The following methods are excerpted from Lovett et al., (2016).
STUDY DESIGN
We used a reciprocal transplant design employing two sites, the
calcium-treated watershed (Watershed 1) and an untreated, control site
of similar elevation, age, and species composition about 500 m away.
Foliar litter of four species was collected at the two sites, and
incubated in mesh decomposition bags at both sites for 6 years. The
four focal species were sugar maple, American beech, yellow birch, and
white ash, henceforth referred to as maple, beech, birch, and ash. A
subset of bags was collected annually, weighed, and chemically
analyzed.
The wollastonite addition to the Ca-treated watershed occurred in
October 1999. Fifty-six metric tons of VANSIL-10, a commercially
available form of wollastonite, was crushed, pelletized with a lignin
sulfonate binder (approximately 2% wet weight), and applied by
helicopter to the 11.8-ha watershed. Collectors placed throughout the
watershed confirmed even application of the mineral. The Ca
application rate from the wollastonite was 1028 kg Ca/ha (Battles and
others 2013). The treatment increased the Ca2+ export in streamwater
immediately due to wollastonite dissolution in the stream channel, and
over the course of the subsequent 9 years, the loss of
wollastonitederived Ca2+ declined and stabilized at about 11 kg of Ca
per year, representing about 30% of the Ca2+ in streamwater (Nezat et
al., 2010).
Foliar litter was collected using nets suspended under the canopy at
both sites (Ca-treated and untreated) during the autumn of 2005, 6
years after the Ca addition. Litter was collected weekly and
composited by site, then sorted to isolate the four focal species and
air-dried. Litter bags were constructed of 1.6-mm mesh fiberglass
window screening heat-sealed to create 20 x 20 cm pockets. Each litter
bag received 10 g of litter of a single species x treatment
combination, plus an identifying tag, and then was heat-sealed shut.
At each of the two sites, five 3 x 3 m plots were selected for
incubation of the litter. These replicate plots were chosen based on
having low to moderate slopes and few surface rocks. Replicate bags of
each species and treatment were included in each plot. Bags were
deployed in a randomized order within the plot and staked to the
ground with stainless steel stakes. Bags were initially staked at the
surface of the forest floor, but by the end of the 6-year incubation
several cm of forest floor had accumulated on top of most of the
remaining bags. All handling of litter and bags (sorting, deployment,
and collection) was done wearing latex or nitrile gloves.
Henceforth, we use the term ‘‘source’’ to refer to the site from which
the litter was collected and ‘‘placement’’ to refer to the site in
which the bags were incubated. For maple and birch, 12 bags (2 sources
x 6 collection times) were set out in each plot. For beech and ash,
only 10 bags (2 sources x 5 collection times) were set out in each
plot due to insufficient litter of those species. For the entire
experiment, there were 440 bags (2 sources x 2 placements x 4 species
x 5 plots x 5 or 6 collection times). In addition, 5 bags of each
combination of species x source x placement were brought to the field
and then immediately returned to the lab as time 0 samples. A larger
sample of each species x source combination was dried and ground for
later analysis of initial concentrations of lignin and fiber.
Bags were set out on November 9–10, 2005, and samples were collected
every autumn for the next 6 years. At each collection time, one bag of
each species x source combination was collected from each plot; thus
for each collection time, there were 5 replicates of each species x
source x placement. Ash and birch bags were collected only in years 1,
2, 3, 4, and 6. Actual collection times in days since November 10,
2005 were 321, 706, 1055, 1447, 1791, and 2170 days for years 1–6,
respectively.
REFERENCES
Lovett, G. M., M. A. Arthur, and K. F. Crowley. 2016. Effects of
Calcium on the Rate and Extent of Litter Decomposition in a Northern
Hardwood Forest. Ecosystems 19:87-97.
Nezat, C. A, J. D. Blum, and C. T .Driscoll. 2010. Patterns Of Ca/sr
and Sr-87/sr-86 Variation Before and After a Whole Watershed Casio3
Addition at the Hubbard Brook Experimental Forest, USA. Geochimica Et
Cosmochimica Acta 74(11): 3129 - 3142.
Van Soest P.J, J. B. Robertson and B. A. Lewis. 1991. Methods for
dietary fiber, neutral detergent fiber, and nonstarch polysaccharides
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