Source water, phenology and growth of two tropical dry forest tree species growing on shallow karst soils

Abstract

Seasonally dry tropical forests are dominated by deciduous and evergreen tree species with a wide range of leaf phenology. We hypothesized that Piscidia piscipula is able to extend leaf senescence until later in the dry season due to deeper and more reliable water sources than Gymnopodium floribundum, which loses leaves earlier in the dry season. Physiological performance was assessed as timing of leaf production and loss, growth, leaf water potential, depth of water uptake determined by stable isotopes, and leaf stable isotopic composition of carbon (d 13 C) and oxygen (d 18 O). P. piscipula took water primarily from shallow sources, whereas G. floribundum took water from shallow and deep sources. The greatest variation in water sources occurred during the onset of the dry season, when G. floribundum was shedding old leaves and growing new leaves, but P. piscipula maintained its leaves from the previous wet season. P. piscipula showed greater relative growth rate, greater leaf expansion rates, and more negative predawn and midday water potentials than G. floribundum. P. piscipula also exhibited greater leaf organic d 13 C and lower d18 O values, indicating that the decrease in photosynthetic carbon isotope discrimination was associated with greater stomatal conductance and greater photosynthesis. Our results indicate that the contrasting early and late dry season leaf loss phenology of these two species is not simply determined by rooting depth, but rather a more complicated suite of characteristics based on opportunistic use of dynamic water sources, maximizing carbon gain, and maintenance of water potential during the dry season.

Rooting depth, water relations and non‐structural carbohydrate dynamics in three woody angiosperms differentially affected by an extreme summer drought

“…Our study is among the few investigating rooting patterns in complex karstic soils, characterized by very shallow soil profiles, coupled to complex fissures and cave systems where roots can penetrate, and that are often filled with clay soils representing potentially important water sources for plants (Estrada-Medina et al 2013a). Contrasting species-specific patterns of rooting depth in karst-type substrates have been previously reported by Nie et al (2012) in Southwest China, Querejeta et al (2007) and Estrada-Medina et al (2013b) in Mexico, but not by Kukowski et al (2013) in Texas nor by Swaffer et al (2014) in South Australia, where all sampled species were found to rely only on precipitation to sustain transpiration, and not on groundwater available in the depth of the Karst features. The Classical Karst area where this study was carried out might represent an ideal location for further studies on plant-soil relationships because of the abundance of natural caves allowing relatively easy collection of soil and root samples at great depth (Johnson et al 2014).…”

Physiological Responses of Species to Microclimate Help explain Population Dynamics along Succession in a Tropical Dry Forest of Yucatan, Mexico

“…A similar relationship between tree size and (in that study) depth of water use; with larger trees preferentially tapping into more shallow water sources was found by Meinzer et al (1999) [45] in Panama. A study by Estrada-Medina et al (2013) [46] analyzed source water use by Piscidia piscipula in Northern Yucatan and found that this species appeared to use primarily shallow water sources. In that study however, only "trees" were sampled.…”

Influence of Heterogeneous Karst Microhabitats on the Root Foraging Ability of Chinese Windmill Palm (Trachycarpus fortunei) Seedlings

“…Forest tree species that typically occur in karst environments show a variety of adaptive characteristics [8,9]. For example, some studies have reported that plants growing in shallow soils in karst regions can extend their roots vertically into the bedrock layers [10,11]. However, other studies have reported that in shallow soils in karst habitats, the vertical root growth of many plant species is highly constrained, and that plant roots typically extend horizontally rather than vertically [12,13].…”