Patterns of exotic plant invasions in fragmented urban and rural grasslands across continents

• Published in: Landscape ecology Vol. 23; no. 10; pp. 1243 - 1256
• Main Authors: Cilliers, Sarel S, Williams, Nicholas S. G, Barnard, Francois J
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Dordrecht Dordrecht : Springer Netherlands 01.12.2008; Springer Netherlands; Springer; Springer Nature B.V
• Subjects: Animal, plant and microbial ecology; Applied ecology; Biodiversity; Biological and medical sciences; Biomedical and Life Sciences; Conservation biology; Continents; Ecology; Environmental Management; Fundamental and applied biological sciences. Psychology; General aspects; Grasslands; Introduced plants; Introduced species; Invasions; Invasive species; Landscape Ecology; Landscape/Regional and Urban Planning; Life Sciences; Natural vegetation; Nature Conservation; Nonnative species; Plant ecology; Research Article; Rural areas; Sustainable Development; Urban areas; Urban environments; Urbanization; Australia; South Africa; Rural; Urban; Grasslands; Exotic species invasion; Gap dynamics; Edge effects; Grassland; Urban . Grasslands; Introduced species; Rural environment; Urban area; Invasion; Fragmentation; Dynamics; Edge effect; Continents; Plant introduction
• ISSN: 0921-2973; 1572-9761
• DOI: 10.1007/s10980-008-9295-7

Linear native grassland remnants in fragmented landscapes are usually at a great risk of exotic species invasion from their edges. Changes in species distribution near habitat edges are extensively studied in ecology as knowledge about edge responses is important to understand the development of patterns and processes in landscapes. However, elucidating robust general principles for edge effects has been difficult as species responses to habitat edges are highly variable and dependent on a large number of attributes which affect the function and structure of edges and therefore the distance that edge effects penetrate into fragmented natural vegetation. The objective of this study was to investigate the generality of exotic species invasion patterns from edges in native grassland patches surrounded by urban and rural landscapes. This was done by comparing the results of research from Victoria, Australia with a similar study from North-West Province, South Africa. Despite their occurrence on different continents, the grasslands are floristically and structurally similar and are dominated by the same grass species. Invasion patterns were quantified using two spatial statistics methods; block kriging and spatially constrained clustering. Two distinct patterns of exotic species invasion were identified in native grassland remnants in South Africa and Australia, namely exotic species invasion from the edge where the cover of exotic species increased with increasing proximity to the edge and a pattern that suggests that gap phase vegetation dynamics may also drive exotic species invasion at urban grasslands. Although urbanization and weed invasions are complex processes similar patterns of exotic species invasion in urban grasslands were found in two different continents suggesting that general patterns may occur. Implications of this for the conservation of native grasslands in contrasting landscapes are discussed.