Abstract
This research extends upon land cover change studies by incorporating methodological approaches, which are compatible with heterogeneous ecosystems, are able to link landscape changes to system processes, such as climate change, and provide potential linkages to concepts of ecological resilience. The study region in southern Africa experienced a significant climatic shift in the 1970s, resulting in drier conditions. The state of these ecosystems and their response to such climatic shock is quantified in terms of vegetation amount and heterogeneity. We monitor these characteristics pre- and post-disturbance using a Landsat image series and examine the utility of continuous characterizations of land cover for measuring ecosystem resilience. Land cover change is evaluated using a mean-variance analysis in concert with a spatial persistence analysis. This investigation indicates that although the impact of the decreased precipitation is evident in the 1980s, recovery occurred by the 1990s and 2000s. We found the continuous methodological approach used holds potential for studying heterogeneous landscapes within a resilience framework.
Highlights
Savanna landscapes occupy the continuum between forest and grasslands, consisting of a continuous layer of grasses interrupted by trees and shrubs [1]
The last two decades of the twentieth century offer an ideal period to investigate the impacts of both a decline in annual precipitation and a greater variability associated with ENSO on vegetation in an ecosystem that is thought to be extremely sensitive to such fluctuations
In terms of landscape resilience, we argue that the system has responded to the ‘shock’ or
Summary
Savanna landscapes occupy the continuum between forest and grasslands, consisting of a continuous layer of grasses interrupted by trees and shrubs [1]. Southern African savannas are thought to be currently experiencing dry land degradation, recurrently associated with changes in floral and faunal biodiversity [24,25] Such degradation can be quantified in terms of vegetation attributes, including (though not limited to) plant cover, heterogeneity and productivity [26,27]. Examining ecosystem characteristics, which serve as indicators of degradation across large spatial and temporal scales, is one way by which the effect of disturbances on landscapes may be considered. Ecosystem indicators, such as vegetation status, can be analyzed using spatially aggregate and/or spatially explicit methods to measure resilience [27]. The following questions are asked: (1) is this approach useful to study landscape changes over a greater temporal extent while still maintaining high spatial fidelity; (2) can this framework help link the biological and climatological systems in such a way that we can begin to understand or hypothesize regarding the system resilience? In addition to these more methodological questions, we are interested in the actual changes being studied here and their implications for this region; as such we ask: (3) what are the long-term vegetation trends post disturbance; (4) does the system return to a similar state with regard to vegetation amount and variance; and (5) how does the vegetation trend vary spatially?
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