CONICET | Buscador de Institutos y Recursos Humanos

The Andean Cordillera is the second highest mountain range in the wordl affter the Himalayas and therefore , one of the places where the criogenic manifestations are more prominent. Tropical Andean glacier usually prewsent an ice-cap form, and various geomorphological forms -rock glaciers, block streams, morainic deposits, cryoplanation surfaces (sometines mixed with volcanic pimices9 with polygon soils, and solifuction terraces-can be disnguished in the surroudings.The study was carreied out in the main glacial zones of Perú: Cordilel4a Blanca, Cordillera Central, Department of Puno (Allincapec and Yuracjasa), Department of Arequipa (Coropuna, Huarancante, Ampatao and Imata plains) and Department of Tacna near the Tutupaca volcano. Above 4000 m (Oro and cryotropical bioclimatic belts) we documented 152 plots using the Braun-Blanquet method, adding 287 relevés fron other authors from Peru , and also fron Venezuela to southern Argentina and Chile. To interpret the variability , geographical distribution and vertical continuum of the association, the concepts of basal community (BC) , derived community (DC), altitudinnal form and geographic race were used. Field and bibliographic tables were syntethesized usin two dendrongrams as a result of applying the Sorensen indez to compare glacial vegetatation betwee Perú and other regions of South Amaerica. Rock glaciers supporta rupicolous vegetation dominated by Valeriana nivalis, and Saxifraga magellanica on the more humid rocks. Block streams contain specific plant communities with Xenophyllum species (X. cililatum, X. dactylophyllum, X. decorum, X. digitatum, and X. poposum), but Chaeanthera is also very important in these biotopes across the Andes. Cryoplantion surfaces , with more stable and deep soils , present a greater diversity of plants , suchs as Anthhochloa lepidula, Dielsiochloa floribunda, Lachemilla frigida, Mnioides coarctata, Nototriche obcuneata, N. pedicularifolia or N. turritella. On solifluction terraces and flood surfaces , communities with Festuca riescens and Trichopohorum rigidum can be distinguishes respectyvely. Deep clayey solis, support smalll pasturages of Deyeuxia minima and Aciachne pulvinata somoetimes grazed, while the cushion vegetation caused by snowbreak streams is represented by Deyeuxia ovata and Werneria aretioidesFrm a syntaxonomical poit of view, 32 Peruvian plant communities were recognized. Rock comunnities are the Senecio bolivarianus community -mono-specific plant comunity on humid rocks distribuited form Huancayo to Cusco, The Asplenio triphylli-Melpomenetum monilifoimis ass. nova- a rupiculous association installed on granitic rocks of the Cordilera Blanca, the Senecio algens community -associated with the basal partt of the rocks of hmid puna, and the senecio culcitiodis -Valerianetum nivalis- a charecteristic rock community usually present on andesistes and basalts from Lima to Cordillera El Barroso (Tacna) (this association includes the subassocitaion saxifragetosum magellanicae, found on semi-permanent humid rocks , the geographic race with Draba cryptandra (Cordillera Central) , the geographic race with Draba brackenridgei (near Cotahuasi Canyon, Arequipa), the geografic race with Draba cuzcoensis (near Colca Canyon, Arequipa) , and the termic altitudinal form with Woodsia montevidensis (Callai, Arequipa)The Xenophyllo-Englerocharion peruvianae alliance is represented by the following communities. Xenophyllo ciliolati-Pletkeetum cryptanthae- a hunid puina association present on block streams and morenic deposits with superfical stones the Cordillera Blanca o Alliancapac (Puno) (this assotiation includes an altitudinal form with Anticona glareophila, from the limits of the vegetation of the Cordillera Cantral, a variant of semi-fixed blocks with Xenophyllum digitatum, a variant of mobile blocks with Xenophyllum cialiolatum, a derived community (DC) wuith Chaetanthera cochlearifolia from Central Perú, found on clayey places that will evolve to the polygon soils solonized by the same enviroments from southern Perú), and the Poa gymnantha-Cerastium peruvianum community , documented on volcanic conglomerates from Callalli (Arequipa).Nototricho obcuneatae- Xenophylletum poposi -installed on semi-fixed blocks of the altiplano of Perú and Bolivia in dry subhumid climate (its variability presents the sub-associations valerianetosum nivalis as a rupiculous aspect, and mmiodetosum coarctateae on higtly sloping soils), Nototricho Mniotetum coaractateae ass . nopva- cryorotropical vegetaction on flat polygon solis enrichede with the volcanic pumices of the altiplano, and the Bello piptolepis -Dissanthelium calycini-that indicates wetter saoils without volcanic punices in the altiplano-belong to the Nototrichon obcuneatae alliance.The Deyeuxion minimae alliance indicates deeper and mores humid solis, wherte we can differentiate five associations: Notrotricho pinnatae- Lachemiletum frigidade - present on the rock cornices and polygon soils coming from intrusive geologic materials of the Cordillera Blanca, Pycnophyllo mollis-Festucetum rigescentis- very typical on solifluction terraces of the hunida puna of Peu and Boilivia , Deyeuxio minimae-Trichophjoretm rigidae- on flooded surfaces of the hunid Peruvian Andes , Azorello diapensoiis -Deyeuxietum minimae-on himid , deep and clayey criogenic soils , sometimes with very little superficial stones (this association includes an altitudinal form with Deuyeuxia rigida, an altitudial form with Pynophyllum molle, a vraiant on incipient solifuction terraces with Dissanthelium macusaniense , and another variant on deep and humid soils with Wer5neria nubighena), and Gnaphalio badii-Achiachnetum pulvinatae grazed vegetation in the orotropical belt.Finalyy, Deyeuxio ovatae- Wernerietum aretioidis ass. nova is a cushion association belonging to the Plantagini- Distiochletea class occurring between 4800 and 5000 m a.s.l.To study the relationships between plant communities and some seleted climatic parameters (T,M,m,It, P,Pm and Hm- see abreviations of the table 6) we have made a biplot from a Principal Component Analyses for each community group (rock communities, Xenophyllo-Englerocharion, Nototrichon obcuneatae, and Deyeuxon minimae and other symntaxa . Plant communities placed at high altitude or in dry puna (Oruro-Arequipa biogeographic province) are linked with the samaller values of the lowest mean tempoerature of the coldest month (m), while those placed in the humid puna (Ancashino-Paceña biogeographic province) are linked with the highest values of the highest mean temperature of the coldest month (M).Finaly , the syntaxa Empetro rubrum-Oreopoletum glacialis , described earlier from Southern Patagonia , are typified.