Coordinated evolution of leaf and stem economics in tropical dry forest trees

Abstract

With data from 15 species in eight families of tropical dry forest trees, we provide evidence of coordination between the stem and leaf economic spectra. Species with low-density, flexible, breakable, hydraulically efficient but cavitationally vulnerable wood shed their leaves rapidly in response to drought and had low leaf mass per area and dry mass content. In contrast, species with the opposite xylem syndrome shed their costlier but more drought-resistant leaves late in the dry season. Our results explain variation in the timing of leaf shedding in tropical dry forests: selection eliminates combinations such as low-productivity leaves atop highly vulnerable xylem or water-greedy leaves supplied by xylem of low conductive efficiency. Across biomes, rather than a fundamental trade-off underlying a single axis of trait covariation, the relationship between leaf and stem economics is likely to occupy a wide space in which multiple combinations are possible.

Functional Traits and Water Transport Strategies in Lowland Tropical Rainforest Trees

“…Similar reports of coordination between the stem and leaf economic spectra, was reported in Méndez-Alonzo et al [32] and Kröber et al [31] in tropical dry forest and in a common garden experiment respectively. We hypothesised that a high vessel area or vessel density may be associated with large stem water storage capacity, which may in turn lead to a less negative maximum and minimum water potential (Ψ L ).…”

“…Given the high tree species richness in the tropics, we hypothesise a commensurate variety of trait strategies involved in the common function of water transport and drought resistance. In recent years, ecologists have used multivariate methods to examine various aspects of these relationships [22, 32] and to characterise water use trait strategies across species [11, 26, 31]. …”

Successional changes in functional composition contrast for dry and wet tropical forest

“…Remarkably, SLA and leaf area decreased with succession, against expectations, as high values of these traits are generally associated with high resource conditions (Poorter et al 2009). Including a gradient of deciduousness, number of months without leaves (Me´ndez-Alonzo et al 2012), and rooting depths may reveal how species The small increase in relative abundance of evergreen species with succession (note that deciduous species dominate throughout the successional gradient) was in line with expectations, as the forests become denser, close their canopy, hold more humidity, and the soil water content increases (Lebrija-Trejos et al 2011). This confirms previous studies showing that deciduousness is especially important during the extra-dry environments in early-successional stages (Pineda-Garcı´a et al 2013).…”

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

“…Such is the case of important genera in the tropical dry forest, such as Ceiba, Bursera, Jatropha, Jacarathia Erythrina and Ipomoea, among others (Borchert 1994). Leaf shedding, another trait that delays water loss in response to drought, has been associated with species with succulent stems (Borchert 1994;Holbrook et al 1995;Méndez-Alonzo et al 2012), suggesting that shallow roots may be part of a group of traits selected together. The role of the trade-off between root depth and water storage in shaping functional strategies at the adult stage is a topic that remains to be investigated.…”