Linking coordinated hydraulic traits to drought and recovery responses in a tropical montane cloud forest

Abstract

PREMISE:Understanding plant hydraulic functioning and water balance during drought has become key in predicting species survival and recovery. However, there are few insightful studies that couple physiological and morphological attributes for many ecosystems, such as the vulnerable Tropical Montane Cloud Forests (TMCF). In this study, we evaluated drought resistance and recovery for saplings for five tree species spanning deciduous to evergreen habits from a Mexican TMCF. METHODS:In drought simulations, water was withheld until plants reached species-specific P 50 or P 88 values (pressures required to induce a 50 or 88% loss in hydraulic conductivity), then they were rewatered. Drought resistance was considered within the isohydricanisohydric framework and compared to leaf gas exchange, water status, pressure-volume curves, specific leaf area, and stomatal density. RESULTS:The TMCF species closed stomata well before significant losses in hydraulic conductivity (isohydric). Yet, despite the coordination of these traits, the traits were not useful for predicting the time needed for the species to reach critical hydraulic thresholds. Instead, maximum photosynthetic rates explained these times, reinforcing the linkage between hydraulic and carbon dynamics. Despite their varying hydraulic conductivities, stomatal responses, and times to hydraulic thresholds, 58 of the 60 study plants recovered after the rewatering. The recovery of photosynthesis and stomatal conductance can be explained by the P 50 values and isohydry. CONCLUSIONS:This study raises new questions surrounding drought management strategies, recovery processes, and how lethal thresholds are defined. Further studies need to consider the role of water and carbon balance in allowing for both survival and recovery from drought.

Sequía experimental en plántulas en un claro y en el sotobosque de un bosque de niebla, Veracruz, México

“…Functional traits have been used as an approach to evaluate plant species performance in different light conditions (Poorter and Bongers, 2006;Saldaña-Acosta et al, 2009;Toledo-Aceves et al, 2017), water availability levels (Amissah et al, 2015) and soil conditions (Vergara-Gómez et al, 2020). Leaf functional traits of each studied species responded accordingly to the functional group they belong in a continuum of light requirements (Poorter and Bongers, 2006), where trees may have different leaf traits responses depending on water availability (Poorter and Markesteijn, 2008;Berry et al, 2019). Trade-offs have been widely reported, but some studies have found that traits and survival of tropical forest tree seedlings respond independently to drought and shade (Amissah et al, 2015).…”

“…Droughts induced by climate change will affect the performance of trees globally, but the direction (positive or negative) and magnitude of these effects will depend on the intensity of droughts and the tolerance of species to water shortage conditions (Allen et al, 2015). Considering that climate change may affect plants differently, increasing number of studies have focused on the responses of tree species and ecosystems to drought stress (Beier et al, 2012;Berry et al, 2019). The climate change responses of tree species have motivated studies on functional traits and there is growing interest in analyzing how these traits vary with increasing drought (Badano et al, 2018(Badano et al, , 2019Berry et al, 2019;Williams-Linera et al, 2022).…”

“…Considering that climate change may affect plants differently, increasing number of studies have focused on the responses of tree species and ecosystems to drought stress (Beier et al, 2012;Berry et al, 2019). The climate change responses of tree species have motivated studies on functional traits and there is growing interest in analyzing how these traits vary with increasing drought (Badano et al, 2018(Badano et al, , 2019Berry et al, 2019;Williams-Linera et al, 2022).…”

“…Moreover, within the same species, LA and SLA vary if trees are established in different types of soil (Vergara-Gómez et al, 2020). In these cloud forests, other studies focused on functional attributes related to drought scenarios caused by climate change (Berry et al, 2019;Williams-Linera et al, 2022). In other tropical forest ecosystems, controlled experiments have been carried out exposing seedlings to low and high levels of water availability (Poorter and Markesteijn, 2008;Badano et al, 2019;Berry et al, 2019), different light levels (Saldaña-Acosta et al, 2009) or combinations of these factors (Amissah et al, 2015).…”

“…In these cloud forests, other studies focused on functional attributes related to drought scenarios caused by climate change (Berry et al, 2019;Williams-Linera et al, 2022). In other tropical forest ecosystems, controlled experiments have been carried out exposing seedlings to low and high levels of water availability (Poorter and Markesteijn, 2008;Badano et al, 2019;Berry et al, 2019), different light levels (Saldaña-Acosta et al, 2009) or combinations of these factors (Amissah et al, 2015). Poorter and Markesteijn (2008) suggested that seedling functional traits affect survival in face of drought, indicating that the mechanisms to deal with water shortage are closely linked to the functional group of a species.…”