The Subnival Vegetation of Moquegua, South Peru: Chasmophytes, Grasslands and Cushion Communities

Abstract

The present work is a phytosociological synthesis and syntaxonomic overview of the vegetation of the highest subnival parts (superpuna) of the open alpine vegetation of the high plateaus (puna) of the Andes of Moquegua, South West Peru, as related to the main environmental gradients. Using TWINSPAN and DCA ordination analysis, 153 phytosociological relevés were analyzed. For each association, subassociation and community, the syntaxonomy, floristic diversity and relation with environmental variables are described. The syntaxonomy and synecology of superpuna vegetation was studied in 19 localities at an altitude of 4450–4800 m. The study area has a pluviseasonal climate with yearly rainfall (December-April). Four main highland vegetation types were distinguished: 1. slope and scree chasmophyte vegetation composed of shrubs, cushions, ground rosettes and grasses, 2. grasslands (grazed and ungrazed) characterized by great species richness in shrubs, cushions, ground rosettes, grasses and herbs, 3. vegetation of plateaus with cushions, shrubs, ground rosettes, herbs and grasses and 4. nitrophilous vegetation with high cover and low species richness. Within the vegetation of the orotropical and cryorotropical bioclimatic belts three phytosociological classes can be distinguished: Argyrochosmetea niveae (chasmophytic vegetation), Calamagrostietea vicunarum (grasslands with cushions), Anthochloo lepidulae-Dielsiochloetea floribundae (highland slopes and plateaus) and a nitrophylous community. One new association from rock and scree slopes was described within the Saxifragion magellanicae (Argyrochosmetea niveae). Within the Calamagrostion minimae, which comprises grasslands with cushions and mat-forming plants, one new association with two subassociations could be distinguished. Within the grassland and cushion associations of the Azorello-Festucion (Calamagrostietea vicunarum), three new associations were described, comprising nine subassociations. In the Anthochloo-Dielsiochloetalia one new and one previously described association and one community are distinguished. In addition, the nitrophilous community of Tarasa nototrichoides and Urtica flabellata has been described. In total the vegetation comprised 172 vascular species belonging to 32 families. Our study provides the first syntaxonomic revision of chasmophytes, cushion associations and high-altitude grasslands in the Andes of North Moquegua. The proposed syntaxonomic scheme contains the associations distributed under similar habitat conditions throughout the Southern Andes of Peru, but also the associations reflecting the local floristic and environmental patterns. The subnival vegetation of Moquegua hosts some rare endangered and/or protected plant species.