Population structure of common shrubs and trees in Wadi Allaqi Biosphere Reserve, South-East Egypt

Abstract

The aim of the present study is to analyze the structure of the populations of eight common shrubs and trees in Wadi Allaqi Biosphere Reserve (South-East Egypt) through demographic survey of the plants. This study is special important for the populations of trees and shrubs that are continuously subjected to overuses such as cutting, overgrazes and other constraints. For achieving this, 1l2 stands were selected at 19 locations distributes in the upstream, midstream and downstream parts, including the different Wadi tributaries. The locations and stands were selected to present a wide range of physiographic and environmental variation in each tributary. In each location, sampling stands were situated randomly. For each species in each stand, the height and several crown diameters of each individual depending on its uniformity were measured. The size frequency distributions of Acacia ehrenbergiana, Tamarix niloti- ca, Salsola imbricata and Leptadenia pyrotechnica populations were either inverse-J-shaped or positively skewed which may represent rapidly growing populations with high reproductive capacity. Such distributions may also indicate a high juvenile mortality. In these populations, the younger individuals are preponderant than the older ones, which is an indication of strength and success of the species, it is mostly due to victorious germination and survival of seedlings. On contrast, the other four species, Acacia tortilis subsp. raddiana, Calotropis procera, Acacia tortilis subsp. tortilis and Balanites aegyptiaca have a tendency towards the J-shaped or negatively skewed distribution. Such distributions characterize the declining population of limited regenerations capacity (the population has higher proportions of large individuals than the smaller ones). ©2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.