Impact of soil texture on plant communities of Raphanus raphanistrum L

Abstract

Our soil study of the chromic soils located in the strip of land between Sierra Morena and the Guadalquivir Valley reveals a pH-value close to neutral in 25 samples. The pH-values are close to 5.5 only in the samples taken from the arenosols of the granitic batholith of Los Pedroches. However, it is the percentage of clay, sand and silt that explains the occurrence of grassland dominated by Raphanus raphanistrum, in the company of species with a psammophilous character such as Linaria spartea, Linaria amethystea and Brassica barrelieri. Our soil analysis reveals the presence of acid or base-poor soils. Consequently, the community of Raphanus raphanistrum found there displays an acidophilous, neutro-basophilous and subarenicolous character. Different types of sabulicolous plant communities appear as a result of the gradation of the soil texture. Since the Raphanus communities cannot be considered as genuinely sabulicolous, we have coined the term ‘subarenicolous’ to describe any plant community whose optimum sand content lies between 50% and 70%. The community of Linaria spartea and Raphanus rapha nistrum is neutro-basophilous and is found in at least the Marianic-Monchiquensean and North Hispalensean sectors. The floristic composition of the association is made up of Raphanus raphanistrum, Linaria spartea, Linaria amethystea, Medicago polymorpha, Hordeum leporinum, Bromus diandrus, Brassica barrelieri.