Daily maximum and minimum temperatures are measured at three locations
on the experimental forest. Daily air temperatures are available for
two upland locations (S2 and S5) and one bog location (S2 Bog). Data
collection at the S2 (South) upland site has been continuous from 1961
to the present, while the S2 bog site data are continuous from July
1989 to the present. Data from the S5 (North) upland site are
continuous from 1962 to the present.
The shelters at the upland sites are in open areas with grass that is
mowed at least every 2 weeks when growing. Optimally, the forest
clearings are maintained with a 45-degree opening from the height of
the thermometers. However, there were periods when this site condition
was not adequately maintained. At both North and South, the clearings
are surrounded by mature aspen (Populus tremuloides, P. balsamifera,
and P. grandidentata) stands. Though hardwood forest stands near snow
course transects have not been managed, forest cover is shifting from
overstory dominance of aspen to balsam fir (Abies balsamea), red maple
(Acer rubrum), basswood (Tilia americana) and red oak (Quercus rubra).
The North and South sites are separated by about 5 km. The South and
S2 bog site are separated by about 0.175 km.
The shelter in the S2 bog (a northern peatland) is beneath a black
spruce (Picea mariana) forest canopy. Sphagnum and low ericaceous
shrubs (Rhododendron groenlandicum, Chamaedaphne calyculata, Vaccinium
angustifolium) grow under and around the shelter. The organic soil
(peat), which is less than 3 m deep where air temperature is measured,
is not stable for data recorders. Therefore, the shelter is mounted on
three treated posts that extend below the maximum frost depth. Water
tables are at or near the peat surface.
All three sites have Belfort model 594-1 hygrothermographs (data
resolution 1-degree Fahrenheit). Each site also has a US Weather
Bureau style maximum and minimum thermometers (hereafter, max min
thermometers) mounted on a Townsend Support (National Weather Service
2014). The instruments are housed in Standard National Weather Service
Shelters. The shelters are 107 cm (42 inches) off the ground, have
louvered sides, vented bottoms, double roofs and are painted white for
protection against direct solar radiation. The sites have been visited
weekly and charts are changed during visits.
The max min thermometers were read weekly and reset during site
visits. The weekly readings were recorded on charts. In the Grand
Rapids Forestry Sciences Laboratory, the weekly maximum and minimum
values were used to calibrate the hygrothermograph temperature
recorder and to prorate the chart values if they differed. The daily
maximum and minimum values were written on charts.
If the hygrothermograph malfunctions (e.g. clock stops, pen stops
inking, other mechanical issues), the daily temps were estimated from
the max min thermometer readings and the chart from one of the other
sites. A Hobo external temperature data logger (Onset Corporation,
Part no. H08-031-08) has been paired with each hygrothermograph and
logged values were used to gap file maximum and minimum daily values.
The Hobo sensors were placed on August 1, 1997 at the North site,
November 15, 2007 at the South site, and September 1, 1999 at the S2
bog site. Hygrothermograph malfunctions were uncommon and, never more
than 1-7 days were affected since the sites were visited weekly.
Hygrothermographs have been cleaned and lubricated on a yearly basis,
or more frequently if subjected to an extreme dust, pollen, or insect
event. Max min thermometers are calibrated with a distilled water ice
bath.
Values were recorded in degrees Fahrenheit on paper tally sheets
before the mid-1990s, and entered into Microsoft Excel spreadsheets
thereafter. All entries were verified and data plots were observed to
detect any suspicious values. The daily maximum and minimum entries
were then converted to metric units and stored in a summary
spreadsheet. All values are presented in degrees Celsius.
The sites and methods are described in further detail in the
publication:
Sebestyen, S.D., C. Dorrance, D.M. Olson, E.S. Verry, R.K. Kolka, A.E.
Elling, and R. Kyllander (2011). Chapter 2: Long-Term Monitoring Sites
and Trends at the Marcell Experimental Forest. In Randall K. Kolka,
Stephen D. Sebestyen, Elon S. Verry, and Kenneth N. Brooks (Ed.).
Peatland Biogeochemistry and Watershed Hydrology at the Marcell
Experimental Forest (pp 15-71). CRC Press, Boca Raton, FL.
https://www.fs.usda.gov/treesearch/pubs/37979.
Citations:
National Weather Service (2014), National Weather Service manual
10-1315: Cooperative station observations and maintenance, 130 pp,
National Weather Service.
