HALOSUBNITROPHILOUS PASTURES OF THE WEST OF THE REGIONAL COMMUNITY OFCASTILLA-Y-LEON (SPAIN)

A study is made of halosubnitrophilous perennial pastures of livestock interest in the Duero Basin (Spain). Characterized floristically and physiognomically by Poa bulbosa and Trifolium ornithopodioides, these pastures have annual halophilous (Frankenia pulverulenta, Hordeum mari num, Hymenolobus procumbens, Parapholis incurva and Scorzonera lacinia ta var. subulata) and perennial (Camphorosma monspeliaca, Plantago mar itima and Puccinellia caespitosa) elements as well as many therophytes belonging to Helianthemetea guttati. From the results emerges a descr iption of the new association Trifolio ornitho-podioidis-Poetum bulbos ae, which we include in the alliance Poo-Astragalion sesamei (Poetalia bulbosae, Poetea bulbosae). The floristic-sociological analysis is co mplemented with edaphological, bioclimatic and dynamic data relating t o the new association.