Annual Medicago species in Morocco. II. Distribution in relation to soil and climate

Abstract

An ecogeographic survey was conducted in six key agricultural zones in Morocco to study the relationship between the natural distribution of medic species and soil and climatic measurements. At each of the 161 sites visited, the presence of medic species was recorded, and soil samples collected. Climatic data were obtained from published records. The influence of soil factors on the presence of medic species was more important than that of climate. With the exception of M. truncatula and M. minima, there were significant soil differences between sites where a species was present and sites where it was absent. Only 5 of the 11 medic species recorded were affected by one or more of the three climatic factors considered. Medics were found most frequently on sites where minimum temperature range was 3-7¦C, pH 6.6-7.5, and with the exception of M. littoralis and M. laciniata, maximum temperature 30-35¦C and rainfall 300-600 mm. M. truncatula was widespread and tolerant of a wide range of edapho-climatic conditions. It was concluded that this well studied species should be given higher priority in future evaluation programs.