The Jonkershoek Valley site is a mountain catchment in the Cape Floristic Region, and serves as the source of the Eerste River. The site has indigenous vegetation is fynbos (chaparral-like). The area has acidic and nutrient poor soil and a mediterranean climate. Long-term catchment experiments began in the valley in the 1930s. Multiple tributaries of the Eerste River were gaged and systematically planted with Pinus radiata plantations while other catchments were kept under their natural fynbos vegetation as controls.
