Approaches to fire management in the savanna ecosystems of the 2-million ha Kruger NationalPark, South Africa, have changed several times over the past six decades. These approaches have included regular and flexible prescribed burning on fixed areas and a policy that sought to establish a lightningdominated fire regime. We sought to establish whether changes in management induced the desired variability in fire regimes over a large area. We used a spatial database of information on all fires in the park between 1957 and 2002 to determine elements of the fire regime associated with each management policy. The area that burned in any given year was independent of the management approach and was strongly related to rainfall (and therefore grass fuels) in the preceding 2 years. On the other hand, management did affect the spatial heterogeneity of fires and their seasonal distribution. Heterogeneity was higher at all scales during the era of prescribed burning, compared with the lightning-fire interval. The lightning-fire interval also resulted in a greater proportion (72% vs. 38%) of the area burning in the dry season. Mean fire-return intervals varied between 5.6 and 7.3 years, and variability in fire-return intervals was strongly influenced by the sequencing of annual rainfall rather than by management. The attempt at creating a lightning-dominated fire regime failed because most fires were ignited by humans, and the policy has been replaced by a more pragmatic approach that combines flexible prescribed burning with lightning-ignited fires.Respuesta de los Regimenes de Fuegos de Sabana a Cambios en las Políticas de Gestión de Fuego en un Parque Nacional Africano Resumen: Durante las seisúltimas décadas, los métodos de gestión de fuego en los ecosistemas de sabana han cambiado varias veces en el Parque Nacional Kruger (2 millones de ha), Sudáfrica. Estos métodos incluyeron quemas prescritas regulares y flexibles enáreas determinadas y una política que buscaba establecer un régimen de fuego dominado por relámpagos. Buscamos establecer si los cambios de gestión indujeron la variabilidad deseada en los regimenes de fuego en unárea extensa. Utilizamos una base de datos espacial de la informaciónde todos los incendios en el parque entre 1957 y 2002 para determinar elementos del régimen de fuego asociados con cada política de gestión. Elárea quemada en cualquier año fue independiente del método de gestión y se relacionaba cercanamente con la precipitación pluvial (y por lo tanto con pastos combustibles) en los dos años precedentes. Por otro lado, la gestión afectó a la heterogeneidad espacial de los incendios y su distribución estacional. En comparación con el intervalo de fuego por relámpagos, la heterogeneidad fue mayor en todas las escalas durante el período de quemas prescritas. El período de fuego por relámpagos también presentó una mayor proporción (72% vs. 38%) deárea quemada durante laépoca de secas. Los intervalos promedio de retorno de fuego variaron entre 5.6 y 7.3 años, y la secuencia de la precipitación anua...

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South Africa has much to offer as a location for the study of biological invasions. It is an ecologically diverse country comprised of nine distinct terrestrial biomes, four recognised marine ecoregions, and two sub-Antarctic Islands. The country has a rich and chequered socio-political history, and a similarly varied history of species introductions. There has been a long tradition of large-scale conservation in the country, and efforts to manage and regulate invasions began in the nineteenth century, with some notable successes, but many setbacks. With the advent of democracy in the early 1990s, South Africa established large alien species control programmes to meet the dual demands of poverty alleviation and conservation, and has since pioneered regulatory approaches to address invasions. In terms of research, South Africa has played an important role in the development of invasion science globally. It continues to have one of the most active communities anywhere in the world, with strengths in theoretical and applied invasion science, and world-leading expertise in specific sub-disciplines (e.g. the classical biological control of invasive plants). In this introductory chapter to the book "Biological Invasions in South Africa", we highlight key events that have affected biological invasions, their management, and the research conducted over the past two centuries. In so doing, we build on earlier reviews-from a national situational review of the state of knowledge in

