Spatial-Temporal Variation in Forage Resource Production in Richtersveld National Park, South Africa
Konje, Martha Muthoni
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Forage production and distribution in rangelands is not uniform but varies with seasons and between landscapes. In arid ecosystems such as Richtersveld National Park (RNP), biotic and abiotic factors affects forage production. production.biotic factors affects forage production. The aim of the study was to assess the effects of biotic and abiotic factors on plant biomass production, species composition and diversity of annual-dominated vegetation in RNP; to assess the spatial and temporal variation in forage production by shrubs and factors that influence forage production and variability in RNP; and to quantify spatial and temporal variation in browse production by seven tree species along the riparian zone and determine the factors that influence browse production in RNP. Stratified sampling of vegetation and soil was done in the five vegetation types found in RNP. Mobile exclosures were placed at 100 m, 500 m and 1000 m from the stock posts to exclude grazing. Soil samples were collected at the same sample plots. Harvest method of clipping vegetation of the current year’s growth was used to calibrate Fraction of Photosynthetic Active Radiation (fPAR) values from remotely sensed MODIS imageries. To determine variation in browse production by trees, plants of the seven most abundant tree species were sampled in three study sites along the river. Biomass production and species diversity of annual plants differed significantly (P<0.05) with distances from the stock posts. Biomass production, species richness and diversity of annual plants were positively correlated to rainfall and soil nutrients. Biomass production by shrubs was significantly higher (P<0.05) in Succulent Karoo than in Desert biome. There was a strong relationship between biomass production and fpar values. Ziziphus mucronata (Willd.), Rhus pendulina (Dr.J.P. Roux) and Acacia karoo (Hayne) were found to be the most browsed tree species by goats. Browse production differed significantly (P<0.05) between the tree species but did not differ between the study sites. Leaves and twigs contributed the highest components of litter. Knowledge spatial-temporal variation in forage production is beneficial in the development of adaptive management policies that would support pastoralism and conservation of plant species in arid ecosystems worldwide. An Integrated Ecological Modelling of biotic, abiotic and social economic factors is recommended for clear understanding of various dynamics found in arid ecosystems. Further studies on the nutritive value of browse forage found in RNP are recommended as well as mapping and identification of landscapes with threatened plant species in RNP.