MEASUREMENT IN SMALL FOREST BASIN
The monitoring of a small forest basin is part of the measurement activities of the Košetice observatory from the very beginning of the station. The monitored catchment area is located 1 km from the observatory, its area is 0.285 km2 and the long-term average annual flow rate is 0.43 l·s-1 with specific outflow of 1.49 l·s-1·km-2. Approximately 90% of the catchment area is forested, with the rest being farmland. The forested part of the river basin is covered mainly by spruce monoculture mostly over 90 years of growth with the addition of pine, beech, larch and birch.
Forest brook is the only permanent tributary of the Anenský creek (the Želivka river basin). The basin is operated within the framework of the ICP-IM (International Cooperative Programme on Integrated Monitoring of Air Pollution Effects on Ecosystems) programme, aiming at improving the knowledge of the material balance and the exchange of substances in small wooded basins in a non-impact area.
Fig. 1 Surroundings of the Košetice observatory with a small forest brook basin.
The catchment area is also part of the Czech GEOMON monitoring system coordinated by the Czech Geological Survey (CGS). From the network of 14 small forest basins, using a common methodology, the input data are collected for the calculation of fluxes of ecologically important components as a way of assessing the status and development of the natural environment. The means of such assessment is the calculation of balance sheets, i.e. inputs and outputs of components in natural units of biosphere represented by small basin. Input to the basin is represented by the throughfall deposition (THF) and the free area precipitation deposition (BULK). Surface outflow from the river basin is considered as an output.
A measuring device — a hydrological weir is located on the 250 m long forest stream at its confluence equipped with an ultrasonic probe with a registration unit for continuous recording of the water level, flow rate and air temperature. Flow rate values are regularly verified by manual measurement together with a water temperature measurement that is not registered automatically. At regular monthly intervals, samples of surface water for chemical analyses are collected from the hydrological weir. Since 2008, the spring area of the stream is also part of the groundwater monitoring network of CHMI.
The soils in the forest brook are developed on biotite to sillimanite paragneiss, the area is part of the oldest geological unit of Bohemian Massif – Moldanubian. These are acid brown forest soils of the dystric cambisol type. Sampling and chemical analysis of soil samples took place in 1979, then in 1991, 1996, 2002, 2007 and 2015. The sampling sites are two soil probes, in proximity to which soil lysimeters were installed for monitoring of soil water chemistry. Sampling takes place at two depth levels, 20 and 40 cm below the surface. Silicone-carbide suction crucibles are used for the sampling by which water is extracted under pressure from an unsaturated zone using a portable vacuum system. Samples are taken monthly.
Atmospheric deposition represents the input of substances from the atmosphere into other components of the natural environment. In addition to the monitoring of precipitation in the open area of the Košetice observatory, the deposition under the forest vegetation is measured. The throughfall deposition monitoring under the crowns of trees is located at the eastern boundary of the forest basin and has been carried out continuously since 1990. 20 sampling devices are placed in stands at 50 x 50 m square diagonals. This device consists of a litre PE bottle attached to a funnel of the catching area 113, 09 cm2. Throughfall precipitation is taken monthly. THF monthly precipitation amount and chemical analysis of precipitation water are determined.
Wet deposition (WET ONLY) measurements are made on the area of the observatory, nowadays it is a daily sampling by the Eigenbrodt automatic precipitation collector. Another type of precipitation sampling is the collection of wet deposition with gravitational deposition of larger particles — total deposition (BULK). This is the same sampling device as the THF located on the open area of the observatory. Three sampling devices are in operation.
Results (only in czech):
Atmosférická depozice NH4-N (1990–2016). Atmosférická depozice NO3-N (1990–2016). pH srážkových vod (1990–2016).
Atmosférická depozice SO4-S (1990–2016). Látková bilance povodí (1990–2016) Látková bilance NH4-N v povodí (1990–2016).
Látková bilance NO3-N v povodí (1990–2016). Látková bilance SO4-S v povodí (1990–2016). Průměrné měsíční průtoky lesního potoka a měsíční podkorunové srážkové úhrny (1990–2016)