The role of land use planning in semi-arid areas
Worldwide, the semi-arid grazing and cropping regions are being subjected to severe overuse. Australian semi-arid regions have been cleared on a vast scale for marginal cropping. Grazing land has been overused and shows widespread signs of vegetation and soil degradation. Ecological realism on land capability based on objective condition monitoring, is essential to land management if sustainable production is to be achieved. The Land Care Movement can markedly influence this achievement. The margins of semi-arid cropland and the application of ecologically-based animal stocking rates require attention in several States. Drought assistance policy requires amendment to safeguard natural pastures. Lease covenants have a potentially central role to play in land administration.
Vegetation ecology of the Soutpansberg and Blouberg area in the Limpopo Province
........................................................................................................ ii List of Tables and Figures ............................................................................. ix Chapter 1: Introduction ................................................................................. 1 Chapter 2: The study area ............................................................................. 7 Location ................................................................. 7 Topography ............................................................. 9 Climate .................................................................. 12 Soutpansberg Centre of Biological Diversity ...................... 15 Chapter 3: Methods ....................................................................................... 17 Introduction ............................................................. 17 Analytical phase ........................................................ 18 Synthetic phase ......................................................... 19 Mapping ................................................................. 23 Limitations on fieldwork and data analysis ........................ 23 Chapter 4: Major Vegetation Types of the Blouberg Nature Reserve and Soutpansberg Conservancy ......................................................... 25 Abstract .................................................................. 26 Introduction ................................................................................. 27 Study Area ................................................................................... 27 Methods ....................................................................................... 34 Results ......................................................................................... 35 Description of Major Vegetation Types ...................................... 36 1. Eragrostis lehmanniana–Sclerocarya birrea BNR Northern Plains Bushveld ..................................................................... 50 2. Euclea divinorum–Acacia tortilis BNR Southern Plains Bushveld ................................................................................ 51 3. Englerophytum magalismontanum–Combretum molle BNR Mountain Bushveld ............................................................... 53 4. Adansonia digitata–Acacia nigrescens Soutpansberg Arid Northern Bushveld ................................................................ 55
Inhibition of Root Growth and Polyamine Metabolism in Sunflower (Helianthus annuus) Seedlings Under Cadmium and Copper Stress
Although sunflower is usually regarded as a highly tolerant crop, impairment of root growth at initial stages of plant development may result in poor crop establishment and higher susceptibility to pathogen attack. In order to evaluate if Cd2+ and Cu2+ may impact on sunflower germination and initial root development, a pot experiment under controlled conditions was carried out. Possible involvement of polyamine metabolism in sunflower response to these stressors was also investigated. Although Cd2+ and Cu2+ treatments affect neither seed germination nor radicle emergence, sunflower seedlings grown in the presence of these heavy metals showed significant inhibition of root growth, being this inhibition greater for Cd2+. Both metals caused significant increases in proline contents at the highest concentrations tested (0.5 and 1 mM), and these increments were more pronounced for Cd2+ treatments, especially between days 3 and 10. Metals also increased putrescine (Put) contents at all concentrations assayed from the seventh day onward, causing no variations on this polyamine time-course pattern. Spermine and spermidine contents, however, were increased only by 1 mM Cd2+. Arginine decarboxylase seems to have been the enzyme responsible for Put increases under both metal treatments. This work demonstrates that initial root growth of sunflower seedlings may be significantly impaired in Cd2+ or Cu2+ contaminated soils. It also shows that polyamines are key biological compounds, which are probably involved in signaling pathways triggered under stress environmental conditions.