A phytosociological study of the páramo along two altitudinal transects in El Carchi province, northern Ecuador

Abstract

We here present a plant composition study of paramo grasslands in the East Andean Cordillera of northern Ecuador that discerns altitudinal distribution patterns. This study took place at two locations: the relatively undisturbed Guandera Biological Reserve site and the highly disturbed El Angel Ecological Reserve site. The analysis included a field survey following the releve method of Braun-Blanquet. The Study focussed oil altitudinal distributions of specific plant communities discernable by our analysis, as well as for traces of human influence in these communities. We examined 100 plots of zonal and azonal paramo vegetation located between 3400 and 4000 in altitude. The phytosociological classification by means of TWINSPAN revealed seven paramo communities at the association level (three for zonal paramo proper and three for azonal bogs), which clustered each into two alliances and one zonal order on the basis of both floristic composition and percentage of cover. The newly described phytosociological order Espeletio pyenophyllae-Calamagrostietalia effusae unifies all the zonal bunchgrass paramos of the Guandera-El Angel study area. There was no structural subparamo community detectable in our study area. Tills can probably be explained by the frequent fires that affect the paramo-forest ecotone and which result into a sharp discontinuity in the vegetation at the upper forest line location in Guandera. For Guandera we described two distinct zonal paramo communities: a bamboo patch and paramo islands in high Andean Forest. In El Angel, the floristic composition of subassociation paspaletosum bonplandiani (bunchgrass paramo at 3430-3550 m) of the Gynoxyo-Calamagrostietum suggests that the vegetation of this syntaxon was probably located on former forested land, as evidenced by the disappearance of high Andean forest and the upper part of Andean forest, combined with the presence of many native and exotic weedy species. The presence of distinct taxa in the subassociation of Paspalum bonplandianum undeniably was a response to habitat alteration induced by human activities. I-or the azonal paramo, we describe three communities at the association level; two of them belonging to the newly established alliance Paepalantho muscosi-Oreobolion cleefii, marking a separate northern Ecuadorian alliance and including the first report of a Xyris cushion bog in Ecuador.