The conifer-curve: fast prediction of hydraulic conductivity loss and vulnerability to cavitation

Research Highlights: novel fast and easily assessable proxies for vulnerability to cavitation of conifer sapwood are proposed that allow reliable estimation at the species level. Background and Objectives: global warming calls for fast and easily applicable methods to measure hydraulic vulnerability in conifers since they are one of the most sensitive plant groups regarding drought stress. Classical methods to determine P12, P50 and P88, i.e., the water potentials resulting in 12, 50 and 88% conductivity loss, respectively, are labour intensive, prone to errors and/or restricted to special facilities. Vulnerability proxies were established based on empirical relationships between hydraulic traits, basic density and sapwood anatomy. Materials and Methods: reference values for hydraulic traits were obtained by means of the air injection method on six conifer species. Datasets for potential P50 proxies comprised relative water loss (RWL), basic density, saturated water content as well as anatomical traits such as double wall thickness, tracheid lumen diameter and wall/lumen ratio. Results: our novel proxy P25W, defined as 25% RWL induced by air injection, was the most reliable estimate for P50 (r = 0.95) and P88 (r = 0.96). Basic wood density (r = −0.92), tangential lumen diameters in earlywood (r = 0.88), wall/lumen ratios measured in the tangential direction (r = −0.86) and the number of radial cell files/mm circumference (CF/mm, r = −0.85) were also strongly related to P50. Moreover, CF/mm was a very good predictor for P12 (r = −0.93). Conclusions: the proxy P25W is regarded a strong phenotyping tool for screening conifer species for vulnerability to cavitation assuming that the relationship between RWL and conductivity loss is robust in conifer sapwood. We also see a high potential for the fast and easily applicable proxy CF/mm as a screening tool for drought sensitivity and for application in dendroecological studies that investigate forest dieback.

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Prediction of hydraulic conductivity loss from relative water loss: new insights into water storage of tree stems and branches

Physiologia Plantarum ◽

10.1111/ppl.12790 ◽

2018 ◽

Vol 165 (4) ◽

pp. 843-854 ◽

Cited By ~ 10

Author(s):

Sabine Rosner ◽

Berthold Heinze ◽

Tadeja Savi ◽

Guillermina Dalla‐Salda

Keyword(s):

Hydraulic Conductivity ◽

Water Loss ◽

Water Storage ◽

Relative Water ◽

Conductivity Loss

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Within-ring variability of wood structure and its relationship to drought sensitivity in Norway spruce trunks

IAWA Journal ◽

10.1163/22941932-40190216 ◽

2019 ◽

Vol 40 (2) ◽

pp. 288-310 ◽

Cited By ~ 2

Author(s):

Saskia Luss ◽

Sven-Olof Lundqvist ◽

Robert Evans ◽

Thomas Grahn ◽

Lars Olsson ◽

...

Keyword(s):

Hydraulic Conductivity ◽

Norway Spruce ◽

Dynamic Process ◽

Anatomical Features ◽

Functional Aspects ◽

Hydraulic Vulnerability ◽

Conduit Wall ◽

Double Wall ◽

Transition Wood ◽

Conductivity Loss

ABSTRACTRelationships between hydraulic vulnerability expressed as P50 (the air pressure causing 50% loss of hydraulic conductivity) and within-ring differences in wood density (WD) and anatomical features were investigated with the aim to find efficient proxies for P50 relating to functional aspects. WD and tracheid dimensions were measured with SilviScan on Norway spruce (Picea abies (L.) Karst.) trunk wood.P50 was strongly related to mean WD (r = -0.64) and conduit wall reinforcement ((t/b)2), the square of the ratio between the tracheid double wall thickness (t) and the lumen width (b), where use of tangential lumen width ((t/bt)2) gave better results (r = -0.54) than radial lumen width (r = -0.31). The correlations of P50 with earlywood (EW), transition wood (TW) and latewood (LW) traits were lower than with the specimen averages, both for WD (r = -0.60 for WDEW, r = -0.56 for WDTW, r = -0.23 for WDLW) and all anatomical traits. The loss of hydraulic conductivity was addressed as a dynamic process and was simulated by defining consecutive phases of 5% theoretical conductivity loss. WD and tracheid traits were calculated and correlated with P50 values of each specimen. Tightest correlations were found for (t/bt)2, at relative cumulated theoretical conductivities until 45 to 50% (r = -0.75).We conclude that WD is one of the best available proxies for P50, but does not necessarily reflect the mechanism behind resistance to cavitation. The new trait, based on estimation of conductivity loss as a dynamic process, provided even stronger correlations.

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Impact of hemlock woolly adelgid (Adelges tsugae) infestation on xylem structure and function and leaf physiology in eastern hemlock (Tsuga canadensis)

Functional Plant Biology ◽

10.1071/fp17233 ◽

2018 ◽

Vol 45 (5) ◽

pp. 501 ◽

Cited By ~ 3

Author(s):

Brett A. Huggett ◽

Jessica A. Savage ◽

Guang-You Hao ◽

Evan L. Preisser ◽

N. Michele Holbrook

Keyword(s):

Hydraulic Conductivity ◽

Net Photosynthesis ◽

Tsuga Canadensis ◽

Hemlock Woolly Adelgid ◽

Adelges Tsugae ◽

Eastern Hemlock ◽

Xylem Structure ◽

Leaf Physiology ◽

Vulnerability To Cavitation ◽

Needle Loss

Hemlock woolly adelgid (Adelges tsugae Annand) (HWA) is an invasive insect that feeds upon the foliage of eastern hemlock (Tsuga canadensis (L.) Carrière) trees, leading to a decline in health and often mortality. The exact mechanism leading to the demise of eastern hemlocks remains uncertain because little is known about how HWA infestation directly alters the host’s physiology. To evaluate the physiological responses of eastern hemlock during early infestation of HWA, we measured needle loss, xylem hydraulic conductivity, vulnerability to cavitation, tracheid anatomy, leaf-level gas exchange, leaf water potential and foliar cation and nutrient levels on HWA-infested and noninfested even-aged trees in an experimental garden. HWA infestation resulted in higher xylem hydraulic conductivity correlated with an increase in average tracheid lumen area and no difference in vulnerability to cavitation, indicating that needle loss associated with HWA infestation could not be attributed to reduced xylem transport capacity. HWA-infested trees exhibited higher rates of net photosynthesis and significant changes in foliar nutrient partitioning, but showed no differences in branch increment growth rates compared with noninfested trees. This study suggests that HWA-induced decline in the health of eastern hemlock trees is not initially caused by compromised water relations or needle loss.

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