Human activity facilitates altitudinal expansion of exotic plants along a road in montane grassland, South Africa

Kalwij, Jesse M., Robertson, Mark P. and van Rensburg, Berndt J. (2008) Human activity facilitates altitudinal expansion of exotic plants along a road in montane grassland, South Africa. Applied Vegetation Science, 11 4: 491-498. doi:10.3170/2008-7-18555


Author Kalwij, Jesse M.
Robertson, Mark P.
van Rensburg, Berndt J.
Title Human activity facilitates altitudinal expansion of exotic plants along a road in montane grassland, South Africa
Journal name Applied Vegetation Science   Check publisher's open access policy
ISSN 1402-2001
1654-109X
Publication date 2008-12-01
Sub-type Article (original research)
DOI 10.3170/2008-7-18555
Volume 11
Issue 4
Start page 491
End page 498
Total pages 8
Place of publication Malden, MA, United States
Publisher Wiley-Blackwell Publishing
Language eng
Formatted abstract
Question: Do anthropogenic activities facilitate the distribution of exotic plants along steep altitudinal gradients?
Location: Sani Pass road, Grassland biome, South Africa.
Methods: On both sides of this road, presence and abundance of exotic plants was recorded in four 25-m long road-verge plots and in parallel 25 m x 2 m adjacent land plots, nested at five altitudinal levels: 1500, 1800, 2100, 2400 and 2700 m a.s.l. Exotic community structure was analyzed using Canonical Correspondence Analysis while a two-level nested Generalized Linear Model was fitted for richness and cover of exotics. We tested the upper altitudinal limits for all exotics along this road for spatial clustering around four potential propagule sources using a t-test.
Results: Community structure, richness and abundance of exotics were negatively correlated with altitude. Greatest invasion by exotics was recorded for adjacent land at the 1500 m level. Of the 45 exotics, 16 were found at higher altitudes than expected and observations were spatially clustered around potential propagule sources.
Conclusions: Spatial clustering of upper altitudinal limits around human inhabited areas suggests that exotics originate from these areas, while exceeding expected altitudinal limits suggests that distribution ranges of exotics are presently underestimated. Exotics are generally characterised by a high propagule pressure and/or persistent seedbanks, thus future tarring of the Sani Pass may result in an increase of exotic species richness and abundance. This would initially result from construction-related soil disturbance and subsequently from increased traffic, water run-off, and altered fire frequency. We suggest examples of management actions to prevent this.
Keyword Alien
Dispersal
Disturbance
Gradient analysis
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Biological Sciences Publications
 
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