Formation of “fertile islands” and elements stocks over 45 years of Renosterveld restoration in the Voëlvlei area, Western Cape, South Africa

Beate Michalzik1, Falko Stier1, Willem P. de Clercq2, Jörg Helmschrot3
1 Soil Science, University of Jena
2 Soil Science Department, Stellenbosch University, South Africa
3 Biocentre Klein Flottbek and Botanical Garden University of Hamburg

O 12.6 in Restoration and rehabilitation of ecosystems

17.07.2014, 15:30-15:50, H19

In the Western Cape region of South Africa, the intensification of agricultural land-use has caused a significant loss of the natural Renosterveld vegetation over the last 100 years. Renosterveld (Elytropappus Rhinocertis, “Renosterbos”) of the Western Cape region forms part of the endemic Fynbos biome located in the South African Cape region. Only 15% of its original distribution remains occurring in fragments across the landscape. The conversion of Renosterveld to agricultural areas (predominately wheat land) causes chemical and physical forms of soil degradation, such as reduced storage of soil organic carbon (SOC), diminished aggregate stability and disrupted nutrient cycles.

In this study, the effects of a 45-year-long Renosterveld restoration on abandoned farmland were tested with regard to the formation of “fertile islands” under Renosterbos shrubs, the status of top soil (25 cm soil depth) pools of C, N and plant nutrients. These results were compared to a wheat field under recent agricultural use. The Renosterbos shrubs were found to concentrate the biogeochemical cycle of Corg, N, Ca and P in “islands of fertility' that are localized under the canopy compared to the intershrub space. In this context, soil pools of Corg, N, Ca and P under the canopy of the shrubs were increased by 60, 37, 256 and 8%, respectively, compared to intershrub spaces. The soil inventory exhibited a significant increase of SOC storage to 70.9 t ha-1 (+160%) under Renosterveld vegetation compared to 27.1 t ha-1 under wheat. Soil N pools under Renosterveld increased as well to 4.15 t ha-1 (+ 36%) compared to 3.05 t ha-1. With regard to plant nutrients (P, K, Ca, Mg, Fe, Mn, Zn, Cu, Na), the restoration with Renosterveld significantly enhanced the top soil pools of manganese, while due to fertilizer application pools of P, K, Mg, Fe, Mn, Cu and Na were significantly higher at the farm site. For calcium, zinc and soil respiration no differences between the two land-use forms became notable.

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last modified 2014-02-14