Different dry-wet pulses favor different functional strategies: A test using tropical dry forest tree species.

In many terrestrial habitats, plants experience temporal heterogeneity in water availability both at the intra and inter annual scales, creating dry-wet pulse scenarios. This variability imposes two concomitant challenges for plants: surviving droughts and efficiently utilizing water when it becomes available, whose responses are closely interconnected. To date, most studies have focused on the response to drought following static designs that do not consider consequences of repeated transitions from one state to the other.

Above- and below-ground trait coordination in tree seedlings depend on the most limiting resource: a test comparing a wet and a dry tropical forest in Mexico.

The study of above- and below-ground organ plant coordination is crucial for understanding the biophysical constraints and trade-offs involved in species' performance under different environmental conditions. Environmental stress is expected to increase constraints on species trait combinations, resulting in stronger coordination among the organs involved in the acquisition and processing of the most limiting resource. To test this hypothesis, we compared the coordination of trait combinations in 94 tree seedling species from two tropical forest systems in Mexico: dry and moist.

Differentiation in the water-use strategies among oak species from central Mexico.

Oak species (Fagaceae: Quercus) differ in their distribution at the landscape scale, specializing to a certain portion of environmental gradients. This suggests that functional differentiation favors habitat partitioning among closely related species. To elucidate the mechanisms of species coexistence in oak forests, we explored patterns of interspecific variation in functional traits involved in water-use strategies.

Exploiting water versus tolerating drought: water-use strategies of trees in a secondary successional tropical dry forest.

In seasonal plant communities where water availability changes dramatically both between and within seasons, understanding the mechanisms that enable plants to exploit water pulses and to survive drought periods is crucial. By measuring rates of physiological processes, we examined the trade-off between water exploitation and drought tolerance among seedlings of trees of a tropical dry forest, and identified biophysical traits most closely associated with plant water-use strategies. We also explored whether early and late secondary successional species occupy different portions of trade-off axes.

Root depth and morphology in response to soil drought: comparing ecological groups along the secondary succession in a tropical dry forest.

Root growth and morphology may play a core role in species-niche partitioning in highly diverse communities, especially along gradients of drought risk, such as that created along the secondary succession of tropical dry forests. We experimentally tested whether root foraging capacity, especially at depth, decreases from early successional species to old-growth forest species. We also tested for a trade-off between two mechanisms for delaying desiccation, the capacity to forage deeper in the soil and the capacity to store water in tissues, and explored whether successional groups separate along such a trade-off.

Drought resistance in early and late secondary successional species from a tropical dry forest: the interplay between xylem resistance to embolism, sapwood water storage and leaf shedding.

The mechanisms of drought resistance that allow plants to successfully establish at different stages of secondary succession in tropical dry forests are not well understood. We characterized mechanisms of drought resistance in early and late-successional species and tested whether risk of drought differs across sites at different successional stages, and whether early and late-successional species differ in resistance to experimentally imposed soil drought. The microenvironment in early successional sites was warmer and drier than in mature forest.

Morphological and physiological differentiation of seedlings between dry and wet habitats in a tropical dry forest.

A common observation in tropical dry forests is the habitat preference of tree species along spatial soil water gradients. This pattern of habitat partitioning might be a result of species differentiation in their strategy for using water, along with competing functions such as maximizing water exploitation and tolerating soil water stress. We tested whether species from drier soil conditions exhibited a tolerance strategy compared with that of wet-habitat species.