Effect of ploughing on plant species abundance and diversity in the northwestern coastal desert of Egypt

摘要

This study focuses on the effect of ploughing on plant abundance, vegetation cover, species richness, and taxonomic diversity during the growing seasons (winter and spring) of 1992 and 2000 in the habitat of inland plateau (natural habitat), 21 km south of Mersa-Matrouh (Egypt). Ninety-five species belonging to 27 families were recorded. High percentages of life-forms and a large number of species were recorded in ploughed and unploughed stripes in the winter and spring of 2000. Higher averages of importance values (IVs) and absolute frequencies were recorded for most perennial and annual species in the unploughed stripes compared to the ploughed ones. This may be attributed to crop failure and consequently unfavourable soil conditions. On the other hand, some shrubby species (e. g. Noaea mucronata and Haloxylon scoparium) and perennial herbs (e. g. Gynandriris sisyrinchium) attained higher IVs in the ploughed stripes compared to unploughed ones. This may be attributed to the cultivation of Prosopis juliflora trees in the elevated part of the ploughed stripes, which have an ecological role in protecting and enriching the soil with organic matter, thus favouring the growth of these shrubs and perennial herbs. Higher species richness and diversity were associated with low concentration of dominance and low taxonomic diversity in the spring of 2000 in ploughed and unploughed stripes compared to the winter of 1992, for both perennials and annuals. The lowest taxonomic diversities were exhibited in the spring of 2000 for ploughed and unploughed stripes where the vegetation had the largest number of congeneric species and confamilial genera. Higher species richness and diversity characterized the vegetation of the unploughed stripes, especially in winter and spring 2000, as compared to those of ploughed ones. The present study also reveals low species richness and diversity of therophytes in winter for both ploughed and unploughed stripes.