Soil Biological Properties and Arbuscular Mycorrhizal Fungal Communities of Representative Crops Established in the Andean Region from Ecuadorian Highlands

Biological activities determine quality, sustainability, health, and fertility of soils. The purpose of this study was to evaluate chemical and biological characteristics of soils from Ecuadorian highlands subjected to different management practices, as well as the density and diversity of arbuscular mycorrhizal fungi (AMF). Soils from naturalized grasslands and other previously cropped plots with Zea mays and Solanum tuberosum were analyzed in laboratory for soil biochemical properties, enzyme activity, and AMF colonization to determine the effect of the soil management over its quality. The characterization of AMF propagules associated to spontaneously colonizing plants in the above soils was also performed. Soil previously cropped with S. tuberosum showed the highest glomalin content; at the same time, naturalized grassland and Z. mays cropped soils showed higher hyphal length. The acid phosphatase activity was higher in naturalized grasslands and Z. mays cropped soils compared with that in the S. tuberosum cropped soils. Moreover, the highest AMF colonization rates and spore number were found in different spontaneous plant species growing in the naturalized grasslands. This study represents the first characterization of AMF propagules of different cropped and naturalized grassland soils, and also is one of the first reports about changes on biochemical and microbial activities occurring in Andean soils from the highlands of Ecuador, undergoing determinant soil management activities.