TEMPORAL AND SPATIAL VARIABILITY OF GRASS PRODUCTIVITY IN THE CENTRAL NAMIB DESERT

Abstract

The production of grass was investigated on the gravel plains of the Central Namib Desert, Namibia, during 10 rainfall seasons sampled between 1989-2003. The aim was to evaluate the rainfall-productivity relationship, to elucidate the relationship between temporal and spatial variability, and to examine the spatial scale of patchiness. We compared two different methods and found that a less accurate rapid assessment of grass cover correlat- ed well with measurements of biomass. Our data were in agreement with previous determina- tions of the desert end of the curve of grassland productivity, and productivity was closely related to the rainfall of the particular season. There was high variability between years at study sites, especially in the west (CV=279%), where it rained more seldom than in the east (CV=86%). During all years rainfall was very patchy at a spatial scale of 5 km, which appar- ently reflected the storm path of individual rain clouds. Long-term monitoring should be continued in order to detect changes of pattern in this rainfall-driven system.