Fine roots biomass and arbuscular mycorrhizae in three high Andean wetlands of southern Ecuador with different degrees of disturbance

Abstract

Fine roots and arbuscular mycorrhizal fungi (AMF) represent alternative strategies in the construction of underground absorbent surfaces, which in turn constitute key functional features for high Andean wetlands. In this work, the biomass of fine roots, the percentage, and the anatomy of colonization by AMF were compared in three wetlands (>3000 m.s.n.m.): 1) Jimbura-Amaluza, 2) Tres Lagunas-Yacuambi, and 3) Chinchilla-Saraguro at three soil depths (0-10, 10-20 and 20-30 cm). The degree of relative geo-ecological disturbance is high in Chinchilla-Saraguro, medium in Tres Lagunas-Yacuambi, and low in Jimbura-Amaluza. Depth had a significant effect on fine root biomass, but not on mycorrhizal colonization. Fine root biomass from 0-10 cm depth at Jimbura-Amaluza was 57% higher than at Tres Lagunas-Yacuambi, and 66.7% higher than at Chinchilla-Saraguro. Mycorrhizal colonization was significantly higher in the most conserved wetlands, than in the least conserved wetland (Chinchilla-Saraguro). The exclusive presence of Paris-type mycorrhizal colonization in the three wetlands coincides with previous reports in alpine ecosystems, and in numerous plants with partial mycoheterotrophy (supplemental supply of carbohydrates from the fungus, for the benefit of the plant). Additionally, in the present study dark septate fungi (HSO) were observed together with AMF, as well as in other high-altitude ecosystems with extreme conditions of temperature, humidity, and radiation. Our results showed that the fine root biomass in the top few centimeters of the soil is highly susceptible to disturbance, while mycorrhizal colonization is less susceptible. This study contributes to the understanding of the impact of disturbances on high Andean wetlands, and provides evidence of the presence of key biotic interactions for their functioning and sustainability.