Measurements of microbial biomass and activity in two snow manipulation experiments at Hubbard Brook Experimental Forest 1998 – 2004

In 1997, as part of a study of the relationships between snow depth,
soil freezing and nutrient cycling
(http://www.ecostudies.org/people_sci_groffman_snow_summary.html), we
established eight 10 x 10-m plots located within four stands; two
dominated (80%) by sugar maple and two dominated by yellow birch, with
one snow reduction (freeze) and one reference plot in each stand. In
2001, we established eight new 10-m x 10-m plots (4 treatment, 4
reference) in four new sites; two high elevation, north facing and two
low elevation, south facing maple-beech-birch stands. To establish
plots for the “freeze” study, we cleared minor amounts of understory
vegetation from all (both freeze and reference) plots (to facilitate
shoveling). We then installed soil solution samplers (zero tension
lysimeters), thermistors for soil temperature monitoring, water
content (time domain) reflectometers (for measuring soil moisture),
soil atmosphere sampling probes, minirhizotron access tubes, and trace
gas flux measurement chambers (described below). All plots were
equipped with dataloggers to allow for continuous monitoring of soil
moisture and temperature. Treatments (keep plots snow free by
shoveling through the end of January) were applied in the winters of
1997/98, 1998/99, 2002/2003 and 2003/2004. Measurements of soil
nitrate (NO 3 - ) and
ammonium (NH 4 + )
concentrations, microbial biomass carbon (C) and nitrogen (N) content,
microbial respiration, potential nitrification and N mineralization
rates, pH, and denitrification potential were measured on these plots
at multiple time points during these studies. These data were gathered as part of the Hubbard Brook Ecosystem Study
(HBES) using funding from the U.S. National Science Foundation. The
HBES is a collaborative effort at the Hubbard Brook Experimental
Forest, which is operated and maintained by the USDA Forest Service,
Northern Research Station.