Plant traits and canopy types: seasonal and local variation in a grazed semideciduous temperate woodland
Arturi, Marcelo F.; Pérez, Carolina A.; Torres Robles, Silvia
In this study the plant functional types approach is used to seek functional groups of herbaceous layer associated to different canopy types – evergreen tree, deciduous tree and no tree cover – in a temperate woodland, Argentina. Such classification could be useful in predicting vegetation changes associated with land use and climate changes affecting the cover of different canopy types. Two sites with different grazing intensity were studied in the cool and warm season using a total of 104 plots. A total of 57 plant species was registered which were grouped on the basis of growth habit (graminoid, erect, creeping and rosette) and growth phenology (warm – cool season). A discriminant analysis was conducted in order to evaluate the discrimination among canopy types attained on the basis of group covers. A comparison was made between the discrimination ability of these a priori groups and that of individual species and random groups. Species belonging to the same group exhibited similar correlations with canopy types. Ecological homogeneity of groups was also supported by the similar discrimination of canopy types attained with the groups and individual species. About 30% (cool season) and 10% (warm season) of random groups discriminated between canopy types so well as a priori groups. However, less than 5% of random groups discriminated similarly to a priori groups when constrained to be at least as strongly correlated to canopy types as a priori groups. The combination of growth habit and phenology yielded ecologically meaningful groups. Erect and graminoid plants exhibited a strong positive correlation with no tree cover. Cool season and warm season creeping plants were associated with deciduous and evergreen tree canopy respectively. A positive association with grazing and deciduous tree canopy was a common trend among cool season plants which were predominantly annual. Plant functional types defined by growth habit and phenology could be useful in predicting changes of grassland and understory vegetation as a response to variations in the canopy cover and type.