Deterioration of natural communities is increasingly alarming to global level, losing ecosystem resilience and natural regeneration mechanisms. Ecological restoration programs in temperate forests using ectomycorrhizal fungi (EMF) as an additional tool for conifer seedling growth, could help to have a better adaptation to water stress and survival increases in plantations. However, most studies have been conducted under nursery conditions using growth variables, but analysis of EMF effect on  ecophysiological response of seedlings in field conditions has been poorly addressed. At the Magdalena River Basin in Mexico City, we carried out a one year study period with four years old Pinus hartwegii and Abies religiosa seedlings. We analyzed four treatments: a) Inocybe splendens inoculum, b) Suillus brevipens inoculum, c) forest soil, and d) agrolite and vermiculite substrate (control), these two last without inoculants. We measured every two months osmotic potential, and stomatal resistance and CO₂ absorbed during the dry and rainy seasons only.

Results/Conclusions

For both species in all treatments an increased of ecophysiological activity during the rainy season was observed; however, in the dry season there was less water stress, lower stomatal resistance and increased CO₂ uptake only in inoculated seedlings. In the dry season, P. hartwegii had the best performance with the S. brevipens treatment, showing a -2.5 MPa osmotic potential; and the highest stress was observed with control treatment (-2.9 MPa). The lower stomatal resistance (9.08 s cm^-1) was obtained in the I. splendens treatment, with an increased amount of CO₂ absorbed (4.04 ppm cm^-2), and a decreased in control and forest soil (10.89 s cm^-1 and 1.48 ppm cm^-2, respectively). In the case of A. religiosa, during the dry season the best treatment was the control (-2.6MPa, 6.02 s cm^-1 and 1.57 ppm cm^-2) and the other treatments had the same pattern. We conclude that there was an effect of the EMF in P. hartwegii seedlings ecophysiological behavior, and previous inoculation is necessary for restoration programs of degraded environments.