Soil solutions were collected fortnightly with 2.1 x 9.5 cm length
porous cup tension lysimeters (Prenart Equipment ApS, Frederiksberg,
Denmark) installed in the B soil horizon in four subplots in each plot
(that is, four lysimeters per plot). Each soil lysimeter was plumbed
to a 1-l glass sample bottle housed in a 15-cm-diameter polyvinyl
chloride (PVC) tube that was buried vertically 50 cm in the ground
with a cap at the surface. Tension (30 kPa) was applied with a vacuum
hand pump the day before samples were collected. Because the bottles
were stored underground, the water samples remained in a cool, dark
environment during the collection period and did not freeze during
winter. The lysimeters were installed in spring 2015, which allowed 4
months for equilibration in the soil before the beginning of the study
period in fall 2015. Soil water samples were stored frozen until
analysis at the USDA Forest Service Laboratory in Durham, New
Hampshire, which occurred within a maximum of one month after they
were collected from the field. Samples were analyzed for sulfate
(SO4), nitrate (NO3), chloride (Cl) and phosphate (PO4) on a Metrohm®
Ion Chromatograph; calcium (Ca), magnesium (Mg), potassium (K), sodium
(Na), and aluminum (Al) on an Agilent® 730 ICP optical emission
spectrometer; Total monomeric aluminum (TMAl) with the pyrocatechol
violet method on a Flow Injection Analysis System (Lachat Quickchem)
and Organic monomeric aluminum (Alo) with the same method as TMAl,
after samples passed through a resin ion exchange column; dissolved
organic carbon (DOC) and total dissolved nitrogen (TDN) on a Shimadzu®
TOCV with a TNM-1 nitrogen (N) detector; and ammonium (NH4) by
colorimetry on a SEAL Analytical AQ2 discrete analyzer at the Louis C
Wyman Forest Sciences Laboratory, Durham, NH. Dissolved organic N
(DON) was calculated as the difference between TDN and inorganic N
(NO3-N + NH4-N). Ionic fluxes are provided (e.g.,
NO3
-) rather than
element fluxes (e.g.,
NO3
--N). Detection
limits for chemical analyses are available at
https://portal.edirepository.org/nis/mapbrowse?scope=knb-lter-hbr&identifier=215.
Additional details about the soil lysimeter sampling are provided in
Weitzman et al. (2020). For more information about the ice application
and experimental design see Campbell et al. (2020) and Rustad et al.
references
Weitzman, J.N., Groffman, P.M., Campbell, J.L., Driscoll, C.T., Fahey,
R.T., Fahey, T.J., Schaberg, P.G., Hawley, G.J., and
Rustad, L.E. 2020. Ecosystem nitrogen
response to a simulated ice storm in a northern hardwood forest.
Ecosystems 23: 1186–1205. doi:
10.1007/s10021-019-00463-w.
Campbell, J.L., Rustad, L.E., Driscoll, C.T., Halm, I., Fahey, T.J.,
Fakhraei, H., Groffman, P.M., Hawley, G.J., Leuenberger, W., Schaberg,
P.G. 2020. Simulating ice storm impacts on forest ecosystems.
Journal of Visualized Experiments (160), e61492,
doi:10.3791/61492 (2020).
Rustad, L., Campbell, J., Driscoll, C., Fahey, T., Groffman, P.,
Schaberg, P., Hawley, G., Halm, I., Bowles, F., Winant, G., Schwaner,
G., Leuenberger, W., A new experimental approach to evaluate impacts
of ice storms on northern forest ecosystems. PLoS
ONE 15: e0239619. doi: 10.1371/journal.pone.0239619.
