Traditionally, numerous criteria have been used for selecting valuable areas for the establishment of nature reserves. In most cases these criteria are applied indiscriminately with the assumption that their generalized use gives them universal validity. In this study we test the value of different variables (area and shape of patches of natural vegetation, degree of internal fragmentation, and diversity of habitats at the periphery of patches) at the landscape level as indicators of plant richness and diversity, and relative abundance of native plants, in a group of natural vegetation relicts ranging from 0.004 km 2 to 1.027 km 2 and surrounded by sub-urban and industrial settings. Species richness, diversity, and number of native and exotic species increased with the area of the patches. The shape of the patch was the second most important variable to influence species richness and diversity. The number of exotic species increased with increasing numbers of native plants. Thus, patch size and plant richness should be carefully used for selecting conservation areas because it could result in choosing places threatened by the presence of exotics. Many of the other variables analysed showed no effects on biodiversity at the temporal and geographic scales considered. Ignoring these outcomes could result in choosing sub-optimal areas. We recommend the critical use of general criteria considering the selection process as an opportunity to evaluate the relevance of each criterion at the local level.
Coastal dunes of the southern Buenos Aires province, in Argentina, are one of the last remnants of biodiversity in the southern Pampa unit, within the Rio de la Plata Grasslands. While the direct loss of grasslands due to the advance of cities and afforestation is conspicuous, the negative effects of the subdivision of the remaining environments on biodiversity and ecosystem dynamics are less considered. Our work aimed to analyze the combined effect of fires and subdivision of grasslands by invasive alien trees. Our results suggest that fragmentation affects the resilience of coastal grasslands after fire and affects the course of succession, promoting the establishment of invasive alien plants. We also suggest that fires favor the advance of pines and acacias towards the interior of grassland remnants, further reducing their area. The effective conservation of the components of Pampas biodiversity that still persist in these coastal ecosystems will depend on preventing, mitigating and compensating the insularization effects associated with forest plantations and the expansion of invasive trees, by means of adequate territorial planning that allows remnants to be maintained in a good state of conservation.
Vegetation’s increased vulnerability to extrinsic disturbances is an important but less studied effect of natural habitat fragmentation. Fire is part of the evolutionary history of grassland ecosystems, but fragmentation by forest plantations can alter the fire regime and influence their resilience. This study compares the successional trajectories after fire in continuous and fragmented grassland in terms of composition and abundance of plant species. Grassland fragments of varying sizes (0.1 to 2.5 ha) surrounded by a forest matrix and grassland controls of an equivalent area in adjacent, non-fragmented sites were selected. Fire was associated with an increase in the abundance of exotic plants in the fragmented grassland whereas the continuous grasslands were much more resistant to invasion. These differences in the species composition between fragments and continuous areas, which were limited to the smaller areas before the fire, were observed one year after the fire throughout the range of sizes analyzed. These results show the impact of fragmentation on grassland resilience and how the effects of this process become evident even months after a disturbance, highlighting the synergistic effect of habitat fragmentation and biological invasions, two factors identified as the main forces of biodiversity erosion.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.