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
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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.
