Primary succession of high-altitude Andean vegetation on lahars of Volcan Cotopaxi, Ecuador
Sklenář , P.; Kovář , P.; Palice, Z.; Stančík, D.; Soldán, Z.
Volcanic events largely determine the species composition, structure, and dynamics of high-Andean ecosystems. We studied changes in species diversity and composition of pioneer páramo vegetation on lahars approximately 130, 250, and 475 years old on the Cotopaxi volcano. We recorded species composition and abundance of vascular plants, bryophytes, and lichens in 3600 vegetation samples of the size 5x5 cm that were hierarchically arranged in larger plots. We employed non-parametric hierarchical ANOVA to quantify the effect of the lahar age on the species composition and diversity that was expressed as species richness, reciprocal of Simpson's dominance index, and equitability. We found a total of 109 species, including 33 lichens, 16 mosses, 1 liverwort, 1 gymnosperm, 44 dicotyledons, and 14 monocotyledons. Diversity is lowest on the youngest lahar, peaks in the middle-aged lahar and declines on the oldest lahar. The plant communities change from lichen-dominated towards vascular plants-dominated (mostly dicots) vegetation, lahar age accounts for about 18% of the total compositional variability. Fruticose lichens are the most abundant form on the youngest lahar, whereas foliose lichens and bryophytes peak on the middle-aged lahar, and herbs, such as cushions plants, prostrate herbs, and subshrubs, dominate on the oldest lahar. The recovery of vegetation is very slow and even after 475 years the “climax” stage of the grass páramo is not reached. It can be expected that the richness and community diversity will continue to decline as the tussock grasses become increasingly dominant.