Diversity and Frequency of Clonal Traits Along Natural and Land-Use Gradients in Grasslands of the Swiss Alps

The frequency of clonal plants in different vegetation types is known to be influenced by environmental and land-use factors. However, the underlying behavior of individual clonal traits or clonal trait diversity has received little attention. Here, we assess for species- and trait-diverse grasslands of the Swiss Alps the relative importance of temperature, soil moisture, land use and species richness on the diversity and frequency of individual compared with all clonal traits. We further analyzed how cover-weighted data alters the relationships found with commonly used presence-absence data. We combined species compositional, land-use and environmental data from 236 28-m(2) grassland plots with clonal trait information for 527 species following the Clonal Growth Organ (CGO) classification. Test results are based on linear models, ANOVAs and ANCOVAs. The grassland sites were 84% dominated by clonal species. Drought-prone grasslands harbored the least clonal species. No increase in clonality was detected with decreasing temperature (= altitude). Mown or pastured grasslands had more clonal species than fallows. Certain sets of traits were correlated. Rhizomatous species especially reacted strongly to climatic and land-use gradients and had highest frequencies in cold, moist and disturbed sites. Clonal diversity was strongly dependent on species richness. Cover-weighted and presence-absence based estimates were largely similar. Overall, our data outlined that common clonal traits react differently to natural and land-use gradients as well as differently to the sum of clonal traits. Also, soil moisture was more decisive than temperature (= altitude) for the presence of clonal species. Lastly, the strong correlation between species-richness and clonal trait diversity needs to be accounted for when interpreting the functional role of clonal traits.