The remnant trees in casttle have a significant ecological importance because they alter the microhabitat and also affect biological interactions. Ali these factors improve mycorrhizal fungi establishment and forest vegetation species proliferation. The objective of this study was to determine space-temporal variation of the morphospecies of arbuscular mycorrhiza and their spores number under remnant trees. This study was carried out in a casttle, in the northern edge of the Biology Station of "Los Tuxtlas", Veracruz, Mexico. Four isolated trees (Ampelocera hottlei, Poulsenia armata and Ficus sp.) were chosen. Soil samples were collected under each tree cover during dry, rainy and "nortes" seasons. Thirteen arbuscular mycorrh izal species of the Glomaceae, Acaulosporaceae and Gigasporaceae families were observed. The number of spores among climatic seasons was significant different, the highest value was presented in "nortes" season and the lowest occurred in the dry season. There were no significant differences among isolated tree species, this could imply that the remnant tree function as a unit. Differential water availability, a long the year, may explain spores production variation.