Cr.M3.mgperkg | Mehlich-3 Cr (mg/kg) | | Ni.M3.mgperkg | Mehlich-3 P (mg/kg) | | Pb.M3.mgperkg | Mehlich-3 P (mg/kg) | | soilpH | soil pH  | | CEC.at.pH7 | cation exchange capacity measured at pH 7 | | OM.LOI.pct | percent of organic matter in the soil, measured by loss on ignition | | pct. sand.0to30cm | sand (0.05 to 2.0 mm) percent of soil mineral particles, for the whole 0 to 30 cm depth profile | | pct .silt.0to30cm | silt (0.002 to 0.05 mm) percent of soil mineral particles, for the whole 0 to 30 cm depth profile | | pc t.totalclay.0to30cm | clay (less than 0.002 mm) percent of total soil mineral particles, for the whole 0 to 30 cm depth profile | | pct.fineclay.0to30cm | fine clay ((&lt; 0.2 ?m diameter) percent of soil mineral particles, for the whole 0 to 30 cm depth profile | | hyphae.mpercm3soil.0to30cm | meters of arbuscular mycorrhizal fungal extramatrical hyphae per cubic centimeter of soil in the 0 to 30 cm depth, ascertained by the gridline intersect method at 400x and 1000x magnification | | bulkdens.0to5cm | Bulk density of the 0 to 5 cm depth increment. Bulk density estimations were made based on the known volume of intact soil core sampling tubes, adjusted for coarse fragment content when present | | bulkdens.05to15cm | bulk density of the 5 to 15 cm depth increment. Bulk density estimations were made based on the known volume of intact soil core sampling tubes, adjusted for coarse fragment content when present | | bulkdens.15to30cm | bulk density of the 15 to 30 cm depth increment. Bulk density estimations were made based on the known volume of intact soil core sampling tubes, adjusted for coarse fragment content when present | | POXC.MgHa.0to5cm | permanganate oxidizable carbon (Megagrams per hectare) in the 0 to 5 cm soil depth increment | | POXC.MgHa.0to30cm | permanganate oxidizable carbon (Megagrams per hectare) in the 0 to 30 cm soil depth increment, calculated as a weighted average from the three depth increments | | POXC.gpergsoil.0to5cm | permanganate oxidizable carbon in grams per gram soil in the 0 to 5 cm soil depth increment, ascertained by color change using a spectrophotometer after a 12-minute oxidation in dilute potassium permanganate  | | POXC.gpergsoil.5to15cm | permanganate oxidizable carbon in grams per gram soil in the 5 to 15 cm soil depth increment, ascertained by color change using a spectrophotometer after a 12-minute oxidation in dilute potassium permanganate  | | POXC.gpergsoil.15to30cm | permanganate oxidizable carbon in grams per gram soil in the 15 to 30 cm soil depth increment, ascertained by color change using a spectrophotometer after a 12-minute oxidation in dilute potassium permanganate  | | totalC.gpergsoil.0to5cm | soil total C in the 0 to 5 cm depth increment,  quantified using a LECO CHN-2000 analyzer | | totalC.gpergsoil.05to15cm | soil total C in the 5 to 15 cm depth increment,  quantified using a LECO CHN-2000 analyzer | | totalC.gpergsoil.15to30cm | soil total C in the 15 to 30 cm depth increment,  quantified using a LECO CHN-2000 analyzer | | N.gpergsoil.0to5cm | soil total N in the 0 to 5 cm depth increment,  quantified using a LECO CHN-2000 analyzer | | N.gpergsoil.05to15cm | soil total N in the 5 to 15 cm depth increment,  quantified using a LECO CHN-2000 analyzer | | N.gpergsoil.15to30cm | soil total N in the 15 to 30 cm depth increment,  quantified using a LECO CHN-2000 analyzer | | totalC.MgHa.0to5cm | total soil carbon (Megagrams per hectare) in the 0 to 5 cm soil depth increment | | totalC.MgHa.0to30cm | total soil carbon (Megagrams per hectare) in the 0 to 30 cm soil depth increment, calculated as a weighted average from the three depth increments |