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Morphological and physiological responses of Guazuma ulmifolia Lam. to different pruning dates

Eloísa Ortega-Vargas, Juan Andrés Burgueño-Ferreira, Catarino Ávila-Reséndiz, William Bruce Campbell, Jesús Jarillo-Rodríguez, Silvia López-Ortiz
Agroforestry systems 2019 v.93 no.2 pp. 461-470
Guazuma ulmifolia, agroforestry, branches, defoliation, dry season, forage production, harvest date, internodes, leaf area, leaves, photosynthesis, physiological response, pruning, rain, regrowth, tree height, trees, wet season
Pruning is an important management practice for regulating tree structure and physiology, and the timing of pruning can enhance forage production during dry periods of the year. Experimental pruning was performed on Guazuma ulmifolia trees to explain the morphological and physiological changes that occur when they are subjected to programmed defoliation to promote regrowth during the dry season. Three prunings (P-1, P-2 and P-3) were conducted from August to October (rainy season), and four foliage harvesting dates (H-a, H-b, H-c and H-d) occurred from February to April (dry season) over 2 years of evaluation. The trees developed similar numbers of branches from pruning and harvesting (P > 0.05). Differing predefined pruning height resulted in greater tree height in P-3. Trees in P-1 developed shorter (P < 0.005) and vigorous branches, in contrast, those in P-3 had longer and less vigorous branches with long internodes. Nonetheless, trees in P-3 added less height from regrowth (P < 0.001) to the total tree height. The first pruning (P-1) induced greater foliage density (P < 0.010) and more senescent leaves (P < 0.001), but this greater senescence was further affected by later leaf harvests (P = 0.001). Trees in P-3 showed greater photosynthetic efficiency (P < 0.001) because they retained lower leaf area and more green foliage during the dry season. The timing of pruning modified the morphology and physiology of G. ulmifolia, but leaf senescence was more affected by harvest date during the dry season. This process can be accelerated or slowed, depending on the pattern of rainfall which varies from year to year.