Tree-ring dating of the common trees in Wadi Allaqi Biosphere Reserve, South-East Egypt

Abstract

Twenty-five increment cores and tree discs were sampled for four common trees in Wadi Allaqi, an extremely arid region in South-East Egypt (19 for Acacia tortilis subsp. raddiana (Savi) Brenan and 2 for each of Balanites aegyptiaca (L.) Delile, Acacia ehrenbergiana Hayne, and Tamarix nilotica (Ehrenb.) Bunge). The main aim of the current study is to achieve a longer temporal perspective on growth, longevity, and marginal parenchyma of the wood samples. The growth ring boundaries of the acacias are differentiated by thin parenchyma bands, which run around the entire stem discs. Samples of Acacia tortilis subsp. raddiana were located along this Wadi from its upstream to downstream parts; based on the mean distance between the bands of marginal parenchyma, longevity, based on the marginal parenchyma bands, indicated that Acacia tortilis subsp. raddiana grew slowly and some of its studied individuals reflected 2 age scenarios in the downstream part, while the measurement interval reflected an established date of around 1884 or 1886. Both scenarios grew fast over a long period of time, and so the chiefly recent growth was dated back to 1885. Approximate dates for the midstream part dated back to 1648, while the overall growth for the upstream part dated back to 1482. Samples of Balanites aegyptiaca may be established between 1608 and 1715, while those of Acacia ehrenbergiana may be established between 1945 and 1975. Tamarix nilotica swiftly established itself, and a new ecosystem replaced the severe arid habitat after the dropping of the water level in 1980s.Two scenarios of age are probably true for the downstream part, implying a date of establishment between 1884 and 1886. It was also discovered that the outdated scenario for B. aegyptiaca and A. ehrenbergiana is more in line with asymptotic value and current growth, indicating larger possibility for future expansion.