Analysis of the population dynamics of Acacia trees in the Negev desert, Israel with a spatially-explicit computer simulation model

Most trees in the Negev desert, Israel, are either Acacia raddiana, A. tort ilis or A. negevensis. They provide food and shelter for many desert animal s and are a major source of livestock feed and firewood for the native Bedo uin people. High mortality and low recruitment of these trees have been rep orted. To develop sustainable conservation strategies it is necessary to un derstand the population dynamics of the Acacia trees. Therefore, on the bas is of demographic data gained by field studies, a spatially-explicit, indiv idual-based computer simulation model of the population dynamics of A. radd iana has been developed. We evaluate the relative importance of different p rocesses such as seed production and seed infestation by parasites, germina tion, mortality, and mistletoe infestation to the survival and recruitment of Acacia trees in the Negev. Mortality rates at different life stages, the production of uninfested seeds and the weather regime were most influentia l. The infection of trees by semi-parasitic mistletoes proved to be of mino r importance. The most important result is that an increase in the germinat ion rate of Acacia seeds, such as may result from passage through the diges tive tract of large mammalian herbivores, is capable of counteracting the d etrimental effect of unfavourable climatic conditions. Consequently, we dis cuss the use of increased large mammalian herbivore densities as a possible management option for enhancing the survival of Acacia populations in the Negev. (C) 1999 Elsevier Science B.V. All rights reserved.