ABSTRACT
Human land use significantly influences important properties of terrestrial ecosystems,
e.g. energy flow, standing crop and biomass turnover. The socio-economic interference
with ecological energy flows may be studied empirically by calculating the „human appropriation
of net primary production“ (in short: „NPP appropriation“) resulting from two
processes: The change in average primary productivity of ecosystems caused by land use
and the harvest of biomass from ecosystems. NPP appropriation is defined as difference
between the NPP of the potential vegetation and the proportion of the actual NPP
remaining in ecosystems after harvest. Land use also influences the amount of biomass
and carbon stored in live vegetation. Changes in land use can thus lead to significant net
carbon flows between the vegetation and the atmosphere. By comparing the standing crop
of the potential vegetation and the actually prevailing vegetation we demonstrate the
human impact on standing crop and the amount of carbon stored in live vegetation. By
relating standing crop and NPP we estimate the impact of land use on biomass turnover.
We discuss these concepts using empirical results for the aboveground vegetation in
Austria calculated from statistical data and from land use and land cover models derived
from remote sensing data. According to our calculations the human appropriation of aboveground
NPP in Austria amounts to 51% today and has gradually declined to this value
from 53% in 1950. The standing crop of the actually prevailing vegetation is about 64%
lower than that of the potential vegetation. Biomass turnover has been accelerated by a
factor of 2.4.
Key words: Land use and cover change, net primary production, standing crop, carbon
flows, remote sensing, human impact on ecosystems.
