Data from: Extractable soil lead (Pb) levels associated with increased soil carbon content in Mid-Atlantic turfgrass soils

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.