Trends in fire patterns in a southern African savanna under alternative land use practices

Abstract

Climate, topography, vegetation and land use interact to influence fire regimes. Variable fire regimes may promote landscape heterogeneity, diversification in vegetation pattern and biotic diversity. The objective was to compare effects of alternative land use practices on landscape heterogeneity. Patch characteristics of fire scars were measured from 21 annual burn maps produced from 1972 to 2001 Landsat imagery. Trends in fire patterns under alternative land use practices were compared across a 250,000 ha savanna in southern Africa partitioned into three land use zones. Zone 1, Madikwe Game Reserve (MGR), has had mostly prescribed fires since 1993. Zone 2, cattle farms near MGR in South Africa (SAF), has experienced occasional fires. Zone 3, communal grazing lands in neighboring Botswana (BOT), has had the fewest fires. Cattle ranching was the predominant land use throughout the study area until 1992, when land use switched to conservation and eco-tourism in MGR. Sixteen landscape metrics were applied to this data set to uncover trends in the patch characteristics of the fire scars. A principal components analysis (PCA) reduced the dimensionality of the results so trends in the 10 most important size, shape, and proximity metrics could be better interpreted. The PCA results showed that more burning over time in MGR, and to a lesser extent in SAF, increased patch size, size variability, shape complexity and proximity, while fire exclusion in BOT produced no change or decreasing trends. We tested for significant differences in these metrics between the three land use zones and between two periods, 1972-1992 and 1993-2001. Most patch characteristics in MGR and SAF differed significantly from those in BOT, especially during the latter period, while between MGR and SAF they did not. Patch area, shape complexity and core area increased significantly between periods in MGR, while patch size, size variability and core area increased significantly between periods in SAF. In BOT, no patch characteristics changed significantly between periods. Within the time span analyzed for the study area, we conclude that increased fire occurrence promoted landscape heterogeneity while fire exclusion did not. Published by Elsevier B.V.

Ecological Implications of Fine-Scale Fire Patchiness and Severity in Tropical Savannas of Northern Australia

“…Various studies have been undertaken to better understand fire patchiness, for a variety of ecological and associated land management purposes, in the USA (Turner et al 1994, Slocum et al 2003, southern Africa (Hudak et al 2004) , Spain (Román-Cuesta et al 2009 and Australia (Russell-Smith et al 1997, Allan 2001, Russell-Smith et al 2002b, RussellSmith and Edwards 2006. Russell-Smith and Edwards (2006) reported that EDS fires have 80% probability of being of low severity and would therefore be expected to have greater internal patchiness than LDS fires.…”

A remote sensing-based analysis on the impact of Wenchuan Earthquake on the core value of World Nature Heritage Sichuan Giant Panda Sanctuary

“…Generally, through pattern index computation, the landscape spatial pattern analysis is powerful in quantitatively characterizing space morphology, structure, and heterogeneity, and comparing landscapes in different places at the same time, the same place and different times, or different places and different times (Lv et al 2007). Such analyses have been applied to natural disturbance studies including wildfires (Hudak et al 2004), deforestation (Venema et al 2005), icestorms (Faccio 2003, and earthquake (Deng et al 2010). Most, if not all, such landscape ecological studies rely on land cover classifications derived from remotely sensed data (Tinker et al 2003;Cifaldi et al 2004).…”

Determination of Veld Fire Hazard Zones in Multiple Tenure Systems in Zimbabwe: Implications for Intervention

“…Fire control where the grassroots are empowered [21,72] to form hierarchical structures, augmented by government initiatives to deal with the fires would help curb the fire challenge as evidenced by high proportion of land that was not burnt, 80%, in communal tenure.…”

“…Unlike in other parts of the world such as Canada where lightning is the major cause of ignition (18), in the study area, ignition of fires is predominantly anthropogenic -stems from use of fires for clearing agricultural land, hunting, warding off animals from crop fields and removing underbrush to improve pasture [18,19]. The seasonal climate (high temperature, high velocity winds and low humidity), seasonal supply of dry biomass (grass and leaf litter) as fuel and terrain conditions (slope and aspect) promote the spread of runaway fires [20][21][22]. Although climatic conditions are generally uniform in the district (7), terrain conditions, human activities and the capacity to tackle the fires differ from one part of the district or tenure system to another.…”