Plant functional traits and groups in a Californian serpentine chaparral

We studied a type of Californian ultramafic chaparral to determine functional groups which can help reduce the complexity of ecosystem management. The study was realized in McLaughlin Reserve, State of California, USA. We analysed the species of a serpentine plant association previously phytosociologically described in the area: Ceanotho albiflori-Quercetum duratae for their functional traits and functional groups. Traits per species were measured building a trait database. We used Principal Component Analysis to identify the combination of functional traits with major weight and a neighbor-joining clustering to define functional groups for this vegetation association. Our results indicated that the studied association is dominated by phanerophytes, with low degree of spinescence. Leaves were mainly malacophyllous with high degree of tomentosity, reduced size and a partial shedding of leaves was observed during summer. We considered six functional groups as the optimum number of clusters in a total of 18 species. The two first functional groups were composed of chamaephytes with brachyblasts and dolichoblasts with differences in the degree of tomentosity. The rest of the functional groups were composed of phanerophytes where the differences between them were based on traits in relation to the branches, leaf size and the horizontal development of the root system. The functional groups obtained show that this serpentine chaparral is composed of species with a wide range of functional traits. The study of other Mediterranean serpentine ecosystems in California and elsewhere could contribute to create new perspectives of functional ecology and help in the management of these valuable ecosystems.