Forest decline and pedobiological characteristics of humus forms in the Šumava National Park

Humus forms dynamics and characteristics of different forest sites were studied in the area of Smrčina Mt. in the Šumava National Park territory. The study was performed in vital Norway spruce forest, dead Norway spruce forest (bark beetle Ips typographus infestation) and on a clear-cut area (site conditions were comparable for all three plots). The amount of surface organic matter was not affected by forest decline or by clear-cut (95.5 t/ha, 73.1 t/ha and 100.2 t/ha, respectively), pH being comparable (between 2.3 and 3.2 pH KCl). A slight favourable effect of grass litter on pH increase was obvious; higher leaching of bases occurred in lower horizons. Nitrogen losses were detected from the L + F horizons, falling from 1.93-1.83% (living stand) to 1.73-1.83% (clear-cut area). Higher ammonia production was documented in substrates (F and H horizons) from the living stand (from 263 and 103 mg/kg before incubation to 610 and 248 mg/kg after incubation - nitrogen content in ammonia form), and higher nitrification rates (nitrogen content in nitrate form) were recorded on the clear-cut area (103 and 80 mg/kg to 153 and 87 mg/kg) and especially in the dead stand (160 and 93 mg/kg to 216 and 139 mg/kg). Respective values for the living stand increased from 52 and 61 mg/kg to 119 and 84 mg/kg. Respiration activity, both potential and basic, was more balanced, indicating more intensive dynamics in the case of dead stand and clear-cut area.