Vegetation spatial heterogeneity in a hyper arid Biosphere Reserve area in north Africa
One hundred and twelve vegetation stands were selected at 19 locations within Wadi Allaqi Biosphere Reserve (S. E. Egypt). The locations and stands were selected to represent a wide range of physiographic and environmental variation in the wadi tributaries. In each location, sampling stands were situated randomly. TWINSPAN and DCA multivariate analyses were applied to summarize the community patterns. Soil samples representing each stand were collected to determine some physical and chemical characters. 98 species of angiosperms belonging to 34 families were identified in the present study: 33.7 % annuals and 66.3 % perennials. The members ofÂ Â Leguminosae contribute 19.4% of the total floraÂ and so considered the most dominant family in Wadi Allaqi. ThreeÂ herbaceous species were recorded for the first time in this region: Iphiona scabra, Chenopodium album and Lotus deserti. According TWINSPAN, 8 vegetation clusters were obtained: I- Balanites aegyptiaca - Acacia tortilis subsp. tortilis, II- Fagonia indica - Leptadenia pyrotechnica - Acacia tortilis subsp. tortilis - Solenostemma arghel, III- Acacia ehrenbergiana - Morettia philaeana, IV- Acacia ehrenbergiana - Aerva javanica - Fagonia indica, V- Acacia ehrenbergiana - Aerva javanica, VI- Acacia ehrenbergiana - Indigofera argentea, VII- Hyoscyamus muticus - Tamarix nilotica - Morettia philaeana- Glinus lotoides and VIII- Tamarix nilotica - Glinus lotoides - Cynodon dactylon. These 8 clusters are categorized along the DCA axes 1 and 2 into 4 distinct groups. Â The stands belong to group A (clusters I and II) are mainly located in the upstream part (Eigat core area) and their soil differ from the others by higher concentration of bicarbonates, calcium, magnesium and chlorides that may be due to animal grazing, rainfall, floods and their effects on the parent rocks. The stands of group B (cluster VI) are located in the middle part, those of group C (clusters III, IV and V) are located in the downstream and middle parts, while those of group D (clusters VII and VIII) are located in the downstream part (some stands are sometimes inundated by the water of Lake Nasser, and their soils are sandy loam).
Multivariate analysis, Tamarix scrubland, life forms, Lake Nasser, plant diversity, AFRICA.
Acta Botanica Croatica: ISSN: 0365-0588