A combination of forage species with different responses to drought can increase year-round productivity in seasonally dry silvopastoral systems

In seasonally dry environments maintaining year-round production of silvopastoral systems can be challenging due to drought effects on vegetation. Different tree species native to dry forests may show contrasting strategies to deal with drought, which could impact silvopastoral productivity. We assessed the differential effect of drought on seedlings of five tree species from a dry tropical forest with high forage potential. The species were subjected to three irrigation schemes (well-watered, mild drought, severe drought) in order to evaluate the effect of water stress on 12 growth and morpho-physiological traits involving above and below ground responses. The species comprised four species of the family Fabaceae (legumes) Albizia lebbeck, Leucaena leucocephala, Piscidia piscipula, and Lysiloma latisiliquum and one of the family Sterculiaceae, Guazuma ulmifolia. This one was the most productive species when well-watered, with the highest forage potential due to high leaf area, leaf mass and fast growth rates. This species was also the most vulnerable to drought, reducing leaf area and other growth parameters dramatically. In contrast, L. latisiliquum showed low leaf area and leaf mass, but was highly resistant to drought. An intermediate species was P. piscipula, which was the most productive of the legume species and exhibited adjustment mechanisms to drought which allowed reduced leaf excision during the severe drought. We propose that combining species with contrasting mechanisms in response to drought can promote year-round productivity in seasonally dry environments.