Long‐term effects of 7‐year warming experiment in the field on leaf hydraulic and economic traits of subtropical tree species

Abstract

Over the past 30 years, global surface temperature has increased by approximately 0.2°C per decade (IPCC, 2018). Clearly, the increase in temperature can affect tree growth and mortality (Bowman et al., 2014; Liu et al., 2016), influencing forest structure and composition in tropical forests (Zhou et al., 2013, 2014). The response of trees to warming depends on whether they can adjust their phenotypic traits; for example, many tree species maintain enhanced growth by increasing photosynthetic capacity (Drake et al., 2015). However, few studies address leaf hydraulic and economic traits, combined with related phenotypic plasticity, in long-term field warming experiments (Grady et al., 2013). Leaf hydraulic traits, such as leaf hydraulic conductance (K leaf), stomatal conductance (g s) and stomatal anatomical traits, play a vital role in regulating leaf gas exchange. K leaf measures water flow efficiency through the leaf, defining leaf water transport capacity (Locke et al., 2013). Under warmer conditions, higher K leaf may increase

Warming Responses of Leaf Morphology Are Highly Variable among Tropical Tree Species

“…Regardless of successional group, LMA declined with warming (i.e., increased with elevation; Table 3, Figure 4) for some species in our study, which confirms the first part of hypothesis #1. This is consistent with observations from both field studies and controlled experiments in the tropics as well as in several other biomes [1,13,15,21,24,36,73]. Within a given species, LMA usually correlates with photosynthesis, since thicker leaves with more palisade parenchyma tissue tend to have both higher LMA and photosynthetic capacity [21,74,75].…”

“…LVA shifts were found to be important for LMA changes in a study on 42 tropical tree species from different habitats in south-east Asia, regardless of environmental factors causing these changes [26], as well as in an elevation-gradient study on six tropical tree species in south China [73]. The conflicting results on LVA and LD contributions to warminginduced changes in LMA in these studies on tropical trees (including our study) compared to global datasets [21] may reflect mixed effects of warming and other factors, especially effects of VPD along elevation gradients.…”

Evaporative flux method of leaf hydraulic conductance estimation: sources of uncertainty and reporting format recommendation

“…Although the field material sampling at the night before the measurement day and rehydrating overnight in the lab are common practice in previous studies [ 5 , 26 – 29 ], to the best of our knowledges, no study investigated the impacts of sampling and storage time on K leaf estimation. The tension in xylem is created by transpiration, but the excessive tension in the daytime poses the inherent risk for xylem cavitation, thus substantially reducing the hydraulic conductivity of plants [ 30 , 31 ].…”

“…The EFM follows the natural transpiration-driven water movement pathway in leaves, and the water enters the leaf through internal transpiration driving rather than through external water gravity pressure which may be caused by lower position of leaves than the water meniscus in the cylinder. However, the relative position difference between leaves and water source was generally ignored in previous studies [ 28 , 29 ]. In this study, the estimated K leaf showed no difference when the leaf was placed below, as high as, or above the meniscus of water in the cylinder.…”

Evaporative Flux Method of Leaf Hydraulic Conductance Estimation: Sources of Uncertainty and Reporting Format Recommendation

“…Although the eld material sampling at the night before measurement date and rehydrating overnight in the lab are common practice in previous studies [5,[24][25][26][27], to the best of our knowledges, few studies have investigated the impacts of sampling time on K leaf estimation. The tension in xylem created by transpiration driver for gas exchange, but the excessive tension in the daytime poses the inherent risk for xylem cavitation, thus substantially reducing the hydraulic conductivity of plants [28,29].…”