The Hydraulic Architecture of Populus

Hacke, Uwe G.

doi:10.1007/978-3-319-15783-2_4

Cited by 18 publications

(21 citation statements)

References 125 publications

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“…By working at the scale of individual trees, it is possible for models of WSTM to test for effects of changing plant hydraulics. Relationships between mortality and purely physical expressions of drought should vary with tree size because water status of the canopy depends, in addition to external hydrological conditions, on the efficiency of water transport from roots to the canopy Novick et al, 2009;Meinzer et al, 2011;Zang et al, 2012;Hacke, 2015). As efficiency of water transport (i.e.…”

Section: Introductionmentioning

confidence: 99%

Relationships between individual‐tree mortality and water‐balance variables indicate positive trends in water stress‐induced tree mortality across North America

Hember

Kurz

Coops

2016

Global Change Biology

108

106

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Accounting for water stress-induced tree mortality in forest productivity models remains a challenge due to uncertainty in stress tolerance of tree populations. In this study, logistic regression models were developed to assess species-specific relationships between probability of mortality (P ) and drought, drawing on 8.1 million observations of change in vital status (m) of individual trees across North America. Drought was defined by standardized (relative) values of soil water content (W ) and reference evapotranspiration (ET ) at each field plot. The models additionally tested for interactions between the water-balance variables, aridity class of the site (AC), and estimated tree height (h). Considering drought improved model performance in 95 (80) per cent of the 64 tested species during calibration (cross-validation). On average, sensitivity to relative drought increased with site AC (i.e. aridity). Interaction between water-balance variables and estimated tree height indicated that drought sensitivity commonly decreased during early height development and increased during late height development, which may reflect expansion of the root system and decreasing whole-plant, leaf-specific hydraulic conductance, respectively. Across North America, predictions suggested that changes in the water balance caused mortality to increase from 1.1% yr in 1951 to 2.0% yr in 2014 (a net change of 0.9 ± 0.3% yr ). Interannual variation in mortality also increased, driven by increasingly severe droughts in 1988, 1998, 2006, 2007 and 2012. With strong confidence, this study indicates that water stress is a common cause of tree mortality. With weak-to-moderate confidence, this study strengthens previous claims attributing positive trends in mortality to increasing levels of water stress. This 'learn-as-we-go' approach - defined by sampling rare drought events as they continue to intensify - will help to constrain the hydraulic limits of dominant tree species and the viability of boreal and temperate forest biomes under continued climate change.

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Section: Introductionmentioning

confidence: 99%

Relationships between individual‐tree mortality and water‐balance variables indicate positive trends in water stress‐induced tree mortality across North America

Hember

Kurz

Coops

2016

Global Change Biology

108

106

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“…Studies found that stem water storage was negatively associated with wood density in five coexisting temperate broad‐leaved tree species (Köcher, Horna, & Leuschner, ), suggesting the higher water storage as lower wood density. Many studies suggest that most Populus species are highly vulnerable to cavitation causing 50% loss of hydraulic conductivity ( P 50 ) occurring between −1 and −2.5 MPa (Hacke, ; Hukin, Cochard, Dreyer, Le Thiec, & Bogeat‐Triboulot, ; Pan, Chen, Chen, Wang, & Ren, ). For P. euphratica , the basic wood density of stem was less than that of the co‐occurring species, T. ramosissima , 0.41 versus 0.73 g/cm 3 (Yu et al., ), suggesting that P. euphratica can store more water than T. ramosissima .…”

Section: Discussionmentioning

confidence: 99%

“…Populus species are highly vulnerable to cavitation causing 50% loss of hydraulic conductivity (P 50 ) occurring between −1 and −2.5 MPa (Hacke, 2015;Hukin, Cochard, Dreyer, Le Thiec, & Bogeat-Triboulot, 2005; Pan, Chen, Chen, Wang, & Ren, 2016). For P. euphratica, the basic wood density of stem was less than that of the co-occurring species, T. ramosissima, 0.41 versus 0.73 g/cm 3 (Yu et al, 2013), suggesting that P. euphratica can store more water than T. ramosissima.…”

