Composition, distribution patterns and habitat divergence of street trees in the greater Cairo city, Egypt.

Abstract

Species diversity of the tree flora of 38 districts in the Greater Cairo city was studied with reference to landscape differentiation of species make-up. Three main habitats including 14 sites with 263 sample plots were considered (35 urban parks, 76 road islands and 152 street verges). Basic statistical treatments were established by using the computer program package SPSS v. 10.0, whereas the multivariate statistical analyses were performed by using the program package MVSP for Windows, v. 3.1. The produced data were subjected to a UPEGMA-clustering based on squared Euclidean distance and the obtained groups were represented in a dendrogram. Principal Coordinates Analysis (PCoA) is preformed using the product-moment correlation as a coefficient. In total, 378 of vascular plant species belonging to 264 genera and 79 families were recorded in urban areas of the Greater Cairo city. The most species-rich (44.7%) families were Fabaceae (36 spp.), Asparagaceae, Poaceae (21 spp.), Moraceae (19 spp.), Asteraceae (17 spp.), Euphorbiaceae and Malvaceae (15 spp.), Arecaceae (14 spp.), Lamiaceae (11 spp.), whereas the remaining families (70) constituted together 193 species. Ficus (18 spp.) was the highest among the species-rich genera, followed by Euphorbia (11 spp.), Asparagus, Brachychiton, Callistemon, Citrus and Pinus (4 spp. each). 257 genera contained only 1-3 species e.g. Cereus, Koelreuteria, Strelitzia, Terminalia, Carica and Toona. Growth form spectra revealed that, the recorded trees (139 spp.) belonged to 32 families; shrubs (79 spp.) to 30 families, herbs and others (160 spp.) to 48 families. Detailed species compositions, classification and their distribution patterns in each of the street verges, road islands and urban park were presented. Taxonomic diversity and growth forms in each habitat were estimated and graphically compared. Interactions between human disturbance, habitat condition and tree composition were discussed and recommendations regarding conservation ecology were suggested.