Plant functional types on gradients of disturbance intensity and resource supply II: transferability across an urban and an agricultural landscape.

Michael Kleyer

The vegetation of an urban landscape was sampled on a range of sites representing gradients of resource supply and disturbance intensity. Groups of plants with similar biological traits become “functional groups”, if they display significant optima or maxima on a gradient plane of these environmental variables. The biological traits refer to expansion, vegetative regeneration, generative reproduction, dispersal, and seed bank longevity. Resource supply is calculated for each site as a combination of soil moisture, nitrogen supply, and available phosphorus using PCA. Disturbance intensity is also recorded for each site. A similar study was performed in a nearby agricultural landscape (Kleyer 1999). The logistic regression models from the urban landscape were applied to the data set of the agricultural landscape and vice versa. For each transfer the association between predicted probabilities and observed occurrences was measured and tested. Although the overall environment of the two landscapes is very different, recurrent patterns can be found for several functional types. At high resource supplies and high disturbance intensities, validated PFT´s encompass species with long-distance dispersal, persistent seed bank, high generative reproduction, and low vertical expansion predominate. At medium disturbance intensities, vertical expansion and vegetative regeneration increase with resource supply, in contrast to lateral expansion, seed bank longevity and generative reproduction.