In the past 10 years we have witnessed the beginnings of the study of soil ecology as a unified science, and the general realization by soil scientists, farmers, and land managers that many of the most important economic aspects of soil health are controlled by biological factors. This research focuses on alterations in a tropical soil microarthropod community under differing intensive agricultural protocols: native vegetation, pastures and cropland, during June, July and August 1998. The effect of pesticides in potato cultivation was also studied. In the Ecuadorean montane forest, 361 morphospecies of soil arthropods, were classified during the three sampling months. August was the month with highest abundance and diversity. Acari, Coleoptera, Collembola, Diptera and Homoptera were the most abundant orders present in all the three types of land management. The native vegetation had the most abundant and diverse representation of all soil arthropod taxa compared to the pastures and croplands. Coleoptera, Diptera, Diplopoda, Diplura and Hemiptera were significantly more diverse in native vegetation than in pastures and croplands. The most abundant functional groups were the fungivores, herbivores and predators. The abundance of functional groups was significantly higher in the native vegetation for predators, herbivores and detritivores. 115 morphospecies of soil arthropods were identified in the study of arthropod response to pesticides in a complete randomized potato plot. Seasonal effects were documented for Acari, Collembola, Diptera, and Homoptera. Predators were most abundant in July and fungivores decreased in September. Neither arthropod orders nor functional groups showed a significant change in abundance between different treatments. Only Homoptera showed an increase in its abundance in the third sampling date and only in the Antracol plots. The potato plants in the whole block showed poor productivity, suggesting that the whole system was stressed by the fungal pest. / Graduation date: 2000