Campbell Scientific (Logan, Utah, USA) custom meteorological stations were installed at two upland and one peatland locations in the Marcell Experimental Forest (MEF) beginning in 2006. The MEF is located in Itasca County, Minnesota and is operated and maintained by the USDA Forest Service, Northern Research Station.
One upland meteorological station has been located in a clearing (NADP) since May 2008. The other upland meteorological station has been located under the forest canopy adjacent to a clearing (S2 forest) since November 2007. The stations are surrounded by upland forests that are dominated by aspen (Populus tremuloides, P. balsamea, or P. grandidentata), white birch (Betula papyrifera), red maple (Acer rubrum), and balsam fir (Abies balsamea), with some red oak (Quercus rubra), basswood (Tilia americana), and pine (Pinus resinosa, P. strobus, or P. banksiana). The upland forests were last harvested during the 1910s. The clearing around the NADP station is covered in mown grass. The soil at the NADP station is a Menagha loamy outwash sand (a mixed, frigid, Typic Udipsamments; an Entisol; Nyberg 1987). The soil at the S2 forest station is a Warba sandy clay loam developed in glacial till atop deep (50 m) outwash sand deposits. The Warba soil series is a fine-loamy, mixed, superactive, frigid Haplic Glossudalfs (an Alfisol; Nyberg 1987).
The third meteorological station was installed in the Bog Lake peatland in October 2006. The Bog Lake peatland is a 44-ha, poor fen covered with leatherleaf (Chamaedaphne calyculata), bog laurel (Kalmia polifolia), Sphagnum mosses, blue flag iris (Iris versicolor), manna grass (Glyceria species), bog rosemary (Andromeda glaucophylla), cranberry (Vaccinium oxycoccos), beak rush (Rhynchospora alba), arrow grass (Scheuchzeria palustris), and sparse, short (under 3 m) tamarack (Larix laricina). Pitcher plants (Sarracenia purpurea) grow across the peatland. In the area with instrumentation for ecosystem monitoring, the peat is 1 to 4 m deep along an east-west transect across the fen. The peat, a Greenwood series organic soil (Dysic, frigid Typic Haplohemists; Nyberg 1987), has hummock and hollow microtopography with areas of relatively homogeneous elevation (lawns).
Each Campbell Scientific meteorological station is outfitted with an HMP45C air temperature and relative humidity probe inside a six-plate shield, a 107 thermistor probe installed 5 cm below the soil surface to measure soil temperature, a 05103-L wind monitor manufactured by R. M. Young, and an LI190 quantum sensor manufactured by LI-COR to monitor photosynthetic photon flux density (PPFD). A CS616 30-cm water content reflectometer to measure soil volumetric water content was installed at the upland sites (S2 forest and NADP). Additional 107 thermistor probes were installed to measure soil temperature at 10, 20, 30, 40, 50, 100 and 200 cm depths at Bog Lake. The meteorological stations were installed on 2006-10-25 at Bog Lake, on 2007-11-06 under the forest canopy adjacent to the S2S runoff collector (Sebestyen et al. 2011), and on 2008-05-09 in the NADP clearing. Data are collected at 30-minute intervals and sensors are leveled periodically.
All sensors were originally installed on a Campbell Scientific CM110 tripod at each location. On 2019-10-28 the sensors on the NADP station were transferred approximately 15 m to the southeast from the tripod onto a 3 m section of a Rohn Tower (25G equilateral triangle design) with concrete base. The belowground sensors were placed within 1 m of the base.
The air temperature and relative humidity probes were installed at approximately 2.5 m above the ground surface. The wind monitor and quantum sensor were mounted on a cross bar about 3 m above the ground. The quantum sensors were swapped and calibrated as follows: NADP on 2013-08-08 and 2021-05-19; S2 forest on 2011-07-13; Bog Lake on 2010-09-12, 2014-05-23, 2017-07-10, and 2020-10-06. PAR data have not been adjusted for sensor drift.
The 107 thermistor sensors and water content reflectometers were vertically inserted into surficial soil (~0-10 cm). The CS616 soil moisture sensors were installed vertically into the soil and each extends from about the soil surface to about a 30-cm belowground depth. Both types of sensors were inserted perpendicular to the slope of the land surface. For the S2 forest station, ingrowth of tree and shrub branches was trimmed as needed, at least once each one- to two-years, to prevent interference with movement of the wind monitor. The factory calibration was used for the water content reflectometers.
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.
REFERENCES:
Nyberg, P. R. (1987), Soil survey of Itasca County, Minnesota, 197 pp, USDA Soil Conservation Service.