Section: Limited Hydraulic Redistribution: Nocturnal Transpiration mentioning

confidence: 99%

Depressed hydraulic redistribution of roots more by stem refilling than by nocturnal transpiration for Populus euphratica Oliv. in situ measurement

Feng

et al. 2018

Ecology and Evolution

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During the night, plant water loss can occur either through the roots, as hydraulic redistribution (HR), or through the leaves via the stoma, as nocturnal transpiration (E n), which was methodologically difficult to separate from stem refilling (R e). While HR and E n have been reported across a range of species, ecosystem, and climate zone, there is little understanding on the interactions between E n and/or R e and HR. As water movement at night occurs via gradients of water potential, it is expected that during periods of high atmospheric vapor pressure deficit (VPD), water loss via E n will override water loss via HR. To test this hypothesis, sap flow in stems and roots of Populus euphratica Oliv. trees, growing in a riparian zone in a hyperarid climate, was measured once in a year. Nocturnal stem sap flow was separated into E n and R e using the “forecasted refilling” method. Substantial nocturnal sap flow (38% of 24‐hr flux on average) was observed and positively correlated with VPD; however, the strength of the correlation was lower (R 2 = .55) than diurnal sap flow (E d) (R 2 = .72), suggesting that nocturnal stem sap flow was attributed to both water loss through the canopy and replenishment of water in stem tissues. Partitioning of nocturnal sap flow shows that R e constituted approximately 80%, and E n ~20%, of nocturnal sap flow. The amount of root sap flow attributed to redistribution was negatively related to E d (R 2 = .69) and the amount of acropetally sap flow in stems, R e (R 2 = .41) and E n (R 2 = .14). It was suggested that the magnitude of HR is more strongly depressed by R e that was recharge to the water loss via E d than by E n. It was consistent with whole‐tree water balance theory, that the nighttime upward sap flow to xylem, stem refilling and transpiration, may depress hydraulic redistribution of roots.

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“…) and various physiological traits of Populus genotypes (Fichot et al . ; Hacke ). If their large water requirements are met, poplars may show fast growth rates.…”

Section: Introductionmentioning

confidence: 99%

“…Populus has emerged as a model tree species (Cooke & Rood 2007;Jansson & Douglas 2007). In the last decade, much has been learned about the transcriptional regulation of xylem formation (Zhong & Ye 2013), the transcriptome-level drought response (Raj et al 2011) and various physiological traits of Populus genotypes (Fichot et al 2015;Hacke 2015). If their large water requirements are met, poplars may show fast growth rates.…”

Section: Introductionmentioning

confidence: 99%

Leaf size serves as a proxy for xylem vulnerability to cavitation in plantation trees

Schreiber

Hacke

Chamberland

et al. 2015

Plant Cell & Environment

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Hybrid poplars are an important renewable forest resource known for their high productivity. At the same time, they are highly vulnerable to water stress. Identifying traits that can serve as indicators for growth performance remains an important task, particularly under field conditions. Understanding which trait combinations translate to improved productivity is key in order to satisfy the demand for poplar wood in an uncertain future climate. In this study, we compared hydraulic and leaf traits among five hybrid poplar clones at 10 plantations in central Alberta. We also assessed the variation of these traits between 2- to 3-year-old branches from the lower to mid-crown and current-year long shoots from the mid to upper crown. Our results showed that (1) hybrid poplars differed in key hydraulic parameters between branch type, (2) variation of hydraulic traits among clones was relatively large for some clones and less for others, and (3) strong relationships between measured hydraulic traits, such as vessel diameter, cavitation resistance, xylem-specific and leaf-specific conductivity and leaf area, were observed. Our results suggest that leaf size could serve as an additional screening tool when selecting for drought-tolerant genotypes in forest management and tree improvement programmes.

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The Hydraulic Architecture of Populus

Cited by 18 publications

References 125 publications

Relationships between individual‐tree mortality and water‐balance variables indicate positive trends in water stress‐induced tree mortality across North America

Relationships between individual‐tree mortality and water‐balance variables indicate positive trends in water stress‐induced tree mortality across North America

Depressed hydraulic redistribution of roots more by stem refilling than by nocturnal transpiration for Populus euphratica Oliv. in situ measurement

Leaf size serves as a proxy for xylem vulnerability to cavitation in plantation trees

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