Abstract: The effect of reforestation of Pinus nigra and Pinus halepensis in central and southern Navarra (northern Spain) on mesostigmatic mite communities inhabiting the soil was studied, and seasonal fluctuation of mite populations over 1 year of sampling. Reforestation causes a clear change in species richness of the community (71-72% drop) and a significant decrease of mite abundance (31-50% loss). There are no significant differences in overall Shannon¿s diversity (H) and evenness (J) when the Mediterranean shrub (H = 2.92, J = 0.66) is replaced by a pine forest (H = 2.73, J = 0.72). However, H and J significantly increased when a pine forest (H = 3.34, J = 0.84) substitutes the natural oak forest (H = 2.80, J = 0.63). Summer is the critical, unfavorable season for Mesostigmata of this region in terms of their abundance and community diversity.