Dendrochoronological Study on the Common Trees in Wadi Allaqi Biosphere Reserve, South-East Egypt

Abstract

Abstract Background Twenty-five increment cores and tree discs were sampled for 4 trees species in Wadi Allaqi, an extremely arid region in South-East Egypt. All the studied species form distinct tree-ring boundaries. Of those, 19 samples for Acacia tortilis subsp. raddiana (Savi) Brenan, 2 for each of Balanites aegyptiaca (L.) Delile, Acacia ehrenbergiana Hayne, and Tamarix nilotica (Ehrenb.) Bunge. So, the main aim of the current study is to achieve a longer temporal perspective on growth and longevity, marginal parenchyma wood samples. Results The growth ring boundaries of the acacias are differentiated by thin parenchyma bands, which run around the entire stem disc. Samples of Acacia tortilis subsp. raddiana were located in the up-, down- and mid-stream parts of this Wadi; and classified, based on the mean distance between the bands of marginal parenchyma, into 6 size classes. 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 an established date of around 1884 or 1886 is suggested. Both scenarios grew fast over a long period of time, and so the chiefly recent growth 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 water level in Wadi Allaqi dropped in the 1980s. Conclusion Two scenarios of age are probably true for the downstream part, implying a date of establishment between 1884–1886. Balanites aegyptiaca was thought to have been established around 1715 or 1608, whereas Acacia ehrenbergiana was thought to have been established around 1975 or 1945. It was also discovered that the outdated scenario for Balanites aegyptiaca and Acacia ehrenbergiana is more in line with asymptotic value and current growth, indicating larger possibility for future expansion.