Brush packing as a restoration technology to restore grazing capacity after bush control in the North West Province

Abstract

The Savanna Biome covers approximately 35% of South Africa’s land area and is considered a precious resource which forms the foundation for livestock production and wildlife-related industries. Evidence accumulated in the past century suggests that savanna ecosystems are being altered by a phenomenon known as ‘bush encroachment’ which causes an imbalance in the tree/grass ratio. Bush encroachment leads to decreased biodiversity and suppressed biomass production, resulting in significant socio-economic implications on both commercial and communal scale. The Bush Expert team of the North-West University (NWU) is conducting research, in collaboration with the Department of Environmental Affairs (DEA), on savanna restoration. The research is conducted through the Working for Water (WfW) and the Female Empowerment (FEMpower) programmes. Priority areas include areas stricken by bush encroachment, especially within communal areas. Brush packing can be implemented as a restoration technology to restore savanna function, which involves covering the degraded soil surface with woody branches and/or other organic material, mostly collected after the control of bush encroachment. This treatment on degraded and denuded soil surfaces simulates the protective cover effect of vegetation, along with various other benefits such as alleviating high soil surface temperatures. Sample plots of 400 m² were assigned at a restoration site nearby Goodwood, a rural village situated within the Ganyesa district in the North-West Province. Six treatments consisting of different combinations of bush clearing, re-seeding, brush packing, and soil disturbance were evaluated. The treatments were evaluated based on its ability to increase biomass production that could serve as fodder for livestock, as well as possibly lead to an increase in biodiversity. Three replicates of each of the six treatments were assigned. These included (1) uncontrolled/still bush thickened, (2) bush controlled only, (3) bush controlled and re-seeding, (4) bush controlled and brush packing, (5) bush controlled, re-seeding and brush packing, and (6) bush controlled, soil disturbance, re-seeding and brush packing. Experimental construction was carried out in 2017 in partnership with Land User Initiatives (LUI’s) who, appointed by DEA, were tasked to clear woody species within bush encroached areas. Biomass and species data were collected in April 2018. All sample plots, which included brush packing, produced significantly more biomass than the other treatments. Treatments containing brush packing indicated improved grazing capacity by up to a 1000% in a degraded semi-arid communal savanna rangeland. Species diversity also increased within treatments containing brush packing, owing to re-seeding and the protective effect from the brush packing. Further monitoring and soil surveys showed that high soil temperature seems to be alleviated by brush packing and soil moisture content seems to also differ among sample plots containing brush packing compared to sample plots without brush packing. It is recommended that brush packing technology must be utilized in order to restore bush encroached semi-arid savanna rangelands.