Application of the phytomass and elemental stock model 'PhytoCalc' under clear-cut conditions.

摘要

The applicability of the phytomass and elemental stock model "PhytoCalc" under clear felled conditions was assessed. Two model versions were consulted, focusing upon 4 widespread and biomass-rich species at small clear felled within even-aged Picea abies stands in central German highlands and 1 appropriate species within them: Oxalis acetosella, Digitalis purpurea, Deschampsia flexuosa, Pteridium aquilinum and Rubus idaeus. Both PhytoCalc versions failed at clear felled sites for now, because the balances of energy, matter and water, influencing the understorey phytomass are significantly different compared to the forest stand. Liming effects, deviations in harvesting time and user bias were found to be possible sources of error as well as the determination of the 2 simple model parameters ground coverage and mean shoot length can be challenging in some special cases. Nevertheless, PhytoCalc was found to be an easy, cheap and fast approach that should be chased further one to obtain dry weight and elemental stocks of understorey phytomass. The model seems to be applicable for wooden species of low height as shown with juvenile, up to 1 m high Picea abies. The calibration efforts should now first focus on reliable functions for dry weight even under extreme conditions like clear felled for as much species as possible.