Patterns of alien plant distribution at multiple spatial scales in a large national park: implications for ecology, management and monitoring

Abstract

Aim Spatial scale is critical for understanding and managing biological invasions. In providing direction to managing alien plant invasions, much emphasis is placed on collecting spatially explicit data. However, insufficient thought is often given to how the data are to be used, frequently resulting in the incompatibility of the data for different uses. This paper explores the role of spatial scale in interpreting, managing and monitoring alien plant invasions in a large protected area.Location Kruger National Park, South Africa.Methods Using 27,000 spatially-explicit records of invasive alien plants for the Kruger National Park (> 20,000 km 2 ) we assessed alien plant species richness per cell at nine different scales of resolution.Results When assessing the patterns of alien plants at the various scales of resolution, almost identical results are obtained when working at scales of quarter-degree grids and quaternary watersheds (the fourth level category in South Africa's river basin classification system). Likewise, insights gained from working at resolutions of 0.1-0.5 km and 1-5 km are similar. At a scale of 0.1 × 0.1 km cells, only 0.4% of the Kruger National Park is invaded, whereas > 90% of the park is invaded when mapped at the quarter-degree cell resolution. Main conclusionsSelecting the appropriate scale of resolution is crucial when evaluating the distribution and abundance of alien plant invasions, understanding ecological processes, and operationalizing management applications and monitoring strategies. Quarter-degree grids and quaternary watersheds are most useful at a regional or national scale. Grid cells of 1 to 25 km 2 are generally useful for establishing priorities for and planning management interventions. Fine-scale data are useful for informing management in areas which are small in extent; they also provide the detail appropriate for assessing patterns and rates of invasion.

Managing invasions at the cost of native habitat? An experimental test of the impact of fire on the invasion of Chromolaena odorata in a South African savanna

“…In contrast, savanna habitats in Africa and Asia are mostly invaded by Neotropical woody plants, such as Lantana camara (L.) and Chromolaena odorata (L.) King and Robinson (Foxcroft et al 2009(Foxcroft et al , 2010. These woody invaders differ from the invasions by grasses in their effect on the fire regime.…”

Generating an agricultural risk map based on limited ecological information: A case study using Sicyos angulatus

“…Furthermore, several techniques involving species distribution models would allow the incorporation of several ecological parameters (Engler et al 2004;Guisan and Thuiller 2005). In addition, refining the geographic grain and extent of the model is very important to both implementation of the management plan and field-level activities (Foxcroft et al 2009;Osawa et al 2011;Akasaka et al 2012). In the present study, we used the 5-km mesh on a prefectural scale (i.e., local government) as the unit of analysis.…”

Constructing Standard Invasion Curves from Herbarium Data—Toward Increased Predictability of Plant Invasions

“…Different spatial scales may explain differing results between studies (Powell et al 2013), and greater insights can be drawn when analyzing data on a finer scale (Wiens 1989). For instance, Foxcroft et al (2009) found Kruger National Park in South Africa to be highly invaded when assessed at a quaternarywatershed level, but the 0.1 by 0.1 km scale revealed finer details, including more significant associations, such as that between the invader, largeleaf lantana [Lantana camara L.], and rivers. These associations may have important management implications but are lost at coarser scales.…”

“…This would allow scaling up (Pyšek and Hulme 2005), which may be useful when comparing the findings with other data collected at a coarser scale (Foxcroft et al 2009). However, based on the studies cited earlier (see also Table 1) and the present capacity of herbarium collection campaigns to include GPS data, we consider quadrats of 10 by 10 km assessed annually for presence/absence to be a good compromise to report abundance in standard invasive species curves.…”