University of Michigan Biological Station

AmeriFlux sites US-UMB and US-UMd

The ecological research site for the UMBS Forest Carbon Cycle Research Program is located at the University of Michigan Biological Station (UMBS) in northern lower Michigan, USA. The research is centered around two meteorological (eddy covariance) towers that are part of the AmeriFlux network: a long-term observation tower and a tower within a disturbed area installed as part of the Forest Accelerated Succession ExperimenT (FASET experiment). For more information on the UMBS area, visit the UMBS research website.

site location map
UMBS is located in northern lower Michigan, approximately 40 km south of the straits of Mackinaw.
site topo map
The research site is about 1.5 km south of Douglas Lake and 3 km west of the UMBS facilities.

UMBS AmeriFlux Towers

There are two meteorological towers at UMBS that are part of the UMBS Forest Carbon Cycle Research Program.

UMBS AmeriFlux Tower (US-UMB)

Site summaries are available from LBL AmeriFlux, ORNL AmeriFlux, and ORNL FLUXNET

Tower instrumentation
45.559722° N
84.713778° W
elevation 234 m amsl

A 46-m, self-supporting tower with associated lab building, power, and communication lines was completed in June, 1998. At the end of June and in July 1998 the instrument booms, data loggers, communication and gas-flow lines, and the eddy correlation and radiation sensors were installed on the two main observation levels of the tower (46 m and 34 m, see the schematic representation of the tower set-up, below). The flow control system was installed in September and data collection on the top level started on September 22, 1998. The profile measurements of mean temperature, humidity and CO2 concentration through the canopy and up to the 46 m level on the tower was completed in March, 1999.

Schematic of the UMBS-Flux tower showing location of sensors and the lab building. Canopy height is approximately 20 m.

On each level on the tower the sensors (sonic, radiation components, temperature and humidity) are interrogated by a CR23X datalogger. Calculation of mean statistics and “on-line” estimates of sensible heat flux and u* are performed by the CR23X and stored in the logger’s data buffer. These CR23X stations are periodically called by a telecommunication program from a Windows NT workstation in the tower lab building. Both 10Hz sonic data and the mean statistics are downloaded via a T1 line and written onto a magneto-optical disk (MO, 4.6 GB capacity). Ambient air is admitted to a teflon tube through an intake funnel close to the sonic anemometer array, to allow eddy correlation. It subsequently passes through a filter and is pumped through a LICOR-6262 IRGA inside the tower lab. All IRGAs are located inside the climatized lab building and are interrogated for CO2, water vapor, cell-pressure and cell-temperature by a CR23X. The lag in the IRGA data collection is accounted for by the post-processing program, using the standard method of correlation optimization, following (e.g.) Leuning and Judd (1996)
. Both the raw eddy correlation data and the mean statistics are routinely stored on MO discs and transferred to Indiana University, where postprocessing and analysis occur.

UMBS-Disturbance AmeriFlux Tower (US-UMd)

Site summaries are available from LBL AmeriFlux, ORNL AmeriFlux, and ORNL FLUXNET

45.5625° N
84.6975° W
elevation 239 m amsl

This tower began operation in 2007 as part of the Forest Accelerated Succession ExperimenT (FASET).

tower sites map
Map of the FASET and Control flux sites. The Control site is the existing AmeriFlux tower and surrounding forest. Closed circles are 0.08 ha permanent sampling plots. Stippled areas denote where girdling of all aspen and paper birch will occur in the spring of 2008.
FASET site map
Detailed map of the FASET site showing grid layout within the girdle treatment area, plant demography plots, and the baseline and intensive 0.08 ha plots. The 21, 0.08 ha plots and the 1.1 ha plot had all trees with a diameter at breast height = 8 cm measured, identified, tagged, and mapped. The intensive plots and the 1.1 ha plot include litter traps, minirhizotron tubes, N mineralization plots, and soil lysimeters.

Vegetation, soils, and climate

The University of Michigan Biological Station lies on lake-border plains in the transition zone between the mixed hardwood and boreal forests. The UMBS AmeriFlux towers lie on level to gently sloping high outwash plain derived from glacial drift, with the gradually ascending slope of an interlobate moraine lying ~1 km to the south. Soils are predominantly excessively drained spodosols. Bigtooth aspen (Populus grandidentata) and trembling aspen (P. tremuloides) dominate within a 1-km radius of the eddy-covariance tower, but with significant representation by red oak (Quercus rubra), beech (Fagus grandifolia), red maple (Acer rubrum), white pine (Pinus strobus), and hemlock (Tsuga canadensis) as well. Understory is dominated by bracken fern (Pteridium aquilium) and saplings of red maple, red oak, beech, and white pine. The presettlement white pine, red pine, hemlock forest was cut around 1880, and the area disturbed repeatedly by fire until 1923.

Latitude: 45° 35′ N
Longitude: 84° 42′ W
Mean annual temperature: 6.20°C
Mean annual N mineralization: 11
Mean annual precipitation: 750 mm
Slope: 1–7 percent


Stand age: 90 years
Canopy height: 20 m
Leaf area index (LAI): 3.7
Basal area: 23.7 (m^2 ha^-1)
Max dbh: 62 cm
Mean dbh: 14 cm


Percent sand/silt/clay: 93/6/1
Texture: loamy med. sands
Classification: entic Haplorthod
pH: ~4.8


Biomass distribution (kg/ha) within the 60 m AmeriFlux plot, 1997

Tree Species Leaves and twigs Live branches Dead branches Bole Total
Acer rubrum 349 1,575 298 8,936 11,158
Amelanchier sp. 0 0 0 2 2
Betula papyrifera 237 1,072 2,997 7,783 12,089
Fagus grandifolia 12 85 167 274 538
Pinus resinosa 36 47 17 403 504
Pinus strobus 2,027 5,608 8 5,618 13,261
Populus grandidentata 1,014 6,184 1,992 57,460 66,649
Populus tremuloides 2 6 3 45 56
Quercus rubra 507 4,019 742 16,029 21,297
Grand total 4,184 18,597 6,223 96,550 125,554


Datasets of precipitation, temperature, evaporation, and other climatological information are available from the UMBS website.