A major challenge for the management of biological invasions is to ensure that data and information from basic inventories and ecological research are used alongside data from the monitoring and evaluation of interventions to trigger and improve policy and management responses. To address this issue, South Africa has committed to report on the status of biological invasions and their management every 3 years. We propose a framework of indicators for reporting on biological invasions at a country level; assess the feasibility of the indicators using South Africa as a case study; and outline steps needed for indicator development. We argue that a national status report on biological invasions should explicitly consider indicators for pathways, species, and sites, and should report on interventions in terms of inputs, outputs, and outcomes. We propose 20 indicators based on data currently available, as well as existing international policy initiatives. For each indicator, we have developed a factsheet that includes different hierarchical metrics (considering data availability) and provide suggestions on assigning confidence levels. We also combine these indicators into four high‐level indicators to facilitate broader reporting and describe how forecasted indicators based on the concept of invasion debt could assist with scenario planning. We found that many of the data required for these indicators are already available in South Africa, but they have been poorly collated to date. However, data for the indicators of most direct value to policy and planning—those dealing with the impact of biological invasions and the outcome of interventions—are scarce. Policy implications. The framework of indicators developed here, for what we believe is the first ever national‐level report on the status of biological invasions and their management, will facilitate the inclusion of biological invasions in environmental reporting at national and international levels. By identifying knowledge gaps, a status report will also focus efforts on determining the size of a country's invasion debt and what can be done to reduce it.

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To reduce the negative impacts of invasive plants, management interventions such as control or eradication are usually necessary. It is often assumed that the impacts of invasive plants will diminish immediately after such interventions. However, in some cases the invader can have legacy effects in the soil that might persist for long periods, preventing the natural restoration of the areas managed. Therefore, to achieve the re-establishment of a functional native ecosystem it is important to understand for how long such legacies can persist in the soil. This paper explores this issue, using Acacia saligna in South Africa as case study. We collected soil samples in invaded, non-invaded and previously invaded sites (representing 2, 6 and 10 years after clearing) and analysed the levels of pH, carbon, nitrogen, available phosphorus, ammonium, nitrate and electrical conductivity. We also analysed enzyme activities (b-1,4-glucosidase, urease and acid phosphatase). Acacia saligna invasion alters overall soil characteristics but specifically raises pH by 0.6-1.8. Moreover, soil characteristics (e.g. pH) are not restored to natural conditions after control (soil legacy effects persist up to 10 years after clearing). Furthermore, A. saligna control elevates soil NO À 3 levels and these can remain higher than in invaded (1.55-6.67 mg kg À1 ) and non-invaded (2.16-4.35 mg kg À1 ) sites up to 10 years after clearing. Elevated NO À 3 often facilitates secondary invasion and/or weedy native species dominance which may hinder the restoration of functional native ecosystems. Therefore, strategies to manage areas previously invaded by A. saligna should take into account the removal of litter from the target invader, secondary invaders and weedy native species.

This paper reviews the options for management of the savanna ecosystems of the Kruger National Park using fire. The major goals of management have shifted from attempts to use fire to achieve a stable vegetation composition, to one of recognising that savanna ecosystems are in constant flux. Fire is a major form of disturbance that helps to maintain a state of flux, and thus to conserve biodiversity. Three candidate approaches for fire management have been put forward@the lightning fire approach, the patch mosaic burning approach, and an approach based on the assessment of ecological criteria. These approaches differ in their underlying philosophies, but not necessarily in their outcomes, although this cannot be predicted with confidence. We propose, therefore, that patterns of fire frequency, season, intensity and spatial distribution be recorded and monitored, and that these patterns should serve as surrogate measures of biodiversity. Guidelines for the definition of thresholds of potential concern with regard to these patterns are discussed. The monitoring of both fire patterns and trends in plant and animal populations can be used to identify interactions between fire and the components of the ecosystem, and these in turn can be used to define a relevant research agenda. The role of management in monitoring and assessing fire patterns (previously regarded as a research responsibility) is emphasised. Convergence in the patterns of fire that result from the different management approaches could also serve as a basis for merging some or all of these approaches in order to simplify management.

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