Evidence on ecotone concepts from switch, environmental and anthropogenic ecotones

Abstract

Abstract. Four contrasting ecotones were sampled to address three questions: (1) Are there ‘ecotonal’ species, (2) Do ecotones possess higher (or lower) species richness than the adjacent communities? and (3) Are exotic species more likely to occur in ecotones? One ecotone was edaphic, one was apparently caused by a positive‐feedback switch, one was environmental/anthropogenic and one was entirely anthropogenic. The exact position of each ecotone was established from the spatial change in ordination scores. Ecotonal species, in the sense of species mainly restricted to the ecotone at the site, were present in all four ecotones. All but one of the ecotonal species were native. The switch ecotone and the purely anthropogenic ecotone also contained native species that were significantly more frequent in the ecotone than in either adjacent community. Species richness was intermediate between that of the two adjacent communities in three of the ecotones. In the environmental/anthropogenic ecotone, species richness was higher than in adjacent communities, but not significantly so. There were appreciable numbers of exotic species in the two ecotones with anthropogenic influence, one of which had a proportion of exotic species intermediate between the two adjacent communities. Contrary to theory, the proportion of exotic species in the second ecotone was significantly lower than in either adjacent community. We conclude that all three features we examined depend on the particular ecological conditions and the ecology of the species present; they are not intrinsic properties of ecotones.

Floristic and phytosociology in a physiognomic gradient of riverine forest in Cerrado, Campinas, SP

“…3 The transition between riparian forests and savannas did not present particular floristic and phytosociological structure. This transition was very variable one to the other, as already observed between different ecotonal areas (Lloyd et al 2000, Kark & Van Rensburg 2006. Small similarity among the analyzed riverine forests highlights particularities of this type of vegetation and the importance of studying these areas for knowing their flora in each region, especially when considering restoration or management actions.…”

“…There are ecotone areas with different environmental characteristics that do not fit the expectation of greater biodiversity than limitrophe areas (Lloyd et al 2000). Biodiversity is not intrinsic property of ecotones, since it depends on the particular ecological conditions of the site and on the ecology of the present species (Lloyd et al 2000).…”

“…Ecotones frequently support high levels of biological diversity (Risser 1995, Van Rensburg et al 2009), though it is controversial whether they represent special areas of speciation and diversity (Kark & Van Rensburg 2006). There are ecotone areas with different environmental characteristics that do not fit the expectation of greater biodiversity than limitrophe areas (Lloyd et al 2000). Biodiversity is not intrinsic property of ecotones, since it depends on the particular ecological conditions of the site and on the ecology of the present species (Lloyd et al 2000).…”

Ecotones as indicators: boundary properties in wetland-woodland transition zones

“…Conflicting theories and evidence for ecotones predict that parameters are higher, lower or intermediate compared to the values found in the neighbouring areas (Lloyd et al 2000, Ries et al 2004, McIntire and Fortin 2006, Brownstein et al 2013. Some predict species richness should be higher within the ecotone than in adjoining communities due to a greater number of potential niches, while others predict species richness to be lower due to stress from environmental fluctuation (van der Maarel 1976, Lek-Ang et al 2007, Liu and Cui 2009 cover indicate that most species are adapted to either a wet or dry environment with very few species spanning the length of the moisture gradient.…”

“…The identity of ecotones (i.e., the type and extent of community composition shifts) can vary spatially and temporally (Danz et al 2013). Ecotones and their properties have been described in a wide range of systems; along gradients of bird distributions (Williams et al 1999), at grassland-forest edges (Danz et al 2013, Erdős et al 2013) and at wetlandforest boundaries (Carter et al 1994, Kirkman et al 1998, Brownstein et al 2013; in both natural and modified habitats (Lloyd et al 2000, Walker et al 2003. However, studies of vegetation dynamics in ecotones often report findings that are contradictory or inconsistent with each other and there is little agreement about how ecotones function.…”