Frost tolerance in Vachellia sieberiana var. woodii in the high-altitude grasslands of southern Africa

摘要: Abstract High altitude grasslands are frequently within a climatic zone that should support trees, yet trees absent. Low temperature is often cited as possible mechanism excludes trees. We investigated the effect of white frost and black on Vachellia sieberiana saplings, preadaptation to frost; strategy employed tolerate whether seeds V. viable after exposure sub-zero temperatures. Seeds collected from at two different altitudes were germinated saplings potted out. Saplings subjected simulated frost. Tissue samples chilled analysed for soluble sugars in cell sap. also exposed temperatures between 0 -9°C then germinated. able coppice extensive damage above-ground tissue result However, unable compensate adequately one growing season loss growth more than 25% topkill. This may keep trap leaving them vulnerable further frost, fire browsing. down -6°C tissue, but prolonged less resulted sapling mortality. grown seed low-altitude site where events frequent exhibited low temperatures, while those high experiencing did not. not increase sap response chilling stress. The resistant maintaining limited viability -9 °C. Frost very therefore, limit establishment recruitment (seed germination). Once has escaped trap, it will be establish itself successfully.