Old Field Plant Succession in the Subtropical Arid Highland of Sana'a, Republic of Yemen PDF

Keywords

Subtropical, Republic of Yemen, Highland, Sana'a

Abstract

The 1-year old field is characterized by having 6 species, which belong to two life forms including therophytes and hemicryptophytes, low plant cover (15%), sandy soil with less humus and lower field capacity (20.2%). The 4-year old field is characterized by having 32 species of a more diverse life forms, including therophytes, hemícryptophyes, chamaephytes and phanerophytes; moderate plant cover (55%); sandy-loam soil with more humus and higher field capacity (33.3%). In both fields most plants started growing in late April, after the beginning of the winter rainfall. Importance value index, measured in late July 1997, at the time of maximum productivity, showed that Cornulaca sp., Lamarckia aurea, Bromus arvensis, Fagonia indica, Zygophyllum simplex were the most prominent species in the 1-year old field. On the other hand, Bromus arvensis, Comulaca sp., Francoeria crispa, Plantago afra, Osteospermum vaillantii were the most prominent species in the 4-year old field. Yet, more perennial species were found in the 4-year old field. For six months, during the relatively dry period of the year, between September and February, not a single plant was seen over the ground surface in the 1-year old field. On the contrary, during the same dry period, in the 4-year old field, many perennial plants were found carrying little leaves. These plants included the ones that behaved as hemicryptophytes, chamaephytes and phanerophytes. They Francoeria cripsa, Ochradenus baccatus, Osteospermum vaillantii, Pulicaria sp.. Solanum nigrum, Solanum schamperi, Solanum sepicula, Solanum villosum, and Ziziphus spina-christi. In the semitropical arid areas as in Sana'a plant species are able to use various tactics to cope with the droughtiness. From the life form viewpoint, plants during the prolonged drought period either die (Therophytes), save water by losing their leaves while keeping their roots and renewal buds (Hemicryptophytes), or extending their roots to the subsoil moisture as in the cases of the dwarf perennial shrubs (Chamaephytes) and the trees Phanerophytes).