Remote sensing patterns of net primary productivity in the Great Limpopo Transfrontier Conservation Area (GLTFCA) in relation to land use and land tenure

Abstract

Net Primary Productivity (NPP) is an important indicator of ecosystem health and its estimation and understanding of factors determining its spatial and temporal variations is critical. Previous studies have mainly attributed NPP variations to biophysical factors. However, the influence of these factors is particularly evident at large spatial/global scales. At small spatial/local/landscape scales, complexity is encountered as biophysical factors tend to account for no or less variance in NPP. In addition, it is difficult to consider some aspects of human management systems such as land-use/land tenure in relation to NPP variations on a global scale analysis than on a local scale analysis. To this end, it is predicted that land use and land tenure would dominate explanation of NPP variations at local scales. Thus, in this study, at the local scale, particularly in a high intensive system of a Southern African savanna-the Great Limpopo Transfrontier Conservation Area (GLTFCA), the hypothesis that land-use/land tenure types influence NPP variations was tested. However, it is important to quantify NPP in order to test the abovementioned hypothesis. Thus firstly, this study tested the extent to which a combination of remote sensing and geographic information system (GIS) modelled shortwave radiation (SWR) can be used to estimate NPP in a Southern African savanna. Results showed that NPP can successfully be mapped using a combination of Moderate Resolution Imaging Spectroradiometer (MODIS) data and GIS modelled SWR. One-way analysis of variance (ANOVA) statistical test was then used to test for group mean NPP differences among the different land-use/land tenure types of the GLTFCA. Results showed that land-use/land tenure types significantly (P=0.000, F(4:42056)=180.162, One- Way ANOVA, Tukey HSD Post Hoc Analysis) explain NPP variations at landscape scales even better than biophysical factors. Furthermore, results showed that biophysical factors remain essential in explaining NPP variations even at local scales. These results exhibited the intricacies that exist between the biophysical and human induced factors in explaining NPP viii variations within ecological landscapes. Also, the findings of this study suggest the importance of human management systems, in this instance, land-use/land tenure factors, as an agent of environmental change through its effect on NPP variations in African savannas.