Objective: We studied the density of length of thin roots (DLRD), less than 6 cm thick, in six agroecosystems that develop in an acid soil characteristic of the Sabana de Huimanguillo, Tabasco, Mexico, an “acahual” was taken as a reference and characterized floristically, identifying 33 species. Design / methodology / approach: A description of a soil profile was made, taking samples from each horizon to perform physical and chemical analyzes. The DRLD was estimated by the monolith method, considering four depths (0-10, 10-20, 20-30 and 30-40 cm), six samples were taken per agroecosystem. Results: The soil corresponded to a Chromic Acrisol (Loamic, Cutanic, Hyperdystric, Humic). The highest values of DRLD occurred in the first 20 cm, being 67, 69.1, 66.5, 81.4, 82.8 and 77.6% for pineapple, eucalyptus, acacia, rubber, grass and acahual, respectively. It was notorious that from 40 cm of depth the DLRD values decreased considerably in all agroecosystems. 33 plant species were identified Limitations of the study/implications: It is necessary to do more research of the DLRD at greater depth and in other savanna soils to establish clear differences of vertical exploration of the radical biomass. Findings / conclusions: The greatest development of DLRD occurs in the first 20 cm in the six agroecosystems, decreasing considerably according to depth. Grass presented the highest values of DLDR in general there were statistical differences between the first and the rest of the depths. No homogeneity of DLRD was observed in the arboreal agroecosystems in the studied depths. ; Objetivo: Estudiar la densidad de longitud de raíces delgadas (DLRD), de menos de 6 cm de grosor, en seis agroecosistemas que se desarrollan en un suelo ácido característico de la Sabana de Huimanguillo, Tabasco (México), se tomó como referencia y se caracterizó florísticamente un acahual. Diseño/metodología/aproximación: Se describió un perfil de suelo tomando muestras de cada horizonte para determinar sus características físicas y químicas. La DRLD ...