EFFECT OF DROUGHT and DEFOLIATION ON THE GROWTH OF SEEDINGS OF THE DRY TROPICAL FOREST IN WESTERN MEXICO

Background: Although drought and defoliation increase the risk of death of the seedlings in tropical dry forests, few studies have evaluated the impact of this combined factors on the response of species. Questions: What is the seedling water management strategy and how does it affect their growth? How does the combination of drought and defoliation impact the growth of the species? Studied species: Guazuma ulmifolia Lam and Pithecellobium dulce (Roxb.) Benth. Study sites and dates: The study was carried out in Autlan, Jalisco, Mexico, between October 2021 and February 2022. Methods: In a greenhouse, the seedlings were submitted to four combined water availability and defoliation treatments. The stomatal conductance and leaf water potential were recorded, and the relative growth rate, final biomass, and biomass allocation were calculated. Results: G. ulmifolia showed to be an anisohydric species, registered higher growth, and was the most affected by drought, while P. dulce was more isohydric, registered lower growth and defoliation was the main stressor. The synergy between Drought x Defoliation negatively impacted the two species' relative growth rate. Conclusions: Regardless of the water management strategy, in the early phases of development, the impact of drought and defoliation was magnified when stressors interacted. Therefore, Drought x Defoliation can limit the regeneration of species within forests, promoting the loss of biodiversity and detriment to the functioning of ecosystems.