Theme 05: Biotic Constraints to Forage Production from Grasslands
Description
The investigation was carried out on a densely wooded area in the Mopani savanna of South Africa. Seven plots were subjected to different intensities of tree thinning, ranging from a totally cleared plot (0 %) to plots thinned to the equivalent of 10 %, 20 %, 35 %, 50 % and 75 % of the leaf biomass of a control plot (100 %). The grasses responded positively to the tree thinning in terms of total dry matter yield. The yields between tree canopies were generally of the same order or higher than under tree canopies, with the yields where trees have been removed initially the highest. At high tree densities, yields differed little between seasons of varying rainfall. No quantitative advantages of C. mopane trees on the grass layer could be established, and the highest grass DM yields were recorded in plots where all trees were removed. The relationship between grass DM yield and tree density (expressed as Evapotranspiration Tree Equivalents ha-1) was curvilinear, best described by the exponential regression equation.
Included in
Relationship between Tree Density and Grass Dry Matter Yield in a Southern African Savanna
The investigation was carried out on a densely wooded area in the Mopani savanna of South Africa. Seven plots were subjected to different intensities of tree thinning, ranging from a totally cleared plot (0 %) to plots thinned to the equivalent of 10 %, 20 %, 35 %, 50 % and 75 % of the leaf biomass of a control plot (100 %). The grasses responded positively to the tree thinning in terms of total dry matter yield. The yields between tree canopies were generally of the same order or higher than under tree canopies, with the yields where trees have been removed initially the highest. At high tree densities, yields differed little between seasons of varying rainfall. No quantitative advantages of C. mopane trees on the grass layer could be established, and the highest grass DM yields were recorded in plots where all trees were removed. The relationship between grass DM yield and tree density (expressed as Evapotranspiration Tree Equivalents ha-1) was curvilinear, best described by the exponential regression equation.
