Native and non-native species in annual grassland vegetation in Mediterranean Chile
Deil, Ulrich; Alvarez, Miguel; Paulini, Inge
Annual grassland in Mediterranean Chile is often considered as secondary vegetation, dominated by neophytic species of Western Palaearctic origin. During a field trip in the 6th Region of Chile we stated many native annuals that characterize the early spring ecophase, when the topsoil is waterlogged. To study the contribution of native and non-native species to grassland and vernal pool vegetation in Mediterranean Chile, 16 relevés were sampled in the open sectors of a grazed Acacia caven woodland near Las Cabras (6th Region). Potential natural vegetation is an evergreen forest with Lithrea caustica and Cryptocarya alba.Hierarchical clustering and CA resulted in two groups. In both clusters, the number of native species is surprisingly high (about 50%). Cluster A is characterised by specialists of ephemeral wetlands. Some of them are endemic to Chile such as Soliva sessilis and Crassula closiana, others are amphi-neotropical vernal pool taxa like Deschampsia danthonioides, or associated to ephemeral wetlands vegetation in Europe (class Isoeto-Nanojuncetea) like Juncus bufonius and Juncus capitatus. They occur on animal footpaths, submitted to strong grazing and trampling, with compacted soil and waterlogging during the rainy season. Vernal pools, embedded into Acacia caven pseudosteppes in other parts of Chile, have not been found in the study area.Cluster B is dominated by species of Euro-Mediterranean origin, colonizing better drained and nutrient poor soils, such as Aira caryophyllea, Leontodon taraxacoides and Filago gallica. They are diagnostic species of the Chaetanthero-Vulpion, a Chilean alliance with floristic and ecological resemblance to the European Helianthemetalia guttati. To which extent the floristic difference of both clusters is an effect of the seasonal dynamic, has to be studied in the future by a permanent plot approach. Vernal pools seem to play a major role as primary habitats for the endemic annual flora of Chile.