T. Wohlgemuth, MODELING FLORISTIC SPECIES RICHNESS ON A REGIONAL-SCALE - A CASE-STUDY IN SWITZERLAND, Biodiversity and conservation, 7(2), 1998, pp. 159-177
In this paper a multivariate linear regression model is proposed for p
redicting and mapping regional species richness in areas below the tim
berline according to environmental variables. The data used in setting
up the model were derived from a floristic inventory. Using a stepwis
e regression technique, five environmental variables were found to exp
lain 48.9% of the variability in the total number of plant species: na
mely temperature range, proximity to a big river or lake, threshold of
minimum annual precipitation, amount of calcareous rock outcrops and
number of soil types. A considerable part of the unexplained variabili
ty is thought to have been influenced by variations in the quality of
the botanical inventory. These results show the importance of systemat
ic floristic sampling in addition to conventional inventories when usi
ng floristic data as a basis in nature conservation. Nevertheless it i
s still possible to interpret the resulting diversity patterns ecologi
cally. Regional species richness in Switzerland appears to be a functi
on of: (i) environmental heterogeneity; (ii) threshold values of minim
um precipitation; and (iii) presence of calcareous rock outcrops. Acco
rding to similar studies, environmental heterogeneity was the stronges
t determinant of total species richness. In contrast to some studies,
high productivity decreased the number of species. Furthermore, the im
plications of this work for climate change scenarios are discussed.