Browsing by Author "Milton, S. J."
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- ItemThe distribution of invasive Pennisetum setaceum along roadsides in western South Africa: the role of corridor interchanges(European Weed Research Society, 2010) Rahlao, S. J.; Milton, S. J.; Esler, K. J.; Barnard, P.Roads and rivers may be dispersal corridors for invasive alien grass seeds that fly and float. These two systems interact at bridge interchanges that are also disturbed artificial habitats. The invasive grass Pennisetum setaceum (perennial fountain grass) establishes on roadsides and river banks and benefits from habitat conditions prevailing at these interchanges. The distribution of the grass across biomes and vegetation types and the influence of environmental variables were assessed. A road survey method was used to record and map the distribution of P. setaceum along 1 km roadside transects at 10 km intervals and at every road-river corridor interchange for 5112 km of South African national roads in the arid and semi-arid parts of the country. Pennisetum setaceum populations occurred in 10% of the total length sampled, including the interchanges. Fynbos Swartland Shale Renosterveld was the most significantly invaded amongst the vegetation types surveyed. Our results indicate that, although P. setaceum performs better on the interchanges, it does not preferentially colonise them over other parts of the landscape. The presence of P. setaceum was, however, closely associated with the presence of water bodies and disturbances away from the roads. Corridor interchanges should be considered important targets of both local and regional efforts to prevent and control P. setaceum invasions.
- ItemNutrient addition and moisture promote the invasiveness of crimson fountaingrass (Pennisetum setaceum)(Weed Science Society of America, 2010) Rahlao, S. J.; Esler, K. J.; Milton, S. J.; Barnard, P.We conducted a greenhouse study to examine the effects of different habitat conditions and environmental resources on the growth rates of crimson fountaingrass, an invasive, alien, perennial grass in South Africa. To help understand the factors promoting the spread of this emergent alien grass, we investigated the effects of temperature regimes, nutrient and moisture addition, and soil type on seedling growth rates and biomass allocation. Our results suggest that crimson fountaingrass seedlings do not tolerate drought because they died within 1 mo without water. Additional nutrients and extra water increased seedling growth rates throughout the study period. Higher temperatures with extra moisture increased seedling growth rates and the development of belowground biomass throughout the study period. This study demonstrates the importance of available environmental resources and their interaction with some habitat conditions in promoting crimson fountaingrass growth. We suggest that soil moisture and nutrient availability are critical factors affecting successful establishment of crimson fountaingrass in arid environments. Managers should target seedlings for removal following precipitation and in areas of nutrient enrichment, such as near rivers and at road–river crossings.
- ItemThe threat of alien invasive grasses to lowland Cape floral diversity : an empirical appraisal of the effectiveness of practical control strategies(Academy of Science for South Africa, 2005) Musil, C. F.; Milton, S. J.; Davis G. W.EUROPEAN ANNUAL GRASSES IN HIGHLY fragmented natural ecosystems along the South African west coast are displacing wildflowers, which form the basis of a growing lucrative, nature-based tourist industry. We examined the cost-effectiveness of different labour-intensive strategies linked to a national poverty relief programme for controlling invasive annual grasses in renosterveld. The treatments tested involved combinations of grass mowing, hand-clearing, light and intense burning and pre-emergent herbicide application randomized over forty-eight 100-m2 plots in the Tienie Versfeld Wildflower Reserve. Springtime vegetation responses were monitored over two successive years; labour, capital equipment and consumable costs were audited. Total clearing costs associated with intense burning of uncut grass (R415/ha), grass mowing (R924/ha) and light intensity burning of mowed grass (R1338/ha) were all less than those (up to R1 927/ha) reported for clearing dense stands of woody aliens. However, costs of hand-clearing of grass (R6743/ha) and pre-emergent herbicide application (R13 380/ha) were much greater. Intense burning, the cheapest strategy overall, was ineffective as this promoted recruitment of both alien invasive annual and perennial grasses and inhibited recruitment of native geophytes. We conclude that mowing of grass-infested renosterveld prior to grass seed maturation, and the removal of the cut grass biomass for use as fodder in restricted feed lots to offset clearing costs, provides the most credible strategy for controlling the annual grass populations to conserve native floral diversity over the short term.