Light management in tree nurseries to produce Pithecellobium dulce seedlings for the reforestation of degraded lands in Southern Mexico's tropical dry forests

The choice of nursery practices is important to the production of high-quality seedlings and to increase the survival rates of reforestation plantations in the dry tropics. However, adequate practices need to be established for native species for which propagation information is scarce. This study suggests that light management in nurseries is a key cultivation practice for future planting success, because of the morpho-physiological changes that plants usually undergo in different light conditions. We examined variations in the morphology, photosynthesis efficiency and growth of Pithecellobium dulce plants produced under four levels of light in nursery conditions (20%, 40%, 60%, and 100% of photosynthetically active radiation [PAR]). We also assessed survival after planting out according to the light conditions under which the plants were grown. Morpho-physiological variables were examined in three-month-old plants. A plantation was established in the field using the nursery-grown plants, and their survival was recorded monthly for 17 months. In the nursery, the light levels had significant effects on morphology, photosynthesis efficiency and growth. The 60% PAR level was favourable to optimum results for most of the variables, whereas the least successful results were found in plants grown at 20% PAR. Seedling survival in the field differed significantly according to the nursery light level, increasing with greater light intensity in the nursery during seedling production. 100% survival was observed in seedlings produced under 100% PAR, whereas the lowest survival rate (53%) was found in seedlings grown under 20% PAR. Light management thus shows potential as a cultivation practice by affecting the quality of P. dulce seedlings, which is improved in the nursery at 60% PAR. However, better survival after planting out is obtained with plants produced under full sun. These results should help to improve nursery management and establishment in the field of P. dulce in projects to restore degraded lands in the dry tropics.