Vegetative phenologies of lianas and trees in two Neotropical forests with contrasting rainfall regimes

Abstract

Summary Among tropical forests, lianas are predicted to have a growth advantage over trees during seasonal drought, with substantial implications for tree and forest dynamics. We tested the hypotheses that lianas maintain higher water status than trees during seasonal drought and that lianas maximize leaf cover to match high, dry‐season light conditions, while trees are more limited by moisture availability during the dry season. We monitored the seasonal dynamics of predawn and midday leaf water potentials and leaf phenology for branches of 16 liana and 16 tree species in the canopies of two lowland tropical forests with contrasting rainfall regimes in Panama. In a wet, weakly seasonal forest, lianas maintained higher water balance than trees and maximized their leaf cover during dry‐season conditions, when light availability was high, while trees experienced drought stress. In a drier, strongly seasonal forest, lianas and trees displayed similar dry season reductions in leaf cover following strong decreases in soil water availability. Greater soil moisture availability and a higher capacity to maintain water status allow lianas to maintain the turgor potentials that are critical for plant growth in a wet and weakly seasonal forest but not in a dry and strongly seasonal forest.

High vapour pressure deficit enhances turgor limitation of stem growth in an Asian tropical rainforest tree

“…High D induces water loss via leaf transpiration and causes an increase in tension of the water column, commonly quantified by more negative leaf water potential measurements ($${\psi }_{\text{leaf}}$$). More negative $${\psi }_{\text{leaf}}$$ relates well to the closure of stomata (Anderegg et al, 2017; Buckley et al, 2003), where tropical species appear to reduce their stomatal conductance to 50% at a $${\psi }_{\text{leaf}}$$ of around −1.5 MPa (Klein, 2014), although its variance is highly species‐specific (e.g., Flo et al, 2021; Johnson et al, 2009; Martínez‐Vilalta & Garcia‐Forner, 2016; Medina‐Vega et al, 2022; Meinzer et al, 1997; Wu et al, 2020). This threshold for stomatal closure is often assumed to optimise carbon assimilation against the threat of significant xylem conductance loss (Brodribb et al, 2017; Joshi et al, 2022; Wang et al, 2020; Wolf et al, 2016), a process occurring well beyond $${\psi }_{\text{leaf}}$$ conditions that limit turgor build‐up for growth (e.g., Muller et al, 2011).…”

Environmental heterogeneity influences liana community differentiation across a Neotropical rainforest landscape

“…Areas where soils have higher water holding capacity are more suitable for liana growth, but slope steepness may increase tree fall probability, ultimately prompting liana proliferation (Addo‐Fordjour et al., 2014 ; Liu et al., 2021 ; Schnitzer, 2018 ). These environmental factors also influence tree community structure and can jointly regulate liana establishment and stem growth (Manzané‐Pinzón et al., 2018 ; Medina‐Vega et al., 2022 , 2021 ).…”

“…These environmental factors also influence tree community structure and can jointly regulate liana establishment and stem growth (Manzané-Pinzón et al, 2018;Medina-Vega et al, 2022.…”

Effects of lianas on forest biogeochemistry during their lives and afterlives

“…Lianas also differ from trees in their vegetative phenologies, with liana having higher growth rates during the dry season than the wet season, the opposite of trees (Schnitzer & van der Heijden, 2019). This seasonal growth advantage allows lianas to maximize leaf cover during the dry season light maximum, when trees are shedding leaves to avoid water stress, although liana and tree phenologies converge in the most seasonal forests, where even lianas are deciduous (Medina‐Vega et al., 2022).…”