Plant phenology and its relation to the cool semi-arid condition of Sana'a

Abstract

In the cool semi-arid highland areas of Sana'a a plant phenological study of forty two species revealed that there was one major outburst of plant emergence corresponding with the first period of the heavy rainfall which take place during March-April. The second period of heavy rainfall which takes place during July-August shows moderate effect on emergence and growth. Plant Species included annuals, biennials and perennials. Perennials showed the following growth forms: hemicryptophytes, chamaephytes, phanerophytes, and cryptophytes. Most plants were herbaceous and a few were woody. Different Individuals of the same species could behave as annuals, biennials or perennials. In areas were soil moisture lasted for a short period plants behaved as annuals, and in areas where moisture lasted for longer periods the plants behaved as biennials or perennials. The prolonged period of leafing, flowering and fruiting experienced by most species also was caused by the moderate temperature which prevailed during the year. Leafing, flowering, and fruiting periods varied among species. However, they prevailed from March to November. Growth of most species was minimal during winter. Most of the species were growing in upright forms, and a few grew in prostrate and rosette forms.