LTER Zöbelboden, Austria, Soil chemistry, 1992

he soil data originates from soil inventory 1992 covering the entire study area of 90 ha.
The forest floor was sampled once with a 30x30cm frame. The mineral soil was sampled with a metal pole with a 70-mm diameter at 3 points within a distance of two meters. Each undisturbed soil core was placed in polystyrene cases and divided into the following geometric horizons (0-5, 5-10, 10-20, 20-30, 30-50 cm). In 1992 all geometric horizons were sampled triply. Subsequently, the corresponding geometric horizons were pooled.

In the laboratory samples were weighted. Green plant material like roots and grasses were separated, weighted, dried at 30°C until constant weight, re-weighted and stored separately. The remaining material was weighted, dried at approximately 30°C until constant weight, whereas coarse aggregates have been crushed and re-weighted again. The dry soil was sieved through a 2.0 mm sieve and subsequently 10 g of the samples were dried at 105° C until constant weight. In contrast to the mineral soil, the forest floor was milled for 15 minutes before sieving and drying at 105°C.
Water content was measured as mass loss at 105° C. Soil pH was measured electrochemically in 0.01 M CaCl2 suspension with a pH electrode (Metrohm 654 pH meter). The total content of C (TC) was analyzed by dry combustion (1300°) of the samples in O2. Released CO2 was detected coulometrically (Ströhlein Cou-lomat 702 and Si 111/6). The total content of CaCO3 (TIC) was measured via ad-dition of HCl and volumetrical determination of the released CO2 (“Scheibler”). The total content of organic C (TOC) was calculated by subtracting the total con-tent of CaCO3 from the total content of C (TC – TIC). The total content of N was primarily determined by a modified Kjeldahl method. The organic N was converted to NH4+ by digestion with H2SO4 and a catalyst (Kjeldahlterm KT8 Gerhardt). The accumulated NH4+ was converted to NH3 (distillation) and measured by potenti-ometric titration. To account for nitrogen oxygen compounds, salicylic acid was added prior to digestion. For the total content of P and heavy metals, samples of 2 g mineral soil and 1 g forest floor, respectively were digested with 5 ml of HNO3 followed by 2 ml of HClO4. In 1992 the element concentrations were determined using an ICP-OES (P, Cu, Cr, Mn, Ni, Pb, Zn) (Jobin-Yvon 70+) and GF-AAS (Cd). In 2004 all heavy metals and P were determined using ICP-OES. The total content of sulphur was analyzed by dry combustion (1300°) of the samples in O2. The released SO2 was detected coulometrically (Ströhlein Coulomat 702 and Si 111/6). In 2004 the total content of S was analysed via digestion with HNO3/HClO4 and ICP-OES. Exchangeable cations (Ca, Mg, K, Na, Mn, Fe, Al) were extracted in 0.01 M BaCl2 and analysed by ICP-OES.