Estudio de la vegetación y flora vascular de la cuenca del río Asón

Abstract

The study zone includes the Asón river basin (Cantabria, N Spain) in an area that extends from the Cantabrian coast to the headwaters of the river. The relief of this zone is very abrupt, especially towards the innermost part, where there are mountains up to 1600 m. The predominant geological materials correspond to the Cretaceous era: urgonian limestone, paraurgonian marls and supraurgonian sandstone of Weald facies.

The catalogue of the vascular flora gathers a total amount of 1088 taxa of which 1062 were collected by us. The distribution area of some of these plants has been enlarged according to the new data. Most noteworthy are: Crassula tillaea, Eleusine tristachya, Salicornia dolichostachya, Salicornia fragilis, Salicornia obscura, Juncus foliosus, Kickxia commutata, Malva parviflora and Verbascum nigrum. The study of the vegetation has resulted in the recognition of 90 plant communities. 20 new syntaxa are described: 1 suballiance, 8 associations and 11 subassociations. New systematic models have been proposed, especially in coastal vegetation.

The following vegetation series have been recognized in the study area:

a)     Climatic series: Basque-Cantabrian and Eastern Asturian ash tree mesophytic serie (Polysticho setiferi-Fraxineto excelsioris S.); Basque-Cantabrian oak oligotrophic serie (Hyperico pulchri-Querceto roboris S.); Basque-Cantabrian Quercus pyrenaica, montane oligotrophic serie (Melampyro-Querceto pyrenaicae S.); Cantabro-Atlantic and Orocantabrian, beech tree mesophytic serie (Carici sylvaticae-Fageto S.); Basque-Cantabrian beech tree oligotrophic serie (Saxifrago hirsutae-Fageto S.)

b)     Edaphic series: Basque-Cantabrian and Eastern Asturian holm oak serie (Lauro nobilis-Querceto ilicis S.); Basque-Cantabrian, Eastern Asturian and Orocantabrian hygrophilic serie of the alder tree (Hyperico androsaemi-Alneto S.)

A map at 1:50.000 scale of the current vegetation in the study area is shown. In this map, the most significant units of vegetation are represented.