Straits Flux long-term carbon flux monitoring station - site description

Latitude	51^o10' 38"
Longitude	00^o50' 53"
Altitude	80 masl
Slope	0^o
Soil	A pelo-stagnogley which has a depth of 80 cm to the C horizon of the cretaceous clay. PH is 4.6 in the upper, organic horizon and 4.8 in the mineral layer.
Stand description and management	The stand dimensions are 900 m x 1000 m, with the whole area planted as a monospecific stand during the 1930s. The mensuration plot was thinned in 1991, 1994, and 1999. The stand is an area of production forest, and as such, management intervention in areas is almost continuous.
Meteorology and pollution climate	Annual precipitation is 779 mm (30 year average); Mean annual temperature = 9.5oC; Global radiation = 3445 MJ m-2; Nitrogen deposition (excluding dry deposition from stomatal uptake) averaged 12.3 kg ha-1 yr-1 between 1995 and 2002; Ozone AOT40 was 4.8 ppmh in 1999. Long term (1950-present) climate data are available (UK met. Office) within 5 km of the site (at the same altitude), and an automatic weather station was installed adjacent to the climatic station in 1994.
Mensuration data	495 trees per hectare; Top height = 20.5 m; DBH = 29.0 cm; Basal area = 23.4 m2/ha; General yield class (MAI) = 6 (m3/ha/yr).
Species	Quercus spp. (Q. robur and Q. petraea) with approximately 10% Fraxinus excelsior.
Ground vegetation	The unserstorey is dominated by Corylus avellana, Crategus mongyna, Rubus spp. with a herbaceous layer of various grasses and herbs. Understorey/ground vegetation leaf area index and biomass were determined during the 1999 growing season; LAI of the understorey varied between 2.3 and 3.6 in July, with primary production of the ground flora ranging between 1.2 and 2.4 t ha-1.
Leaf area index of overstorey (in 1998)	Litter traps analysis indicates an overstorey LAI of 6.2 (varying between 6.0 and 7.5) for the ICP forests, level II intensive forest health monitoring plot. This value was used to calibrate the derived measurements of LAI from diffuse light transmission, yielding a value of 4.8 for the area immediately surrounding the flux tower. A full LAI survey of the stand was carried out in 1999.
Instrumentation	Edisol Eddy correlation system; Net radiometer; Solarimeter; Tube solarimeters above and below canopy; Psychrometer; Annemometer; Wind vane; Soil moisture (theta probe); Soil temperature all 30 minute mean values; Soil TDR probes at 0-15, 15-30, 30-60, 60-90, 90-120 cm which are measured once per week. Automatic girth bands were installed on five trees in April 1998.
Flux data	The equipment was installed in March 1998. 85 % data capture has been exceeded since the beginning of May 1998 (>95% for most months). Mean NEP is 3.6 t ha/yr. Respiratory fluxes are based upon a base rate of 4.19 nmol/m2/s with a Q10 of 2.28 (1998 night-time data). Measurement height is approximately 8 m above the canopy.

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